staticcheck (#313)

* CI: use staticcheck for linting

This commit switches the linter for Go code from golint to staticcheck.
Golint has been deprecated since last year and staticcheck is a
recommended replacement.

Signed-off-by: Lucas Servén Marín <lserven@gmail.com>

* revendor

Signed-off-by: Lucas Servén Marín <lserven@gmail.com>

* cmd,pkg: fix lint warnings

Signed-off-by: Lucas Servén Marín <lserven@gmail.com>

Makefile

@@ -38,14 +38,14 @@ DOCS_GEN_BINARY := bin/docs-gen
 DEEPCOPY_GEN_BINARY := bin/deepcopy-gen
 INFORMER_GEN_BINARY := bin/informer-gen
 LISTER_GEN_BINARY := bin/lister-gen
-GOLINT_BINARY := bin/golint
+STATICCHECK_BINARY := bin/staticcheck
 EMBEDMD_BINARY := bin/embedmd
 KIND_BINARY := $(shell pwd)/bin/kind
 KUBECTL_BINARY := $(shell pwd)/bin/kubectl
 BASH_UNIT := $(shell pwd)/bin/bash_unit
 BASH_UNIT_FLAGS :=
 
-BUILD_IMAGE ?= golang:1.18
+BUILD_IMAGE ?= golang:1.18.0
 BASE_IMAGE ?= alpine:3.15
 
 build: $(BINS)
@@ -165,7 +165,7 @@ fmt:
 	@echo $(GO_PKGS)
 	gofmt -w -s $(GO_FILES)
 
-lint: header $(GOLINT_BINARY)
+lint: header $(STATICCHECK_BINARY)
 	@echo 'go vet $(GO_PKGS)'
 	@vet_res=$$(GO111MODULE=on go vet -mod=vendor $(GO_PKGS) 2>&1); if [ -n "$$vet_res" ]; then \
 		echo ""; \
@@ -174,10 +174,10 @@ lint: header $(GOLINT_BINARY)
 		echo "$$vet_res"; \
 		exit 1; \
 	fi
-	@echo '$(GOLINT_BINARY) $(GO_PKGS)'
-	@lint_res=$$($(GOLINT_BINARY) $(GO_PKGS)); if [ -n "$$lint_res" ]; then \
+	@echo '$(STATICCHECK_BINARY) $(GO_PKGS)'
+	@lint_res=$$($(STATICCHECK_BINARY) $(GO_PKGS)); if [ -n "$$lint_res" ]; then \
 		echo ""; \
-		echo "Golint found style issues. Please check the reported issues"; \
+		echo "Staticcheck found style issues. Please check the reported issues"; \
 		echo "and fix them if necessary before submitting the code for review:"; \
 		echo "$$lint_res"; \
 		exit 1; \
@@ -358,8 +358,8 @@ $(LISTER_GEN_BINARY):
 $(DOCS_GEN_BINARY): cmd/docs-gen/main.go
 	go build -mod=vendor -o $@ ./cmd/docs-gen
 
-$(GOLINT_BINARY):
-	go build -mod=vendor -o $@ golang.org/x/lint/golint
+$(STATICCHECK_BINARY):
+	go build -mod=vendor -o $@ honnef.co/go/tools/cmd/staticcheck
 
 $(EMBEDMD_BINARY):
 	go build -mod=vendor -o $@ github.com/campoy/embedmd

cmd/kgctl/connect_linux.go

@@ -276,8 +276,6 @@ func cleanUp(iface int, t *route.Table, logger log.Logger) {
 	if err := t.CleanUp(); err != nil {
 		level.Error(logger).Log("failed to clean up routes: %v", err)
 	}
-
-	return
 }
 
 func sync(table *route.Table, peerName string, privateKey wgtypes.Key, iface int, logger log.Logger) error {

go.mod

@@ -15,9 +15,9 @@ require (
 	github.com/prometheus/client_golang v1.11.0
 	github.com/spf13/cobra v1.2.1
 	github.com/vishvananda/netlink v1.1.1-0.20210330154013-f5de75959ad5
-	golang.org/x/lint v0.0.0-20210508222113-6edffad5e616
 	golang.org/x/sys v0.0.0-20211124211545-fe61309f8881
 	golang.zx2c4.com/wireguard/wgctrl v0.0.0-20211124212657-dd7407c86d22
+	honnef.co/go/tools v0.3.1
 	k8s.io/api v0.23.6
 	k8s.io/apiextensions-apiserver v0.23.6
 	k8s.io/apimachinery v0.23.6
@@ -27,6 +27,7 @@ require (
 )
 
 require (
+	github.com/BurntSushi/toml v0.4.1 // indirect
 	github.com/beorn7/perks v1.0.1 // indirect
 	github.com/cespare/xxhash/v2 v2.1.1 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
@@ -62,13 +63,14 @@ require (
 	github.com/spf13/pflag v1.0.5 // indirect
 	github.com/vishvananda/netns v0.0.0-20210104183010-2eb08e3e575f // indirect
 	golang.org/x/crypto v0.0.0-20211117183948-ae814b36b871 // indirect
-	golang.org/x/mod v0.4.2 // indirect
+	golang.org/x/exp/typeparams v0.0.0-20220218215828-6cf2b201936e // indirect
+	golang.org/x/mod v0.6.0-dev.0.20220106191415-9b9b3d81d5e3 // indirect
 	golang.org/x/net v0.0.0-20211209124913-491a49abca63 // indirect
 	golang.org/x/oauth2 v0.0.0-20210819190943-2bc19b11175f // indirect
 	golang.org/x/term v0.0.0-20210615171337-6886f2dfbf5b // indirect
 	golang.org/x/text v0.3.7 // indirect
 	golang.org/x/time v0.0.0-20210723032227-1f47c861a9ac // indirect
-	golang.org/x/tools v0.1.6-0.20210820212750-d4cc65f0b2ff // indirect
+	golang.org/x/tools v0.1.11-0.20220316014157-77aa08bb151a // indirect
 	golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 // indirect
 	golang.zx2c4.com/wireguard v0.0.0-20211123210315-387f7c461a16 // indirect
 	google.golang.org/appengine v1.6.7 // indirect

go.sum

@@ -47,6 +47,8 @@ github.com/Azure/go-autorest/autorest/mocks v0.4.1/go.mod h1:LTp+uSrOhSkaKrUy935
 github.com/Azure/go-autorest/logger v0.2.1/go.mod h1:T9E3cAhj2VqvPOtCYAvby9aBXkZmbF5NWuPV8+WeEW8=
 github.com/Azure/go-autorest/tracing v0.6.0/go.mod h1:+vhtPC754Xsa23ID7GlGsrdKBpUA79WCAKPPZVC2DeU=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
+github.com/BurntSushi/toml v0.4.1 h1:GaI7EiDXDRfa8VshkTj7Fym7ha+y8/XxIgD2okUIjLw=
+github.com/BurntSushi/toml v0.4.1/go.mod h1:CxXYINrC8qIiEnFrOxCa7Jy5BFHlXnUU2pbicEuybxQ=
 github.com/BurntSushi/xgb v0.0.0-20160522181843-27f122750802/go.mod h1:IVnqGOEym/WlBOVXweHU+Q+/VP0lqqI8lqeDx9IjBqo=
 github.com/DATA-DOG/go-sqlmock v1.4.1 h1:ThlnYciV1iM/V0OSF/dtkqWb6xo5qITT1TJBG1MRDJM=
 github.com/DATA-DOG/go-sqlmock v1.4.1/go.mod h1:f/Ixk793poVmq4qj/V1dPUg2JEAKC73Q5eFN3EC/SaM=
@@ -574,6 +576,8 @@ golang.org/x/exp v0.0.0-20191227195350-da58074b4299/go.mod h1:2RIsYlXP63K8oxa1u0
 golang.org/x/exp v0.0.0-20200119233911-0405dc783f0a/go.mod h1:2RIsYlXP63K8oxa1u096TMicItID8zy7Y6sNkU49FU4=
 golang.org/x/exp v0.0.0-20200207192155-f17229e696bd/go.mod h1:J/WKrq2StrnmMY6+EHIKF9dgMWnmCNThgcyBT1FY9mM=
 golang.org/x/exp v0.0.0-20200224162631-6cc2880d07d6/go.mod h1:3jZMyOhIsHpP37uCMkUooju7aAi5cS1Q23tOzKc+0MU=
+golang.org/x/exp/typeparams v0.0.0-20220218215828-6cf2b201936e h1:qyrTQ++p1afMkO4DPEeLGq/3oTsdlvdH4vqZUBWzUKM=
+golang.org/x/exp/typeparams v0.0.0-20220218215828-6cf2b201936e/go.mod h1:AbB0pIl9nAr9wVwH+Z2ZpaocVmF5I4GyWCDIsVjR0bk=
 golang.org/x/image v0.0.0-20190227222117-0694c2d4d067/go.mod h1:kZ7UVZpmo3dzQBMxlp+ypCbDeSB+sBbTgSJuh5dn5js=
 golang.org/x/image v0.0.0-20190802002840-cff245a6509b/go.mod h1:FeLwcggjj3mMvU+oOTbSwawSJRM1uh48EjtB4UJZlP0=
 golang.org/x/lint v0.0.0-20181026193005-c67002cb31c3/go.mod h1:UVdnD1Gm6xHRNCYTkRU2/jEulfH38KcIWyp/GAMgvoE=
@@ -587,7 +591,6 @@ golang.org/x/lint v0.0.0-20191125180803-fdd1cda4f05f/go.mod h1:5qLYkcX4OjUUV8bRu
 golang.org/x/lint v0.0.0-20200130185559-910be7a94367/go.mod h1:3xt1FjdF8hUf6vQPIChWIBhFzV8gjjsPE/fR3IyQdNY=
 golang.org/x/lint v0.0.0-20200302205851-738671d3881b/go.mod h1:3xt1FjdF8hUf6vQPIChWIBhFzV8gjjsPE/fR3IyQdNY=
 golang.org/x/lint v0.0.0-20201208152925-83fdc39ff7b5/go.mod h1:3xt1FjdF8hUf6vQPIChWIBhFzV8gjjsPE/fR3IyQdNY=
-golang.org/x/lint v0.0.0-20210508222113-6edffad5e616 h1:VLliZ0d+/avPrXXH+OakdXhpJuEoBZuwh1m2j7U6Iug=
 golang.org/x/lint v0.0.0-20210508222113-6edffad5e616/go.mod h1:3xt1FjdF8hUf6vQPIChWIBhFzV8gjjsPE/fR3IyQdNY=
 golang.org/x/mobile v0.0.0-20190312151609-d3739f865fa6/go.mod h1:z+o9i4GpDbdi3rU15maQ/Ox0txvL9dWGYEHz965HBQE=
 golang.org/x/mobile v0.0.0-20190719004257-d2bd2a29d028/go.mod h1:E/iHnbuqvinMTCcRqshq8CkpyQDoeVncDDYHnLhea+o=
@@ -599,8 +602,9 @@ golang.org/x/mod v0.2.0/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
 golang.org/x/mod v0.3.0/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
 golang.org/x/mod v0.4.0/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
 golang.org/x/mod v0.4.1/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
-golang.org/x/mod v0.4.2 h1:Gz96sIWK3OalVv/I/qNygP42zyoKp3xptRVCWRFEBvo=
 golang.org/x/mod v0.4.2/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
+golang.org/x/mod v0.6.0-dev.0.20220106191415-9b9b3d81d5e3 h1:kQgndtyPBW/JIYERgdxfwMYh3AVStj88WQTlNDi2a+o=
+golang.org/x/mod v0.6.0-dev.0.20220106191415-9b9b3d81d5e3/go.mod h1:3p9vT2HGsQu2K1YbXdKPJLVgG5VJdoTa1poYQBtP1AY=
 golang.org/x/net v0.0.0-20180724234803-3673e40ba225/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20180826012351-8a410e7b638d/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20180906233101-161cd47e91fd/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
@@ -839,8 +843,9 @@ golang.org/x/tools v0.0.0-20210106214847-113979e3529a/go.mod h1:emZCQorbCU4vsT4f
 golang.org/x/tools v0.1.0/go.mod h1:xkSsbof2nBLbhDlRMhhhyNLN/zl3eTqcnHD5viDpcZ0=
 golang.org/x/tools v0.1.2/go.mod h1:o0xws9oXOQQZyjljx8fwUC0k7L1pTE6eaCbjGeHmOkk=
 golang.org/x/tools v0.1.5/go.mod h1:o0xws9oXOQQZyjljx8fwUC0k7L1pTE6eaCbjGeHmOkk=
-golang.org/x/tools v0.1.6-0.20210820212750-d4cc65f0b2ff h1:VX/uD7MK0AHXGiScH3fsieUQUcpmRERPDYtqZdJnA+Q=
 golang.org/x/tools v0.1.6-0.20210820212750-d4cc65f0b2ff/go.mod h1:YD9qOF0M9xpSpdWTBbzEl5e/RnCefISl8E5Noe10jFM=
+golang.org/x/tools v0.1.11-0.20220316014157-77aa08bb151a h1:ofrrl6c6NG5/IOSx/R1cyiQxxjqlur0h/TvbUhkH0II=
+golang.org/x/tools v0.1.11-0.20220316014157-77aa08bb151a/go.mod h1:Uh6Zz+xoGYZom868N8YTex3t7RhtHDBrE8Gzo9bV56E=
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
@@ -1003,6 +1008,8 @@ honnef.co/go/tools v0.0.0-20190523083050-ea95bdfd59fc/go.mod h1:rf3lG4BRIbNafJWh
 honnef.co/go/tools v0.0.1-2019.2.3/go.mod h1:a3bituU0lyd329TUQxRnasdCoJDkEUEAqEt0JzvZhAg=
 honnef.co/go/tools v0.0.1-2020.1.3/go.mod h1:X/FiERA/W4tHapMX5mGpAtMSVEeEUOyHaw9vFzvIQ3k=
 honnef.co/go/tools v0.0.1-2020.1.4/go.mod h1:X/FiERA/W4tHapMX5mGpAtMSVEeEUOyHaw9vFzvIQ3k=
+honnef.co/go/tools v0.3.1 h1:1kJlrWJLkaGXgcaeosRXViwviqjI7nkBvU2+sZW0AYc=
+honnef.co/go/tools v0.3.1/go.mod h1:vlRD9XErLMGT+mDuofSr0mMMquscM/1nQqtRSsh6m70=
 k8s.io/api v0.23.6 h1:yOK34wbYECH4RsJbQ9sfkFK3O7f/DUHRlzFehkqZyVw=
 k8s.io/api v0.23.6/go.mod h1:1kFaYxGCFHYp3qd6a85DAj/yW8aVD6XLZMqJclkoi9g=
 k8s.io/apiextensions-apiserver v0.23.6 h1:v58cQ6Z0/GK1IXYr+oW0fnYl52o9LTY0WgoWvI8uv5Q=

pkg/mesh/mesh.go

@@ -62,7 +62,6 @@ type Mesh struct {
 	ipTables            *iptables.Controller
 	kiloIface           int
 	kiloIfaceName       string
-	key                 []byte
 	local               bool
 	port                int
 	priv                wgtypes.Key
@@ -94,6 +93,9 @@ func New(backend Backend, enc encapsulation.Encapsulator, granularity Granularit
 		return nil, fmt.Errorf("failed to create directory to store configuration: %v", err)
 	}
 	privateB, err := ioutil.ReadFile(privateKeyPath)
+	if err != nil && !os.IsNotExist(err) {
+		return nil, fmt.Errorf("failed to read private key file: %v", err)
+	}
 	privateB = bytes.Trim(privateB, "\n")
 	private, err := wgtypes.ParseKey(string(privateB))
 	if err != nil {

pkg/mesh/topology_test.go

@@ -16,7 +16,6 @@ package mesh
 
 import (
 	"net"
-	"strings"
 	"testing"
 	"time"
 
@@ -27,10 +26,6 @@ import (
 	"github.com/squat/kilo/pkg/wireguard"
 )
 
-func allowedIPs(ips ...string) string {
-	return strings.Join(ips, ", ")
-}
-
 func mustParseCIDR(s string) (r net.IPNet) {
 	if _, ip, err := net.ParseCIDR(s); err != nil {
 		panic("failed to parse CIDR")

pkg/wireguard/conf.go

@@ -183,7 +183,7 @@ func (e *Endpoint) Resolved() bool {
 // UDPAddr() will not try to resolve a DN name, if the Endpoint is not yet resolved.
 func (e *Endpoint) UDPAddr(resolve bool) (*net.UDPAddr, error) {
 	if !e.Ready() {
-		return nil, errors.New("Enpoint is not ready")
+		return nil, errors.New("endpoint is not ready")
 	}
 	if e.udpAddr != nil {
 		// Make a copy of the UDPAddr to protect it from modification outside this package.
@@ -191,7 +191,7 @@ func (e *Endpoint) UDPAddr(resolve bool) (*net.UDPAddr, error) {
 		return &h, nil
 	}
 	if !resolve {
-		return nil, errors.New("Endpoint is not resolved")
+		return nil, errors.New("endpoint is not resolved")
 	}
 	var err error
 	if e.udpAddr, err = net.ResolveUDPAddr("udp", e.addr); err != nil {
@@ -358,19 +358,13 @@ func (c *Conf) Equal(d *wgtypes.Device) (bool, string) {
 
 func sortPeerConfigs(peers []wgtypes.Peer) {
 	sort.Slice(peers, func(i, j int) bool {
-		if peers[i].PublicKey.String() < peers[j].PublicKey.String() {
-			return true
-		}
-		return false
+		return peers[i].PublicKey.String() < peers[j].PublicKey.String()
 	})
 }
 
 func sortPeers(peers []Peer) {
 	sort.Slice(peers, func(i, j int) bool {
-		if peers[i].PublicKey.String() < peers[j].PublicKey.String() {
-			return true
-		}
-		return false
+		return peers[i].PublicKey.String() < peers[j].PublicKey.String()
 	})
 }
 

tools.go

@@ -19,7 +19,7 @@ package main
 
 import (
 	_ "github.com/campoy/embedmd"
-	_ "golang.org/x/lint/golint"
+	_ "honnef.co/go/tools/cmd/staticcheck"
 	_ "k8s.io/code-generator/cmd/client-gen"
 	_ "k8s.io/code-generator/cmd/deepcopy-gen"
 	_ "k8s.io/code-generator/cmd/informer-gen"

vendor/github.com/BurntSushi/toml/.gitignore

@@ -0,0 +1,2 @@
+toml.test
+/toml-test

vendor/github.com/BurntSushi/toml/COMPATIBLE

@@ -0,0 +1 @@
+Compatible with TOML version [v1.0.0](https://toml.io/en/v1.0.0).

vendor/github.com/BurntSushi/toml/COPYING

@@ -0,0 +1,21 @@
+The MIT License (MIT)
+
+Copyright (c) 2013 TOML authors
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

vendor/github.com/BurntSushi/toml/README.md

@@ -0,0 +1,220 @@
+## TOML parser and encoder for Go with reflection
+
+TOML stands for Tom's Obvious, Minimal Language. This Go package provides a
+reflection interface similar to Go's standard library `json` and `xml`
+packages. This package also supports the `encoding.TextUnmarshaler` and
+`encoding.TextMarshaler` interfaces so that you can define custom data
+representations. (There is an example of this below.)
+
+Compatible with TOML version [v1.0.0](https://toml.io/en/v1.0.0).
+
+Documentation: https://godocs.io/github.com/BurntSushi/toml
+
+See the [releases page](https://github.com/BurntSushi/toml/releases) for a
+changelog; this information is also in the git tag annotations (e.g. `git show
+v0.4.0`).
+
+This library requires Go 1.13 or newer; install it with:
+
+    $ go get github.com/BurntSushi/toml
+
+It also comes with a TOML validator CLI tool:
+
+    $ go get github.com/BurntSushi/toml/cmd/tomlv
+    $ tomlv some-toml-file.toml
+
+### Testing
+
+This package passes all tests in
+[toml-test](https://github.com/BurntSushi/toml-test) for both the decoder
+and the encoder.
+
+### Examples
+
+This package works similarly to how the Go standard library handles XML and
+JSON. Namely, data is loaded into Go values via reflection.
+
+For the simplest example, consider some TOML file as just a list of keys
+and values:
+
+```toml
+Age = 25
+Cats = [ "Cauchy", "Plato" ]
+Pi = 3.14
+Perfection = [ 6, 28, 496, 8128 ]
+DOB = 1987-07-05T05:45:00Z
+```
+
+Which could be defined in Go as:
+
+```go
+type Config struct {
+	Age        int
+	Cats       []string
+	Pi         float64
+	Perfection []int
+	DOB        time.Time // requires `import time`
+}
+```
+
+And then decoded with:
+
+```go
+var conf Config
+if _, err := toml.Decode(tomlData, &conf); err != nil {
+  // handle error
+}
+```
+
+You can also use struct tags if your struct field name doesn't map to a TOML
+key value directly:
+
+```toml
+some_key_NAME = "wat"
+```
+
+```go
+type TOML struct {
+  ObscureKey string `toml:"some_key_NAME"`
+}
+```
+
+Beware that like other most other decoders **only exported fields** are
+considered when encoding and decoding; private fields are silently ignored.
+
+### Using the `encoding.TextUnmarshaler` interface
+
+Here's an example that automatically parses duration strings into
+`time.Duration` values:
+
+```toml
+[[song]]
+name = "Thunder Road"
+duration = "4m49s"
+
+[[song]]
+name = "Stairway to Heaven"
+duration = "8m03s"
+```
+
+Which can be decoded with:
+
+```go
+type song struct {
+	Name     string
+	Duration duration
+}
+type songs struct {
+	Song []song
+}
+var favorites songs
+if _, err := toml.Decode(blob, &favorites); err != nil {
+	log.Fatal(err)
+}
+
+for _, s := range favorites.Song {
+	fmt.Printf("%s (%s)\n", s.Name, s.Duration)
+}
+```
+
+And you'll also need a `duration` type that satisfies the
+`encoding.TextUnmarshaler` interface:
+
+```go
+type duration struct {
+	time.Duration
+}
+
+func (d *duration) UnmarshalText(text []byte) error {
+	var err error
+	d.Duration, err = time.ParseDuration(string(text))
+	return err
+}
+```
+
+To target TOML specifically you can implement `UnmarshalTOML` TOML interface in
+a similar way.
+
+### More complex usage
+
+Here's an example of how to load the example from the official spec page:
+
+```toml
+# This is a TOML document. Boom.
+
+title = "TOML Example"
+
+[owner]
+name = "Tom Preston-Werner"
+organization = "GitHub"
+bio = "GitHub Cofounder & CEO\nLikes tater tots and beer."
+dob = 1979-05-27T07:32:00Z # First class dates? Why not?
+
+[database]
+server = "192.168.1.1"
+ports = [ 8001, 8001, 8002 ]
+connection_max = 5000
+enabled = true
+
+[servers]
+
+  # You can indent as you please. Tabs or spaces. TOML don't care.
+  [servers.alpha]
+  ip = "10.0.0.1"
+  dc = "eqdc10"
+
+  [servers.beta]
+  ip = "10.0.0.2"
+  dc = "eqdc10"
+
+[clients]
+data = [ ["gamma", "delta"], [1, 2] ] # just an update to make sure parsers support it
+
+# Line breaks are OK when inside arrays
+hosts = [
+  "alpha",
+  "omega"
+]
+```
+
+And the corresponding Go types are:
+
+```go
+type tomlConfig struct {
+	Title   string
+	Owner   ownerInfo
+	DB      database `toml:"database"`
+	Servers map[string]server
+	Clients clients
+}
+
+type ownerInfo struct {
+	Name string
+	Org  string `toml:"organization"`
+	Bio  string
+	DOB  time.Time
+}
+
+type database struct {
+	Server  string
+	Ports   []int
+	ConnMax int `toml:"connection_max"`
+	Enabled bool
+}
+
+type server struct {
+	IP string
+	DC string
+}
+
+type clients struct {
+	Data  [][]interface{}
+	Hosts []string
+}
+```
+
+Note that a case insensitive match will be tried if an exact match can't be
+found.
+
+A working example of the above can be found in `_examples/example.{go,toml}`.
+

vendor/github.com/BurntSushi/toml/decode.go

@@ -0,0 +1,511 @@
+package toml
+
+import (
+	"encoding"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"math"
+	"os"
+	"reflect"
+	"strings"
+	"time"
+)
+
+// Unmarshaler is the interface implemented by objects that can unmarshal a
+// TOML description of themselves.
+type Unmarshaler interface {
+	UnmarshalTOML(interface{}) error
+}
+
+// Unmarshal decodes the contents of `p` in TOML format into a pointer `v`.
+func Unmarshal(p []byte, v interface{}) error {
+	_, err := Decode(string(p), v)
+	return err
+}
+
+// Primitive is a TOML value that hasn't been decoded into a Go value.
+//
+// This type can be used for any value, which will cause decoding to be delayed.
+// You can use the PrimitiveDecode() function to "manually" decode these values.
+//
+// NOTE: The underlying representation of a `Primitive` value is subject to
+// change. Do not rely on it.
+//
+// NOTE: Primitive values are still parsed, so using them will only avoid the
+// overhead of reflection. They can be useful when you don't know the exact type
+// of TOML data until runtime.
+type Primitive struct {
+	undecoded interface{}
+	context   Key
+}
+
+// PrimitiveDecode is just like the other `Decode*` functions, except it
+// decodes a TOML value that has already been parsed. Valid primitive values
+// can *only* be obtained from values filled by the decoder functions,
+// including this method. (i.e., `v` may contain more `Primitive`
+// values.)
+//
+// Meta data for primitive values is included in the meta data returned by
+// the `Decode*` functions with one exception: keys returned by the Undecoded
+// method will only reflect keys that were decoded. Namely, any keys hidden
+// behind a Primitive will be considered undecoded. Executing this method will
+// update the undecoded keys in the meta data. (See the example.)
+func (md *MetaData) PrimitiveDecode(primValue Primitive, v interface{}) error {
+	md.context = primValue.context
+	defer func() { md.context = nil }()
+	return md.unify(primValue.undecoded, rvalue(v))
+}
+
+// Decoder decodes TOML data.
+//
+// TOML tables correspond to Go structs or maps (dealer's choice – they can be
+// used interchangeably).
+//
+// TOML table arrays correspond to either a slice of structs or a slice of maps.
+//
+// TOML datetimes correspond to Go time.Time values. Local datetimes are parsed
+// in the local timezone.
+//
+// All other TOML types (float, string, int, bool and array) correspond to the
+// obvious Go types.
+//
+// An exception to the above rules is if a type implements the TextUnmarshaler
+// interface, in which case any primitive TOML value (floats, strings, integers,
+// booleans, datetimes) will be converted to a []byte and given to the value's
+// UnmarshalText method. See the Unmarshaler example for a demonstration with
+// time duration strings.
+//
+// Key mapping
+//
+// TOML keys can map to either keys in a Go map or field names in a Go struct.
+// The special `toml` struct tag can be used to map TOML keys to struct fields
+// that don't match the key name exactly (see the example). A case insensitive
+// match to struct names will be tried if an exact match can't be found.
+//
+// The mapping between TOML values and Go values is loose. That is, there may
+// exist TOML values that cannot be placed into your representation, and there
+// may be parts of your representation that do not correspond to TOML values.
+// This loose mapping can be made stricter by using the IsDefined and/or
+// Undecoded methods on the MetaData returned.
+//
+// This decoder does not handle cyclic types. Decode will not terminate if a
+// cyclic type is passed.
+type Decoder struct {
+	r io.Reader
+}
+
+// NewDecoder creates a new Decoder.
+func NewDecoder(r io.Reader) *Decoder {
+	return &Decoder{r: r}
+}
+
+// Decode TOML data in to the pointer `v`.
+func (dec *Decoder) Decode(v interface{}) (MetaData, error) {
+	rv := reflect.ValueOf(v)
+	if rv.Kind() != reflect.Ptr {
+		return MetaData{}, e("Decode of non-pointer %s", reflect.TypeOf(v))
+	}
+	if rv.IsNil() {
+		return MetaData{}, e("Decode of nil %s", reflect.TypeOf(v))
+	}
+
+	// TODO: have parser should read from io.Reader? Or at the very least, make
+	// it read from []byte rather than string
+	data, err := ioutil.ReadAll(dec.r)
+	if err != nil {
+		return MetaData{}, err
+	}
+
+	p, err := parse(string(data))
+	if err != nil {
+		return MetaData{}, err
+	}
+	md := MetaData{
+		p.mapping, p.types, p.ordered,
+		make(map[string]bool, len(p.ordered)), nil,
+	}
+	return md, md.unify(p.mapping, indirect(rv))
+}
+
+// Decode the TOML data in to the pointer v.
+//
+// See the documentation on Decoder for a description of the decoding process.
+func Decode(data string, v interface{}) (MetaData, error) {
+	return NewDecoder(strings.NewReader(data)).Decode(v)
+}
+
+// DecodeFile is just like Decode, except it will automatically read the
+// contents of the file at path and decode it for you.
+func DecodeFile(path string, v interface{}) (MetaData, error) {
+	fp, err := os.Open(path)
+	if err != nil {
+		return MetaData{}, err
+	}
+	defer fp.Close()
+	return NewDecoder(fp).Decode(v)
+}
+
+// unify performs a sort of type unification based on the structure of `rv`,
+// which is the client representation.
+//
+// Any type mismatch produces an error. Finding a type that we don't know
+// how to handle produces an unsupported type error.
+func (md *MetaData) unify(data interface{}, rv reflect.Value) error {
+	// Special case. Look for a `Primitive` value.
+	// TODO: #76 would make this superfluous after implemented.
+	if rv.Type() == reflect.TypeOf((*Primitive)(nil)).Elem() {
+		// Save the undecoded data and the key context into the primitive
+		// value.
+		context := make(Key, len(md.context))
+		copy(context, md.context)
+		rv.Set(reflect.ValueOf(Primitive{
+			undecoded: data,
+			context:   context,
+		}))
+		return nil
+	}
+
+	// Special case. Unmarshaler Interface support.
+	if rv.CanAddr() {
+		if v, ok := rv.Addr().Interface().(Unmarshaler); ok {
+			return v.UnmarshalTOML(data)
+		}
+	}
+
+	// Special case. Look for a value satisfying the TextUnmarshaler interface.
+	if v, ok := rv.Interface().(encoding.TextUnmarshaler); ok {
+		return md.unifyText(data, v)
+	}
+	// TODO:
+	// The behavior here is incorrect whenever a Go type satisfies the
+	// encoding.TextUnmarshaler interface but also corresponds to a TOML hash or
+	// array. In particular, the unmarshaler should only be applied to primitive
+	// TOML values. But at this point, it will be applied to all kinds of values
+	// and produce an incorrect error whenever those values are hashes or arrays
+	// (including arrays of tables).
+
+	k := rv.Kind()
+
+	// laziness
+	if k >= reflect.Int && k <= reflect.Uint64 {
+		return md.unifyInt(data, rv)
+	}
+	switch k {
+	case reflect.Ptr:
+		elem := reflect.New(rv.Type().Elem())
+		err := md.unify(data, reflect.Indirect(elem))
+		if err != nil {
+			return err
+		}
+		rv.Set(elem)
+		return nil
+	case reflect.Struct:
+		return md.unifyStruct(data, rv)
+	case reflect.Map:
+		return md.unifyMap(data, rv)
+	case reflect.Array:
+		return md.unifyArray(data, rv)
+	case reflect.Slice:
+		return md.unifySlice(data, rv)
+	case reflect.String:
+		return md.unifyString(data, rv)
+	case reflect.Bool:
+		return md.unifyBool(data, rv)
+	case reflect.Interface:
+		// we only support empty interfaces.
+		if rv.NumMethod() > 0 {
+			return e("unsupported type %s", rv.Type())
+		}
+		return md.unifyAnything(data, rv)
+	case reflect.Float32:
+		fallthrough
+	case reflect.Float64:
+		return md.unifyFloat64(data, rv)
+	}
+	return e("unsupported type %s", rv.Kind())
+}
+
+func (md *MetaData) unifyStruct(mapping interface{}, rv reflect.Value) error {
+	tmap, ok := mapping.(map[string]interface{})
+	if !ok {
+		if mapping == nil {
+			return nil
+		}
+		return e("type mismatch for %s: expected table but found %T",
+			rv.Type().String(), mapping)
+	}
+
+	for key, datum := range tmap {
+		var f *field
+		fields := cachedTypeFields(rv.Type())
+		for i := range fields {
+			ff := &fields[i]
+			if ff.name == key {
+				f = ff
+				break
+			}
+			if f == nil && strings.EqualFold(ff.name, key) {
+				f = ff
+			}
+		}
+		if f != nil {
+			subv := rv
+			for _, i := range f.index {
+				subv = indirect(subv.Field(i))
+			}
+			if isUnifiable(subv) {
+				md.decoded[md.context.add(key).String()] = true
+				md.context = append(md.context, key)
+				if err := md.unify(datum, subv); err != nil {
+					return err
+				}
+				md.context = md.context[0 : len(md.context)-1]
+			} else if f.name != "" {
+				// Bad user! No soup for you!
+				return e("cannot write unexported field %s.%s",
+					rv.Type().String(), f.name)
+			}
+		}
+	}
+	return nil
+}
+
+func (md *MetaData) unifyMap(mapping interface{}, rv reflect.Value) error {
+	if k := rv.Type().Key().Kind(); k != reflect.String {
+		return fmt.Errorf(
+			"toml: cannot decode to a map with non-string key type (%s in %q)",
+			k, rv.Type())
+	}
+
+	tmap, ok := mapping.(map[string]interface{})
+	if !ok {
+		if tmap == nil {
+			return nil
+		}
+		return badtype("map", mapping)
+	}
+	if rv.IsNil() {
+		rv.Set(reflect.MakeMap(rv.Type()))
+	}
+	for k, v := range tmap {
+		md.decoded[md.context.add(k).String()] = true
+		md.context = append(md.context, k)
+
+		rvkey := indirect(reflect.New(rv.Type().Key()))
+		rvval := reflect.Indirect(reflect.New(rv.Type().Elem()))
+		if err := md.unify(v, rvval); err != nil {
+			return err
+		}
+		md.context = md.context[0 : len(md.context)-1]
+
+		rvkey.SetString(k)
+		rv.SetMapIndex(rvkey, rvval)
+	}
+	return nil
+}
+
+func (md *MetaData) unifyArray(data interface{}, rv reflect.Value) error {
+	datav := reflect.ValueOf(data)
+	if datav.Kind() != reflect.Slice {
+		if !datav.IsValid() {
+			return nil
+		}
+		return badtype("slice", data)
+	}
+	if l := datav.Len(); l != rv.Len() {
+		return e("expected array length %d; got TOML array of length %d", rv.Len(), l)
+	}
+	return md.unifySliceArray(datav, rv)
+}
+
+func (md *MetaData) unifySlice(data interface{}, rv reflect.Value) error {
+	datav := reflect.ValueOf(data)
+	if datav.Kind() != reflect.Slice {
+		if !datav.IsValid() {
+			return nil
+		}
+		return badtype("slice", data)
+	}
+	n := datav.Len()
+	if rv.IsNil() || rv.Cap() < n {
+		rv.Set(reflect.MakeSlice(rv.Type(), n, n))
+	}
+	rv.SetLen(n)
+	return md.unifySliceArray(datav, rv)
+}
+
+func (md *MetaData) unifySliceArray(data, rv reflect.Value) error {
+	l := data.Len()
+	for i := 0; i < l; i++ {
+		err := md.unify(data.Index(i).Interface(), indirect(rv.Index(i)))
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (md *MetaData) unifyDatetime(data interface{}, rv reflect.Value) error {
+	if _, ok := data.(time.Time); ok {
+		rv.Set(reflect.ValueOf(data))
+		return nil
+	}
+	return badtype("time.Time", data)
+}
+
+func (md *MetaData) unifyString(data interface{}, rv reflect.Value) error {
+	if s, ok := data.(string); ok {
+		rv.SetString(s)
+		return nil
+	}
+	return badtype("string", data)
+}
+
+func (md *MetaData) unifyFloat64(data interface{}, rv reflect.Value) error {
+	if num, ok := data.(float64); ok {
+		switch rv.Kind() {
+		case reflect.Float32:
+			fallthrough
+		case reflect.Float64:
+			rv.SetFloat(num)
+		default:
+			panic("bug")
+		}
+		return nil
+	}
+	return badtype("float", data)
+}
+
+func (md *MetaData) unifyInt(data interface{}, rv reflect.Value) error {
+	if num, ok := data.(int64); ok {
+		if rv.Kind() >= reflect.Int && rv.Kind() <= reflect.Int64 {
+			switch rv.Kind() {
+			case reflect.Int, reflect.Int64:
+				// No bounds checking necessary.
+			case reflect.Int8:
+				if num < math.MinInt8 || num > math.MaxInt8 {
+					return e("value %d is out of range for int8", num)
+				}
+			case reflect.Int16:
+				if num < math.MinInt16 || num > math.MaxInt16 {
+					return e("value %d is out of range for int16", num)
+				}
+			case reflect.Int32:
+				if num < math.MinInt32 || num > math.MaxInt32 {
+					return e("value %d is out of range for int32", num)
+				}
+			}
+			rv.SetInt(num)
+		} else if rv.Kind() >= reflect.Uint && rv.Kind() <= reflect.Uint64 {
+			unum := uint64(num)
+			switch rv.Kind() {
+			case reflect.Uint, reflect.Uint64:
+				// No bounds checking necessary.
+			case reflect.Uint8:
+				if num < 0 || unum > math.MaxUint8 {
+					return e("value %d is out of range for uint8", num)
+				}
+			case reflect.Uint16:
+				if num < 0 || unum > math.MaxUint16 {
+					return e("value %d is out of range for uint16", num)
+				}
+			case reflect.Uint32:
+				if num < 0 || unum > math.MaxUint32 {
+					return e("value %d is out of range for uint32", num)
+				}
+			}
+			rv.SetUint(unum)
+		} else {
+			panic("unreachable")
+		}
+		return nil
+	}
+	return badtype("integer", data)
+}
+
+func (md *MetaData) unifyBool(data interface{}, rv reflect.Value) error {
+	if b, ok := data.(bool); ok {
+		rv.SetBool(b)
+		return nil
+	}
+	return badtype("boolean", data)
+}
+
+func (md *MetaData) unifyAnything(data interface{}, rv reflect.Value) error {
+	rv.Set(reflect.ValueOf(data))
+	return nil
+}
+
+func (md *MetaData) unifyText(data interface{}, v encoding.TextUnmarshaler) error {
+	var s string
+	switch sdata := data.(type) {
+	case TextMarshaler:
+		text, err := sdata.MarshalText()
+		if err != nil {
+			return err
+		}
+		s = string(text)
+	case fmt.Stringer:
+		s = sdata.String()
+	case string:
+		s = sdata
+	case bool:
+		s = fmt.Sprintf("%v", sdata)
+	case int64:
+		s = fmt.Sprintf("%d", sdata)
+	case float64:
+		s = fmt.Sprintf("%f", sdata)
+	default:
+		return badtype("primitive (string-like)", data)
+	}
+	if err := v.UnmarshalText([]byte(s)); err != nil {
+		return err
+	}
+	return nil
+}
+
+// rvalue returns a reflect.Value of `v`. All pointers are resolved.
+func rvalue(v interface{}) reflect.Value {
+	return indirect(reflect.ValueOf(v))
+}
+
+// indirect returns the value pointed to by a pointer.
+// Pointers are followed until the value is not a pointer.
+// New values are allocated for each nil pointer.
+//
+// An exception to this rule is if the value satisfies an interface of
+// interest to us (like encoding.TextUnmarshaler).
+func indirect(v reflect.Value) reflect.Value {
+	if v.Kind() != reflect.Ptr {
+		if v.CanSet() {
+			pv := v.Addr()
+			if _, ok := pv.Interface().(encoding.TextUnmarshaler); ok {
+				return pv
+			}
+		}
+		return v
+	}
+	if v.IsNil() {
+		v.Set(reflect.New(v.Type().Elem()))
+	}
+	return indirect(reflect.Indirect(v))
+}
+
+func isUnifiable(rv reflect.Value) bool {
+	if rv.CanSet() {
+		return true
+	}
+	if _, ok := rv.Interface().(encoding.TextUnmarshaler); ok {
+		return true
+	}
+	return false
+}
+
+func e(format string, args ...interface{}) error {
+	return fmt.Errorf("toml: "+format, args...)
+}
+
+func badtype(expected string, data interface{}) error {
+	return e("cannot load TOML value of type %T into a Go %s", data, expected)
+}

vendor/github.com/BurntSushi/toml/decode_go116.go

@@ -0,0 +1,18 @@
+// +build go1.16
+
+package toml
+
+import (
+	"io/fs"
+)
+
+// DecodeFS is just like Decode, except it will automatically read the contents
+// of the file at `path` from a fs.FS instance.
+func DecodeFS(fsys fs.FS, path string, v interface{}) (MetaData, error) {
+	fp, err := fsys.Open(path)
+	if err != nil {
+		return MetaData{}, err
+	}
+	defer fp.Close()
+	return NewDecoder(fp).Decode(v)
+}

vendor/github.com/BurntSushi/toml/decode_meta.go

@@ -0,0 +1,123 @@
+package toml
+
+import "strings"
+
+// MetaData allows access to meta information about TOML data that may not be
+// inferable via reflection. In particular, whether a key has been defined and
+// the TOML type of a key.
+type MetaData struct {
+	mapping map[string]interface{}
+	types   map[string]tomlType
+	keys    []Key
+	decoded map[string]bool
+	context Key // Used only during decoding.
+}
+
+// IsDefined reports if the key exists in the TOML data.
+//
+// The key should be specified hierarchically, for example to access the TOML
+// key "a.b.c" you would use:
+//
+//	IsDefined("a", "b", "c")
+//
+// IsDefined will return false if an empty key given. Keys are case sensitive.
+func (md *MetaData) IsDefined(key ...string) bool {
+	if len(key) == 0 {
+		return false
+	}
+
+	var hash map[string]interface{}
+	var ok bool
+	var hashOrVal interface{} = md.mapping
+	for _, k := range key {
+		if hash, ok = hashOrVal.(map[string]interface{}); !ok {
+			return false
+		}
+		if hashOrVal, ok = hash[k]; !ok {
+			return false
+		}
+	}
+	return true
+}
+
+// Type returns a string representation of the type of the key specified.
+//
+// Type will return the empty string if given an empty key or a key that does
+// not exist. Keys are case sensitive.
+func (md *MetaData) Type(key ...string) string {
+	fullkey := strings.Join(key, ".")
+	if typ, ok := md.types[fullkey]; ok {
+		return typ.typeString()
+	}
+	return ""
+}
+
+// Key represents any TOML key, including key groups. Use (MetaData).Keys to get
+// values of this type.
+type Key []string
+
+func (k Key) String() string { return strings.Join(k, ".") }
+
+func (k Key) maybeQuotedAll() string {
+	var ss []string
+	for i := range k {
+		ss = append(ss, k.maybeQuoted(i))
+	}
+	return strings.Join(ss, ".")
+}
+
+func (k Key) maybeQuoted(i int) string {
+	if k[i] == "" {
+		return `""`
+	}
+	quote := false
+	for _, c := range k[i] {
+		if !isBareKeyChar(c) {
+			quote = true
+			break
+		}
+	}
+	if quote {
+		return `"` + quotedReplacer.Replace(k[i]) + `"`
+	}
+	return k[i]
+}
+
+func (k Key) add(piece string) Key {
+	newKey := make(Key, len(k)+1)
+	copy(newKey, k)
+	newKey[len(k)] = piece
+	return newKey
+}
+
+// Keys returns a slice of every key in the TOML data, including key groups.
+//
+// Each key is itself a slice, where the first element is the top of the
+// hierarchy and the last is the most specific. The list will have the same
+// order as the keys appeared in the TOML data.
+//
+// All keys returned are non-empty.
+func (md *MetaData) Keys() []Key {
+	return md.keys
+}
+
+// Undecoded returns all keys that have not been decoded in the order in which
+// they appear in the original TOML document.
+//
+// This includes keys that haven't been decoded because of a Primitive value.
+// Once the Primitive value is decoded, the keys will be considered decoded.
+//
+// Also note that decoding into an empty interface will result in no decoding,
+// and so no keys will be considered decoded.
+//
+// In this sense, the Undecoded keys correspond to keys in the TOML document
+// that do not have a concrete type in your representation.
+func (md *MetaData) Undecoded() []Key {
+	undecoded := make([]Key, 0, len(md.keys))
+	for _, key := range md.keys {
+		if !md.decoded[key.String()] {
+			undecoded = append(undecoded, key)
+		}
+	}
+	return undecoded
+}

vendor/github.com/BurntSushi/toml/deprecated.go

@@ -0,0 +1,33 @@
+package toml
+
+import (
+	"encoding"
+	"io"
+)
+
+// DEPRECATED!
+//
+// Use the identical encoding.TextMarshaler instead. It is defined here to
+// support Go 1.1 and older.
+type TextMarshaler encoding.TextMarshaler
+
+// DEPRECATED!
+//
+// Use the identical encoding.TextUnmarshaler instead. It is defined here to
+// support Go 1.1 and older.
+type TextUnmarshaler encoding.TextUnmarshaler
+
+// DEPRECATED!
+//
+// Use MetaData.PrimitiveDecode instead.
+func PrimitiveDecode(primValue Primitive, v interface{}) error {
+	md := MetaData{decoded: make(map[string]bool)}
+	return md.unify(primValue.undecoded, rvalue(v))
+}
+
+// DEPRECATED!
+//
+// Use NewDecoder(reader).Decode(&v) instead.
+func DecodeReader(r io.Reader, v interface{}) (MetaData, error) {
+	return NewDecoder(r).Decode(v)
+}

vendor/github.com/BurntSushi/toml/doc.go

@@ -0,0 +1,13 @@
+/*
+Package toml implements decoding and encoding of TOML files.
+
+This package supports TOML v1.0.0, as listed on https://toml.io
+
+There is also support for delaying decoding with the Primitive type, and
+querying the set of keys in a TOML document with the MetaData type.
+
+The github.com/BurntSushi/toml/cmd/tomlv package implements a TOML validator,
+and can be used to verify if TOML document is valid. It can also be used to
+print the type of each key.
+*/
+package toml

vendor/github.com/BurntSushi/toml/encode.go

@@ -0,0 +1,650 @@
+package toml
+
+import (
+	"bufio"
+	"encoding"
+	"errors"
+	"fmt"
+	"io"
+	"math"
+	"reflect"
+	"sort"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/BurntSushi/toml/internal"
+)
+
+type tomlEncodeError struct{ error }
+
+var (
+	errArrayNilElement = errors.New("toml: cannot encode array with nil element")
+	errNonString       = errors.New("toml: cannot encode a map with non-string key type")
+	errAnonNonStruct   = errors.New("toml: cannot encode an anonymous field that is not a struct")
+	errNoKey           = errors.New("toml: top-level values must be Go maps or structs")
+	errAnything        = errors.New("") // used in testing
+)
+
+var quotedReplacer = strings.NewReplacer(
+	"\"", "\\\"",
+	"\\", "\\\\",
+	"\x00", `\u0000`,
+	"\x01", `\u0001`,
+	"\x02", `\u0002`,
+	"\x03", `\u0003`,
+	"\x04", `\u0004`,
+	"\x05", `\u0005`,
+	"\x06", `\u0006`,
+	"\x07", `\u0007`,
+	"\b", `\b`,
+	"\t", `\t`,
+	"\n", `\n`,
+	"\x0b", `\u000b`,
+	"\f", `\f`,
+	"\r", `\r`,
+	"\x0e", `\u000e`,
+	"\x0f", `\u000f`,
+	"\x10", `\u0010`,
+	"\x11", `\u0011`,
+	"\x12", `\u0012`,
+	"\x13", `\u0013`,
+	"\x14", `\u0014`,
+	"\x15", `\u0015`,
+	"\x16", `\u0016`,
+	"\x17", `\u0017`,
+	"\x18", `\u0018`,
+	"\x19", `\u0019`,
+	"\x1a", `\u001a`,
+	"\x1b", `\u001b`,
+	"\x1c", `\u001c`,
+	"\x1d", `\u001d`,
+	"\x1e", `\u001e`,
+	"\x1f", `\u001f`,
+	"\x7f", `\u007f`,
+)
+
+// Encoder encodes a Go to a TOML document.
+//
+// The mapping between Go values and TOML values should be precisely the same as
+// for the Decode* functions. Similarly, the TextMarshaler interface is
+// supported by encoding the resulting bytes as strings. If you want to write
+// arbitrary binary data then you will need to use something like base64 since
+// TOML does not have any binary types.
+//
+// When encoding TOML hashes (Go maps or structs), keys without any sub-hashes
+// are encoded first.
+//
+// Go maps will be sorted alphabetically by key for deterministic output.
+//
+// Encoding Go values without a corresponding TOML representation will return an
+// error. Examples of this includes maps with non-string keys, slices with nil
+// elements, embedded non-struct types, and nested slices containing maps or
+// structs. (e.g. [][]map[string]string is not allowed but []map[string]string
+// is okay, as is []map[string][]string).
+//
+// NOTE: Only exported keys are encoded due to the use of reflection. Unexported
+// keys are silently discarded.
+type Encoder struct {
+	// The string to use for a single indentation level. The default is two
+	// spaces.
+	Indent string
+
+	// hasWritten is whether we have written any output to w yet.
+	hasWritten bool
+	w          *bufio.Writer
+}
+
+// NewEncoder create a new Encoder.
+func NewEncoder(w io.Writer) *Encoder {
+	return &Encoder{
+		w:      bufio.NewWriter(w),
+		Indent: "  ",
+	}
+}
+
+// Encode writes a TOML representation of the Go value to the Encoder's writer.
+//
+// An error is returned if the value given cannot be encoded to a valid TOML
+// document.
+func (enc *Encoder) Encode(v interface{}) error {
+	rv := eindirect(reflect.ValueOf(v))
+	if err := enc.safeEncode(Key([]string{}), rv); err != nil {
+		return err
+	}
+	return enc.w.Flush()
+}
+
+func (enc *Encoder) safeEncode(key Key, rv reflect.Value) (err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			if terr, ok := r.(tomlEncodeError); ok {
+				err = terr.error
+				return
+			}
+			panic(r)
+		}
+	}()
+	enc.encode(key, rv)
+	return nil
+}
+
+func (enc *Encoder) encode(key Key, rv reflect.Value) {
+	// Special case. Time needs to be in ISO8601 format.
+	// Special case. If we can marshal the type to text, then we used that.
+	// Basically, this prevents the encoder for handling these types as
+	// generic structs (or whatever the underlying type of a TextMarshaler is).
+	switch t := rv.Interface().(type) {
+	case time.Time, encoding.TextMarshaler:
+		enc.writeKeyValue(key, rv, false)
+		return
+	// TODO: #76 would make this superfluous after implemented.
+	case Primitive:
+		enc.encode(key, reflect.ValueOf(t.undecoded))
+		return
+	}
+
+	k := rv.Kind()
+	switch k {
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32,
+		reflect.Int64,
+		reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32,
+		reflect.Uint64,
+		reflect.Float32, reflect.Float64, reflect.String, reflect.Bool:
+		enc.writeKeyValue(key, rv, false)
+	case reflect.Array, reflect.Slice:
+		if typeEqual(tomlArrayHash, tomlTypeOfGo(rv)) {
+			enc.eArrayOfTables(key, rv)
+		} else {
+			enc.writeKeyValue(key, rv, false)
+		}
+	case reflect.Interface:
+		if rv.IsNil() {
+			return
+		}
+		enc.encode(key, rv.Elem())
+	case reflect.Map:
+		if rv.IsNil() {
+			return
+		}
+		enc.eTable(key, rv)
+	case reflect.Ptr:
+		if rv.IsNil() {
+			return
+		}
+		enc.encode(key, rv.Elem())
+	case reflect.Struct:
+		enc.eTable(key, rv)
+	default:
+		encPanic(fmt.Errorf("unsupported type for key '%s': %s", key, k))
+	}
+}
+
+// eElement encodes any value that can be an array element.
+func (enc *Encoder) eElement(rv reflect.Value) {
+	switch v := rv.Interface().(type) {
+	case time.Time: // Using TextMarshaler adds extra quotes, which we don't want.
+		format := time.RFC3339Nano
+		switch v.Location() {
+		case internal.LocalDatetime:
+			format = "2006-01-02T15:04:05.999999999"
+		case internal.LocalDate:
+			format = "2006-01-02"
+		case internal.LocalTime:
+			format = "15:04:05.999999999"
+		}
+		switch v.Location() {
+		default:
+			enc.wf(v.Format(format))
+		case internal.LocalDatetime, internal.LocalDate, internal.LocalTime:
+			enc.wf(v.In(time.UTC).Format(format))
+		}
+		return
+	case encoding.TextMarshaler:
+		// Use text marshaler if it's available for this value.
+		if s, err := v.MarshalText(); err != nil {
+			encPanic(err)
+		} else {
+			enc.writeQuoted(string(s))
+		}
+		return
+	}
+
+	switch rv.Kind() {
+	case reflect.String:
+		enc.writeQuoted(rv.String())
+	case reflect.Bool:
+		enc.wf(strconv.FormatBool(rv.Bool()))
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		enc.wf(strconv.FormatInt(rv.Int(), 10))
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+		enc.wf(strconv.FormatUint(rv.Uint(), 10))
+	case reflect.Float32:
+		f := rv.Float()
+		if math.IsNaN(f) {
+			enc.wf("nan")
+		} else if math.IsInf(f, 0) {
+			enc.wf("%cinf", map[bool]byte{true: '-', false: '+'}[math.Signbit(f)])
+		} else {
+			enc.wf(floatAddDecimal(strconv.FormatFloat(f, 'f', -1, 32)))
+		}
+	case reflect.Float64:
+		f := rv.Float()
+		if math.IsNaN(f) {
+			enc.wf("nan")
+		} else if math.IsInf(f, 0) {
+			enc.wf("%cinf", map[bool]byte{true: '-', false: '+'}[math.Signbit(f)])
+		} else {
+			enc.wf(floatAddDecimal(strconv.FormatFloat(f, 'f', -1, 64)))
+		}
+	case reflect.Array, reflect.Slice:
+		enc.eArrayOrSliceElement(rv)
+	case reflect.Struct:
+		enc.eStruct(nil, rv, true)
+	case reflect.Map:
+		enc.eMap(nil, rv, true)
+	case reflect.Interface:
+		enc.eElement(rv.Elem())
+	default:
+		encPanic(fmt.Errorf("unexpected primitive type: %T", rv.Interface()))
+	}
+}
+
+// By the TOML spec, all floats must have a decimal with at least one number on
+// either side.
+func floatAddDecimal(fstr string) string {
+	if !strings.Contains(fstr, ".") {
+		return fstr + ".0"
+	}
+	return fstr
+}
+
+func (enc *Encoder) writeQuoted(s string) {
+	enc.wf("\"%s\"", quotedReplacer.Replace(s))
+}
+
+func (enc *Encoder) eArrayOrSliceElement(rv reflect.Value) {
+	length := rv.Len()
+	enc.wf("[")
+	for i := 0; i < length; i++ {
+		elem := rv.Index(i)
+		enc.eElement(elem)
+		if i != length-1 {
+			enc.wf(", ")
+		}
+	}
+	enc.wf("]")
+}
+
+func (enc *Encoder) eArrayOfTables(key Key, rv reflect.Value) {
+	if len(key) == 0 {
+		encPanic(errNoKey)
+	}
+	for i := 0; i < rv.Len(); i++ {
+		trv := rv.Index(i)
+		if isNil(trv) {
+			continue
+		}
+		enc.newline()
+		enc.wf("%s[[%s]]", enc.indentStr(key), key.maybeQuotedAll())
+		enc.newline()
+		enc.eMapOrStruct(key, trv, false)
+	}
+}
+
+func (enc *Encoder) eTable(key Key, rv reflect.Value) {
+	if len(key) == 1 {
+		// Output an extra newline between top-level tables.
+		// (The newline isn't written if nothing else has been written though.)
+		enc.newline()
+	}
+	if len(key) > 0 {
+		enc.wf("%s[%s]", enc.indentStr(key), key.maybeQuotedAll())
+		enc.newline()
+	}
+	enc.eMapOrStruct(key, rv, false)
+}
+
+func (enc *Encoder) eMapOrStruct(key Key, rv reflect.Value, inline bool) {
+	switch rv := eindirect(rv); rv.Kind() {
+	case reflect.Map:
+		enc.eMap(key, rv, inline)
+	case reflect.Struct:
+		enc.eStruct(key, rv, inline)
+	default:
+		// Should never happen?
+		panic("eTable: unhandled reflect.Value Kind: " + rv.Kind().String())
+	}
+}
+
+func (enc *Encoder) eMap(key Key, rv reflect.Value, inline bool) {
+	rt := rv.Type()
+	if rt.Key().Kind() != reflect.String {
+		encPanic(errNonString)
+	}
+
+	// Sort keys so that we have deterministic output. And write keys directly
+	// underneath this key first, before writing sub-structs or sub-maps.
+	var mapKeysDirect, mapKeysSub []string
+	for _, mapKey := range rv.MapKeys() {
+		k := mapKey.String()
+		if typeIsHash(tomlTypeOfGo(rv.MapIndex(mapKey))) {
+			mapKeysSub = append(mapKeysSub, k)
+		} else {
+			mapKeysDirect = append(mapKeysDirect, k)
+		}
+	}
+
+	var writeMapKeys = func(mapKeys []string, trailC bool) {
+		sort.Strings(mapKeys)
+		for i, mapKey := range mapKeys {
+			val := rv.MapIndex(reflect.ValueOf(mapKey))
+			if isNil(val) {
+				continue
+			}
+
+			if inline {
+				enc.writeKeyValue(Key{mapKey}, val, true)
+				if trailC || i != len(mapKeys)-1 {
+					enc.wf(", ")
+				}
+			} else {
+				enc.encode(key.add(mapKey), val)
+			}
+		}
+	}
+
+	if inline {
+		enc.wf("{")
+	}
+	writeMapKeys(mapKeysDirect, len(mapKeysSub) > 0)
+	writeMapKeys(mapKeysSub, false)
+	if inline {
+		enc.wf("}")
+	}
+}
+
+func (enc *Encoder) eStruct(key Key, rv reflect.Value, inline bool) {
+	// Write keys for fields directly under this key first, because if we write
+	// a field that creates a new table then all keys under it will be in that
+	// table (not the one we're writing here).
+	//
+	// Fields is a [][]int: for fieldsDirect this always has one entry (the
+	// struct index). For fieldsSub it contains two entries: the parent field
+	// index from tv, and the field indexes for the fields of the sub.
+	var (
+		rt                      = rv.Type()
+		fieldsDirect, fieldsSub [][]int
+		addFields               func(rt reflect.Type, rv reflect.Value, start []int)
+	)
+	addFields = func(rt reflect.Type, rv reflect.Value, start []int) {
+		for i := 0; i < rt.NumField(); i++ {
+			f := rt.Field(i)
+			if f.PkgPath != "" && !f.Anonymous { /// Skip unexported fields.
+				continue
+			}
+
+			frv := rv.Field(i)
+
+			// Treat anonymous struct fields with tag names as though they are
+			// not anonymous, like encoding/json does.
+			//
+			// Non-struct anonymous fields use the normal encoding logic.
+			if f.Anonymous {
+				t := f.Type
+				switch t.Kind() {
+				case reflect.Struct:
+					if getOptions(f.Tag).name == "" {
+						addFields(t, frv, append(start, f.Index...))
+						continue
+					}
+				case reflect.Ptr:
+					if t.Elem().Kind() == reflect.Struct && getOptions(f.Tag).name == "" {
+						if !frv.IsNil() {
+							addFields(t.Elem(), frv.Elem(), append(start, f.Index...))
+						}
+						continue
+					}
+				}
+			}
+
+			if typeIsHash(tomlTypeOfGo(frv)) {
+				fieldsSub = append(fieldsSub, append(start, f.Index...))
+			} else {
+				fieldsDirect = append(fieldsDirect, append(start, f.Index...))
+			}
+		}
+	}
+	addFields(rt, rv, nil)
+
+	writeFields := func(fields [][]int) {
+		for _, fieldIndex := range fields {
+			fieldType := rt.FieldByIndex(fieldIndex)
+			fieldVal := rv.FieldByIndex(fieldIndex)
+
+			if isNil(fieldVal) { /// Don't write anything for nil fields.
+				continue
+			}
+
+			opts := getOptions(fieldType.Tag)
+			if opts.skip {
+				continue
+			}
+			keyName := fieldType.Name
+			if opts.name != "" {
+				keyName = opts.name
+			}
+			if opts.omitempty && isEmpty(fieldVal) {
+				continue
+			}
+			if opts.omitzero && isZero(fieldVal) {
+				continue
+			}
+
+			if inline {
+				enc.writeKeyValue(Key{keyName}, fieldVal, true)
+				if fieldIndex[0] != len(fields)-1 {
+					enc.wf(", ")
+				}
+			} else {
+				enc.encode(key.add(keyName), fieldVal)
+			}
+		}
+	}
+
+	if inline {
+		enc.wf("{")
+	}
+	writeFields(fieldsDirect)
+	writeFields(fieldsSub)
+	if inline {
+		enc.wf("}")
+	}
+}
+
+// tomlTypeName returns the TOML type name of the Go value's type. It is
+// used to determine whether the types of array elements are mixed (which is
+// forbidden). If the Go value is nil, then it is illegal for it to be an array
+// element, and valueIsNil is returned as true.
+
+// Returns the TOML type of a Go value. The type may be `nil`, which means
+// no concrete TOML type could be found.
+func tomlTypeOfGo(rv reflect.Value) tomlType {
+	if isNil(rv) || !rv.IsValid() {
+		return nil
+	}
+	switch rv.Kind() {
+	case reflect.Bool:
+		return tomlBool
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32,
+		reflect.Int64,
+		reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32,
+		reflect.Uint64:
+		return tomlInteger
+	case reflect.Float32, reflect.Float64:
+		return tomlFloat
+	case reflect.Array, reflect.Slice:
+		if typeEqual(tomlHash, tomlArrayType(rv)) {
+			return tomlArrayHash
+		}
+		return tomlArray
+	case reflect.Ptr, reflect.Interface:
+		return tomlTypeOfGo(rv.Elem())
+	case reflect.String:
+		return tomlString
+	case reflect.Map:
+		return tomlHash
+	case reflect.Struct:
+		switch rv.Interface().(type) {
+		case time.Time:
+			return tomlDatetime
+		case encoding.TextMarshaler:
+			return tomlString
+		default:
+			// Someone used a pointer receiver: we can make it work for pointer
+			// values.
+			if rv.CanAddr() {
+				_, ok := rv.Addr().Interface().(encoding.TextMarshaler)
+				if ok {
+					return tomlString
+				}
+			}
+			return tomlHash
+		}
+	default:
+		_, ok := rv.Interface().(encoding.TextMarshaler)
+		if ok {
+			return tomlString
+		}
+		encPanic(errors.New("unsupported type: " + rv.Kind().String()))
+		panic("") // Need *some* return value
+	}
+}
+
+// tomlArrayType returns the element type of a TOML array. The type returned
+// may be nil if it cannot be determined (e.g., a nil slice or a zero length
+// slize). This function may also panic if it finds a type that cannot be
+// expressed in TOML (such as nil elements, heterogeneous arrays or directly
+// nested arrays of tables).
+func tomlArrayType(rv reflect.Value) tomlType {
+	if isNil(rv) || !rv.IsValid() || rv.Len() == 0 {
+		return nil
+	}
+
+	/// Don't allow nil.
+	rvlen := rv.Len()
+	for i := 1; i < rvlen; i++ {
+		if tomlTypeOfGo(rv.Index(i)) == nil {
+			encPanic(errArrayNilElement)
+		}
+	}
+
+	firstType := tomlTypeOfGo(rv.Index(0))
+	if firstType == nil {
+		encPanic(errArrayNilElement)
+	}
+	return firstType
+}
+
+type tagOptions struct {
+	skip      bool // "-"
+	name      string
+	omitempty bool
+	omitzero  bool
+}
+
+func getOptions(tag reflect.StructTag) tagOptions {
+	t := tag.Get("toml")
+	if t == "-" {
+		return tagOptions{skip: true}
+	}
+	var opts tagOptions
+	parts := strings.Split(t, ",")
+	opts.name = parts[0]
+	for _, s := range parts[1:] {
+		switch s {
+		case "omitempty":
+			opts.omitempty = true
+		case "omitzero":
+			opts.omitzero = true
+		}
+	}
+	return opts
+}
+
+func isZero(rv reflect.Value) bool {
+	switch rv.Kind() {
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return rv.Int() == 0
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+		return rv.Uint() == 0
+	case reflect.Float32, reflect.Float64:
+		return rv.Float() == 0.0
+	}
+	return false
+}
+
+func isEmpty(rv reflect.Value) bool {
+	switch rv.Kind() {
+	case reflect.Array, reflect.Slice, reflect.Map, reflect.String:
+		return rv.Len() == 0
+	case reflect.Bool:
+		return !rv.Bool()
+	}
+	return false
+}
+
+func (enc *Encoder) newline() {
+	if enc.hasWritten {
+		enc.wf("\n")
+	}
+}
+
+// Write a key/value pair:
+//
+//   key = <any value>
+//
+// If inline is true it won't add a newline at the end.
+func (enc *Encoder) writeKeyValue(key Key, val reflect.Value, inline bool) {
+	if len(key) == 0 {
+		encPanic(errNoKey)
+	}
+	enc.wf("%s%s = ", enc.indentStr(key), key.maybeQuoted(len(key)-1))
+	enc.eElement(val)
+	if !inline {
+		enc.newline()
+	}
+}
+
+func (enc *Encoder) wf(format string, v ...interface{}) {
+	if _, err := fmt.Fprintf(enc.w, format, v...); err != nil {
+		encPanic(err)
+	}
+	enc.hasWritten = true
+}
+
+func (enc *Encoder) indentStr(key Key) string {
+	return strings.Repeat(enc.Indent, len(key)-1)
+}
+
+func encPanic(err error) {
+	panic(tomlEncodeError{err})
+}
+
+func eindirect(v reflect.Value) reflect.Value {
+	switch v.Kind() {
+	case reflect.Ptr, reflect.Interface:
+		return eindirect(v.Elem())
+	default:
+		return v
+	}
+}
+
+func isNil(rv reflect.Value) bool {
+	switch rv.Kind() {
+	case reflect.Interface, reflect.Map, reflect.Ptr, reflect.Slice:
+		return rv.IsNil()
+	default:
+		return false
+	}
+}

vendor/github.com/BurntSushi/toml/internal/tz.go

@@ -0,0 +1,36 @@
+package internal
+
+import "time"
+
+// Timezones used for local datetime, date, and time TOML types.
+//
+// The exact way times and dates without a timezone should be interpreted is not
+// well-defined in the TOML specification and left to the implementation. These
+// defaults to current local timezone offset of the computer, but this can be
+// changed by changing these variables before decoding.
+//
+// TODO:
+// Ideally we'd like to offer people the ability to configure the used timezone
+// by setting Decoder.Timezone and Encoder.Timezone; however, this is a bit
+// tricky: the reason we use three different variables for this is to support
+// round-tripping – without these specific TZ names we wouldn't know which
+// format to use.
+//
+// There isn't a good way to encode this right now though, and passing this sort
+// of information also ties in to various related issues such as string format
+// encoding, encoding of comments, etc.
+//
+// So, for the time being, just put this in internal until we can write a good
+// comprehensive API for doing all of this.
+//
+// The reason they're exported is because they're referred from in e.g.
+// internal/tag.
+//
+// Note that this behaviour is valid according to the TOML spec as the exact
+// behaviour is left up to implementations.
+var (
+	localOffset   = func() int { _, o := time.Now().Zone(); return o }()
+	LocalDatetime = time.FixedZone("datetime-local", localOffset)
+	LocalDate     = time.FixedZone("date-local", localOffset)
+	LocalTime     = time.FixedZone("time-local", localOffset)
+)

vendor/github.com/BurntSushi/toml/lex.go

@@ -0,0 +1,1225 @@
+package toml
+
+import (
+	"fmt"
+	"reflect"
+	"runtime"
+	"strings"
+	"unicode"
+	"unicode/utf8"
+)
+
+type itemType int
+
+const (
+	itemError itemType = iota
+	itemNIL            // used in the parser to indicate no type
+	itemEOF
+	itemText
+	itemString
+	itemRawString
+	itemMultilineString
+	itemRawMultilineString
+	itemBool
+	itemInteger
+	itemFloat
+	itemDatetime
+	itemArray // the start of an array
+	itemArrayEnd
+	itemTableStart
+	itemTableEnd
+	itemArrayTableStart
+	itemArrayTableEnd
+	itemKeyStart
+	itemKeyEnd
+	itemCommentStart
+	itemInlineTableStart
+	itemInlineTableEnd
+)
+
+const (
+	eof              = 0
+	comma            = ','
+	tableStart       = '['
+	tableEnd         = ']'
+	arrayTableStart  = '['
+	arrayTableEnd    = ']'
+	tableSep         = '.'
+	keySep           = '='
+	arrayStart       = '['
+	arrayEnd         = ']'
+	commentStart     = '#'
+	stringStart      = '"'
+	stringEnd        = '"'
+	rawStringStart   = '\''
+	rawStringEnd     = '\''
+	inlineTableStart = '{'
+	inlineTableEnd   = '}'
+)
+
+type stateFn func(lx *lexer) stateFn
+
+type lexer struct {
+	input string
+	start int
+	pos   int
+	line  int
+	state stateFn
+	items chan item
+
+	// Allow for backing up up to four runes.
+	// This is necessary because TOML contains 3-rune tokens (""" and ''').
+	prevWidths [4]int
+	nprev      int // how many of prevWidths are in use
+	// If we emit an eof, we can still back up, but it is not OK to call
+	// next again.
+	atEOF bool
+
+	// A stack of state functions used to maintain context.
+	// The idea is to reuse parts of the state machine in various places.
+	// For example, values can appear at the top level or within arbitrarily
+	// nested arrays. The last state on the stack is used after a value has
+	// been lexed. Similarly for comments.
+	stack []stateFn
+}
+
+type item struct {
+	typ  itemType
+	val  string
+	line int
+}
+
+func (lx *lexer) nextItem() item {
+	for {
+		select {
+		case item := <-lx.items:
+			return item
+		default:
+			lx.state = lx.state(lx)
+			//fmt.Printf("     STATE %-24s   current: %-10q   stack: %s\n", lx.state, lx.current(), lx.stack)
+		}
+	}
+}
+
+func lex(input string) *lexer {
+	lx := &lexer{
+		input: input,
+		state: lexTop,
+		line:  1,
+		items: make(chan item, 10),
+		stack: make([]stateFn, 0, 10),
+	}
+	return lx
+}
+
+func (lx *lexer) push(state stateFn) {
+	lx.stack = append(lx.stack, state)
+}
+
+func (lx *lexer) pop() stateFn {
+	if len(lx.stack) == 0 {
+		return lx.errorf("BUG in lexer: no states to pop")
+	}
+	last := lx.stack[len(lx.stack)-1]
+	lx.stack = lx.stack[0 : len(lx.stack)-1]
+	return last
+}
+
+func (lx *lexer) current() string {
+	return lx.input[lx.start:lx.pos]
+}
+
+func (lx *lexer) emit(typ itemType) {
+	lx.items <- item{typ, lx.current(), lx.line}
+	lx.start = lx.pos
+}
+
+func (lx *lexer) emitTrim(typ itemType) {
+	lx.items <- item{typ, strings.TrimSpace(lx.current()), lx.line}
+	lx.start = lx.pos
+}
+
+func (lx *lexer) next() (r rune) {
+	if lx.atEOF {
+		panic("BUG in lexer: next called after EOF")
+	}
+	if lx.pos >= len(lx.input) {
+		lx.atEOF = true
+		return eof
+	}
+
+	if lx.input[lx.pos] == '\n' {
+		lx.line++
+	}
+	lx.prevWidths[3] = lx.prevWidths[2]
+	lx.prevWidths[2] = lx.prevWidths[1]
+	lx.prevWidths[1] = lx.prevWidths[0]
+	if lx.nprev < 4 {
+		lx.nprev++
+	}
+
+	r, w := utf8.DecodeRuneInString(lx.input[lx.pos:])
+	if r == utf8.RuneError {
+		lx.errorf("invalid UTF-8 byte at position %d (line %d): 0x%02x", lx.pos, lx.line, lx.input[lx.pos])
+		return utf8.RuneError
+	}
+
+	lx.prevWidths[0] = w
+	lx.pos += w
+	return r
+}
+
+// ignore skips over the pending input before this point.
+func (lx *lexer) ignore() {
+	lx.start = lx.pos
+}
+
+// backup steps back one rune. Can be called 4 times between calls to next.
+func (lx *lexer) backup() {
+	if lx.atEOF {
+		lx.atEOF = false
+		return
+	}
+	if lx.nprev < 1 {
+		panic("BUG in lexer: backed up too far")
+	}
+	w := lx.prevWidths[0]
+	lx.prevWidths[0] = lx.prevWidths[1]
+	lx.prevWidths[1] = lx.prevWidths[2]
+	lx.prevWidths[2] = lx.prevWidths[3]
+	lx.nprev--
+	lx.pos -= w
+	if lx.pos < len(lx.input) && lx.input[lx.pos] == '\n' {
+		lx.line--
+	}
+}
+
+// accept consumes the next rune if it's equal to `valid`.
+func (lx *lexer) accept(valid rune) bool {
+	if lx.next() == valid {
+		return true
+	}
+	lx.backup()
+	return false
+}
+
+// peek returns but does not consume the next rune in the input.
+func (lx *lexer) peek() rune {
+	r := lx.next()
+	lx.backup()
+	return r
+}
+
+// skip ignores all input that matches the given predicate.
+func (lx *lexer) skip(pred func(rune) bool) {
+	for {
+		r := lx.next()
+		if pred(r) {
+			continue
+		}
+		lx.backup()
+		lx.ignore()
+		return
+	}
+}
+
+// errorf stops all lexing by emitting an error and returning `nil`.
+// Note that any value that is a character is escaped if it's a special
+// character (newlines, tabs, etc.).
+func (lx *lexer) errorf(format string, values ...interface{}) stateFn {
+	lx.items <- item{
+		itemError,
+		fmt.Sprintf(format, values...),
+		lx.line,
+	}
+	return nil
+}
+
+// lexTop consumes elements at the top level of TOML data.
+func lexTop(lx *lexer) stateFn {
+	r := lx.next()
+	if isWhitespace(r) || isNL(r) {
+		return lexSkip(lx, lexTop)
+	}
+	switch r {
+	case commentStart:
+		lx.push(lexTop)
+		return lexCommentStart
+	case tableStart:
+		return lexTableStart
+	case eof:
+		if lx.pos > lx.start {
+			return lx.errorf("unexpected EOF")
+		}
+		lx.emit(itemEOF)
+		return nil
+	}
+
+	// At this point, the only valid item can be a key, so we back up
+	// and let the key lexer do the rest.
+	lx.backup()
+	lx.push(lexTopEnd)
+	return lexKeyStart
+}
+
+// lexTopEnd is entered whenever a top-level item has been consumed. (A value
+// or a table.) It must see only whitespace, and will turn back to lexTop
+// upon a newline. If it sees EOF, it will quit the lexer successfully.
+func lexTopEnd(lx *lexer) stateFn {
+	r := lx.next()
+	switch {
+	case r == commentStart:
+		// a comment will read to a newline for us.
+		lx.push(lexTop)
+		return lexCommentStart
+	case isWhitespace(r):
+		return lexTopEnd
+	case isNL(r):
+		lx.ignore()
+		return lexTop
+	case r == eof:
+		lx.emit(itemEOF)
+		return nil
+	}
+	return lx.errorf(
+		"expected a top-level item to end with a newline, comment, or EOF, but got %q instead",
+		r)
+}
+
+// lexTable lexes the beginning of a table. Namely, it makes sure that
+// it starts with a character other than '.' and ']'.
+// It assumes that '[' has already been consumed.
+// It also handles the case that this is an item in an array of tables.
+// e.g., '[[name]]'.
+func lexTableStart(lx *lexer) stateFn {
+	if lx.peek() == arrayTableStart {
+		lx.next()
+		lx.emit(itemArrayTableStart)
+		lx.push(lexArrayTableEnd)
+	} else {
+		lx.emit(itemTableStart)
+		lx.push(lexTableEnd)
+	}
+	return lexTableNameStart
+}
+
+func lexTableEnd(lx *lexer) stateFn {
+	lx.emit(itemTableEnd)
+	return lexTopEnd
+}
+
+func lexArrayTableEnd(lx *lexer) stateFn {
+	if r := lx.next(); r != arrayTableEnd {
+		return lx.errorf(
+			"expected end of table array name delimiter %q, but got %q instead",
+			arrayTableEnd, r)
+	}
+	lx.emit(itemArrayTableEnd)
+	return lexTopEnd
+}
+
+func lexTableNameStart(lx *lexer) stateFn {
+	lx.skip(isWhitespace)
+	switch r := lx.peek(); {
+	case r == tableEnd || r == eof:
+		return lx.errorf("unexpected end of table name (table names cannot be empty)")
+	case r == tableSep:
+		return lx.errorf("unexpected table separator (table names cannot be empty)")
+	case r == stringStart || r == rawStringStart:
+		lx.ignore()
+		lx.push(lexTableNameEnd)
+		return lexQuotedName
+	default:
+		lx.push(lexTableNameEnd)
+		return lexBareName
+	}
+}
+
+// lexTableNameEnd reads the end of a piece of a table name, optionally
+// consuming whitespace.
+func lexTableNameEnd(lx *lexer) stateFn {
+	lx.skip(isWhitespace)
+	switch r := lx.next(); {
+	case isWhitespace(r):
+		return lexTableNameEnd
+	case r == tableSep:
+		lx.ignore()
+		return lexTableNameStart
+	case r == tableEnd:
+		return lx.pop()
+	default:
+		return lx.errorf("expected '.' or ']' to end table name, but got %q instead", r)
+	}
+}
+
+// lexBareName lexes one part of a key or table.
+//
+// It assumes that at least one valid character for the table has already been
+// read.
+//
+// Lexes only one part, e.g. only 'a' inside 'a.b'.
+func lexBareName(lx *lexer) stateFn {
+	r := lx.next()
+	if isBareKeyChar(r) {
+		return lexBareName
+	}
+	lx.backup()
+	lx.emit(itemText)
+	return lx.pop()
+}
+
+// lexBareName lexes one part of a key or table.
+//
+// It assumes that at least one valid character for the table has already been
+// read.
+//
+// Lexes only one part, e.g. only '"a"' inside '"a".b'.
+func lexQuotedName(lx *lexer) stateFn {
+	r := lx.next()
+	switch {
+	case isWhitespace(r):
+		return lexSkip(lx, lexValue)
+	case r == stringStart:
+		lx.ignore() // ignore the '"'
+		return lexString
+	case r == rawStringStart:
+		lx.ignore() // ignore the "'"
+		return lexRawString
+	case r == eof:
+		return lx.errorf("unexpected EOF; expected value")
+	default:
+		return lx.errorf("expected value but found %q instead", r)
+	}
+}
+
+// lexKeyStart consumes all key parts until a '='.
+func lexKeyStart(lx *lexer) stateFn {
+	lx.skip(isWhitespace)
+	switch r := lx.peek(); {
+	case r == '=' || r == eof:
+		return lx.errorf("unexpected '=': key name appears blank")
+	case r == '.':
+		return lx.errorf("unexpected '.': keys cannot start with a '.'")
+	case r == stringStart || r == rawStringStart:
+		lx.ignore()
+		fallthrough
+	default: // Bare key
+		lx.emit(itemKeyStart)
+		return lexKeyNameStart
+	}
+}
+
+func lexKeyNameStart(lx *lexer) stateFn {
+	lx.skip(isWhitespace)
+	switch r := lx.peek(); {
+	case r == '=' || r == eof:
+		return lx.errorf("unexpected '='")
+	case r == '.':
+		return lx.errorf("unexpected '.'")
+	case r == stringStart || r == rawStringStart:
+		lx.ignore()
+		lx.push(lexKeyEnd)
+		return lexQuotedName
+	default:
+		lx.push(lexKeyEnd)
+		return lexBareName
+	}
+}
+
+// lexKeyEnd consumes the end of a key and trims whitespace (up to the key
+// separator).
+func lexKeyEnd(lx *lexer) stateFn {
+	lx.skip(isWhitespace)
+	switch r := lx.next(); {
+	case isWhitespace(r):
+		return lexSkip(lx, lexKeyEnd)
+	case r == eof:
+		return lx.errorf("unexpected EOF; expected key separator %q", keySep)
+	case r == '.':
+		lx.ignore()
+		return lexKeyNameStart
+	case r == '=':
+		lx.emit(itemKeyEnd)
+		return lexSkip(lx, lexValue)
+	default:
+		return lx.errorf("expected '.' or '=', but got %q instead", r)
+	}
+}
+
+// lexValue starts the consumption of a value anywhere a value is expected.
+// lexValue will ignore whitespace.
+// After a value is lexed, the last state on the next is popped and returned.
+func lexValue(lx *lexer) stateFn {
+	// We allow whitespace to precede a value, but NOT newlines.
+	// In array syntax, the array states are responsible for ignoring newlines.
+	r := lx.next()
+	switch {
+	case isWhitespace(r):
+		return lexSkip(lx, lexValue)
+	case isDigit(r):
+		lx.backup() // avoid an extra state and use the same as above
+		return lexNumberOrDateStart
+	}
+	switch r {
+	case arrayStart:
+		lx.ignore()
+		lx.emit(itemArray)
+		return lexArrayValue
+	case inlineTableStart:
+		lx.ignore()
+		lx.emit(itemInlineTableStart)
+		return lexInlineTableValue
+	case stringStart:
+		if lx.accept(stringStart) {
+			if lx.accept(stringStart) {
+				lx.ignore() // Ignore """
+				return lexMultilineString
+			}
+			lx.backup()
+		}
+		lx.ignore() // ignore the '"'
+		return lexString
+	case rawStringStart:
+		if lx.accept(rawStringStart) {
+			if lx.accept(rawStringStart) {
+				lx.ignore() // Ignore """
+				return lexMultilineRawString
+			}
+			lx.backup()
+		}
+		lx.ignore() // ignore the "'"
+		return lexRawString
+	case '.': // special error case, be kind to users
+		return lx.errorf("floats must start with a digit, not '.'")
+	case 'i', 'n':
+		if (lx.accept('n') && lx.accept('f')) || (lx.accept('a') && lx.accept('n')) {
+			lx.emit(itemFloat)
+			return lx.pop()
+		}
+	case '-', '+':
+		return lexDecimalNumberStart
+	}
+	if unicode.IsLetter(r) {
+		// Be permissive here; lexBool will give a nice error if the
+		// user wrote something like
+		//   x = foo
+		// (i.e. not 'true' or 'false' but is something else word-like.)
+		lx.backup()
+		return lexBool
+	}
+	if r == eof {
+		return lx.errorf("unexpected EOF; expected value")
+	}
+	return lx.errorf("expected value but found %q instead", r)
+}
+
+// lexArrayValue consumes one value in an array. It assumes that '[' or ','
+// have already been consumed. All whitespace and newlines are ignored.
+func lexArrayValue(lx *lexer) stateFn {
+	r := lx.next()
+	switch {
+	case isWhitespace(r) || isNL(r):
+		return lexSkip(lx, lexArrayValue)
+	case r == commentStart:
+		lx.push(lexArrayValue)
+		return lexCommentStart
+	case r == comma:
+		return lx.errorf("unexpected comma")
+	case r == arrayEnd:
+		// NOTE(caleb): The spec isn't clear about whether you can have
+		// a trailing comma or not, so we'll allow it.
+		return lexArrayEnd
+	}
+
+	lx.backup()
+	lx.push(lexArrayValueEnd)
+	return lexValue
+}
+
+// lexArrayValueEnd consumes everything between the end of an array value and
+// the next value (or the end of the array): it ignores whitespace and newlines
+// and expects either a ',' or a ']'.
+func lexArrayValueEnd(lx *lexer) stateFn {
+	r := lx.next()
+	switch {
+	case isWhitespace(r) || isNL(r):
+		return lexSkip(lx, lexArrayValueEnd)
+	case r == commentStart:
+		lx.push(lexArrayValueEnd)
+		return lexCommentStart
+	case r == comma:
+		lx.ignore()
+		return lexArrayValue // move on to the next value
+	case r == arrayEnd:
+		return lexArrayEnd
+	}
+	return lx.errorf(
+		"expected a comma or array terminator %q, but got %s instead",
+		arrayEnd, runeOrEOF(r))
+}
+
+// lexArrayEnd finishes the lexing of an array.
+// It assumes that a ']' has just been consumed.
+func lexArrayEnd(lx *lexer) stateFn {
+	lx.ignore()
+	lx.emit(itemArrayEnd)
+	return lx.pop()
+}
+
+// lexInlineTableValue consumes one key/value pair in an inline table.
+// It assumes that '{' or ',' have already been consumed. Whitespace is ignored.
+func lexInlineTableValue(lx *lexer) stateFn {
+	r := lx.next()
+	switch {
+	case isWhitespace(r):
+		return lexSkip(lx, lexInlineTableValue)
+	case isNL(r):
+		return lx.errorf("newlines not allowed within inline tables")
+	case r == commentStart:
+		lx.push(lexInlineTableValue)
+		return lexCommentStart
+	case r == comma:
+		return lx.errorf("unexpected comma")
+	case r == inlineTableEnd:
+		return lexInlineTableEnd
+	}
+	lx.backup()
+	lx.push(lexInlineTableValueEnd)
+	return lexKeyStart
+}
+
+// lexInlineTableValueEnd consumes everything between the end of an inline table
+// key/value pair and the next pair (or the end of the table):
+// it ignores whitespace and expects either a ',' or a '}'.
+func lexInlineTableValueEnd(lx *lexer) stateFn {
+	switch r := lx.next(); {
+	case isWhitespace(r):
+		return lexSkip(lx, lexInlineTableValueEnd)
+	case isNL(r):
+		return lx.errorf("newlines not allowed within inline tables")
+	case r == commentStart:
+		lx.push(lexInlineTableValueEnd)
+		return lexCommentStart
+	case r == comma:
+		lx.ignore()
+		lx.skip(isWhitespace)
+		if lx.peek() == '}' {
+			return lx.errorf("trailing comma not allowed in inline tables")
+		}
+		return lexInlineTableValue
+	case r == inlineTableEnd:
+		return lexInlineTableEnd
+	default:
+		return lx.errorf(
+			"expected a comma or an inline table terminator %q, but got %s instead",
+			inlineTableEnd, runeOrEOF(r))
+	}
+}
+
+func runeOrEOF(r rune) string {
+	if r == eof {
+		return "end of file"
+	}
+	return "'" + string(r) + "'"
+}
+
+// lexInlineTableEnd finishes the lexing of an inline table.
+// It assumes that a '}' has just been consumed.
+func lexInlineTableEnd(lx *lexer) stateFn {
+	lx.ignore()
+	lx.emit(itemInlineTableEnd)
+	return lx.pop()
+}
+
+// lexString consumes the inner contents of a string. It assumes that the
+// beginning '"' has already been consumed and ignored.
+func lexString(lx *lexer) stateFn {
+	r := lx.next()
+	switch {
+	case r == eof:
+		return lx.errorf(`unexpected EOF; expected '"'`)
+	case isControl(r) || r == '\r':
+		return lx.errorf("control characters are not allowed inside strings: '0x%02x'", r)
+	case isNL(r):
+		return lx.errorf("strings cannot contain newlines")
+	case r == '\\':
+		lx.push(lexString)
+		return lexStringEscape
+	case r == stringEnd:
+		lx.backup()
+		lx.emit(itemString)
+		lx.next()
+		lx.ignore()
+		return lx.pop()
+	}
+	return lexString
+}
+
+// lexMultilineString consumes the inner contents of a string. It assumes that
+// the beginning '"""' has already been consumed and ignored.
+func lexMultilineString(lx *lexer) stateFn {
+	r := lx.next()
+	switch r {
+	case eof:
+		return lx.errorf(`unexpected EOF; expected '"""'`)
+	case '\r':
+		if lx.peek() != '\n' {
+			return lx.errorf("control characters are not allowed inside strings: '0x%02x'", r)
+		}
+		return lexMultilineString
+	case '\\':
+		return lexMultilineStringEscape
+	case stringEnd:
+		/// Found " → try to read two more "".
+		if lx.accept(stringEnd) {
+			if lx.accept(stringEnd) {
+				/// Peek ahead: the string can contain " and "", including at the
+				/// end: """str"""""
+				/// 6 or more at the end, however, is an error.
+				if lx.peek() == stringEnd {
+					/// Check if we already lexed 5 's; if so we have 6 now, and
+					/// that's just too many man!
+					if strings.HasSuffix(lx.current(), `"""""`) {
+						return lx.errorf(`unexpected '""""""'`)
+					}
+					lx.backup()
+					lx.backup()
+					return lexMultilineString
+				}
+
+				lx.backup() /// backup: don't include the """ in the item.
+				lx.backup()
+				lx.backup()
+				lx.emit(itemMultilineString)
+				lx.next() /// Read over ''' again and discard it.
+				lx.next()
+				lx.next()
+				lx.ignore()
+				return lx.pop()
+			}
+			lx.backup()
+		}
+	}
+
+	if isControl(r) {
+		return lx.errorf("control characters are not allowed inside strings: '0x%02x'", r)
+	}
+	return lexMultilineString
+}
+
+// lexRawString consumes a raw string. Nothing can be escaped in such a string.
+// It assumes that the beginning "'" has already been consumed and ignored.
+func lexRawString(lx *lexer) stateFn {
+	r := lx.next()
+	switch {
+	case r == eof:
+		return lx.errorf(`unexpected EOF; expected "'"`)
+	case isControl(r) || r == '\r':
+		return lx.errorf("control characters are not allowed inside strings: '0x%02x'", r)
+	case isNL(r):
+		return lx.errorf("strings cannot contain newlines")
+	case r == rawStringEnd:
+		lx.backup()
+		lx.emit(itemRawString)
+		lx.next()
+		lx.ignore()
+		return lx.pop()
+	}
+	return lexRawString
+}
+
+// lexMultilineRawString consumes a raw string. Nothing can be escaped in such
+// a string. It assumes that the beginning "'''" has already been consumed and
+// ignored.
+func lexMultilineRawString(lx *lexer) stateFn {
+	r := lx.next()
+	switch r {
+	case eof:
+		return lx.errorf(`unexpected EOF; expected "'''"`)
+	case '\r':
+		if lx.peek() != '\n' {
+			return lx.errorf("control characters are not allowed inside strings: '0x%02x'", r)
+		}
+		return lexMultilineRawString
+	case rawStringEnd:
+		/// Found ' → try to read two more ''.
+		if lx.accept(rawStringEnd) {
+			if lx.accept(rawStringEnd) {
+				/// Peek ahead: the string can contain ' and '', including at the
+				/// end: '''str'''''
+				/// 6 or more at the end, however, is an error.
+				if lx.peek() == rawStringEnd {
+					/// Check if we already lexed 5 's; if so we have 6 now, and
+					/// that's just too many man!
+					if strings.HasSuffix(lx.current(), "'''''") {
+						return lx.errorf(`unexpected "''''''"`)
+					}
+					lx.backup()
+					lx.backup()
+					return lexMultilineRawString
+				}
+
+				lx.backup() /// backup: don't include the ''' in the item.
+				lx.backup()
+				lx.backup()
+				lx.emit(itemRawMultilineString)
+				lx.next() /// Read over ''' again and discard it.
+				lx.next()
+				lx.next()
+				lx.ignore()
+				return lx.pop()
+			}
+			lx.backup()
+		}
+	}
+
+	if isControl(r) {
+		return lx.errorf("control characters are not allowed inside strings: '0x%02x'", r)
+	}
+	return lexMultilineRawString
+}
+
+// lexMultilineStringEscape consumes an escaped character. It assumes that the
+// preceding '\\' has already been consumed.
+func lexMultilineStringEscape(lx *lexer) stateFn {
+	// Handle the special case first:
+	if isNL(lx.next()) {
+		return lexMultilineString
+	}
+	lx.backup()
+	lx.push(lexMultilineString)
+	return lexStringEscape(lx)
+}
+
+func lexStringEscape(lx *lexer) stateFn {
+	r := lx.next()
+	switch r {
+	case 'b':
+		fallthrough
+	case 't':
+		fallthrough
+	case 'n':
+		fallthrough
+	case 'f':
+		fallthrough
+	case 'r':
+		fallthrough
+	case '"':
+		fallthrough
+	case ' ', '\t':
+		// Inside """ .. """ strings you can use \ to escape newlines, and any
+		// amount of whitespace can be between the \ and \n.
+		fallthrough
+	case '\\':
+		return lx.pop()
+	case 'u':
+		return lexShortUnicodeEscape
+	case 'U':
+		return lexLongUnicodeEscape
+	}
+	return lx.errorf("invalid escape character %q; only the following escape characters are allowed: "+
+		`\b, \t, \n, \f, \r, \", \\, \uXXXX, and \UXXXXXXXX`, r)
+}
+
+func lexShortUnicodeEscape(lx *lexer) stateFn {
+	var r rune
+	for i := 0; i < 4; i++ {
+		r = lx.next()
+		if !isHexadecimal(r) {
+			return lx.errorf(
+				`expected four hexadecimal digits after '\u', but got %q instead`,
+				lx.current())
+		}
+	}
+	return lx.pop()
+}
+
+func lexLongUnicodeEscape(lx *lexer) stateFn {
+	var r rune
+	for i := 0; i < 8; i++ {
+		r = lx.next()
+		if !isHexadecimal(r) {
+			return lx.errorf(
+				`expected eight hexadecimal digits after '\U', but got %q instead`,
+				lx.current())
+		}
+	}
+	return lx.pop()
+}
+
+// lexNumberOrDateStart processes the first character of a value which begins
+// with a digit. It exists to catch values starting with '0', so that
+// lexBaseNumberOrDate can differentiate base prefixed integers from other
+// types.
+func lexNumberOrDateStart(lx *lexer) stateFn {
+	r := lx.next()
+	switch r {
+	case '0':
+		return lexBaseNumberOrDate
+	}
+
+	if !isDigit(r) {
+		// The only way to reach this state is if the value starts
+		// with a digit, so specifically treat anything else as an
+		// error.
+		return lx.errorf("expected a digit but got %q", r)
+	}
+
+	return lexNumberOrDate
+}
+
+// lexNumberOrDate consumes either an integer, float or datetime.
+func lexNumberOrDate(lx *lexer) stateFn {
+	r := lx.next()
+	if isDigit(r) {
+		return lexNumberOrDate
+	}
+	switch r {
+	case '-', ':':
+		return lexDatetime
+	case '_':
+		return lexDecimalNumber
+	case '.', 'e', 'E':
+		return lexFloat
+	}
+
+	lx.backup()
+	lx.emit(itemInteger)
+	return lx.pop()
+}
+
+// lexDatetime consumes a Datetime, to a first approximation.
+// The parser validates that it matches one of the accepted formats.
+func lexDatetime(lx *lexer) stateFn {
+	r := lx.next()
+	if isDigit(r) {
+		return lexDatetime
+	}
+	switch r {
+	case '-', ':', 'T', 't', ' ', '.', 'Z', 'z', '+':
+		return lexDatetime
+	}
+
+	lx.backup()
+	lx.emitTrim(itemDatetime)
+	return lx.pop()
+}
+
+// lexHexInteger consumes a hexadecimal integer after seeing the '0x' prefix.
+func lexHexInteger(lx *lexer) stateFn {
+	r := lx.next()
+	if isHexadecimal(r) {
+		return lexHexInteger
+	}
+	switch r {
+	case '_':
+		return lexHexInteger
+	}
+
+	lx.backup()
+	lx.emit(itemInteger)
+	return lx.pop()
+}
+
+// lexOctalInteger consumes an octal integer after seeing the '0o' prefix.
+func lexOctalInteger(lx *lexer) stateFn {
+	r := lx.next()
+	if isOctal(r) {
+		return lexOctalInteger
+	}
+	switch r {
+	case '_':
+		return lexOctalInteger
+	}
+
+	lx.backup()
+	lx.emit(itemInteger)
+	return lx.pop()
+}
+
+// lexBinaryInteger consumes a binary integer after seeing the '0b' prefix.
+func lexBinaryInteger(lx *lexer) stateFn {
+	r := lx.next()
+	if isBinary(r) {
+		return lexBinaryInteger
+	}
+	switch r {
+	case '_':
+		return lexBinaryInteger
+	}
+
+	lx.backup()
+	lx.emit(itemInteger)
+	return lx.pop()
+}
+
+// lexDecimalNumber consumes a decimal float or integer.
+func lexDecimalNumber(lx *lexer) stateFn {
+	r := lx.next()
+	if isDigit(r) {
+		return lexDecimalNumber
+	}
+	switch r {
+	case '.', 'e', 'E':
+		return lexFloat
+	case '_':
+		return lexDecimalNumber
+	}
+
+	lx.backup()
+	lx.emit(itemInteger)
+	return lx.pop()
+}
+
+// lexDecimalNumber consumes the first digit of a number beginning with a sign.
+// It assumes the sign has already been consumed. Values which start with a sign
+// are only allowed to be decimal integers or floats.
+//
+// The special "nan" and "inf" values are also recognized.
+func lexDecimalNumberStart(lx *lexer) stateFn {
+	r := lx.next()
+
+	// Special error cases to give users better error messages
+	switch r {
+	case 'i':
+		if !lx.accept('n') || !lx.accept('f') {
+			return lx.errorf("invalid float: '%s'", lx.current())
+		}
+		lx.emit(itemFloat)
+		return lx.pop()
+	case 'n':
+		if !lx.accept('a') || !lx.accept('n') {
+			return lx.errorf("invalid float: '%s'", lx.current())
+		}
+		lx.emit(itemFloat)
+		return lx.pop()
+	case '0':
+		p := lx.peek()
+		switch p {
+		case 'b', 'o', 'x':
+			return lx.errorf("cannot use sign with non-decimal numbers: '%s%c'", lx.current(), p)
+		}
+	case '.':
+		return lx.errorf("floats must start with a digit, not '.'")
+	}
+
+	if isDigit(r) {
+		return lexDecimalNumber
+	}
+
+	return lx.errorf("expected a digit but got %q", r)
+}
+
+// lexBaseNumberOrDate differentiates between the possible values which
+// start with '0'. It assumes that before reaching this state, the initial '0'
+// has been consumed.
+func lexBaseNumberOrDate(lx *lexer) stateFn {
+	r := lx.next()
+	// Note: All datetimes start with at least two digits, so we don't
+	// handle date characters (':', '-', etc.) here.
+	if isDigit(r) {
+		return lexNumberOrDate
+	}
+	switch r {
+	case '_':
+		// Can only be decimal, because there can't be an underscore
+		// between the '0' and the base designator, and dates can't
+		// contain underscores.
+		return lexDecimalNumber
+	case '.', 'e', 'E':
+		return lexFloat
+	case 'b':
+		r = lx.peek()
+		if !isBinary(r) {
+			lx.errorf("not a binary number: '%s%c'", lx.current(), r)
+		}
+		return lexBinaryInteger
+	case 'o':
+		r = lx.peek()
+		if !isOctal(r) {
+			lx.errorf("not an octal number: '%s%c'", lx.current(), r)
+		}
+		return lexOctalInteger
+	case 'x':
+		r = lx.peek()
+		if !isHexadecimal(r) {
+			lx.errorf("not a hexidecimal number: '%s%c'", lx.current(), r)
+		}
+		return lexHexInteger
+	}
+
+	lx.backup()
+	lx.emit(itemInteger)
+	return lx.pop()
+}
+
+// lexFloat consumes the elements of a float. It allows any sequence of
+// float-like characters, so floats emitted by the lexer are only a first
+// approximation and must be validated by the parser.
+func lexFloat(lx *lexer) stateFn {
+	r := lx.next()
+	if isDigit(r) {
+		return lexFloat
+	}
+	switch r {
+	case '_', '.', '-', '+', 'e', 'E':
+		return lexFloat
+	}
+
+	lx.backup()
+	lx.emit(itemFloat)
+	return lx.pop()
+}
+
+// lexBool consumes a bool string: 'true' or 'false.
+func lexBool(lx *lexer) stateFn {
+	var rs []rune
+	for {
+		r := lx.next()
+		if !unicode.IsLetter(r) {
+			lx.backup()
+			break
+		}
+		rs = append(rs, r)
+	}
+	s := string(rs)
+	switch s {
+	case "true", "false":
+		lx.emit(itemBool)
+		return lx.pop()
+	}
+	return lx.errorf("expected value but found %q instead", s)
+}
+
+// lexCommentStart begins the lexing of a comment. It will emit
+// itemCommentStart and consume no characters, passing control to lexComment.
+func lexCommentStart(lx *lexer) stateFn {
+	lx.ignore()
+	lx.emit(itemCommentStart)
+	return lexComment
+}
+
+// lexComment lexes an entire comment. It assumes that '#' has been consumed.
+// It will consume *up to* the first newline character, and pass control
+// back to the last state on the stack.
+func lexComment(lx *lexer) stateFn {
+	switch r := lx.next(); {
+	case isNL(r) || r == eof:
+		lx.backup()
+		lx.emit(itemText)
+		return lx.pop()
+	case isControl(r):
+		return lx.errorf("control characters are not allowed inside comments: '0x%02x'", r)
+	default:
+		return lexComment
+	}
+}
+
+// lexSkip ignores all slurped input and moves on to the next state.
+func lexSkip(lx *lexer, nextState stateFn) stateFn {
+	lx.ignore()
+	return nextState
+}
+
+// isWhitespace returns true if `r` is a whitespace character according
+// to the spec.
+func isWhitespace(r rune) bool {
+	return r == '\t' || r == ' '
+}
+
+func isNL(r rune) bool {
+	return r == '\n' || r == '\r'
+}
+
+// Control characters except \n, \t
+func isControl(r rune) bool {
+	switch r {
+	case '\t', '\r', '\n':
+		return false
+	default:
+		return (r >= 0x00 && r <= 0x1f) || r == 0x7f
+	}
+}
+
+func isDigit(r rune) bool {
+	return r >= '0' && r <= '9'
+}
+
+func isHexadecimal(r rune) bool {
+	return (r >= '0' && r <= '9') ||
+		(r >= 'a' && r <= 'f') ||
+		(r >= 'A' && r <= 'F')
+}
+
+func isOctal(r rune) bool {
+	return r >= '0' && r <= '7'
+}
+
+func isBinary(r rune) bool {
+	return r == '0' || r == '1'
+}
+
+func isBareKeyChar(r rune) bool {
+	return (r >= 'A' && r <= 'Z') ||
+		(r >= 'a' && r <= 'z') ||
+		(r >= '0' && r <= '9') ||
+		r == '_' ||
+		r == '-'
+}
+
+func (s stateFn) String() string {
+	name := runtime.FuncForPC(reflect.ValueOf(s).Pointer()).Name()
+	if i := strings.LastIndexByte(name, '.'); i > -1 {
+		name = name[i+1:]
+	}
+	if s == nil {
+		name = "<nil>"
+	}
+	return name + "()"
+}
+
+func (itype itemType) String() string {
+	switch itype {
+	case itemError:
+		return "Error"
+	case itemNIL:
+		return "NIL"
+	case itemEOF:
+		return "EOF"
+	case itemText:
+		return "Text"
+	case itemString, itemRawString, itemMultilineString, itemRawMultilineString:
+		return "String"
+	case itemBool:
+		return "Bool"
+	case itemInteger:
+		return "Integer"
+	case itemFloat:
+		return "Float"
+	case itemDatetime:
+		return "DateTime"
+	case itemTableStart:
+		return "TableStart"
+	case itemTableEnd:
+		return "TableEnd"
+	case itemKeyStart:
+		return "KeyStart"
+	case itemKeyEnd:
+		return "KeyEnd"
+	case itemArray:
+		return "Array"
+	case itemArrayEnd:
+		return "ArrayEnd"
+	case itemCommentStart:
+		return "CommentStart"
+	case itemInlineTableStart:
+		return "InlineTableStart"
+	case itemInlineTableEnd:
+		return "InlineTableEnd"
+	}
+	panic(fmt.Sprintf("BUG: Unknown type '%d'.", int(itype)))
+}
+
+func (item item) String() string {
+	return fmt.Sprintf("(%s, %s)", item.typ.String(), item.val)
+}

vendor/github.com/BurntSushi/toml/parse.go

@@ -0,0 +1,739 @@
+package toml
+
+import (
+	"errors"
+	"fmt"
+	"strconv"
+	"strings"
+	"time"
+	"unicode/utf8"
+
+	"github.com/BurntSushi/toml/internal"
+)
+
+type parser struct {
+	mapping map[string]interface{}
+	types   map[string]tomlType
+	lx      *lexer
+
+	ordered    []Key           // List of keys in the order that they appear in the TOML data.
+	context    Key             // Full key for the current hash in scope.
+	currentKey string          // Base key name for everything except hashes.
+	approxLine int             // Rough approximation of line number
+	implicits  map[string]bool // Record implied keys (e.g. 'key.group.names').
+}
+
+// ParseError is used when a file can't be parsed: for example invalid integer
+// literals, duplicate keys, etc.
+type ParseError struct {
+	Message string
+	Line    int
+	LastKey string
+}
+
+func (pe ParseError) Error() string {
+	return fmt.Sprintf("Near line %d (last key parsed '%s'): %s",
+		pe.Line, pe.LastKey, pe.Message)
+}
+
+func parse(data string) (p *parser, err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			var ok bool
+			if err, ok = r.(ParseError); ok {
+				return
+			}
+			panic(r)
+		}
+	}()
+
+	// Read over BOM; do this here as the lexer calls utf8.DecodeRuneInString()
+	// which mangles stuff.
+	if strings.HasPrefix(data, "\xff\xfe") || strings.HasPrefix(data, "\xfe\xff") {
+		data = data[2:]
+	}
+
+	// Examine first few bytes for NULL bytes; this probably means it's a UTF-16
+	// file (second byte in surrogate pair being NULL). Again, do this here to
+	// avoid having to deal with UTF-8/16 stuff in the lexer.
+	ex := 6
+	if len(data) < 6 {
+		ex = len(data)
+	}
+	if strings.ContainsRune(data[:ex], 0) {
+		return nil, errors.New("files cannot contain NULL bytes; probably using UTF-16; TOML files must be UTF-8")
+	}
+
+	p = &parser{
+		mapping:   make(map[string]interface{}),
+		types:     make(map[string]tomlType),
+		lx:        lex(data),
+		ordered:   make([]Key, 0),
+		implicits: make(map[string]bool),
+	}
+	for {
+		item := p.next()
+		if item.typ == itemEOF {
+			break
+		}
+		p.topLevel(item)
+	}
+
+	return p, nil
+}
+
+func (p *parser) panicf(format string, v ...interface{}) {
+	msg := fmt.Sprintf(format, v...)
+	panic(ParseError{
+		Message: msg,
+		Line:    p.approxLine,
+		LastKey: p.current(),
+	})
+}
+
+func (p *parser) next() item {
+	it := p.lx.nextItem()
+	//fmt.Printf("ITEM %-18s line %-3d │ %q\n", it.typ, it.line, it.val)
+	if it.typ == itemError {
+		p.panicf("%s", it.val)
+	}
+	return it
+}
+
+func (p *parser) bug(format string, v ...interface{}) {
+	panic(fmt.Sprintf("BUG: "+format+"\n\n", v...))
+}
+
+func (p *parser) expect(typ itemType) item {
+	it := p.next()
+	p.assertEqual(typ, it.typ)
+	return it
+}
+
+func (p *parser) assertEqual(expected, got itemType) {
+	if expected != got {
+		p.bug("Expected '%s' but got '%s'.", expected, got)
+	}
+}
+
+func (p *parser) topLevel(item item) {
+	switch item.typ {
+	case itemCommentStart: // # ..
+		p.approxLine = item.line
+		p.expect(itemText)
+	case itemTableStart: // [ .. ]
+		name := p.next()
+		p.approxLine = name.line
+
+		var key Key
+		for ; name.typ != itemTableEnd && name.typ != itemEOF; name = p.next() {
+			key = append(key, p.keyString(name))
+		}
+		p.assertEqual(itemTableEnd, name.typ)
+
+		p.addContext(key, false)
+		p.setType("", tomlHash)
+		p.ordered = append(p.ordered, key)
+	case itemArrayTableStart: // [[ .. ]]
+		name := p.next()
+		p.approxLine = name.line
+
+		var key Key
+		for ; name.typ != itemArrayTableEnd && name.typ != itemEOF; name = p.next() {
+			key = append(key, p.keyString(name))
+		}
+		p.assertEqual(itemArrayTableEnd, name.typ)
+
+		p.addContext(key, true)
+		p.setType("", tomlArrayHash)
+		p.ordered = append(p.ordered, key)
+	case itemKeyStart: // key = ..
+		outerContext := p.context
+		/// Read all the key parts (e.g. 'a' and 'b' in 'a.b')
+		k := p.next()
+		p.approxLine = k.line
+		var key Key
+		for ; k.typ != itemKeyEnd && k.typ != itemEOF; k = p.next() {
+			key = append(key, p.keyString(k))
+		}
+		p.assertEqual(itemKeyEnd, k.typ)
+
+		/// The current key is the last part.
+		p.currentKey = key[len(key)-1]
+
+		/// All the other parts (if any) are the context; need to set each part
+		/// as implicit.
+		context := key[:len(key)-1]
+		for i := range context {
+			p.addImplicitContext(append(p.context, context[i:i+1]...))
+		}
+
+		/// Set value.
+		val, typ := p.value(p.next(), false)
+		p.set(p.currentKey, val, typ)
+		p.ordered = append(p.ordered, p.context.add(p.currentKey))
+
+		/// Remove the context we added (preserving any context from [tbl] lines).
+		p.context = outerContext
+		p.currentKey = ""
+	default:
+		p.bug("Unexpected type at top level: %s", item.typ)
+	}
+}
+
+// Gets a string for a key (or part of a key in a table name).
+func (p *parser) keyString(it item) string {
+	switch it.typ {
+	case itemText:
+		return it.val
+	case itemString, itemMultilineString,
+		itemRawString, itemRawMultilineString:
+		s, _ := p.value(it, false)
+		return s.(string)
+	default:
+		p.bug("Unexpected key type: %s", it.typ)
+	}
+	panic("unreachable")
+}
+
+var datetimeRepl = strings.NewReplacer(
+	"z", "Z",
+	"t", "T",
+	" ", "T")
+
+// value translates an expected value from the lexer into a Go value wrapped
+// as an empty interface.
+func (p *parser) value(it item, parentIsArray bool) (interface{}, tomlType) {
+	switch it.typ {
+	case itemString:
+		return p.replaceEscapes(it.val), p.typeOfPrimitive(it)
+	case itemMultilineString:
+		return p.replaceEscapes(stripFirstNewline(stripEscapedNewlines(it.val))), p.typeOfPrimitive(it)
+	case itemRawString:
+		return it.val, p.typeOfPrimitive(it)
+	case itemRawMultilineString:
+		return stripFirstNewline(it.val), p.typeOfPrimitive(it)
+	case itemInteger:
+		return p.valueInteger(it)
+	case itemFloat:
+		return p.valueFloat(it)
+	case itemBool:
+		switch it.val {
+		case "true":
+			return true, p.typeOfPrimitive(it)
+		case "false":
+			return false, p.typeOfPrimitive(it)
+		default:
+			p.bug("Expected boolean value, but got '%s'.", it.val)
+		}
+	case itemDatetime:
+		return p.valueDatetime(it)
+	case itemArray:
+		return p.valueArray(it)
+	case itemInlineTableStart:
+		return p.valueInlineTable(it, parentIsArray)
+	default:
+		p.bug("Unexpected value type: %s", it.typ)
+	}
+	panic("unreachable")
+}
+
+func (p *parser) valueInteger(it item) (interface{}, tomlType) {
+	if !numUnderscoresOK(it.val) {
+		p.panicf("Invalid integer %q: underscores must be surrounded by digits", it.val)
+	}
+	if numHasLeadingZero(it.val) {
+		p.panicf("Invalid integer %q: cannot have leading zeroes", it.val)
+	}
+
+	num, err := strconv.ParseInt(it.val, 0, 64)
+	if err != nil {
+		// Distinguish integer values. Normally, it'd be a bug if the lexer
+		// provides an invalid integer, but it's possible that the number is
+		// out of range of valid values (which the lexer cannot determine).
+		// So mark the former as a bug but the latter as a legitimate user
+		// error.
+		if e, ok := err.(*strconv.NumError); ok && e.Err == strconv.ErrRange {
+			p.panicf("Integer '%s' is out of the range of 64-bit signed integers.", it.val)
+		} else {
+			p.bug("Expected integer value, but got '%s'.", it.val)
+		}
+	}
+	return num, p.typeOfPrimitive(it)
+}
+
+func (p *parser) valueFloat(it item) (interface{}, tomlType) {
+	parts := strings.FieldsFunc(it.val, func(r rune) bool {
+		switch r {
+		case '.', 'e', 'E':
+			return true
+		}
+		return false
+	})
+	for _, part := range parts {
+		if !numUnderscoresOK(part) {
+			p.panicf("Invalid float %q: underscores must be surrounded by digits", it.val)
+		}
+	}
+	if len(parts) > 0 && numHasLeadingZero(parts[0]) {
+		p.panicf("Invalid float %q: cannot have leading zeroes", it.val)
+	}
+	if !numPeriodsOK(it.val) {
+		// As a special case, numbers like '123.' or '1.e2',
+		// which are valid as far as Go/strconv are concerned,
+		// must be rejected because TOML says that a fractional
+		// part consists of '.' followed by 1+ digits.
+		p.panicf("Invalid float %q: '.' must be followed by one or more digits", it.val)
+	}
+	val := strings.Replace(it.val, "_", "", -1)
+	if val == "+nan" || val == "-nan" { // Go doesn't support this, but TOML spec does.
+		val = "nan"
+	}
+	num, err := strconv.ParseFloat(val, 64)
+	if err != nil {
+		if e, ok := err.(*strconv.NumError); ok && e.Err == strconv.ErrRange {
+			p.panicf("Float '%s' is out of the range of 64-bit IEEE-754 floating-point numbers.", it.val)
+		} else {
+			p.panicf("Invalid float value: %q", it.val)
+		}
+	}
+	return num, p.typeOfPrimitive(it)
+}
+
+var dtTypes = []struct {
+	fmt  string
+	zone *time.Location
+}{
+	{time.RFC3339Nano, time.Local},
+	{"2006-01-02T15:04:05.999999999", internal.LocalDatetime},
+	{"2006-01-02", internal.LocalDate},
+	{"15:04:05.999999999", internal.LocalTime},
+}
+
+func (p *parser) valueDatetime(it item) (interface{}, tomlType) {
+	it.val = datetimeRepl.Replace(it.val)
+	var (
+		t   time.Time
+		ok  bool
+		err error
+	)
+	for _, dt := range dtTypes {
+		t, err = time.ParseInLocation(dt.fmt, it.val, dt.zone)
+		if err == nil {
+			ok = true
+			break
+		}
+	}
+	if !ok {
+		p.panicf("Invalid TOML Datetime: %q.", it.val)
+	}
+	return t, p.typeOfPrimitive(it)
+}
+
+func (p *parser) valueArray(it item) (interface{}, tomlType) {
+	p.setType(p.currentKey, tomlArray)
+
+	// p.setType(p.currentKey, typ)
+	var (
+		array []interface{}
+		types []tomlType
+	)
+	for it = p.next(); it.typ != itemArrayEnd; it = p.next() {
+		if it.typ == itemCommentStart {
+			p.expect(itemText)
+			continue
+		}
+
+		val, typ := p.value(it, true)
+		array = append(array, val)
+		types = append(types, typ)
+	}
+	return array, tomlArray
+}
+
+func (p *parser) valueInlineTable(it item, parentIsArray bool) (interface{}, tomlType) {
+	var (
+		hash         = make(map[string]interface{})
+		outerContext = p.context
+		outerKey     = p.currentKey
+	)
+
+	p.context = append(p.context, p.currentKey)
+	prevContext := p.context
+	p.currentKey = ""
+
+	p.addImplicit(p.context)
+	p.addContext(p.context, parentIsArray)
+
+	/// Loop over all table key/value pairs.
+	for it := p.next(); it.typ != itemInlineTableEnd; it = p.next() {
+		if it.typ == itemCommentStart {
+			p.expect(itemText)
+			continue
+		}
+
+		/// Read all key parts.
+		k := p.next()
+		p.approxLine = k.line
+		var key Key
+		for ; k.typ != itemKeyEnd && k.typ != itemEOF; k = p.next() {
+			key = append(key, p.keyString(k))
+		}
+		p.assertEqual(itemKeyEnd, k.typ)
+
+		/// The current key is the last part.
+		p.currentKey = key[len(key)-1]
+
+		/// All the other parts (if any) are the context; need to set each part
+		/// as implicit.
+		context := key[:len(key)-1]
+		for i := range context {
+			p.addImplicitContext(append(p.context, context[i:i+1]...))
+		}
+
+		/// Set the value.
+		val, typ := p.value(p.next(), false)
+		p.set(p.currentKey, val, typ)
+		p.ordered = append(p.ordered, p.context.add(p.currentKey))
+		hash[p.currentKey] = val
+
+		/// Restore context.
+		p.context = prevContext
+	}
+	p.context = outerContext
+	p.currentKey = outerKey
+	return hash, tomlHash
+}
+
+// numHasLeadingZero checks if this number has leading zeroes, allowing for '0',
+// +/- signs, and base prefixes.
+func numHasLeadingZero(s string) bool {
+	if len(s) > 1 && s[0] == '0' && isDigit(rune(s[1])) { // >1 to allow "0" and isDigit to allow 0x
+		return true
+	}
+	if len(s) > 2 && (s[0] == '-' || s[0] == '+') && s[1] == '0' {
+		return true
+	}
+	return false
+}
+
+// numUnderscoresOK checks whether each underscore in s is surrounded by
+// characters that are not underscores.
+func numUnderscoresOK(s string) bool {
+	switch s {
+	case "nan", "+nan", "-nan", "inf", "-inf", "+inf":
+		return true
+	}
+	accept := false
+	for _, r := range s {
+		if r == '_' {
+			if !accept {
+				return false
+			}
+		}
+
+		// isHexadecimal is a superset of all the permissable characters
+		// surrounding an underscore.
+		accept = isHexadecimal(r)
+	}
+	return accept
+}
+
+// numPeriodsOK checks whether every period in s is followed by a digit.
+func numPeriodsOK(s string) bool {
+	period := false
+	for _, r := range s {
+		if period && !isDigit(r) {
+			return false
+		}
+		period = r == '.'
+	}
+	return !period
+}
+
+// Set the current context of the parser, where the context is either a hash or
+// an array of hashes, depending on the value of the `array` parameter.
+//
+// Establishing the context also makes sure that the key isn't a duplicate, and
+// will create implicit hashes automatically.
+func (p *parser) addContext(key Key, array bool) {
+	var ok bool
+
+	// Always start at the top level and drill down for our context.
+	hashContext := p.mapping
+	keyContext := make(Key, 0)
+
+	// We only need implicit hashes for key[0:-1]
+	for _, k := range key[0 : len(key)-1] {
+		_, ok = hashContext[k]
+		keyContext = append(keyContext, k)
+
+		// No key? Make an implicit hash and move on.
+		if !ok {
+			p.addImplicit(keyContext)
+			hashContext[k] = make(map[string]interface{})
+		}
+
+		// If the hash context is actually an array of tables, then set
+		// the hash context to the last element in that array.
+		//
+		// Otherwise, it better be a table, since this MUST be a key group (by
+		// virtue of it not being the last element in a key).
+		switch t := hashContext[k].(type) {
+		case []map[string]interface{}:
+			hashContext = t[len(t)-1]
+		case map[string]interface{}:
+			hashContext = t
+		default:
+			p.panicf("Key '%s' was already created as a hash.", keyContext)
+		}
+	}
+
+	p.context = keyContext
+	if array {
+		// If this is the first element for this array, then allocate a new
+		// list of tables for it.
+		k := key[len(key)-1]
+		if _, ok := hashContext[k]; !ok {
+			hashContext[k] = make([]map[string]interface{}, 0, 4)
+		}
+
+		// Add a new table. But make sure the key hasn't already been used
+		// for something else.
+		if hash, ok := hashContext[k].([]map[string]interface{}); ok {
+			hashContext[k] = append(hash, make(map[string]interface{}))
+		} else {
+			p.panicf("Key '%s' was already created and cannot be used as an array.", keyContext)
+		}
+	} else {
+		p.setValue(key[len(key)-1], make(map[string]interface{}))
+	}
+	p.context = append(p.context, key[len(key)-1])
+}
+
+// set calls setValue and setType.
+func (p *parser) set(key string, val interface{}, typ tomlType) {
+	p.setValue(p.currentKey, val)
+	p.setType(p.currentKey, typ)
+}
+
+// setValue sets the given key to the given value in the current context.
+// It will make sure that the key hasn't already been defined, account for
+// implicit key groups.
+func (p *parser) setValue(key string, value interface{}) {
+	var (
+		tmpHash    interface{}
+		ok         bool
+		hash       = p.mapping
+		keyContext Key
+	)
+	for _, k := range p.context {
+		keyContext = append(keyContext, k)
+		if tmpHash, ok = hash[k]; !ok {
+			p.bug("Context for key '%s' has not been established.", keyContext)
+		}
+		switch t := tmpHash.(type) {
+		case []map[string]interface{}:
+			// The context is a table of hashes. Pick the most recent table
+			// defined as the current hash.
+			hash = t[len(t)-1]
+		case map[string]interface{}:
+			hash = t
+		default:
+			p.panicf("Key '%s' has already been defined.", keyContext)
+		}
+	}
+	keyContext = append(keyContext, key)
+
+	if _, ok := hash[key]; ok {
+		// Normally redefining keys isn't allowed, but the key could have been
+		// defined implicitly and it's allowed to be redefined concretely. (See
+		// the `valid/implicit-and-explicit-after.toml` in toml-test)
+		//
+		// But we have to make sure to stop marking it as an implicit. (So that
+		// another redefinition provokes an error.)
+		//
+		// Note that since it has already been defined (as a hash), we don't
+		// want to overwrite it. So our business is done.
+		if p.isArray(keyContext) {
+			p.removeImplicit(keyContext)
+			hash[key] = value
+			return
+		}
+		if p.isImplicit(keyContext) {
+			p.removeImplicit(keyContext)
+			return
+		}
+
+		// Otherwise, we have a concrete key trying to override a previous
+		// key, which is *always* wrong.
+		p.panicf("Key '%s' has already been defined.", keyContext)
+	}
+
+	hash[key] = value
+}
+
+// setType sets the type of a particular value at a given key.
+// It should be called immediately AFTER setValue.
+//
+// Note that if `key` is empty, then the type given will be applied to the
+// current context (which is either a table or an array of tables).
+func (p *parser) setType(key string, typ tomlType) {
+	keyContext := make(Key, 0, len(p.context)+1)
+	for _, k := range p.context {
+		keyContext = append(keyContext, k)
+	}
+	if len(key) > 0 { // allow type setting for hashes
+		keyContext = append(keyContext, key)
+	}
+	p.types[keyContext.String()] = typ
+}
+
+// Implicit keys need to be created when tables are implied in "a.b.c.d = 1" and
+// "[a.b.c]" (the "a", "b", and "c" hashes are never created explicitly).
+func (p *parser) addImplicit(key Key)     { p.implicits[key.String()] = true }
+func (p *parser) removeImplicit(key Key)  { p.implicits[key.String()] = false }
+func (p *parser) isImplicit(key Key) bool { return p.implicits[key.String()] }
+func (p *parser) isArray(key Key) bool    { return p.types[key.String()] == tomlArray }
+func (p *parser) addImplicitContext(key Key) {
+	p.addImplicit(key)
+	p.addContext(key, false)
+}
+
+// current returns the full key name of the current context.
+func (p *parser) current() string {
+	if len(p.currentKey) == 0 {
+		return p.context.String()
+	}
+	if len(p.context) == 0 {
+		return p.currentKey
+	}
+	return fmt.Sprintf("%s.%s", p.context, p.currentKey)
+}
+
+func stripFirstNewline(s string) string {
+	if len(s) > 0 && s[0] == '\n' {
+		return s[1:]
+	}
+	if len(s) > 1 && s[0] == '\r' && s[1] == '\n' {
+		return s[2:]
+	}
+	return s
+}
+
+// Remove newlines inside triple-quoted strings if a line ends with "\".
+func stripEscapedNewlines(s string) string {
+	split := strings.Split(s, "\n")
+	if len(split) < 1 {
+		return s
+	}
+
+	escNL := false // Keep track of the last non-blank line was escaped.
+	for i, line := range split {
+		line = strings.TrimRight(line, " \t\r")
+
+		if len(line) == 0 || line[len(line)-1] != '\\' {
+			split[i] = strings.TrimRight(split[i], "\r")
+			if !escNL && i != len(split)-1 {
+				split[i] += "\n"
+			}
+			continue
+		}
+
+		escBS := true
+		for j := len(line) - 1; j >= 0 && line[j] == '\\'; j-- {
+			escBS = !escBS
+		}
+		if escNL {
+			line = strings.TrimLeft(line, " \t\r")
+		}
+		escNL = !escBS
+
+		if escBS {
+			split[i] += "\n"
+			continue
+		}
+
+		split[i] = line[:len(line)-1] // Remove \
+		if len(split)-1 > i {
+			split[i+1] = strings.TrimLeft(split[i+1], " \t\r")
+		}
+	}
+	return strings.Join(split, "")
+}
+
+func (p *parser) replaceEscapes(str string) string {
+	var replaced []rune
+	s := []byte(str)
+	r := 0
+	for r < len(s) {
+		if s[r] != '\\' {
+			c, size := utf8.DecodeRune(s[r:])
+			r += size
+			replaced = append(replaced, c)
+			continue
+		}
+		r += 1
+		if r >= len(s) {
+			p.bug("Escape sequence at end of string.")
+			return ""
+		}
+		switch s[r] {
+		default:
+			p.bug("Expected valid escape code after \\, but got %q.", s[r])
+			return ""
+		case ' ', '\t':
+			p.panicf("invalid escape: '\\%c'", s[r])
+			return ""
+		case 'b':
+			replaced = append(replaced, rune(0x0008))
+			r += 1
+		case 't':
+			replaced = append(replaced, rune(0x0009))
+			r += 1
+		case 'n':
+			replaced = append(replaced, rune(0x000A))
+			r += 1
+		case 'f':
+			replaced = append(replaced, rune(0x000C))
+			r += 1
+		case 'r':
+			replaced = append(replaced, rune(0x000D))
+			r += 1
+		case '"':
+			replaced = append(replaced, rune(0x0022))
+			r += 1
+		case '\\':
+			replaced = append(replaced, rune(0x005C))
+			r += 1
+		case 'u':
+			// At this point, we know we have a Unicode escape of the form
+			// `uXXXX` at [r, r+5). (Because the lexer guarantees this
+			// for us.)
+			escaped := p.asciiEscapeToUnicode(s[r+1 : r+5])
+			replaced = append(replaced, escaped)
+			r += 5
+		case 'U':
+			// At this point, we know we have a Unicode escape of the form
+			// `uXXXX` at [r, r+9). (Because the lexer guarantees this
+			// for us.)
+			escaped := p.asciiEscapeToUnicode(s[r+1 : r+9])
+			replaced = append(replaced, escaped)
+			r += 9
+		}
+	}
+	return string(replaced)
+}
+
+func (p *parser) asciiEscapeToUnicode(bs []byte) rune {
+	s := string(bs)
+	hex, err := strconv.ParseUint(strings.ToLower(s), 16, 32)
+	if err != nil {
+		p.bug("Could not parse '%s' as a hexadecimal number, but the "+
+			"lexer claims it's OK: %s", s, err)
+	}
+	if !utf8.ValidRune(rune(hex)) {
+		p.panicf("Escaped character '\\u%s' is not valid UTF-8.", s)
+	}
+	return rune(hex)
+}

vendor/github.com/BurntSushi/toml/type_check.go

@@ -0,0 +1,70 @@
+package toml
+
+// tomlType represents any Go type that corresponds to a TOML type.
+// While the first draft of the TOML spec has a simplistic type system that
+// probably doesn't need this level of sophistication, we seem to be militating
+// toward adding real composite types.
+type tomlType interface {
+	typeString() string
+}
+
+// typeEqual accepts any two types and returns true if they are equal.
+func typeEqual(t1, t2 tomlType) bool {
+	if t1 == nil || t2 == nil {
+		return false
+	}
+	return t1.typeString() == t2.typeString()
+}
+
+func typeIsHash(t tomlType) bool {
+	return typeEqual(t, tomlHash) || typeEqual(t, tomlArrayHash)
+}
+
+type tomlBaseType string
+
+func (btype tomlBaseType) typeString() string {
+	return string(btype)
+}
+
+func (btype tomlBaseType) String() string {
+	return btype.typeString()
+}
+
+var (
+	tomlInteger   tomlBaseType = "Integer"
+	tomlFloat     tomlBaseType = "Float"
+	tomlDatetime  tomlBaseType = "Datetime"
+	tomlString    tomlBaseType = "String"
+	tomlBool      tomlBaseType = "Bool"
+	tomlArray     tomlBaseType = "Array"
+	tomlHash      tomlBaseType = "Hash"
+	tomlArrayHash tomlBaseType = "ArrayHash"
+)
+
+// typeOfPrimitive returns a tomlType of any primitive value in TOML.
+// Primitive values are: Integer, Float, Datetime, String and Bool.
+//
+// Passing a lexer item other than the following will cause a BUG message
+// to occur: itemString, itemBool, itemInteger, itemFloat, itemDatetime.
+func (p *parser) typeOfPrimitive(lexItem item) tomlType {
+	switch lexItem.typ {
+	case itemInteger:
+		return tomlInteger
+	case itemFloat:
+		return tomlFloat
+	case itemDatetime:
+		return tomlDatetime
+	case itemString:
+		return tomlString
+	case itemMultilineString:
+		return tomlString
+	case itemRawString:
+		return tomlString
+	case itemRawMultilineString:
+		return tomlString
+	case itemBool:
+		return tomlBool
+	}
+	p.bug("Cannot infer primitive type of lex item '%s'.", lexItem)
+	panic("unreachable")
+}

vendor/github.com/BurntSushi/toml/type_fields.go

@@ -0,0 +1,242 @@
+package toml
+
+// Struct field handling is adapted from code in encoding/json:
+//
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the Go distribution.
+
+import (
+	"reflect"
+	"sort"
+	"sync"
+)
+
+// A field represents a single field found in a struct.
+type field struct {
+	name  string       // the name of the field (`toml` tag included)
+	tag   bool         // whether field has a `toml` tag
+	index []int        // represents the depth of an anonymous field
+	typ   reflect.Type // the type of the field
+}
+
+// byName sorts field by name, breaking ties with depth,
+// then breaking ties with "name came from toml tag", then
+// breaking ties with index sequence.
+type byName []field
+
+func (x byName) Len() int { return len(x) }
+
+func (x byName) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
+
+func (x byName) Less(i, j int) bool {
+	if x[i].name != x[j].name {
+		return x[i].name < x[j].name
+	}
+	if len(x[i].index) != len(x[j].index) {
+		return len(x[i].index) < len(x[j].index)
+	}
+	if x[i].tag != x[j].tag {
+		return x[i].tag
+	}
+	return byIndex(x).Less(i, j)
+}
+
+// byIndex sorts field by index sequence.
+type byIndex []field
+
+func (x byIndex) Len() int { return len(x) }
+
+func (x byIndex) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
+
+func (x byIndex) Less(i, j int) bool {
+	for k, xik := range x[i].index {
+		if k >= len(x[j].index) {
+			return false
+		}
+		if xik != x[j].index[k] {
+			return xik < x[j].index[k]
+		}
+	}
+	return len(x[i].index) < len(x[j].index)
+}
+
+// typeFields returns a list of fields that TOML should recognize for the given
+// type. The algorithm is breadth-first search over the set of structs to
+// include - the top struct and then any reachable anonymous structs.
+func typeFields(t reflect.Type) []field {
+	// Anonymous fields to explore at the current level and the next.
+	current := []field{}
+	next := []field{{typ: t}}
+
+	// Count of queued names for current level and the next.
+	count := map[reflect.Type]int{}
+	nextCount := map[reflect.Type]int{}
+
+	// Types already visited at an earlier level.
+	visited := map[reflect.Type]bool{}
+
+	// Fields found.
+	var fields []field
+
+	for len(next) > 0 {
+		current, next = next, current[:0]
+		count, nextCount = nextCount, map[reflect.Type]int{}
+
+		for _, f := range current {
+			if visited[f.typ] {
+				continue
+			}
+			visited[f.typ] = true
+
+			// Scan f.typ for fields to include.
+			for i := 0; i < f.typ.NumField(); i++ {
+				sf := f.typ.Field(i)
+				if sf.PkgPath != "" && !sf.Anonymous { // unexported
+					continue
+				}
+				opts := getOptions(sf.Tag)
+				if opts.skip {
+					continue
+				}
+				index := make([]int, len(f.index)+1)
+				copy(index, f.index)
+				index[len(f.index)] = i
+
+				ft := sf.Type
+				if ft.Name() == "" && ft.Kind() == reflect.Ptr {
+					// Follow pointer.
+					ft = ft.Elem()
+				}
+
+				// Record found field and index sequence.
+				if opts.name != "" || !sf.Anonymous || ft.Kind() != reflect.Struct {
+					tagged := opts.name != ""
+					name := opts.name
+					if name == "" {
+						name = sf.Name
+					}
+					fields = append(fields, field{name, tagged, index, ft})
+					if count[f.typ] > 1 {
+						// If there were multiple instances, add a second,
+						// so that the annihilation code will see a duplicate.
+						// It only cares about the distinction between 1 or 2,
+						// so don't bother generating any more copies.
+						fields = append(fields, fields[len(fields)-1])
+					}
+					continue
+				}
+
+				// Record new anonymous struct to explore in next round.
+				nextCount[ft]++
+				if nextCount[ft] == 1 {
+					f := field{name: ft.Name(), index: index, typ: ft}
+					next = append(next, f)
+				}
+			}
+		}
+	}
+
+	sort.Sort(byName(fields))
+
+	// Delete all fields that are hidden by the Go rules for embedded fields,
+	// except that fields with TOML tags are promoted.
+
+	// The fields are sorted in primary order of name, secondary order
+	// of field index length. Loop over names; for each name, delete
+	// hidden fields by choosing the one dominant field that survives.
+	out := fields[:0]
+	for advance, i := 0, 0; i < len(fields); i += advance {
+		// One iteration per name.
+		// Find the sequence of fields with the name of this first field.
+		fi := fields[i]
+		name := fi.name
+		for advance = 1; i+advance < len(fields); advance++ {
+			fj := fields[i+advance]
+			if fj.name != name {
+				break
+			}
+		}
+		if advance == 1 { // Only one field with this name
+			out = append(out, fi)
+			continue
+		}
+		dominant, ok := dominantField(fields[i : i+advance])
+		if ok {
+			out = append(out, dominant)
+		}
+	}
+
+	fields = out
+	sort.Sort(byIndex(fields))
+
+	return fields
+}
+
+// dominantField looks through the fields, all of which are known to
+// have the same name, to find the single field that dominates the
+// others using Go's embedding rules, modified by the presence of
+// TOML tags. If there are multiple top-level fields, the boolean
+// will be false: This condition is an error in Go and we skip all
+// the fields.
+func dominantField(fields []field) (field, bool) {
+	// The fields are sorted in increasing index-length order. The winner
+	// must therefore be one with the shortest index length. Drop all
+	// longer entries, which is easy: just truncate the slice.
+	length := len(fields[0].index)
+	tagged := -1 // Index of first tagged field.
+	for i, f := range fields {
+		if len(f.index) > length {
+			fields = fields[:i]
+			break
+		}
+		if f.tag {
+			if tagged >= 0 {
+				// Multiple tagged fields at the same level: conflict.
+				// Return no field.
+				return field{}, false
+			}
+			tagged = i
+		}
+	}
+	if tagged >= 0 {
+		return fields[tagged], true
+	}
+	// All remaining fields have the same length. If there's more than one,
+	// we have a conflict (two fields named "X" at the same level) and we
+	// return no field.
+	if len(fields) > 1 {
+		return field{}, false
+	}
+	return fields[0], true
+}
+
+var fieldCache struct {
+	sync.RWMutex
+	m map[reflect.Type][]field
+}
+
+// cachedTypeFields is like typeFields but uses a cache to avoid repeated work.
+func cachedTypeFields(t reflect.Type) []field {
+	fieldCache.RLock()
+	f := fieldCache.m[t]
+	fieldCache.RUnlock()
+	if f != nil {
+		return f
+	}
+
+	// Compute fields without lock.
+	// Might duplicate effort but won't hold other computations back.
+	f = typeFields(t)
+	if f == nil {
+		f = []field{}
+	}
+
+	fieldCache.Lock()
+	if fieldCache.m == nil {
+		fieldCache.m = map[reflect.Type][]field{}
+	}
+	fieldCache.m[t] = f
+	fieldCache.Unlock()
+	return f
+}

vendor/golang.org/x/lint/LICENSE → vendor/golang.org/x/exp/typeparams/LICENSE

@@ -1,4 +1,4 @@
-Copyright (c) 2013 The Go Authors. All rights reserved.
+Copyright (c) 2009 The Go Authors. All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are

vendor/golang.org/x/exp/typeparams/common.go

@@ -0,0 +1,186 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package typeparams contains common utilities for writing tools that interact
+// with generic Go code, as introduced with Go 1.18.
+//
+// THIS PACKAGE IS CURRENTLY EXPERIMENTAL AND MAY CHANGE. While the API is
+// being tested, we may find the need for improvement. This caveat will be
+// removed shortly.
+//
+// Many of the types and functions in this package are proxies for the new APIs
+// introduced in the standard library with Go 1.18. For example, the
+// typeparams.Union type is an alias for go/types.Union, and the ForTypeSpec
+// function returns the value of the go/ast.TypeSpec.TypeParams field. At Go
+// versions older than 1.18 these helpers are implemented as stubs, allowing
+// users of this package to write code that handles generic constructs inline,
+// even if the Go version being used to compile does not support generics.
+//
+// Additionally, this package contains common utilities for working with the
+// new generic constructs, to supplement the standard library APIs. Notably,
+// the NormalTerms API computes a minimal representation of the structural
+// restrictions on a type parameter. In the future, these supplemental APIs may
+// be available in the standard library..
+package typeparams
+
+import (
+	"go/ast"
+	"go/token"
+	"go/types"
+)
+
+// Enabled reports whether type parameters are enabled in the current build
+// environment.
+func Enabled() bool {
+	return enabled
+}
+
+// UnpackIndexExpr extracts data from AST nodes that represent index
+// expressions.
+//
+// For an ast.IndexExpr, the resulting indices slice will contain exactly one
+// index expression. For an ast.IndexListExpr (go1.18+), it may have a variable
+// number of index expressions.
+//
+// For nodes that don't represent index expressions, the first return value of
+// UnpackIndexExpr will be nil.
+func UnpackIndexExpr(n ast.Node) (x ast.Expr, lbrack token.Pos, indices []ast.Expr, rbrack token.Pos) {
+	switch e := n.(type) {
+	case *ast.IndexExpr:
+		return e.X, e.Lbrack, []ast.Expr{e.Index}, e.Rbrack
+	case *IndexListExpr:
+		return e.X, e.Lbrack, e.Indices, e.Rbrack
+	}
+	return nil, token.NoPos, nil, token.NoPos
+}
+
+// PackIndexExpr returns an *ast.IndexExpr or *ast.IndexListExpr, depending on
+// the cardinality of indices. Calling PackIndexExpr with len(indices) == 0
+// will panic.
+func PackIndexExpr(x ast.Expr, lbrack token.Pos, indices []ast.Expr, rbrack token.Pos) ast.Expr {
+	switch len(indices) {
+	case 0:
+		panic("empty indices")
+	case 1:
+		return &ast.IndexExpr{
+			X:      x,
+			Lbrack: lbrack,
+			Index:  indices[0],
+			Rbrack: rbrack,
+		}
+	default:
+		return &IndexListExpr{
+			X:       x,
+			Lbrack:  lbrack,
+			Indices: indices,
+			Rbrack:  rbrack,
+		}
+	}
+}
+
+// IsTypeParam reports whether t is a type parameter.
+func IsTypeParam(t types.Type) bool {
+	_, ok := t.(*TypeParam)
+	return ok
+}
+
+// OriginMethod returns the origin method associated with the method fn. For
+// methods on a non-generic receiver base type, this is just fn. However, for
+// methods with a generic receiver, OriginMethod returns the corresponding
+// method in the method set of the origin type.
+//
+// As a special case, if fn is not a method (has no receiver), OriginMethod
+// returns fn.
+func OriginMethod(fn *types.Func) *types.Func {
+	recv := fn.Type().(*types.Signature).Recv()
+	if recv == nil {
+		return fn
+	}
+	base := recv.Type()
+	p, isPtr := base.(*types.Pointer)
+	if isPtr {
+		base = p.Elem()
+	}
+	named, isNamed := base.(*types.Named)
+	if !isNamed {
+		// Receiver is a *types.Interface.
+		return fn
+	}
+	if ForNamed(named).Len() == 0 {
+		// Receiver base has no type parameters, so we can avoid the lookup below.
+		return fn
+	}
+	orig := NamedTypeOrigin(named)
+	gfn, _, _ := types.LookupFieldOrMethod(orig, true, fn.Pkg(), fn.Name())
+	return gfn.(*types.Func)
+}
+
+// GenericAssignableTo is a generalization of types.AssignableTo that
+// implements the following rule for uninstantiated generic types:
+//
+// If V and T are generic named types, then V is considered assignable to T if,
+// for every possible instantation of V[A_1, ..., A_N], the instantiation
+// T[A_1, ..., A_N] is valid and V[A_1, ..., A_N] implements T[A_1, ..., A_N].
+//
+// If T has structural constraints, they must be satisfied by V.
+//
+// For example, consider the following type declarations:
+//
+//  type Interface[T any] interface {
+//  	Accept(T)
+//  }
+//
+//  type Container[T any] struct {
+//  	Element T
+//  }
+//
+//  func (c Container[T]) Accept(t T) { c.Element = t }
+//
+// In this case, GenericAssignableTo reports that instantiations of Container
+// are assignable to the corresponding instantiation of Interface.
+func GenericAssignableTo(ctxt *Context, V, T types.Type) bool {
+	// If V and T are not both named, or do not have matching non-empty type
+	// parameter lists, fall back on types.AssignableTo.
+
+	VN, Vnamed := V.(*types.Named)
+	TN, Tnamed := T.(*types.Named)
+	if !Vnamed || !Tnamed {
+		return types.AssignableTo(V, T)
+	}
+
+	vtparams := ForNamed(VN)
+	ttparams := ForNamed(TN)
+	if vtparams.Len() == 0 || vtparams.Len() != ttparams.Len() || NamedTypeArgs(VN).Len() != 0 || NamedTypeArgs(TN).Len() != 0 {
+		return types.AssignableTo(V, T)
+	}
+
+	// V and T have the same (non-zero) number of type params. Instantiate both
+	// with the type parameters of V. This must always succeed for V, and will
+	// succeed for T if and only if the type set of each type parameter of V is a
+	// subset of the type set of the corresponding type parameter of T, meaning
+	// that every instantiation of V corresponds to a valid instantiation of T.
+
+	// Minor optimization: ensure we share a context across the two
+	// instantiations below.
+	if ctxt == nil {
+		ctxt = NewContext()
+	}
+
+	var targs []types.Type
+	for i := 0; i < vtparams.Len(); i++ {
+		targs = append(targs, vtparams.At(i))
+	}
+
+	vinst, err := Instantiate(ctxt, V, targs, true)
+	if err != nil {
+		panic("type parameters should satisfy their own constraints")
+	}
+
+	tinst, err := Instantiate(ctxt, T, targs, true)
+	if err != nil {
+		return false
+	}
+
+	return types.AssignableTo(vinst, tinst)
+}

vendor/golang.org/x/exp/typeparams/normalize.go

@@ -0,0 +1,200 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package typeparams
+
+import (
+	"errors"
+	"fmt"
+	"go/types"
+	"os"
+	"strings"
+)
+
+const debug = false
+
+// ErrEmptyTypeSet is returned if a type set computation results in a type set
+// with no types.
+var ErrEmptyTypeSet = errors.New("empty type set")
+
+// NormalTerms returns a slice of terms representing the normalized structural
+// type restrictions of a type, if any.
+//
+// For all types other than *types.TypeParam, *types.Interface, and
+// *types.Union, this is just a single term with Tilde() == false and
+// Type() == typ. For *types.TypeParam, *types.Interface, and *types.Union, see
+// below.
+//
+// Structural type restrictions of a type parameter are created via
+// non-interface types embedded in its constraint interface (directly, or via a
+// chain of interface embeddings). For example, in the declaration type
+// T[P interface{~int; m()}] int the structural restriction of the type
+// parameter P is ~int.
+//
+// With interface embedding and unions, the specification of structural type
+// restrictions may be arbitrarily complex. For example, consider the
+// following:
+//
+//  type A interface{ ~string|~[]byte }
+//
+//  type B interface{ int|string }
+//
+//  type C interface { ~string|~int }
+//
+//  type T[P interface{ A|B; C }] int
+//
+// In this example, the structural type restriction of P is ~string|int: A|B
+// expands to ~string|~[]byte|int|string, which reduces to ~string|~[]byte|int,
+// which when intersected with C (~string|~int) yields ~string|int.
+//
+// NormalTerms computes these expansions and reductions, producing a
+// "normalized" form of the embeddings. A structural restriction is normalized
+// if it is a single union containing no interface terms, and is minimal in the
+// sense that removing any term changes the set of types satisfying the
+// constraint. It is left as a proof for the reader that, modulo sorting, there
+// is exactly one such normalized form.
+//
+// Because the minimal representation always takes this form, NormalTerms
+// returns a slice of tilde terms corresponding to the terms of the union in
+// the normalized structural restriction. An error is returned if the type is
+// invalid, exceeds complexity bounds, or has an empty type set. In the latter
+// case, NormalTerms returns ErrEmptyTypeSet.
+//
+// NormalTerms makes no guarantees about the order of terms, except that it
+// is deterministic.
+func NormalTerms(typ types.Type) ([]*Term, error) {
+	if tparam, ok := typ.(*TypeParam); ok {
+		constraint := tparam.Constraint()
+		if constraint == nil {
+			return nil, fmt.Errorf("%s has nil constraint", tparam)
+		}
+		iface, _ := constraint.Underlying().(*types.Interface)
+		if iface == nil {
+			return nil, fmt.Errorf("constraint is %T, not *types.Interface", constraint.Underlying())
+		}
+		typ = iface
+	}
+	tset, err := computeTermSetInternal(typ, make(map[types.Type]*termSet), 0)
+	if err != nil {
+		return nil, err
+	}
+	if tset.terms.isEmpty() {
+		return nil, ErrEmptyTypeSet
+	}
+	if tset.terms.isAll() {
+		return nil, nil
+	}
+	var terms []*Term
+	for _, term := range tset.terms {
+		terms = append(terms, NewTerm(term.tilde, term.typ))
+	}
+	return terms, nil
+}
+
+// A termSet holds the normalized set of terms for a given type.
+//
+// The name termSet is intentionally distinct from 'type set': a type set is
+// all types that implement a type (and includes method restrictions), whereas
+// a term set just represents the structural restrictions on a type.
+type termSet struct {
+	complete bool
+	terms    termlist
+}
+
+func indentf(depth int, format string, args ...interface{}) {
+	fmt.Fprintf(os.Stderr, strings.Repeat(".", depth)+format+"\n", args...)
+}
+
+func computeTermSetInternal(t types.Type, seen map[types.Type]*termSet, depth int) (res *termSet, err error) {
+	if t == nil {
+		panic("nil type")
+	}
+
+	if debug {
+		indentf(depth, "%s", t.String())
+		defer func() {
+			if err != nil {
+				indentf(depth, "=> %s", err)
+			} else {
+				indentf(depth, "=> %s", res.terms.String())
+			}
+		}()
+	}
+
+	const maxTermCount = 100
+	if tset, ok := seen[t]; ok {
+		if !tset.complete {
+			return nil, fmt.Errorf("cycle detected in the declaration of %s", t)
+		}
+		return tset, nil
+	}
+
+	// Mark the current type as seen to avoid infinite recursion.
+	tset := new(termSet)
+	defer func() {
+		tset.complete = true
+	}()
+	seen[t] = tset
+
+	switch u := t.Underlying().(type) {
+	case *types.Interface:
+		// The term set of an interface is the intersection of the term sets of its
+		// embedded types.
+		tset.terms = allTermlist
+		for i := 0; i < u.NumEmbeddeds(); i++ {
+			embedded := u.EmbeddedType(i)
+			if _, ok := embedded.Underlying().(*TypeParam); ok {
+				return nil, fmt.Errorf("invalid embedded type %T", embedded)
+			}
+			tset2, err := computeTermSetInternal(embedded, seen, depth+1)
+			if err != nil {
+				return nil, err
+			}
+			tset.terms = tset.terms.intersect(tset2.terms)
+		}
+	case *Union:
+		// The term set of a union is the union of term sets of its terms.
+		tset.terms = nil
+		for i := 0; i < u.Len(); i++ {
+			t := u.Term(i)
+			var terms termlist
+			switch t.Type().Underlying().(type) {
+			case *types.Interface:
+				tset2, err := computeTermSetInternal(t.Type(), seen, depth+1)
+				if err != nil {
+					return nil, err
+				}
+				terms = tset2.terms
+			case *TypeParam, *Union:
+				// A stand-alone type parameter or union is not permitted as union
+				// term.
+				return nil, fmt.Errorf("invalid union term %T", t)
+			default:
+				if t.Type() == types.Typ[types.Invalid] {
+					continue
+				}
+				terms = termlist{{t.Tilde(), t.Type()}}
+			}
+			tset.terms = tset.terms.union(terms)
+			if len(tset.terms) > maxTermCount {
+				return nil, fmt.Errorf("exceeded max term count %d", maxTermCount)
+			}
+		}
+	case *TypeParam:
+		panic("unreachable")
+	default:
+		// For all other types, the term set is just a single non-tilde term
+		// holding the type itself.
+		if u != types.Typ[types.Invalid] {
+			tset.terms = termlist{{false, t}}
+		}
+	}
+	return tset, nil
+}
+
+// under is a facade for the go/types internal function of the same name. It is
+// used by typeterm.go.
+func under(t types.Type) types.Type {
+	return t.Underlying()
+}

vendor/golang.org/x/exp/typeparams/termlist.go

@@ -0,0 +1,172 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Code generated by copytermlist.go DO NOT EDIT.
+
+package typeparams
+
+import (
+	"bytes"
+	"go/types"
+)
+
+// A termlist represents the type set represented by the union
+// t1 ∪ y2 ∪ ... tn of the type sets of the terms t1 to tn.
+// A termlist is in normal form if all terms are disjoint.
+// termlist operations don't require the operands to be in
+// normal form.
+type termlist []*term
+
+// allTermlist represents the set of all types.
+// It is in normal form.
+var allTermlist = termlist{new(term)}
+
+// String prints the termlist exactly (without normalization).
+func (xl termlist) String() string {
+	if len(xl) == 0 {
+		return "∅"
+	}
+	var buf bytes.Buffer
+	for i, x := range xl {
+		if i > 0 {
+			buf.WriteString(" ∪ ")
+		}
+		buf.WriteString(x.String())
+	}
+	return buf.String()
+}
+
+// isEmpty reports whether the termlist xl represents the empty set of types.
+func (xl termlist) isEmpty() bool {
+	// If there's a non-nil term, the entire list is not empty.
+	// If the termlist is in normal form, this requires at most
+	// one iteration.
+	for _, x := range xl {
+		if x != nil {
+			return false
+		}
+	}
+	return true
+}
+
+// isAll reports whether the termlist xl represents the set of all types.
+func (xl termlist) isAll() bool {
+	// If there's a 𝓤 term, the entire list is 𝓤.
+	// If the termlist is in normal form, this requires at most
+	// one iteration.
+	for _, x := range xl {
+		if x != nil && x.typ == nil {
+			return true
+		}
+	}
+	return false
+}
+
+// norm returns the normal form of xl.
+func (xl termlist) norm() termlist {
+	// Quadratic algorithm, but good enough for now.
+	// TODO(gri) fix asymptotic performance
+	used := make([]bool, len(xl))
+	var rl termlist
+	for i, xi := range xl {
+		if xi == nil || used[i] {
+			continue
+		}
+		for j := i + 1; j < len(xl); j++ {
+			xj := xl[j]
+			if xj == nil || used[j] {
+				continue
+			}
+			if u1, u2 := xi.union(xj); u2 == nil {
+				// If we encounter a 𝓤 term, the entire list is 𝓤.
+				// Exit early.
+				// (Note that this is not just an optimization;
+				// if we continue, we may end up with a 𝓤 term
+				// and other terms and the result would not be
+				// in normal form.)
+				if u1.typ == nil {
+					return allTermlist
+				}
+				xi = u1
+				used[j] = true // xj is now unioned into xi - ignore it in future iterations
+			}
+		}
+		rl = append(rl, xi)
+	}
+	return rl
+}
+
+// If the type set represented by xl is specified by a single (non-𝓤) term,
+// singleType returns that type. Otherwise it returns nil.
+func (xl termlist) singleType() types.Type {
+	if nl := xl.norm(); len(nl) == 1 {
+		return nl[0].typ // if nl.isAll() then typ is nil, which is ok
+	}
+	return nil
+}
+
+// union returns the union xl ∪ yl.
+func (xl termlist) union(yl termlist) termlist {
+	return append(xl, yl...).norm()
+}
+
+// intersect returns the intersection xl ∩ yl.
+func (xl termlist) intersect(yl termlist) termlist {
+	if xl.isEmpty() || yl.isEmpty() {
+		return nil
+	}
+
+	// Quadratic algorithm, but good enough for now.
+	// TODO(gri) fix asymptotic performance
+	var rl termlist
+	for _, x := range xl {
+		for _, y := range yl {
+			if r := x.intersect(y); r != nil {
+				rl = append(rl, r)
+			}
+		}
+	}
+	return rl.norm()
+}
+
+// equal reports whether xl and yl represent the same type set.
+func (xl termlist) equal(yl termlist) bool {
+	// TODO(gri) this should be more efficient
+	return xl.subsetOf(yl) && yl.subsetOf(xl)
+}
+
+// includes reports whether t ∈ xl.
+func (xl termlist) includes(t types.Type) bool {
+	for _, x := range xl {
+		if x.includes(t) {
+			return true
+		}
+	}
+	return false
+}
+
+// supersetOf reports whether y ⊆ xl.
+func (xl termlist) supersetOf(y *term) bool {
+	for _, x := range xl {
+		if y.subsetOf(x) {
+			return true
+		}
+	}
+	return false
+}
+
+// subsetOf reports whether xl ⊆ yl.
+func (xl termlist) subsetOf(yl termlist) bool {
+	if yl.isEmpty() {
+		return xl.isEmpty()
+	}
+
+	// each term x of xl must be a subset of yl
+	for _, x := range xl {
+		if !yl.supersetOf(x) {
+			return false // x is not a subset yl
+		}
+	}
+	return true
+}

vendor/golang.org/x/exp/typeparams/typeparams_go117.go

@@ -0,0 +1,202 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build !go1.18
+// +build !go1.18
+
+package typeparams
+
+import (
+	"go/ast"
+	"go/token"
+	"go/types"
+)
+
+const enabled = false
+
+func unsupported() {
+	panic("type parameters are unsupported at this go version")
+}
+
+// IndexListExpr is a placeholder type, as type parameters are not supported at
+// this Go version. Its methods panic on use.
+type IndexListExpr struct {
+	ast.Expr
+	X       ast.Expr   // expression
+	Lbrack  token.Pos  // position of "["
+	Indices []ast.Expr // index expressions
+	Rbrack  token.Pos  // position of "]"
+}
+
+func (*IndexListExpr) Pos() token.Pos { unsupported(); return token.NoPos }
+func (*IndexListExpr) End() token.Pos { unsupported(); return token.NoPos }
+
+// ForTypeSpec returns an empty field list, as type parameters on not supported
+// at this Go version.
+func ForTypeSpec(*ast.TypeSpec) *ast.FieldList {
+	return nil
+}
+
+// ForFuncType returns an empty field list, as type parameters are not
+// supported at this Go version.
+func ForFuncType(*ast.FuncType) *ast.FieldList {
+	return nil
+}
+
+// TypeParam is a placeholder type, as type parameters are not supported at
+// this Go version. Its methods panic on use.
+type TypeParam struct{ types.Type }
+
+func (*TypeParam) String() string           { unsupported(); return "" }
+func (*TypeParam) Underlying() types.Type   { unsupported(); return nil }
+func (*TypeParam) Index() int               { unsupported(); return 0 }
+func (*TypeParam) Constraint() types.Type   { unsupported(); return nil }
+func (*TypeParam) SetConstraint(types.Type) { unsupported() }
+func (*TypeParam) Obj() *types.TypeName     { unsupported(); return nil }
+
+// TypeParamList is a placeholder for an empty type parameter list.
+type TypeParamList struct{}
+
+func (*TypeParamList) Len() int          { return 0 }
+func (*TypeParamList) At(int) *TypeParam { unsupported(); return nil }
+
+// TypeList is a placeholder for an empty type list.
+type TypeList struct{}
+
+func (*TypeList) Len() int          { return 0 }
+func (*TypeList) At(int) types.Type { unsupported(); return nil }
+
+// NewTypeParam is unsupported at this Go version, and panics.
+func NewTypeParam(name *types.TypeName, constraint types.Type) *TypeParam {
+	unsupported()
+	return nil
+}
+
+// NewSignatureType calls types.NewSignature, panicking if recvTypeParams or
+// typeParams is non-empty.
+func NewSignatureType(recv *types.Var, recvTypeParams, typeParams []*TypeParam, params, results *types.Tuple, variadic bool) *types.Signature {
+	if len(recvTypeParams) != 0 || len(typeParams) != 0 {
+		unsupported()
+	}
+	return types.NewSignature(recv, params, results, variadic)
+}
+
+// ForSignature returns an empty slice.
+func ForSignature(*types.Signature) *TypeParamList {
+	return nil
+}
+
+// RecvTypeParams returns a nil slice.
+func RecvTypeParams(sig *types.Signature) *TypeParamList {
+	return nil
+}
+
+// IsComparable returns false, as no interfaces are type-restricted at this Go
+// version.
+func IsComparable(*types.Interface) bool {
+	return false
+}
+
+// IsMethodSet returns true, as no interfaces are type-restricted at this Go
+// version.
+func IsMethodSet(*types.Interface) bool {
+	return true
+}
+
+// IsImplicit returns false, as no interfaces are implicit at this Go version.
+func IsImplicit(*types.Interface) bool {
+	return false
+}
+
+// MarkImplicit does nothing, because this Go version does not have implicit
+// interfaces.
+func MarkImplicit(*types.Interface) {}
+
+// ForNamed returns an empty type parameter list, as type parameters are not
+// supported at this Go version.
+func ForNamed(*types.Named) *TypeParamList {
+	return nil
+}
+
+// SetForNamed panics if tparams is non-empty.
+func SetForNamed(_ *types.Named, tparams []*TypeParam) {
+	if len(tparams) > 0 {
+		unsupported()
+	}
+}
+
+// NamedTypeArgs returns nil.
+func NamedTypeArgs(*types.Named) *TypeList {
+	return nil
+}
+
+// NamedTypeOrigin is the identity method at this Go version.
+func NamedTypeOrigin(named *types.Named) types.Type {
+	return named
+}
+
+// Term holds information about a structural type restriction.
+type Term struct {
+	tilde bool
+	typ   types.Type
+}
+
+func (m *Term) Tilde() bool      { return m.tilde }
+func (m *Term) Type() types.Type { return m.typ }
+func (m *Term) String() string {
+	pre := ""
+	if m.tilde {
+		pre = "~"
+	}
+	return pre + m.typ.String()
+}
+
+// NewTerm creates a new placeholder term type.
+func NewTerm(tilde bool, typ types.Type) *Term {
+	return &Term{tilde, typ}
+}
+
+// Union is a placeholder type, as type parameters are not supported at this Go
+// version. Its methods panic on use.
+type Union struct{ types.Type }
+
+func (*Union) String() string         { unsupported(); return "" }
+func (*Union) Underlying() types.Type { unsupported(); return nil }
+func (*Union) Len() int               { return 0 }
+func (*Union) Term(i int) *Term       { unsupported(); return nil }
+
+// NewUnion is unsupported at this Go version, and panics.
+func NewUnion(terms []*Term) *Union {
+	unsupported()
+	return nil
+}
+
+// InitInstances is a noop at this Go version.
+func InitInstances(*types.Info) {}
+
+// Instance is a placeholder type, as type parameters are not supported at this
+// Go version.
+type Instance struct {
+	TypeArgs *TypeList
+	Type     types.Type
+}
+
+// GetInstances returns a nil map, as type parameters are not supported at this
+// Go version.
+func GetInstances(info *types.Info) map[*ast.Ident]Instance { return nil }
+
+// Context is a placeholder type, as type parameters are not supported at
+// this Go version.
+type Context struct{}
+
+// NewContext returns a placeholder Context instance.
+func NewContext() *Context {
+	return &Context{}
+}
+
+// Instantiate is unsupported on this Go version, and panics.
+func Instantiate(ctxt *Context, typ types.Type, targs []types.Type, validate bool) (types.Type, error) {
+	unsupported()
+	return nil, nil
+}

vendor/golang.org/x/exp/typeparams/typeparams_go118.go

@@ -0,0 +1,148 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build go1.18
+// +build go1.18
+
+package typeparams
+
+import (
+	"go/ast"
+	"go/types"
+)
+
+const enabled = true
+
+// IndexListExpr is an alias for ast.IndexListExpr.
+type IndexListExpr = ast.IndexListExpr
+
+// ForTypeSpec returns n.TypeParams.
+func ForTypeSpec(n *ast.TypeSpec) *ast.FieldList {
+	if n == nil {
+		return nil
+	}
+	return n.TypeParams
+}
+
+// ForFuncType returns n.TypeParams.
+func ForFuncType(n *ast.FuncType) *ast.FieldList {
+	if n == nil {
+		return nil
+	}
+	return n.TypeParams
+}
+
+// TypeParam is an alias for types.TypeParam
+type TypeParam = types.TypeParam
+
+// TypeParamList is an alias for types.TypeParamList
+type TypeParamList = types.TypeParamList
+
+// TypeList is an alias for types.TypeList
+type TypeList = types.TypeList
+
+// NewTypeParam calls types.NewTypeParam.
+func NewTypeParam(name *types.TypeName, constraint types.Type) *TypeParam {
+	return types.NewTypeParam(name, constraint)
+}
+
+// NewSignatureType calls types.NewSignatureType.
+func NewSignatureType(recv *types.Var, recvTypeParams, typeParams []*TypeParam, params, results *types.Tuple, variadic bool) *types.Signature {
+	return types.NewSignatureType(recv, recvTypeParams, typeParams, params, results, variadic)
+}
+
+// ForSignature returns sig.TypeParams()
+func ForSignature(sig *types.Signature) *TypeParamList {
+	return sig.TypeParams()
+}
+
+// RecvTypeParams returns sig.RecvTypeParams().
+func RecvTypeParams(sig *types.Signature) *TypeParamList {
+	return sig.RecvTypeParams()
+}
+
+// IsComparable calls iface.IsComparable().
+func IsComparable(iface *types.Interface) bool {
+	return iface.IsComparable()
+}
+
+// IsMethodSet calls iface.IsMethodSet().
+func IsMethodSet(iface *types.Interface) bool {
+	return iface.IsMethodSet()
+}
+
+// IsImplicit calls iface.IsImplicit().
+func IsImplicit(iface *types.Interface) bool {
+	return iface.IsImplicit()
+}
+
+// MarkImplicit calls iface.MarkImplicit().
+func MarkImplicit(iface *types.Interface) {
+	iface.MarkImplicit()
+}
+
+// ForNamed extracts the (possibly empty) type parameter object list from
+// named.
+func ForNamed(named *types.Named) *TypeParamList {
+	return named.TypeParams()
+}
+
+// SetForNamed sets the type params tparams on n. Each tparam must be of
+// dynamic type *types.TypeParam.
+func SetForNamed(n *types.Named, tparams []*TypeParam) {
+	n.SetTypeParams(tparams)
+}
+
+// NamedTypeArgs returns named.TypeArgs().
+func NamedTypeArgs(named *types.Named) *TypeList {
+	return named.TypeArgs()
+}
+
+// NamedTypeOrigin returns named.Orig().
+func NamedTypeOrigin(named *types.Named) types.Type {
+	return named.Origin()
+}
+
+// Term is an alias for types.Term.
+type Term = types.Term
+
+// NewTerm calls types.NewTerm.
+func NewTerm(tilde bool, typ types.Type) *Term {
+	return types.NewTerm(tilde, typ)
+}
+
+// Union is an alias for types.Union
+type Union = types.Union
+
+// NewUnion calls types.NewUnion.
+func NewUnion(terms []*Term) *Union {
+	return types.NewUnion(terms)
+}
+
+// InitInstances initializes info to record information about type and function
+// instances.
+func InitInstances(info *types.Info) {
+	info.Instances = make(map[*ast.Ident]types.Instance)
+}
+
+// Instance is an alias for types.Instance.
+type Instance = types.Instance
+
+// GetInstances returns info.Instances.
+func GetInstances(info *types.Info) map[*ast.Ident]Instance {
+	return info.Instances
+}
+
+// Context is an alias for types.Context.
+type Context = types.Context
+
+// NewContext calls types.NewContext.
+func NewContext() *Context {
+	return types.NewContext()
+}
+
+// Instantiate calls types.Instantiate.
+func Instantiate(ctxt *Context, typ types.Type, targs []types.Type, validate bool) (types.Type, error) {
+	return types.Instantiate(ctxt, typ, targs, validate)
+}

vendor/golang.org/x/exp/typeparams/typeterm.go

@@ -0,0 +1,170 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Code generated by copytermlist.go DO NOT EDIT.
+
+package typeparams
+
+import "go/types"
+
+// A term describes elementary type sets:
+//
+//   ∅:  (*term)(nil)     == ∅                      // set of no types (empty set)
+//   𝓤:  &term{}          == 𝓤                      // set of all types (𝓤niverse)
+//   T:  &term{false, T}  == {T}                    // set of type T
+//  ~t:  &term{true, t}   == {t' | under(t') == t}  // set of types with underlying type t
+//
+type term struct {
+	tilde bool // valid if typ != nil
+	typ   types.Type
+}
+
+func (x *term) String() string {
+	switch {
+	case x == nil:
+		return "∅"
+	case x.typ == nil:
+		return "𝓤"
+	case x.tilde:
+		return "~" + x.typ.String()
+	default:
+		return x.typ.String()
+	}
+}
+
+// equal reports whether x and y represent the same type set.
+func (x *term) equal(y *term) bool {
+	// easy cases
+	switch {
+	case x == nil || y == nil:
+		return x == y
+	case x.typ == nil || y.typ == nil:
+		return x.typ == y.typ
+	}
+	// ∅ ⊂ x, y ⊂ 𝓤
+
+	return x.tilde == y.tilde && types.Identical(x.typ, y.typ)
+}
+
+// union returns the union x ∪ y: zero, one, or two non-nil terms.
+func (x *term) union(y *term) (_, _ *term) {
+	// easy cases
+	switch {
+	case x == nil && y == nil:
+		return nil, nil // ∅ ∪ ∅ == ∅
+	case x == nil:
+		return y, nil // ∅ ∪ y == y
+	case y == nil:
+		return x, nil // x ∪ ∅ == x
+	case x.typ == nil:
+		return x, nil // 𝓤 ∪ y == 𝓤
+	case y.typ == nil:
+		return y, nil // x ∪ 𝓤 == 𝓤
+	}
+	// ∅ ⊂ x, y ⊂ 𝓤
+
+	if x.disjoint(y) {
+		return x, y // x ∪ y == (x, y) if x ∩ y == ∅
+	}
+	// x.typ == y.typ
+
+	// ~t ∪ ~t == ~t
+	// ~t ∪  T == ~t
+	//  T ∪ ~t == ~t
+	//  T ∪  T ==  T
+	if x.tilde || !y.tilde {
+		return x, nil
+	}
+	return y, nil
+}
+
+// intersect returns the intersection x ∩ y.
+func (x *term) intersect(y *term) *term {
+	// easy cases
+	switch {
+	case x == nil || y == nil:
+		return nil // ∅ ∩ y == ∅ and ∩ ∅ == ∅
+	case x.typ == nil:
+		return y // 𝓤 ∩ y == y
+	case y.typ == nil:
+		return x // x ∩ 𝓤 == x
+	}
+	// ∅ ⊂ x, y ⊂ 𝓤
+
+	if x.disjoint(y) {
+		return nil // x ∩ y == ∅ if x ∩ y == ∅
+	}
+	// x.typ == y.typ
+
+	// ~t ∩ ~t == ~t
+	// ~t ∩  T ==  T
+	//  T ∩ ~t ==  T
+	//  T ∩  T ==  T
+	if !x.tilde || y.tilde {
+		return x
+	}
+	return y
+}
+
+// includes reports whether t ∈ x.
+func (x *term) includes(t types.Type) bool {
+	// easy cases
+	switch {
+	case x == nil:
+		return false // t ∈ ∅ == false
+	case x.typ == nil:
+		return true // t ∈ 𝓤 == true
+	}
+	// ∅ ⊂ x ⊂ 𝓤
+
+	u := t
+	if x.tilde {
+		u = under(u)
+	}
+	return types.Identical(x.typ, u)
+}
+
+// subsetOf reports whether x ⊆ y.
+func (x *term) subsetOf(y *term) bool {
+	// easy cases
+	switch {
+	case x == nil:
+		return true // ∅ ⊆ y == true
+	case y == nil:
+		return false // x ⊆ ∅ == false since x != ∅
+	case y.typ == nil:
+		return true // x ⊆ 𝓤 == true
+	case x.typ == nil:
+		return false // 𝓤 ⊆ y == false since y != 𝓤
+	}
+	// ∅ ⊂ x, y ⊂ 𝓤
+
+	if x.disjoint(y) {
+		return false // x ⊆ y == false if x ∩ y == ∅
+	}
+	// x.typ == y.typ
+
+	// ~t ⊆ ~t == true
+	// ~t ⊆ T == false
+	//  T ⊆ ~t == true
+	//  T ⊆  T == true
+	return !x.tilde || y.tilde
+}
+
+// disjoint reports whether x ∩ y == ∅.
+// x.typ and y.typ must not be nil.
+func (x *term) disjoint(y *term) bool {
+	if debug && (x.typ == nil || y.typ == nil) {
+		panic("invalid argument(s)")
+	}
+	ux := x.typ
+	if y.tilde {
+		ux = under(ux)
+	}
+	uy := y.typ
+	if x.tilde {
+		uy = under(uy)
+	}
+	return !types.Identical(ux, uy)
+}

vendor/golang.org/x/lint/.travis.yml

@@ -1,19 +0,0 @@
-sudo: false
-language: go
-go:
-  - 1.10.x
-  - 1.11.x
-  - master
-
-go_import_path: golang.org/x/lint
-
-install:
-  - go get -t -v ./...
-
-script:
-  - go test -v -race ./...
-
-matrix:
-  allow_failures:
-    - go: master
-  fast_finish: true

vendor/golang.org/x/lint/CONTRIBUTING.md

@@ -1,15 +0,0 @@
-# Contributing to Golint
-
-## Before filing an issue:
-
-### Are you having trouble building golint?
-
-Check you have the latest version of its dependencies. Run
-```
-go get -u golang.org/x/lint/golint
-```
-If you still have problems, consider searching for existing issues before filing a new issue.
-
-## Before sending a pull request:
-
-Have you understood the purpose of golint? Make sure to carefully read `README`.

vendor/golang.org/x/lint/README.md

@@ -1,93 +0,0 @@
-**NOTE:** Golint is [deprecated and frozen](https://github.com/golang/go/issues/38968).
-There's no drop-in replacement for it, but tools such as [Staticcheck](https://staticcheck.io/)
-and `go vet` should be used instead.
-
-Golint is a linter for Go source code.
-
-[![Go Reference](https://pkg.go.dev/badge/golang.org/x/lint.svg)](https://pkg.go.dev/golang.org/x/lint)
-[![Build Status](https://travis-ci.org/golang/lint.svg?branch=master)](https://travis-ci.org/golang/lint)
-
-## Installation
-
-Golint requires a
-[supported release of Go](https://golang.org/doc/devel/release.html#policy).
-
-    go get -u golang.org/x/lint/golint
-
-To find out where `golint` was installed you can run `go list -f {{.Target}} golang.org/x/lint/golint`. For `golint` to be used globally add that directory to the `$PATH` environment setting.
-
-## Usage
-
-Invoke `golint` with one or more filenames, directories, or packages named
-by its import path. Golint uses the same
-[import path syntax](https://golang.org/cmd/go/#hdr-Import_path_syntax) as
-the `go` command and therefore
-also supports relative import paths like `./...`. Additionally the `...`
-wildcard can be used as suffix on relative and absolute file paths to recurse
-into them.
-
-The output of this tool is a list of suggestions in Vim quickfix format,
-which is accepted by lots of different editors.
-
-## Purpose
-
-Golint differs from gofmt. Gofmt reformats Go source code, whereas
-golint prints out style mistakes.
-
-Golint differs from govet. Govet is concerned with correctness, whereas
-golint is concerned with coding style. Golint is in use at Google, and it
-seeks to match the accepted style of the open source Go project.
-
-The suggestions made by golint are exactly that: suggestions.
-Golint is not perfect, and has both false positives and false negatives.
-Do not treat its output as a gold standard. We will not be adding pragmas
-or other knobs to suppress specific warnings, so do not expect or require
-code to be completely "lint-free".
-In short, this tool is not, and will never be, trustworthy enough for its
-suggestions to be enforced automatically, for example as part of a build process.
-Golint makes suggestions for many of the mechanically checkable items listed in
-[Effective Go](https://golang.org/doc/effective_go.html) and the
-[CodeReviewComments wiki page](https://golang.org/wiki/CodeReviewComments).
-
-## Scope
-
-Golint is meant to carry out the stylistic conventions put forth in
-[Effective Go](https://golang.org/doc/effective_go.html) and
-[CodeReviewComments](https://golang.org/wiki/CodeReviewComments).
-Changes that are not aligned with those documents will not be considered.
-
-## Contributions
-
-Contributions to this project are welcome provided they are [in scope](#scope),
-though please send mail before starting work on anything major.
-Contributors retain their copyright, so we need you to fill out
-[a short form](https://developers.google.com/open-source/cla/individual)
-before we can accept your contribution.
-
-## Vim
-
-Add this to your ~/.vimrc:
-
-    set rtp+=$GOPATH/src/golang.org/x/lint/misc/vim
-
-If you have multiple entries in your GOPATH, replace `$GOPATH` with the right value.
-
-Running `:Lint` will run golint on the current file and populate the quickfix list.
-
-Optionally, add this to your `~/.vimrc` to automatically run `golint` on `:w`
-
-    autocmd BufWritePost,FileWritePost *.go execute 'Lint' | cwindow
-
-
-## Emacs
-
-Add this to your `.emacs` file:
-
-    (add-to-list 'load-path (concat (getenv "GOPATH")  "/src/golang.org/x/lint/misc/emacs/"))
-    (require 'golint)
-
-If you have multiple entries in your GOPATH, replace `$GOPATH` with the right value.
-
-Running M-x golint will run golint on the current file.
-
-For more usage, see [Compilation-Mode](http://www.gnu.org/software/emacs/manual/html_node/emacs/Compilation-Mode.html).

vendor/golang.org/x/lint/golint/golint.go

@@ -1,159 +0,0 @@
-// Copyright (c) 2013 The Go Authors. All rights reserved.
-//
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file or at
-// https://developers.google.com/open-source/licenses/bsd.
-
-// golint lints the Go source files named on its command line.
-package main
-
-import (
-	"flag"
-	"fmt"
-	"go/build"
-	"io/ioutil"
-	"os"
-	"path/filepath"
-	"strings"
-
-	"golang.org/x/lint"
-)
-
-var (
-	minConfidence = flag.Float64("min_confidence", 0.8, "minimum confidence of a problem to print it")
-	setExitStatus = flag.Bool("set_exit_status", false, "set exit status to 1 if any issues are found")
-	suggestions   int
-)
-
-func usage() {
-	fmt.Fprintf(os.Stderr, "Usage of %s:\n", os.Args[0])
-	fmt.Fprintf(os.Stderr, "\tgolint [flags] # runs on package in current directory\n")
-	fmt.Fprintf(os.Stderr, "\tgolint [flags] [packages]\n")
-	fmt.Fprintf(os.Stderr, "\tgolint [flags] [directories] # where a '/...' suffix includes all sub-directories\n")
-	fmt.Fprintf(os.Stderr, "\tgolint [flags] [files] # all must belong to a single package\n")
-	fmt.Fprintf(os.Stderr, "Flags:\n")
-	flag.PrintDefaults()
-}
-
-func main() {
-	flag.Usage = usage
-	flag.Parse()
-
-	if flag.NArg() == 0 {
-		lintDir(".")
-	} else {
-		// dirsRun, filesRun, and pkgsRun indicate whether golint is applied to
-		// directory, file or package targets. The distinction affects which
-		// checks are run. It is no valid to mix target types.
-		var dirsRun, filesRun, pkgsRun int
-		var args []string
-		for _, arg := range flag.Args() {
-			if strings.HasSuffix(arg, "/...") && isDir(arg[:len(arg)-len("/...")]) {
-				dirsRun = 1
-				for _, dirname := range allPackagesInFS(arg) {
-					args = append(args, dirname)
-				}
-			} else if isDir(arg) {
-				dirsRun = 1
-				args = append(args, arg)
-			} else if exists(arg) {
-				filesRun = 1
-				args = append(args, arg)
-			} else {
-				pkgsRun = 1
-				args = append(args, arg)
-			}
-		}
-
-		if dirsRun+filesRun+pkgsRun != 1 {
-			usage()
-			os.Exit(2)
-		}
-		switch {
-		case dirsRun == 1:
-			for _, dir := range args {
-				lintDir(dir)
-			}
-		case filesRun == 1:
-			lintFiles(args...)
-		case pkgsRun == 1:
-			for _, pkg := range importPaths(args) {
-				lintPackage(pkg)
-			}
-		}
-	}
-
-	if *setExitStatus && suggestions > 0 {
-		fmt.Fprintf(os.Stderr, "Found %d lint suggestions; failing.\n", suggestions)
-		os.Exit(1)
-	}
-}
-
-func isDir(filename string) bool {
-	fi, err := os.Stat(filename)
-	return err == nil && fi.IsDir()
-}
-
-func exists(filename string) bool {
-	_, err := os.Stat(filename)
-	return err == nil
-}
-
-func lintFiles(filenames ...string) {
-	files := make(map[string][]byte)
-	for _, filename := range filenames {
-		src, err := ioutil.ReadFile(filename)
-		if err != nil {
-			fmt.Fprintln(os.Stderr, err)
-			continue
-		}
-		files[filename] = src
-	}
-
-	l := new(lint.Linter)
-	ps, err := l.LintFiles(files)
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "%v\n", err)
-		return
-	}
-	for _, p := range ps {
-		if p.Confidence >= *minConfidence {
-			fmt.Printf("%v: %s\n", p.Position, p.Text)
-			suggestions++
-		}
-	}
-}
-
-func lintDir(dirname string) {
-	pkg, err := build.ImportDir(dirname, 0)
-	lintImportedPackage(pkg, err)
-}
-
-func lintPackage(pkgname string) {
-	pkg, err := build.Import(pkgname, ".", 0)
-	lintImportedPackage(pkg, err)
-}
-
-func lintImportedPackage(pkg *build.Package, err error) {
-	if err != nil {
-		if _, nogo := err.(*build.NoGoError); nogo {
-			// Don't complain if the failure is due to no Go source files.
-			return
-		}
-		fmt.Fprintln(os.Stderr, err)
-		return
-	}
-
-	var files []string
-	files = append(files, pkg.GoFiles...)
-	files = append(files, pkg.CgoFiles...)
-	files = append(files, pkg.TestGoFiles...)
-	if pkg.Dir != "." {
-		for i, f := range files {
-			files[i] = filepath.Join(pkg.Dir, f)
-		}
-	}
-	// TODO(dsymonds): Do foo_test too (pkg.XTestGoFiles)
-
-	lintFiles(files...)
-}

vendor/golang.org/x/lint/golint/import.go

@@ -1,309 +0,0 @@
-package main
-
-/*
-
-This file holds a direct copy of the import path matching code of
-https://github.com/golang/go/blob/master/src/cmd/go/main.go. It can be
-replaced when https://golang.org/issue/8768 is resolved.
-
-It has been updated to follow upstream changes in a few ways.
-
-*/
-
-import (
-	"fmt"
-	"go/build"
-	"log"
-	"os"
-	"path"
-	"path/filepath"
-	"regexp"
-	"runtime"
-	"strings"
-)
-
-var (
-	buildContext = build.Default
-	goroot       = filepath.Clean(runtime.GOROOT())
-	gorootSrc    = filepath.Join(goroot, "src")
-)
-
-// importPathsNoDotExpansion returns the import paths to use for the given
-// command line, but it does no ... expansion.
-func importPathsNoDotExpansion(args []string) []string {
-	if len(args) == 0 {
-		return []string{"."}
-	}
-	var out []string
-	for _, a := range args {
-		// Arguments are supposed to be import paths, but
-		// as a courtesy to Windows developers, rewrite \ to /
-		// in command-line arguments.  Handles .\... and so on.
-		if filepath.Separator == '\\' {
-			a = strings.Replace(a, `\`, `/`, -1)
-		}
-
-		// Put argument in canonical form, but preserve leading ./.
-		if strings.HasPrefix(a, "./") {
-			a = "./" + path.Clean(a)
-			if a == "./." {
-				a = "."
-			}
-		} else {
-			a = path.Clean(a)
-		}
-		if a == "all" || a == "std" {
-			out = append(out, allPackages(a)...)
-			continue
-		}
-		out = append(out, a)
-	}
-	return out
-}
-
-// importPaths returns the import paths to use for the given command line.
-func importPaths(args []string) []string {
-	args = importPathsNoDotExpansion(args)
-	var out []string
-	for _, a := range args {
-		if strings.Contains(a, "...") {
-			if build.IsLocalImport(a) {
-				out = append(out, allPackagesInFS(a)...)
-			} else {
-				out = append(out, allPackages(a)...)
-			}
-			continue
-		}
-		out = append(out, a)
-	}
-	return out
-}
-
-// matchPattern(pattern)(name) reports whether
-// name matches pattern.  Pattern is a limited glob
-// pattern in which '...' means 'any string' and there
-// is no other special syntax.
-func matchPattern(pattern string) func(name string) bool {
-	re := regexp.QuoteMeta(pattern)
-	re = strings.Replace(re, `\.\.\.`, `.*`, -1)
-	// Special case: foo/... matches foo too.
-	if strings.HasSuffix(re, `/.*`) {
-		re = re[:len(re)-len(`/.*`)] + `(/.*)?`
-	}
-	reg := regexp.MustCompile(`^` + re + `$`)
-	return func(name string) bool {
-		return reg.MatchString(name)
-	}
-}
-
-// hasPathPrefix reports whether the path s begins with the
-// elements in prefix.
-func hasPathPrefix(s, prefix string) bool {
-	switch {
-	default:
-		return false
-	case len(s) == len(prefix):
-		return s == prefix
-	case len(s) > len(prefix):
-		if prefix != "" && prefix[len(prefix)-1] == '/' {
-			return strings.HasPrefix(s, prefix)
-		}
-		return s[len(prefix)] == '/' && s[:len(prefix)] == prefix
-	}
-}
-
-// treeCanMatchPattern(pattern)(name) reports whether
-// name or children of name can possibly match pattern.
-// Pattern is the same limited glob accepted by matchPattern.
-func treeCanMatchPattern(pattern string) func(name string) bool {
-	wildCard := false
-	if i := strings.Index(pattern, "..."); i >= 0 {
-		wildCard = true
-		pattern = pattern[:i]
-	}
-	return func(name string) bool {
-		return len(name) <= len(pattern) && hasPathPrefix(pattern, name) ||
-			wildCard && strings.HasPrefix(name, pattern)
-	}
-}
-
-// allPackages returns all the packages that can be found
-// under the $GOPATH directories and $GOROOT matching pattern.
-// The pattern is either "all" (all packages), "std" (standard packages)
-// or a path including "...".
-func allPackages(pattern string) []string {
-	pkgs := matchPackages(pattern)
-	if len(pkgs) == 0 {
-		fmt.Fprintf(os.Stderr, "warning: %q matched no packages\n", pattern)
-	}
-	return pkgs
-}
-
-func matchPackages(pattern string) []string {
-	match := func(string) bool { return true }
-	treeCanMatch := func(string) bool { return true }
-	if pattern != "all" && pattern != "std" {
-		match = matchPattern(pattern)
-		treeCanMatch = treeCanMatchPattern(pattern)
-	}
-
-	have := map[string]bool{
-		"builtin": true, // ignore pseudo-package that exists only for documentation
-	}
-	if !buildContext.CgoEnabled {
-		have["runtime/cgo"] = true // ignore during walk
-	}
-	var pkgs []string
-
-	// Commands
-	cmd := filepath.Join(goroot, "src/cmd") + string(filepath.Separator)
-	filepath.Walk(cmd, func(path string, fi os.FileInfo, err error) error {
-		if err != nil || !fi.IsDir() || path == cmd {
-			return nil
-		}
-		name := path[len(cmd):]
-		if !treeCanMatch(name) {
-			return filepath.SkipDir
-		}
-		// Commands are all in cmd/, not in subdirectories.
-		if strings.Contains(name, string(filepath.Separator)) {
-			return filepath.SkipDir
-		}
-
-		// We use, e.g., cmd/gofmt as the pseudo import path for gofmt.
-		name = "cmd/" + name
-		if have[name] {
-			return nil
-		}
-		have[name] = true
-		if !match(name) {
-			return nil
-		}
-		_, err = buildContext.ImportDir(path, 0)
-		if err != nil {
-			if _, noGo := err.(*build.NoGoError); !noGo {
-				log.Print(err)
-			}
-			return nil
-		}
-		pkgs = append(pkgs, name)
-		return nil
-	})
-
-	for _, src := range buildContext.SrcDirs() {
-		if (pattern == "std" || pattern == "cmd") && src != gorootSrc {
-			continue
-		}
-		src = filepath.Clean(src) + string(filepath.Separator)
-		root := src
-		if pattern == "cmd" {
-			root += "cmd" + string(filepath.Separator)
-		}
-		filepath.Walk(root, func(path string, fi os.FileInfo, err error) error {
-			if err != nil || !fi.IsDir() || path == src {
-				return nil
-			}
-
-			// Avoid .foo, _foo, and testdata directory trees.
-			_, elem := filepath.Split(path)
-			if strings.HasPrefix(elem, ".") || strings.HasPrefix(elem, "_") || elem == "testdata" {
-				return filepath.SkipDir
-			}
-
-			name := filepath.ToSlash(path[len(src):])
-			if pattern == "std" && (strings.Contains(name, ".") || name == "cmd") {
-				// The name "std" is only the standard library.
-				// If the name is cmd, it's the root of the command tree.
-				return filepath.SkipDir
-			}
-			if !treeCanMatch(name) {
-				return filepath.SkipDir
-			}
-			if have[name] {
-				return nil
-			}
-			have[name] = true
-			if !match(name) {
-				return nil
-			}
-			_, err = buildContext.ImportDir(path, 0)
-			if err != nil {
-				if _, noGo := err.(*build.NoGoError); noGo {
-					return nil
-				}
-			}
-			pkgs = append(pkgs, name)
-			return nil
-		})
-	}
-	return pkgs
-}
-
-// allPackagesInFS is like allPackages but is passed a pattern
-// beginning ./ or ../, meaning it should scan the tree rooted
-// at the given directory.  There are ... in the pattern too.
-func allPackagesInFS(pattern string) []string {
-	pkgs := matchPackagesInFS(pattern)
-	if len(pkgs) == 0 {
-		fmt.Fprintf(os.Stderr, "warning: %q matched no packages\n", pattern)
-	}
-	return pkgs
-}
-
-func matchPackagesInFS(pattern string) []string {
-	// Find directory to begin the scan.
-	// Could be smarter but this one optimization
-	// is enough for now, since ... is usually at the
-	// end of a path.
-	i := strings.Index(pattern, "...")
-	dir, _ := path.Split(pattern[:i])
-
-	// pattern begins with ./ or ../.
-	// path.Clean will discard the ./ but not the ../.
-	// We need to preserve the ./ for pattern matching
-	// and in the returned import paths.
-	prefix := ""
-	if strings.HasPrefix(pattern, "./") {
-		prefix = "./"
-	}
-	match := matchPattern(pattern)
-
-	var pkgs []string
-	filepath.Walk(dir, func(path string, fi os.FileInfo, err error) error {
-		if err != nil || !fi.IsDir() {
-			return nil
-		}
-		if path == dir {
-			// filepath.Walk starts at dir and recurses. For the recursive case,
-			// the path is the result of filepath.Join, which calls filepath.Clean.
-			// The initial case is not Cleaned, though, so we do this explicitly.
-			//
-			// This converts a path like "./io/" to "io". Without this step, running
-			// "cd $GOROOT/src/pkg; go list ./io/..." would incorrectly skip the io
-			// package, because prepending the prefix "./" to the unclean path would
-			// result in "././io", and match("././io") returns false.
-			path = filepath.Clean(path)
-		}
-
-		// Avoid .foo, _foo, and testdata directory trees, but do not avoid "." or "..".
-		_, elem := filepath.Split(path)
-		dot := strings.HasPrefix(elem, ".") && elem != "." && elem != ".."
-		if dot || strings.HasPrefix(elem, "_") || elem == "testdata" {
-			return filepath.SkipDir
-		}
-
-		name := prefix + filepath.ToSlash(path)
-		if !match(name) {
-			return nil
-		}
-		if _, err = build.ImportDir(path, 0); err != nil {
-			if _, noGo := err.(*build.NoGoError); !noGo {
-				log.Print(err)
-			}
-			return nil
-		}
-		pkgs = append(pkgs, name)
-		return nil
-	})
-	return pkgs
-}

vendor/golang.org/x/lint/golint/importcomment.go

@@ -1,13 +0,0 @@
-// Copyright (c) 2018 The Go Authors. All rights reserved.
-//
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file or at
-// https://developers.google.com/open-source/licenses/bsd.
-
-// +build go1.12
-
-// Require use of the correct import path only for Go 1.12+ users, so
-// any breakages coincide with people updating their CI configs or
-// whatnot.
-
-package main // import "golang.org/x/lint/golint"

vendor/golang.org/x/lint/lint.go

@@ -1,1615 +0,0 @@
-// Copyright (c) 2013 The Go Authors. All rights reserved.
-//
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file or at
-// https://developers.google.com/open-source/licenses/bsd.
-
-// Package lint contains a linter for Go source code.
-package lint // import "golang.org/x/lint"
-
-import (
-	"bufio"
-	"bytes"
-	"fmt"
-	"go/ast"
-	"go/parser"
-	"go/printer"
-	"go/token"
-	"go/types"
-	"regexp"
-	"sort"
-	"strconv"
-	"strings"
-	"unicode"
-	"unicode/utf8"
-
-	"golang.org/x/tools/go/ast/astutil"
-	"golang.org/x/tools/go/gcexportdata"
-)
-
-const styleGuideBase = "https://golang.org/wiki/CodeReviewComments"
-
-// A Linter lints Go source code.
-type Linter struct {
-}
-
-// Problem represents a problem in some source code.
-type Problem struct {
-	Position   token.Position // position in source file
-	Text       string         // the prose that describes the problem
-	Link       string         // (optional) the link to the style guide for the problem
-	Confidence float64        // a value in (0,1] estimating the confidence in this problem's correctness
-	LineText   string         // the source line
-	Category   string         // a short name for the general category of the problem
-
-	// If the problem has a suggested fix (the minority case),
-	// ReplacementLine is a full replacement for the relevant line of the source file.
-	ReplacementLine string
-}
-
-func (p *Problem) String() string {
-	if p.Link != "" {
-		return p.Text + "\n\n" + p.Link
-	}
-	return p.Text
-}
-
-type byPosition []Problem
-
-func (p byPosition) Len() int      { return len(p) }
-func (p byPosition) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
-
-func (p byPosition) Less(i, j int) bool {
-	pi, pj := p[i].Position, p[j].Position
-
-	if pi.Filename != pj.Filename {
-		return pi.Filename < pj.Filename
-	}
-	if pi.Line != pj.Line {
-		return pi.Line < pj.Line
-	}
-	if pi.Column != pj.Column {
-		return pi.Column < pj.Column
-	}
-
-	return p[i].Text < p[j].Text
-}
-
-// Lint lints src.
-func (l *Linter) Lint(filename string, src []byte) ([]Problem, error) {
-	return l.LintFiles(map[string][]byte{filename: src})
-}
-
-// LintFiles lints a set of files of a single package.
-// The argument is a map of filename to source.
-func (l *Linter) LintFiles(files map[string][]byte) ([]Problem, error) {
-	pkg := &pkg{
-		fset:  token.NewFileSet(),
-		files: make(map[string]*file),
-	}
-	var pkgName string
-	for filename, src := range files {
-		if isGenerated(src) {
-			continue // See issue #239
-		}
-		f, err := parser.ParseFile(pkg.fset, filename, src, parser.ParseComments)
-		if err != nil {
-			return nil, err
-		}
-		if pkgName == "" {
-			pkgName = f.Name.Name
-		} else if f.Name.Name != pkgName {
-			return nil, fmt.Errorf("%s is in package %s, not %s", filename, f.Name.Name, pkgName)
-		}
-		pkg.files[filename] = &file{
-			pkg:      pkg,
-			f:        f,
-			fset:     pkg.fset,
-			src:      src,
-			filename: filename,
-		}
-	}
-	if len(pkg.files) == 0 {
-		return nil, nil
-	}
-	return pkg.lint(), nil
-}
-
-var (
-	genHdr = []byte("// Code generated ")
-	genFtr = []byte(" DO NOT EDIT.")
-)
-
-// isGenerated reports whether the source file is generated code
-// according the rules from https://golang.org/s/generatedcode.
-func isGenerated(src []byte) bool {
-	sc := bufio.NewScanner(bytes.NewReader(src))
-	for sc.Scan() {
-		b := sc.Bytes()
-		if bytes.HasPrefix(b, genHdr) && bytes.HasSuffix(b, genFtr) && len(b) >= len(genHdr)+len(genFtr) {
-			return true
-		}
-	}
-	return false
-}
-
-// pkg represents a package being linted.
-type pkg struct {
-	fset  *token.FileSet
-	files map[string]*file
-
-	typesPkg  *types.Package
-	typesInfo *types.Info
-
-	// sortable is the set of types in the package that implement sort.Interface.
-	sortable map[string]bool
-	// main is whether this is a "main" package.
-	main bool
-
-	problems []Problem
-}
-
-func (p *pkg) lint() []Problem {
-	if err := p.typeCheck(); err != nil {
-		/* TODO(dsymonds): Consider reporting these errors when golint operates on entire packages.
-		if e, ok := err.(types.Error); ok {
-			pos := p.fset.Position(e.Pos)
-			conf := 1.0
-			if strings.Contains(e.Msg, "can't find import: ") {
-				// Golint is probably being run in a context that doesn't support
-				// typechecking (e.g. package files aren't found), so don't warn about it.
-				conf = 0
-			}
-			if conf > 0 {
-				p.errorfAt(pos, conf, category("typechecking"), e.Msg)
-			}
-
-			// TODO(dsymonds): Abort if !e.Soft?
-		}
-		*/
-	}
-
-	p.scanSortable()
-	p.main = p.isMain()
-
-	for _, f := range p.files {
-		f.lint()
-	}
-
-	sort.Sort(byPosition(p.problems))
-
-	return p.problems
-}
-
-// file represents a file being linted.
-type file struct {
-	pkg      *pkg
-	f        *ast.File
-	fset     *token.FileSet
-	src      []byte
-	filename string
-}
-
-func (f *file) isTest() bool { return strings.HasSuffix(f.filename, "_test.go") }
-
-func (f *file) lint() {
-	f.lintPackageComment()
-	f.lintImports()
-	f.lintBlankImports()
-	f.lintExported()
-	f.lintNames()
-	f.lintElses()
-	f.lintRanges()
-	f.lintErrorf()
-	f.lintErrors()
-	f.lintErrorStrings()
-	f.lintReceiverNames()
-	f.lintIncDec()
-	f.lintErrorReturn()
-	f.lintUnexportedReturn()
-	f.lintTimeNames()
-	f.lintContextKeyTypes()
-	f.lintContextArgs()
-}
-
-type link string
-type category string
-
-// The variadic arguments may start with link and category types,
-// and must end with a format string and any arguments.
-// It returns the new Problem.
-func (f *file) errorf(n ast.Node, confidence float64, args ...interface{}) *Problem {
-	pos := f.fset.Position(n.Pos())
-	if pos.Filename == "" {
-		pos.Filename = f.filename
-	}
-	return f.pkg.errorfAt(pos, confidence, args...)
-}
-
-func (p *pkg) errorfAt(pos token.Position, confidence float64, args ...interface{}) *Problem {
-	problem := Problem{
-		Position:   pos,
-		Confidence: confidence,
-	}
-	if pos.Filename != "" {
-		// The file might not exist in our mapping if a //line directive was encountered.
-		if f, ok := p.files[pos.Filename]; ok {
-			problem.LineText = srcLine(f.src, pos)
-		}
-	}
-
-argLoop:
-	for len(args) > 1 { // always leave at least the format string in args
-		switch v := args[0].(type) {
-		case link:
-			problem.Link = string(v)
-		case category:
-			problem.Category = string(v)
-		default:
-			break argLoop
-		}
-		args = args[1:]
-	}
-
-	problem.Text = fmt.Sprintf(args[0].(string), args[1:]...)
-
-	p.problems = append(p.problems, problem)
-	return &p.problems[len(p.problems)-1]
-}
-
-var newImporter = func(fset *token.FileSet) types.ImporterFrom {
-	return gcexportdata.NewImporter(fset, make(map[string]*types.Package))
-}
-
-func (p *pkg) typeCheck() error {
-	config := &types.Config{
-		// By setting a no-op error reporter, the type checker does as much work as possible.
-		Error:    func(error) {},
-		Importer: newImporter(p.fset),
-	}
-	info := &types.Info{
-		Types:  make(map[ast.Expr]types.TypeAndValue),
-		Defs:   make(map[*ast.Ident]types.Object),
-		Uses:   make(map[*ast.Ident]types.Object),
-		Scopes: make(map[ast.Node]*types.Scope),
-	}
-	var anyFile *file
-	var astFiles []*ast.File
-	for _, f := range p.files {
-		anyFile = f
-		astFiles = append(astFiles, f.f)
-	}
-	pkg, err := config.Check(anyFile.f.Name.Name, p.fset, astFiles, info)
-	// Remember the typechecking info, even if config.Check failed,
-	// since we will get partial information.
-	p.typesPkg = pkg
-	p.typesInfo = info
-	return err
-}
-
-func (p *pkg) typeOf(expr ast.Expr) types.Type {
-	if p.typesInfo == nil {
-		return nil
-	}
-	return p.typesInfo.TypeOf(expr)
-}
-
-func (p *pkg) isNamedType(typ types.Type, importPath, name string) bool {
-	n, ok := typ.(*types.Named)
-	if !ok {
-		return false
-	}
-	tn := n.Obj()
-	return tn != nil && tn.Pkg() != nil && tn.Pkg().Path() == importPath && tn.Name() == name
-}
-
-// scopeOf returns the tightest scope encompassing id.
-func (p *pkg) scopeOf(id *ast.Ident) *types.Scope {
-	var scope *types.Scope
-	if obj := p.typesInfo.ObjectOf(id); obj != nil {
-		scope = obj.Parent()
-	}
-	if scope == p.typesPkg.Scope() {
-		// We were given a top-level identifier.
-		// Use the file-level scope instead of the package-level scope.
-		pos := id.Pos()
-		for _, f := range p.files {
-			if f.f.Pos() <= pos && pos < f.f.End() {
-				scope = p.typesInfo.Scopes[f.f]
-				break
-			}
-		}
-	}
-	return scope
-}
-
-func (p *pkg) scanSortable() {
-	p.sortable = make(map[string]bool)
-
-	// bitfield for which methods exist on each type.
-	const (
-		Len = 1 << iota
-		Less
-		Swap
-	)
-	nmap := map[string]int{"Len": Len, "Less": Less, "Swap": Swap}
-	has := make(map[string]int)
-	for _, f := range p.files {
-		f.walk(func(n ast.Node) bool {
-			fn, ok := n.(*ast.FuncDecl)
-			if !ok || fn.Recv == nil || len(fn.Recv.List) == 0 {
-				return true
-			}
-			// TODO(dsymonds): We could check the signature to be more precise.
-			recv := receiverType(fn)
-			if i, ok := nmap[fn.Name.Name]; ok {
-				has[recv] |= i
-			}
-			return false
-		})
-	}
-	for typ, ms := range has {
-		if ms == Len|Less|Swap {
-			p.sortable[typ] = true
-		}
-	}
-}
-
-func (p *pkg) isMain() bool {
-	for _, f := range p.files {
-		if f.isMain() {
-			return true
-		}
-	}
-	return false
-}
-
-func (f *file) isMain() bool {
-	if f.f.Name.Name == "main" {
-		return true
-	}
-	return false
-}
-
-// lintPackageComment checks package comments. It complains if
-// there is no package comment, or if it is not of the right form.
-// This has a notable false positive in that a package comment
-// could rightfully appear in a different file of the same package,
-// but that's not easy to fix since this linter is file-oriented.
-func (f *file) lintPackageComment() {
-	if f.isTest() {
-		return
-	}
-
-	const ref = styleGuideBase + "#package-comments"
-	prefix := "Package " + f.f.Name.Name + " "
-
-	// Look for a detached package comment.
-	// First, scan for the last comment that occurs before the "package" keyword.
-	var lastCG *ast.CommentGroup
-	for _, cg := range f.f.Comments {
-		if cg.Pos() > f.f.Package {
-			// Gone past "package" keyword.
-			break
-		}
-		lastCG = cg
-	}
-	if lastCG != nil && strings.HasPrefix(lastCG.Text(), prefix) {
-		endPos := f.fset.Position(lastCG.End())
-		pkgPos := f.fset.Position(f.f.Package)
-		if endPos.Line+1 < pkgPos.Line {
-			// There isn't a great place to anchor this error;
-			// the start of the blank lines between the doc and the package statement
-			// is at least pointing at the location of the problem.
-			pos := token.Position{
-				Filename: endPos.Filename,
-				// Offset not set; it is non-trivial, and doesn't appear to be needed.
-				Line:   endPos.Line + 1,
-				Column: 1,
-			}
-			f.pkg.errorfAt(pos, 0.9, link(ref), category("comments"), "package comment is detached; there should be no blank lines between it and the package statement")
-			return
-		}
-	}
-
-	if f.f.Doc == nil {
-		f.errorf(f.f, 0.2, link(ref), category("comments"), "should have a package comment, unless it's in another file for this package")
-		return
-	}
-	s := f.f.Doc.Text()
-	if ts := strings.TrimLeft(s, " \t"); ts != s {
-		f.errorf(f.f.Doc, 1, link(ref), category("comments"), "package comment should not have leading space")
-		s = ts
-	}
-	// Only non-main packages need to keep to this form.
-	if !f.pkg.main && !strings.HasPrefix(s, prefix) {
-		f.errorf(f.f.Doc, 1, link(ref), category("comments"), `package comment should be of the form "%s..."`, prefix)
-	}
-}
-
-// lintBlankImports complains if a non-main package has blank imports that are
-// not documented.
-func (f *file) lintBlankImports() {
-	// In package main and in tests, we don't complain about blank imports.
-	if f.pkg.main || f.isTest() {
-		return
-	}
-
-	// The first element of each contiguous group of blank imports should have
-	// an explanatory comment of some kind.
-	for i, imp := range f.f.Imports {
-		pos := f.fset.Position(imp.Pos())
-
-		if !isBlank(imp.Name) {
-			continue // Ignore non-blank imports.
-		}
-		if i > 0 {
-			prev := f.f.Imports[i-1]
-			prevPos := f.fset.Position(prev.Pos())
-			if isBlank(prev.Name) && prevPos.Line+1 == pos.Line {
-				continue // A subsequent blank in a group.
-			}
-		}
-
-		// This is the first blank import of a group.
-		if imp.Doc == nil && imp.Comment == nil {
-			ref := ""
-			f.errorf(imp, 1, link(ref), category("imports"), "a blank import should be only in a main or test package, or have a comment justifying it")
-		}
-	}
-}
-
-// lintImports examines import blocks.
-func (f *file) lintImports() {
-	for i, is := range f.f.Imports {
-		_ = i
-		if is.Name != nil && is.Name.Name == "." && !f.isTest() {
-			f.errorf(is, 1, link(styleGuideBase+"#import-dot"), category("imports"), "should not use dot imports")
-		}
-
-	}
-}
-
-const docCommentsLink = styleGuideBase + "#doc-comments"
-
-// lintExported examines the exported names.
-// It complains if any required doc comments are missing,
-// or if they are not of the right form. The exact rules are in
-// lintFuncDoc, lintTypeDoc and lintValueSpecDoc; this function
-// also tracks the GenDecl structure being traversed to permit
-// doc comments for constants to be on top of the const block.
-// It also complains if the names stutter when combined with
-// the package name.
-func (f *file) lintExported() {
-	if f.isTest() {
-		return
-	}
-
-	var lastGen *ast.GenDecl // last GenDecl entered.
-
-	// Set of GenDecls that have already had missing comments flagged.
-	genDeclMissingComments := make(map[*ast.GenDecl]bool)
-
-	f.walk(func(node ast.Node) bool {
-		switch v := node.(type) {
-		case *ast.GenDecl:
-			if v.Tok == token.IMPORT {
-				return false
-			}
-			// token.CONST, token.TYPE or token.VAR
-			lastGen = v
-			return true
-		case *ast.FuncDecl:
-			f.lintFuncDoc(v)
-			if v.Recv == nil {
-				// Only check for stutter on functions, not methods.
-				// Method names are not used package-qualified.
-				f.checkStutter(v.Name, "func")
-			}
-			// Don't proceed inside funcs.
-			return false
-		case *ast.TypeSpec:
-			// inside a GenDecl, which usually has the doc
-			doc := v.Doc
-			if doc == nil {
-				doc = lastGen.Doc
-			}
-			f.lintTypeDoc(v, doc)
-			f.checkStutter(v.Name, "type")
-			// Don't proceed inside types.
-			return false
-		case *ast.ValueSpec:
-			f.lintValueSpecDoc(v, lastGen, genDeclMissingComments)
-			return false
-		}
-		return true
-	})
-}
-
-var (
-	allCapsRE = regexp.MustCompile(`^[A-Z0-9_]+$`)
-	anyCapsRE = regexp.MustCompile(`[A-Z]`)
-)
-
-// knownNameExceptions is a set of names that are known to be exempt from naming checks.
-// This is usually because they are constrained by having to match names in the
-// standard library.
-var knownNameExceptions = map[string]bool{
-	"LastInsertId": true, // must match database/sql
-	"kWh":          true,
-}
-
-func isInTopLevel(f *ast.File, ident *ast.Ident) bool {
-	path, _ := astutil.PathEnclosingInterval(f, ident.Pos(), ident.End())
-	for _, f := range path {
-		switch f.(type) {
-		case *ast.File, *ast.GenDecl, *ast.ValueSpec, *ast.Ident:
-			continue
-		}
-		return false
-	}
-	return true
-}
-
-// lintNames examines all names in the file.
-// It complains if any use underscores or incorrect known initialisms.
-func (f *file) lintNames() {
-	// Package names need slightly different handling than other names.
-	if strings.Contains(f.f.Name.Name, "_") && !strings.HasSuffix(f.f.Name.Name, "_test") {
-		f.errorf(f.f, 1, link("http://golang.org/doc/effective_go.html#package-names"), category("naming"), "don't use an underscore in package name")
-	}
-	if anyCapsRE.MatchString(f.f.Name.Name) {
-		f.errorf(f.f, 1, link("http://golang.org/doc/effective_go.html#package-names"), category("mixed-caps"), "don't use MixedCaps in package name; %s should be %s", f.f.Name.Name, strings.ToLower(f.f.Name.Name))
-	}
-
-	check := func(id *ast.Ident, thing string) {
-		if id.Name == "_" {
-			return
-		}
-		if knownNameExceptions[id.Name] {
-			return
-		}
-
-		// Handle two common styles from other languages that don't belong in Go.
-		if len(id.Name) >= 5 && allCapsRE.MatchString(id.Name) && strings.Contains(id.Name, "_") {
-			capCount := 0
-			for _, c := range id.Name {
-				if 'A' <= c && c <= 'Z' {
-					capCount++
-				}
-			}
-			if capCount >= 2 {
-				f.errorf(id, 0.8, link(styleGuideBase+"#mixed-caps"), category("naming"), "don't use ALL_CAPS in Go names; use CamelCase")
-				return
-			}
-		}
-		if thing == "const" || (thing == "var" && isInTopLevel(f.f, id)) {
-			if len(id.Name) > 2 && id.Name[0] == 'k' && id.Name[1] >= 'A' && id.Name[1] <= 'Z' {
-				should := string(id.Name[1]+'a'-'A') + id.Name[2:]
-				f.errorf(id, 0.8, link(styleGuideBase+"#mixed-caps"), category("naming"), "don't use leading k in Go names; %s %s should be %s", thing, id.Name, should)
-			}
-		}
-
-		should := lintName(id.Name)
-		if id.Name == should {
-			return
-		}
-
-		if len(id.Name) > 2 && strings.Contains(id.Name[1:], "_") {
-			f.errorf(id, 0.9, link("http://golang.org/doc/effective_go.html#mixed-caps"), category("naming"), "don't use underscores in Go names; %s %s should be %s", thing, id.Name, should)
-			return
-		}
-		f.errorf(id, 0.8, link(styleGuideBase+"#initialisms"), category("naming"), "%s %s should be %s", thing, id.Name, should)
-	}
-	checkList := func(fl *ast.FieldList, thing string) {
-		if fl == nil {
-			return
-		}
-		for _, f := range fl.List {
-			for _, id := range f.Names {
-				check(id, thing)
-			}
-		}
-	}
-	f.walk(func(node ast.Node) bool {
-		switch v := node.(type) {
-		case *ast.AssignStmt:
-			if v.Tok == token.ASSIGN {
-				return true
-			}
-			for _, exp := range v.Lhs {
-				if id, ok := exp.(*ast.Ident); ok {
-					check(id, "var")
-				}
-			}
-		case *ast.FuncDecl:
-			if f.isTest() && (strings.HasPrefix(v.Name.Name, "Example") || strings.HasPrefix(v.Name.Name, "Test") || strings.HasPrefix(v.Name.Name, "Benchmark")) {
-				return true
-			}
-
-			thing := "func"
-			if v.Recv != nil {
-				thing = "method"
-			}
-
-			// Exclude naming warnings for functions that are exported to C but
-			// not exported in the Go API.
-			// See https://github.com/golang/lint/issues/144.
-			if ast.IsExported(v.Name.Name) || !isCgoExported(v) {
-				check(v.Name, thing)
-			}
-
-			checkList(v.Type.Params, thing+" parameter")
-			checkList(v.Type.Results, thing+" result")
-		case *ast.GenDecl:
-			if v.Tok == token.IMPORT {
-				return true
-			}
-			var thing string
-			switch v.Tok {
-			case token.CONST:
-				thing = "const"
-			case token.TYPE:
-				thing = "type"
-			case token.VAR:
-				thing = "var"
-			}
-			for _, spec := range v.Specs {
-				switch s := spec.(type) {
-				case *ast.TypeSpec:
-					check(s.Name, thing)
-				case *ast.ValueSpec:
-					for _, id := range s.Names {
-						check(id, thing)
-					}
-				}
-			}
-		case *ast.InterfaceType:
-			// Do not check interface method names.
-			// They are often constrainted by the method names of concrete types.
-			for _, x := range v.Methods.List {
-				ft, ok := x.Type.(*ast.FuncType)
-				if !ok { // might be an embedded interface name
-					continue
-				}
-				checkList(ft.Params, "interface method parameter")
-				checkList(ft.Results, "interface method result")
-			}
-		case *ast.RangeStmt:
-			if v.Tok == token.ASSIGN {
-				return true
-			}
-			if id, ok := v.Key.(*ast.Ident); ok {
-				check(id, "range var")
-			}
-			if id, ok := v.Value.(*ast.Ident); ok {
-				check(id, "range var")
-			}
-		case *ast.StructType:
-			for _, f := range v.Fields.List {
-				for _, id := range f.Names {
-					check(id, "struct field")
-				}
-			}
-		}
-		return true
-	})
-}
-
-// lintName returns a different name if it should be different.
-func lintName(name string) (should string) {
-	// Fast path for simple cases: "_" and all lowercase.
-	if name == "_" {
-		return name
-	}
-	allLower := true
-	for _, r := range name {
-		if !unicode.IsLower(r) {
-			allLower = false
-			break
-		}
-	}
-	if allLower {
-		return name
-	}
-
-	// Split camelCase at any lower->upper transition, and split on underscores.
-	// Check each word for common initialisms.
-	runes := []rune(name)
-	w, i := 0, 0 // index of start of word, scan
-	for i+1 <= len(runes) {
-		eow := false // whether we hit the end of a word
-		if i+1 == len(runes) {
-			eow = true
-		} else if runes[i+1] == '_' {
-			// underscore; shift the remainder forward over any run of underscores
-			eow = true
-			n := 1
-			for i+n+1 < len(runes) && runes[i+n+1] == '_' {
-				n++
-			}
-
-			// Leave at most one underscore if the underscore is between two digits
-			if i+n+1 < len(runes) && unicode.IsDigit(runes[i]) && unicode.IsDigit(runes[i+n+1]) {
-				n--
-			}
-
-			copy(runes[i+1:], runes[i+n+1:])
-			runes = runes[:len(runes)-n]
-		} else if unicode.IsLower(runes[i]) && !unicode.IsLower(runes[i+1]) {
-			// lower->non-lower
-			eow = true
-		}
-		i++
-		if !eow {
-			continue
-		}
-
-		// [w,i) is a word.
-		word := string(runes[w:i])
-		if u := strings.ToUpper(word); commonInitialisms[u] {
-			// Keep consistent case, which is lowercase only at the start.
-			if w == 0 && unicode.IsLower(runes[w]) {
-				u = strings.ToLower(u)
-			}
-			// All the common initialisms are ASCII,
-			// so we can replace the bytes exactly.
-			copy(runes[w:], []rune(u))
-		} else if w > 0 && strings.ToLower(word) == word {
-			// already all lowercase, and not the first word, so uppercase the first character.
-			runes[w] = unicode.ToUpper(runes[w])
-		}
-		w = i
-	}
-	return string(runes)
-}
-
-// commonInitialisms is a set of common initialisms.
-// Only add entries that are highly unlikely to be non-initialisms.
-// For instance, "ID" is fine (Freudian code is rare), but "AND" is not.
-var commonInitialisms = map[string]bool{
-	"ACL":   true,
-	"API":   true,
-	"ASCII": true,
-	"CPU":   true,
-	"CSS":   true,
-	"DNS":   true,
-	"EOF":   true,
-	"GUID":  true,
-	"HTML":  true,
-	"HTTP":  true,
-	"HTTPS": true,
-	"ID":    true,
-	"IP":    true,
-	"JSON":  true,
-	"LHS":   true,
-	"QPS":   true,
-	"RAM":   true,
-	"RHS":   true,
-	"RPC":   true,
-	"SLA":   true,
-	"SMTP":  true,
-	"SQL":   true,
-	"SSH":   true,
-	"TCP":   true,
-	"TLS":   true,
-	"TTL":   true,
-	"UDP":   true,
-	"UI":    true,
-	"UID":   true,
-	"UUID":  true,
-	"URI":   true,
-	"URL":   true,
-	"UTF8":  true,
-	"VM":    true,
-	"XML":   true,
-	"XMPP":  true,
-	"XSRF":  true,
-	"XSS":   true,
-}
-
-// lintTypeDoc examines the doc comment on a type.
-// It complains if they are missing from an exported type,
-// or if they are not of the standard form.
-func (f *file) lintTypeDoc(t *ast.TypeSpec, doc *ast.CommentGroup) {
-	if !ast.IsExported(t.Name.Name) {
-		return
-	}
-	if doc == nil {
-		f.errorf(t, 1, link(docCommentsLink), category("comments"), "exported type %v should have comment or be unexported", t.Name)
-		return
-	}
-
-	s := doc.Text()
-	articles := [...]string{"A", "An", "The"}
-	for _, a := range articles {
-		if strings.HasPrefix(s, a+" ") {
-			s = s[len(a)+1:]
-			break
-		}
-	}
-	if !strings.HasPrefix(s, t.Name.Name+" ") {
-		f.errorf(doc, 1, link(docCommentsLink), category("comments"), `comment on exported type %v should be of the form "%v ..." (with optional leading article)`, t.Name, t.Name)
-	}
-}
-
-var commonMethods = map[string]bool{
-	"Error":     true,
-	"Read":      true,
-	"ServeHTTP": true,
-	"String":    true,
-	"Write":     true,
-	"Unwrap":    true,
-}
-
-// lintFuncDoc examines doc comments on functions and methods.
-// It complains if they are missing, or not of the right form.
-// It has specific exclusions for well-known methods (see commonMethods above).
-func (f *file) lintFuncDoc(fn *ast.FuncDecl) {
-	if !ast.IsExported(fn.Name.Name) {
-		// func is unexported
-		return
-	}
-	kind := "function"
-	name := fn.Name.Name
-	if fn.Recv != nil && len(fn.Recv.List) > 0 {
-		// method
-		kind = "method"
-		recv := receiverType(fn)
-		if !ast.IsExported(recv) {
-			// receiver is unexported
-			return
-		}
-		if commonMethods[name] {
-			return
-		}
-		switch name {
-		case "Len", "Less", "Swap":
-			if f.pkg.sortable[recv] {
-				return
-			}
-		}
-		name = recv + "." + name
-	}
-	if fn.Doc == nil {
-		f.errorf(fn, 1, link(docCommentsLink), category("comments"), "exported %s %s should have comment or be unexported", kind, name)
-		return
-	}
-	s := fn.Doc.Text()
-	prefix := fn.Name.Name + " "
-	if !strings.HasPrefix(s, prefix) {
-		f.errorf(fn.Doc, 1, link(docCommentsLink), category("comments"), `comment on exported %s %s should be of the form "%s..."`, kind, name, prefix)
-	}
-}
-
-// lintValueSpecDoc examines package-global variables and constants.
-// It complains if they are not individually declared,
-// or if they are not suitably documented in the right form (unless they are in a block that is commented).
-func (f *file) lintValueSpecDoc(vs *ast.ValueSpec, gd *ast.GenDecl, genDeclMissingComments map[*ast.GenDecl]bool) {
-	kind := "var"
-	if gd.Tok == token.CONST {
-		kind = "const"
-	}
-
-	if len(vs.Names) > 1 {
-		// Check that none are exported except for the first.
-		for _, n := range vs.Names[1:] {
-			if ast.IsExported(n.Name) {
-				f.errorf(vs, 1, category("comments"), "exported %s %s should have its own declaration", kind, n.Name)
-				return
-			}
-		}
-	}
-
-	// Only one name.
-	name := vs.Names[0].Name
-	if !ast.IsExported(name) {
-		return
-	}
-
-	if vs.Doc == nil && gd.Doc == nil {
-		if genDeclMissingComments[gd] {
-			return
-		}
-		block := ""
-		if kind == "const" && gd.Lparen.IsValid() {
-			block = " (or a comment on this block)"
-		}
-		f.errorf(vs, 1, link(docCommentsLink), category("comments"), "exported %s %s should have comment%s or be unexported", kind, name, block)
-		genDeclMissingComments[gd] = true
-		return
-	}
-	// If this GenDecl has parens and a comment, we don't check its comment form.
-	if gd.Lparen.IsValid() && gd.Doc != nil {
-		return
-	}
-	// The relevant text to check will be on either vs.Doc or gd.Doc.
-	// Use vs.Doc preferentially.
-	doc := vs.Doc
-	if doc == nil {
-		doc = gd.Doc
-	}
-	prefix := name + " "
-	if !strings.HasPrefix(doc.Text(), prefix) {
-		f.errorf(doc, 1, link(docCommentsLink), category("comments"), `comment on exported %s %s should be of the form "%s..."`, kind, name, prefix)
-	}
-}
-
-func (f *file) checkStutter(id *ast.Ident, thing string) {
-	pkg, name := f.f.Name.Name, id.Name
-	if !ast.IsExported(name) {
-		// unexported name
-		return
-	}
-	// A name stutters if the package name is a strict prefix
-	// and the next character of the name starts a new word.
-	if len(name) <= len(pkg) {
-		// name is too short to stutter.
-		// This permits the name to be the same as the package name.
-		return
-	}
-	if !strings.EqualFold(pkg, name[:len(pkg)]) {
-		return
-	}
-	// We can assume the name is well-formed UTF-8.
-	// If the next rune after the package name is uppercase or an underscore
-	// the it's starting a new word and thus this name stutters.
-	rem := name[len(pkg):]
-	if next, _ := utf8.DecodeRuneInString(rem); next == '_' || unicode.IsUpper(next) {
-		f.errorf(id, 0.8, link(styleGuideBase+"#package-names"), category("naming"), "%s name will be used as %s.%s by other packages, and that stutters; consider calling this %s", thing, pkg, name, rem)
-	}
-}
-
-// zeroLiteral is a set of ast.BasicLit values that are zero values.
-// It is not exhaustive.
-var zeroLiteral = map[string]bool{
-	"false": true, // bool
-	// runes
-	`'\x00'`: true,
-	`'\000'`: true,
-	// strings
-	`""`: true,
-	"``": true,
-	// numerics
-	"0":   true,
-	"0.":  true,
-	"0.0": true,
-	"0i":  true,
-}
-
-// lintElses examines else blocks. It complains about any else block whose if block ends in a return.
-func (f *file) lintElses() {
-	// We don't want to flag if { } else if { } else { } constructions.
-	// They will appear as an IfStmt whose Else field is also an IfStmt.
-	// Record such a node so we ignore it when we visit it.
-	ignore := make(map[*ast.IfStmt]bool)
-
-	f.walk(func(node ast.Node) bool {
-		ifStmt, ok := node.(*ast.IfStmt)
-		if !ok || ifStmt.Else == nil {
-			return true
-		}
-		if elseif, ok := ifStmt.Else.(*ast.IfStmt); ok {
-			ignore[elseif] = true
-			return true
-		}
-		if ignore[ifStmt] {
-			return true
-		}
-		if _, ok := ifStmt.Else.(*ast.BlockStmt); !ok {
-			// only care about elses without conditions
-			return true
-		}
-		if len(ifStmt.Body.List) == 0 {
-			return true
-		}
-		shortDecl := false // does the if statement have a ":=" initialization statement?
-		if ifStmt.Init != nil {
-			if as, ok := ifStmt.Init.(*ast.AssignStmt); ok && as.Tok == token.DEFINE {
-				shortDecl = true
-			}
-		}
-		lastStmt := ifStmt.Body.List[len(ifStmt.Body.List)-1]
-		if _, ok := lastStmt.(*ast.ReturnStmt); ok {
-			extra := ""
-			if shortDecl {
-				extra = " (move short variable declaration to its own line if necessary)"
-			}
-			f.errorf(ifStmt.Else, 1, link(styleGuideBase+"#indent-error-flow"), category("indent"), "if block ends with a return statement, so drop this else and outdent its block"+extra)
-		}
-		return true
-	})
-}
-
-// lintRanges examines range clauses. It complains about redundant constructions.
-func (f *file) lintRanges() {
-	f.walk(func(node ast.Node) bool {
-		rs, ok := node.(*ast.RangeStmt)
-		if !ok {
-			return true
-		}
-
-		if isIdent(rs.Key, "_") && (rs.Value == nil || isIdent(rs.Value, "_")) {
-			p := f.errorf(rs.Key, 1, category("range-loop"), "should omit values from range; this loop is equivalent to `for range ...`")
-
-			newRS := *rs // shallow copy
-			newRS.Value = nil
-			newRS.Key = nil
-			p.ReplacementLine = f.firstLineOf(&newRS, rs)
-
-			return true
-		}
-
-		if isIdent(rs.Value, "_") {
-			p := f.errorf(rs.Value, 1, category("range-loop"), "should omit 2nd value from range; this loop is equivalent to `for %s %s range ...`", f.render(rs.Key), rs.Tok)
-
-			newRS := *rs // shallow copy
-			newRS.Value = nil
-			p.ReplacementLine = f.firstLineOf(&newRS, rs)
-		}
-
-		return true
-	})
-}
-
-// lintErrorf examines errors.New and testing.Error calls. It complains if its only argument is an fmt.Sprintf invocation.
-func (f *file) lintErrorf() {
-	f.walk(func(node ast.Node) bool {
-		ce, ok := node.(*ast.CallExpr)
-		if !ok || len(ce.Args) != 1 {
-			return true
-		}
-		isErrorsNew := isPkgDot(ce.Fun, "errors", "New")
-		var isTestingError bool
-		se, ok := ce.Fun.(*ast.SelectorExpr)
-		if ok && se.Sel.Name == "Error" {
-			if typ := f.pkg.typeOf(se.X); typ != nil {
-				isTestingError = typ.String() == "*testing.T"
-			}
-		}
-		if !isErrorsNew && !isTestingError {
-			return true
-		}
-		if !f.imports("errors") {
-			return true
-		}
-		arg := ce.Args[0]
-		ce, ok = arg.(*ast.CallExpr)
-		if !ok || !isPkgDot(ce.Fun, "fmt", "Sprintf") {
-			return true
-		}
-		errorfPrefix := "fmt"
-		if isTestingError {
-			errorfPrefix = f.render(se.X)
-		}
-		p := f.errorf(node, 1, category("errors"), "should replace %s(fmt.Sprintf(...)) with %s.Errorf(...)", f.render(se), errorfPrefix)
-
-		m := f.srcLineWithMatch(ce, `^(.*)`+f.render(se)+`\(fmt\.Sprintf\((.*)\)\)(.*)$`)
-		if m != nil {
-			p.ReplacementLine = m[1] + errorfPrefix + ".Errorf(" + m[2] + ")" + m[3]
-		}
-
-		return true
-	})
-}
-
-// lintErrors examines global error vars. It complains if they aren't named in the standard way.
-func (f *file) lintErrors() {
-	for _, decl := range f.f.Decls {
-		gd, ok := decl.(*ast.GenDecl)
-		if !ok || gd.Tok != token.VAR {
-			continue
-		}
-		for _, spec := range gd.Specs {
-			spec := spec.(*ast.ValueSpec)
-			if len(spec.Names) != 1 || len(spec.Values) != 1 {
-				continue
-			}
-			ce, ok := spec.Values[0].(*ast.CallExpr)
-			if !ok {
-				continue
-			}
-			if !isPkgDot(ce.Fun, "errors", "New") && !isPkgDot(ce.Fun, "fmt", "Errorf") {
-				continue
-			}
-
-			id := spec.Names[0]
-			prefix := "err"
-			if id.IsExported() {
-				prefix = "Err"
-			}
-			if !strings.HasPrefix(id.Name, prefix) {
-				f.errorf(id, 0.9, category("naming"), "error var %s should have name of the form %sFoo", id.Name, prefix)
-			}
-		}
-	}
-}
-
-func lintErrorString(s string) (isClean bool, conf float64) {
-	const basicConfidence = 0.8
-	const capConfidence = basicConfidence - 0.2
-	first, firstN := utf8.DecodeRuneInString(s)
-	last, _ := utf8.DecodeLastRuneInString(s)
-	if last == '.' || last == ':' || last == '!' || last == '\n' {
-		return false, basicConfidence
-	}
-	if unicode.IsUpper(first) {
-		// People use proper nouns and exported Go identifiers in error strings,
-		// so decrease the confidence of warnings for capitalization.
-		if len(s) <= firstN {
-			return false, capConfidence
-		}
-		// Flag strings starting with something that doesn't look like an initialism.
-		if second, _ := utf8.DecodeRuneInString(s[firstN:]); !unicode.IsUpper(second) {
-			return false, capConfidence
-		}
-	}
-	return true, 0
-}
-
-// lintErrorStrings examines error strings.
-// It complains if they are capitalized or end in punctuation or a newline.
-func (f *file) lintErrorStrings() {
-	f.walk(func(node ast.Node) bool {
-		ce, ok := node.(*ast.CallExpr)
-		if !ok {
-			return true
-		}
-		if !isPkgDot(ce.Fun, "errors", "New") && !isPkgDot(ce.Fun, "fmt", "Errorf") {
-			return true
-		}
-		if len(ce.Args) < 1 {
-			return true
-		}
-		str, ok := ce.Args[0].(*ast.BasicLit)
-		if !ok || str.Kind != token.STRING {
-			return true
-		}
-		s, _ := strconv.Unquote(str.Value) // can assume well-formed Go
-		if s == "" {
-			return true
-		}
-		clean, conf := lintErrorString(s)
-		if clean {
-			return true
-		}
-
-		f.errorf(str, conf, link(styleGuideBase+"#error-strings"), category("errors"),
-			"error strings should not be capitalized or end with punctuation or a newline")
-		return true
-	})
-}
-
-// lintReceiverNames examines receiver names. It complains about inconsistent
-// names used for the same type and names such as "this".
-func (f *file) lintReceiverNames() {
-	typeReceiver := map[string]string{}
-	f.walk(func(n ast.Node) bool {
-		fn, ok := n.(*ast.FuncDecl)
-		if !ok || fn.Recv == nil || len(fn.Recv.List) == 0 {
-			return true
-		}
-		names := fn.Recv.List[0].Names
-		if len(names) < 1 {
-			return true
-		}
-		name := names[0].Name
-		const ref = styleGuideBase + "#receiver-names"
-		if name == "_" {
-			f.errorf(n, 1, link(ref), category("naming"), `receiver name should not be an underscore, omit the name if it is unused`)
-			return true
-		}
-		if name == "this" || name == "self" {
-			f.errorf(n, 1, link(ref), category("naming"), `receiver name should be a reflection of its identity; don't use generic names such as "this" or "self"`)
-			return true
-		}
-		recv := receiverType(fn)
-		if prev, ok := typeReceiver[recv]; ok && prev != name {
-			f.errorf(n, 1, link(ref), category("naming"), "receiver name %s should be consistent with previous receiver name %s for %s", name, prev, recv)
-			return true
-		}
-		typeReceiver[recv] = name
-		return true
-	})
-}
-
-// lintIncDec examines statements that increment or decrement a variable.
-// It complains if they don't use x++ or x--.
-func (f *file) lintIncDec() {
-	f.walk(func(n ast.Node) bool {
-		as, ok := n.(*ast.AssignStmt)
-		if !ok {
-			return true
-		}
-		if len(as.Lhs) != 1 {
-			return true
-		}
-		if !isOne(as.Rhs[0]) {
-			return true
-		}
-		var suffix string
-		switch as.Tok {
-		case token.ADD_ASSIGN:
-			suffix = "++"
-		case token.SUB_ASSIGN:
-			suffix = "--"
-		default:
-			return true
-		}
-		f.errorf(as, 0.8, category("unary-op"), "should replace %s with %s%s", f.render(as), f.render(as.Lhs[0]), suffix)
-		return true
-	})
-}
-
-// lintErrorReturn examines function declarations that return an error.
-// It complains if the error isn't the last parameter.
-func (f *file) lintErrorReturn() {
-	f.walk(func(n ast.Node) bool {
-		fn, ok := n.(*ast.FuncDecl)
-		if !ok || fn.Type.Results == nil {
-			return true
-		}
-		ret := fn.Type.Results.List
-		if len(ret) <= 1 {
-			return true
-		}
-		if isIdent(ret[len(ret)-1].Type, "error") {
-			return true
-		}
-		// An error return parameter should be the last parameter.
-		// Flag any error parameters found before the last.
-		for _, r := range ret[:len(ret)-1] {
-			if isIdent(r.Type, "error") {
-				f.errorf(fn, 0.9, category("arg-order"), "error should be the last type when returning multiple items")
-				break // only flag one
-			}
-		}
-		return true
-	})
-}
-
-// lintUnexportedReturn examines exported function declarations.
-// It complains if any return an unexported type.
-func (f *file) lintUnexportedReturn() {
-	f.walk(func(n ast.Node) bool {
-		fn, ok := n.(*ast.FuncDecl)
-		if !ok {
-			return true
-		}
-		if fn.Type.Results == nil {
-			return false
-		}
-		if !fn.Name.IsExported() {
-			return false
-		}
-		thing := "func"
-		if fn.Recv != nil && len(fn.Recv.List) > 0 {
-			thing = "method"
-			if !ast.IsExported(receiverType(fn)) {
-				// Don't report exported methods of unexported types,
-				// such as private implementations of sort.Interface.
-				return false
-			}
-		}
-		for _, ret := range fn.Type.Results.List {
-			typ := f.pkg.typeOf(ret.Type)
-			if exportedType(typ) {
-				continue
-			}
-			f.errorf(ret.Type, 0.8, category("unexported-type-in-api"),
-				"exported %s %s returns unexported type %s, which can be annoying to use",
-				thing, fn.Name.Name, typ)
-			break // only flag one
-		}
-		return false
-	})
-}
-
-// exportedType reports whether typ is an exported type.
-// It is imprecise, and will err on the side of returning true,
-// such as for composite types.
-func exportedType(typ types.Type) bool {
-	switch T := typ.(type) {
-	case *types.Named:
-		// Builtin types have no package.
-		return T.Obj().Pkg() == nil || T.Obj().Exported()
-	case *types.Map:
-		return exportedType(T.Key()) && exportedType(T.Elem())
-	case interface {
-		Elem() types.Type
-	}: // array, slice, pointer, chan
-		return exportedType(T.Elem())
-	}
-	// Be conservative about other types, such as struct, interface, etc.
-	return true
-}
-
-// timeSuffixes is a list of name suffixes that imply a time unit.
-// This is not an exhaustive list.
-var timeSuffixes = []string{
-	"Sec", "Secs", "Seconds",
-	"Msec", "Msecs",
-	"Milli", "Millis", "Milliseconds",
-	"Usec", "Usecs", "Microseconds",
-	"MS", "Ms",
-}
-
-func (f *file) lintTimeNames() {
-	f.walk(func(node ast.Node) bool {
-		v, ok := node.(*ast.ValueSpec)
-		if !ok {
-			return true
-		}
-		for _, name := range v.Names {
-			origTyp := f.pkg.typeOf(name)
-			// Look for time.Duration or *time.Duration;
-			// the latter is common when using flag.Duration.
-			typ := origTyp
-			if pt, ok := typ.(*types.Pointer); ok {
-				typ = pt.Elem()
-			}
-			if !f.pkg.isNamedType(typ, "time", "Duration") {
-				continue
-			}
-			suffix := ""
-			for _, suf := range timeSuffixes {
-				if strings.HasSuffix(name.Name, suf) {
-					suffix = suf
-					break
-				}
-			}
-			if suffix == "" {
-				continue
-			}
-			f.errorf(v, 0.9, category("time"), "var %s is of type %v; don't use unit-specific suffix %q", name.Name, origTyp, suffix)
-		}
-		return true
-	})
-}
-
-// lintContextKeyTypes checks for call expressions to context.WithValue with
-// basic types used for the key argument.
-// See: https://golang.org/issue/17293
-func (f *file) lintContextKeyTypes() {
-	f.walk(func(node ast.Node) bool {
-		switch node := node.(type) {
-		case *ast.CallExpr:
-			f.checkContextKeyType(node)
-		}
-
-		return true
-	})
-}
-
-// checkContextKeyType reports an error if the call expression calls
-// context.WithValue with a key argument of basic type.
-func (f *file) checkContextKeyType(x *ast.CallExpr) {
-	sel, ok := x.Fun.(*ast.SelectorExpr)
-	if !ok {
-		return
-	}
-	pkg, ok := sel.X.(*ast.Ident)
-	if !ok || pkg.Name != "context" {
-		return
-	}
-	if sel.Sel.Name != "WithValue" {
-		return
-	}
-
-	// key is second argument to context.WithValue
-	if len(x.Args) != 3 {
-		return
-	}
-	key := f.pkg.typesInfo.Types[x.Args[1]]
-
-	if ktyp, ok := key.Type.(*types.Basic); ok && ktyp.Kind() != types.Invalid {
-		f.errorf(x, 1.0, category("context"), fmt.Sprintf("should not use basic type %s as key in context.WithValue", key.Type))
-	}
-}
-
-// lintContextArgs examines function declarations that contain an
-// argument with a type of context.Context
-// It complains if that argument isn't the first parameter.
-func (f *file) lintContextArgs() {
-	f.walk(func(n ast.Node) bool {
-		fn, ok := n.(*ast.FuncDecl)
-		if !ok || len(fn.Type.Params.List) <= 1 {
-			return true
-		}
-		// A context.Context should be the first parameter of a function.
-		// Flag any that show up after the first.
-		for _, arg := range fn.Type.Params.List[1:] {
-			if isPkgDot(arg.Type, "context", "Context") {
-				f.errorf(fn, 0.9, link("https://golang.org/pkg/context/"), category("arg-order"), "context.Context should be the first parameter of a function")
-				break // only flag one
-			}
-		}
-		return true
-	})
-}
-
-// containsComments returns whether the interval [start, end) contains any
-// comments without "// MATCH " prefix.
-func (f *file) containsComments(start, end token.Pos) bool {
-	for _, cgroup := range f.f.Comments {
-		comments := cgroup.List
-		if comments[0].Slash >= end {
-			// All comments starting with this group are after end pos.
-			return false
-		}
-		if comments[len(comments)-1].Slash < start {
-			// Comments group ends before start pos.
-			continue
-		}
-		for _, c := range comments {
-			if start <= c.Slash && c.Slash < end && !strings.HasPrefix(c.Text, "// MATCH ") {
-				return true
-			}
-		}
-	}
-	return false
-}
-
-// receiverType returns the named type of the method receiver, sans "*",
-// or "invalid-type" if fn.Recv is ill formed.
-func receiverType(fn *ast.FuncDecl) string {
-	switch e := fn.Recv.List[0].Type.(type) {
-	case *ast.Ident:
-		return e.Name
-	case *ast.StarExpr:
-		if id, ok := e.X.(*ast.Ident); ok {
-			return id.Name
-		}
-	}
-	// The parser accepts much more than just the legal forms.
-	return "invalid-type"
-}
-
-func (f *file) walk(fn func(ast.Node) bool) {
-	ast.Walk(walker(fn), f.f)
-}
-
-func (f *file) render(x interface{}) string {
-	var buf bytes.Buffer
-	if err := printer.Fprint(&buf, f.fset, x); err != nil {
-		panic(err)
-	}
-	return buf.String()
-}
-
-func (f *file) debugRender(x interface{}) string {
-	var buf bytes.Buffer
-	if err := ast.Fprint(&buf, f.fset, x, nil); err != nil {
-		panic(err)
-	}
-	return buf.String()
-}
-
-// walker adapts a function to satisfy the ast.Visitor interface.
-// The function return whether the walk should proceed into the node's children.
-type walker func(ast.Node) bool
-
-func (w walker) Visit(node ast.Node) ast.Visitor {
-	if w(node) {
-		return w
-	}
-	return nil
-}
-
-func isIdent(expr ast.Expr, ident string) bool {
-	id, ok := expr.(*ast.Ident)
-	return ok && id.Name == ident
-}
-
-// isBlank returns whether id is the blank identifier "_".
-// If id == nil, the answer is false.
-func isBlank(id *ast.Ident) bool { return id != nil && id.Name == "_" }
-
-func isPkgDot(expr ast.Expr, pkg, name string) bool {
-	sel, ok := expr.(*ast.SelectorExpr)
-	return ok && isIdent(sel.X, pkg) && isIdent(sel.Sel, name)
-}
-
-func isOne(expr ast.Expr) bool {
-	lit, ok := expr.(*ast.BasicLit)
-	return ok && lit.Kind == token.INT && lit.Value == "1"
-}
-
-func isCgoExported(f *ast.FuncDecl) bool {
-	if f.Recv != nil || f.Doc == nil {
-		return false
-	}
-
-	cgoExport := regexp.MustCompile(fmt.Sprintf("(?m)^//export %s$", regexp.QuoteMeta(f.Name.Name)))
-	for _, c := range f.Doc.List {
-		if cgoExport.MatchString(c.Text) {
-			return true
-		}
-	}
-	return false
-}
-
-var basicTypeKinds = map[types.BasicKind]string{
-	types.UntypedBool:    "bool",
-	types.UntypedInt:     "int",
-	types.UntypedRune:    "rune",
-	types.UntypedFloat:   "float64",
-	types.UntypedComplex: "complex128",
-	types.UntypedString:  "string",
-}
-
-// isUntypedConst reports whether expr is an untyped constant,
-// and indicates what its default type is.
-// scope may be nil.
-func (f *file) isUntypedConst(expr ast.Expr) (defType string, ok bool) {
-	// Re-evaluate expr outside of its context to see if it's untyped.
-	// (An expr evaluated within, for example, an assignment context will get the type of the LHS.)
-	exprStr := f.render(expr)
-	tv, err := types.Eval(f.fset, f.pkg.typesPkg, expr.Pos(), exprStr)
-	if err != nil {
-		return "", false
-	}
-	if b, ok := tv.Type.(*types.Basic); ok {
-		if dt, ok := basicTypeKinds[b.Kind()]; ok {
-			return dt, true
-		}
-	}
-
-	return "", false
-}
-
-// firstLineOf renders the given node and returns its first line.
-// It will also match the indentation of another node.
-func (f *file) firstLineOf(node, match ast.Node) string {
-	line := f.render(node)
-	if i := strings.Index(line, "\n"); i >= 0 {
-		line = line[:i]
-	}
-	return f.indentOf(match) + line
-}
-
-func (f *file) indentOf(node ast.Node) string {
-	line := srcLine(f.src, f.fset.Position(node.Pos()))
-	for i, r := range line {
-		switch r {
-		case ' ', '\t':
-		default:
-			return line[:i]
-		}
-	}
-	return line // unusual or empty line
-}
-
-func (f *file) srcLineWithMatch(node ast.Node, pattern string) (m []string) {
-	line := srcLine(f.src, f.fset.Position(node.Pos()))
-	line = strings.TrimSuffix(line, "\n")
-	rx := regexp.MustCompile(pattern)
-	return rx.FindStringSubmatch(line)
-}
-
-// imports returns true if the current file imports the specified package path.
-func (f *file) imports(importPath string) bool {
-	all := astutil.Imports(f.fset, f.f)
-	for _, p := range all {
-		for _, i := range p {
-			uq, err := strconv.Unquote(i.Path.Value)
-			if err == nil && importPath == uq {
-				return true
-			}
-		}
-	}
-	return false
-}
-
-// srcLine returns the complete line at p, including the terminating newline.
-func srcLine(src []byte, p token.Position) string {
-	// Run to end of line in both directions if not at line start/end.
-	lo, hi := p.Offset, p.Offset+1
-	for lo > 0 && src[lo-1] != '\n' {
-		lo--
-	}
-	for hi < len(src) && src[hi-1] != '\n' {
-		hi++
-	}
-	return string(src[lo:hi])
-}

vendor/golang.org/x/mod/internal/lazyregexp/lazyre.go

@@ -0,0 +1,78 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package lazyregexp is a thin wrapper over regexp, allowing the use of global
+// regexp variables without forcing them to be compiled at init.
+package lazyregexp
+
+import (
+	"os"
+	"regexp"
+	"strings"
+	"sync"
+)
+
+// Regexp is a wrapper around regexp.Regexp, where the underlying regexp will be
+// compiled the first time it is needed.
+type Regexp struct {
+	str  string
+	once sync.Once
+	rx   *regexp.Regexp
+}
+
+func (r *Regexp) re() *regexp.Regexp {
+	r.once.Do(r.build)
+	return r.rx
+}
+
+func (r *Regexp) build() {
+	r.rx = regexp.MustCompile(r.str)
+	r.str = ""
+}
+
+func (r *Regexp) FindSubmatch(s []byte) [][]byte {
+	return r.re().FindSubmatch(s)
+}
+
+func (r *Regexp) FindStringSubmatch(s string) []string {
+	return r.re().FindStringSubmatch(s)
+}
+
+func (r *Regexp) FindStringSubmatchIndex(s string) []int {
+	return r.re().FindStringSubmatchIndex(s)
+}
+
+func (r *Regexp) ReplaceAllString(src, repl string) string {
+	return r.re().ReplaceAllString(src, repl)
+}
+
+func (r *Regexp) FindString(s string) string {
+	return r.re().FindString(s)
+}
+
+func (r *Regexp) FindAllString(s string, n int) []string {
+	return r.re().FindAllString(s, n)
+}
+
+func (r *Regexp) MatchString(s string) bool {
+	return r.re().MatchString(s)
+}
+
+func (r *Regexp) SubexpNames() []string {
+	return r.re().SubexpNames()
+}
+
+var inTest = len(os.Args) > 0 && strings.HasSuffix(strings.TrimSuffix(os.Args[0], ".exe"), ".test")
+
+// New creates a new lazy regexp, delaying the compiling work until it is first
+// needed. If the code is being run as part of tests, the regexp compiling will
+// happen immediately.
+func New(str string) *Regexp {
+	lr := &Regexp{str: str}
+	if inTest {
+		// In tests, always compile the regexps early.
+		lr.re()
+	}
+	return lr
+}

vendor/golang.org/x/mod/module/module.go

@@ -192,6 +192,21 @@ func (e *InvalidVersionError) Error() string {
 
 func (e *InvalidVersionError) Unwrap() error { return e.Err }
 
+// An InvalidPathError indicates a module, import, or file path doesn't
+// satisfy all naming constraints. See CheckPath, CheckImportPath,
+// and CheckFilePath for specific restrictions.
+type InvalidPathError struct {
+	Kind string // "module", "import", or "file"
+	Path string
+	Err  error
+}
+
+func (e *InvalidPathError) Error() string {
+	return fmt.Sprintf("malformed %s path %q: %v", e.Kind, e.Path, e.Err)
+}
+
+func (e *InvalidPathError) Unwrap() error { return e.Err }
+
 // Check checks that a given module path, version pair is valid.
 // In addition to the path being a valid module path
 // and the version being a valid semantic version,
@@ -271,12 +286,7 @@ func fileNameOK(r rune) bool {
 		if '0' <= r && r <= '9' || 'A' <= r && r <= 'Z' || 'a' <= r && r <= 'z' {
 			return true
 		}
-		for i := 0; i < len(allowed); i++ {
-			if rune(allowed[i]) == r {
-				return true
-			}
-		}
-		return false
+		return strings.ContainsRune(allowed, r)
 	}
 	// It may be OK to add more ASCII punctuation here, but only carefully.
 	// For example Windows disallows < > \, and macOS disallows :, so we must not allow those.
@@ -296,30 +306,36 @@ func fileNameOK(r rune) bool {
 // this second requirement is replaced by a requirement that the path
 // follow the gopkg.in server's conventions.
 // Third, no path element may begin with a dot.
-func CheckPath(path string) error {
+func CheckPath(path string) (err error) {
+	defer func() {
+		if err != nil {
+			err = &InvalidPathError{Kind: "module", Path: path, Err: err}
+		}
+	}()
+
 	if err := checkPath(path, modulePath); err != nil {
-		return fmt.Errorf("malformed module path %q: %v", path, err)
+		return err
 	}
 	i := strings.Index(path, "/")
 	if i < 0 {
 		i = len(path)
 	}
 	if i == 0 {
-		return fmt.Errorf("malformed module path %q: leading slash", path)
+		return fmt.Errorf("leading slash")
 	}
 	if !strings.Contains(path[:i], ".") {
-		return fmt.Errorf("malformed module path %q: missing dot in first path element", path)
+		return fmt.Errorf("missing dot in first path element")
 	}
 	if path[0] == '-' {
-		return fmt.Errorf("malformed module path %q: leading dash in first path element", path)
+		return fmt.Errorf("leading dash in first path element")
 	}
 	for _, r := range path[:i] {
 		if !firstPathOK(r) {
-			return fmt.Errorf("malformed module path %q: invalid char %q in first path element", path, r)
+			return fmt.Errorf("invalid char %q in first path element", r)
 		}
 	}
 	if _, _, ok := SplitPathVersion(path); !ok {
-		return fmt.Errorf("malformed module path %q: invalid version", path)
+		return fmt.Errorf("invalid version")
 	}
 	return nil
 }
@@ -343,7 +359,7 @@ func CheckPath(path string) error {
 // subtleties of Unicode.
 func CheckImportPath(path string) error {
 	if err := checkPath(path, importPath); err != nil {
-		return fmt.Errorf("malformed import path %q: %v", path, err)
+		return &InvalidPathError{Kind: "import", Path: path, Err: err}
 	}
 	return nil
 }
@@ -358,12 +374,13 @@ const (
 	filePath
 )
 
-// checkPath checks that a general path is valid.
-// It returns an error describing why but not mentioning path.
-// Because these checks apply to both module paths and import paths,
-// the caller is expected to add the "malformed ___ path %q: " prefix.
-// fileName indicates whether the final element of the path is a file name
-// (as opposed to a directory name).
+// checkPath checks that a general path is valid. kind indicates what
+// specific constraints should be applied.
+//
+// checkPath returns an error describing why the path is not valid.
+// Because these checks apply to module, import, and file paths,
+// and because other checks may be applied, the caller is expected to wrap
+// this error with InvalidPathError.
 func checkPath(path string, kind pathKind) error {
 	if !utf8.ValidString(path) {
 		return fmt.Errorf("invalid UTF-8")
@@ -371,7 +388,7 @@ func checkPath(path string, kind pathKind) error {
 	if path == "" {
 		return fmt.Errorf("empty string")
 	}
-	if path[0] == '-' {
+	if path[0] == '-' && kind != filePath {
 		return fmt.Errorf("leading dash")
 	}
 	if strings.Contains(path, "//") {
@@ -477,7 +494,7 @@ func checkElem(elem string, kind pathKind) error {
 // subtleties of Unicode.
 func CheckFilePath(path string) error {
 	if err := checkPath(path, filePath); err != nil {
-		return fmt.Errorf("malformed file path %q: %v", path, err)
+		return &InvalidPathError{Kind: "file", Path: path, Err: err}
 	}
 	return nil
 }
@@ -781,6 +798,7 @@ func unescapeString(escaped string) (string, bool) {
 // GOPRIVATE environment variable, as described by 'go help module-private'.
 //
 // It ignores any empty or malformed patterns in the list.
+// Trailing slashes on patterns are ignored.
 func MatchPrefixPatterns(globs, target string) bool {
 	for globs != "" {
 		// Extract next non-empty glob in comma-separated list.
@@ -790,6 +808,7 @@ func MatchPrefixPatterns(globs, target string) bool {
 		} else {
 			glob, globs = globs, ""
 		}
+		glob = strings.TrimSuffix(glob, "/")
 		if glob == "" {
 			continue
 		}

vendor/golang.org/x/mod/module/pseudo.go

@@ -0,0 +1,250 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Pseudo-versions
+//
+// Code authors are expected to tag the revisions they want users to use,
+// including prereleases. However, not all authors tag versions at all,
+// and not all commits a user might want to try will have tags.
+// A pseudo-version is a version with a special form that allows us to
+// address an untagged commit and order that version with respect to
+// other versions we might encounter.
+//
+// A pseudo-version takes one of the general forms:
+//
+//	(1) vX.0.0-yyyymmddhhmmss-abcdef123456
+//	(2) vX.Y.(Z+1)-0.yyyymmddhhmmss-abcdef123456
+//	(3) vX.Y.(Z+1)-0.yyyymmddhhmmss-abcdef123456+incompatible
+//	(4) vX.Y.Z-pre.0.yyyymmddhhmmss-abcdef123456
+//	(5) vX.Y.Z-pre.0.yyyymmddhhmmss-abcdef123456+incompatible
+//
+// If there is no recently tagged version with the right major version vX,
+// then form (1) is used, creating a space of pseudo-versions at the bottom
+// of the vX version range, less than any tagged version, including the unlikely v0.0.0.
+//
+// If the most recent tagged version before the target commit is vX.Y.Z or vX.Y.Z+incompatible,
+// then the pseudo-version uses form (2) or (3), making it a prerelease for the next
+// possible semantic version after vX.Y.Z. The leading 0 segment in the prerelease string
+// ensures that the pseudo-version compares less than possible future explicit prereleases
+// like vX.Y.(Z+1)-rc1 or vX.Y.(Z+1)-1.
+//
+// If the most recent tagged version before the target commit is vX.Y.Z-pre or vX.Y.Z-pre+incompatible,
+// then the pseudo-version uses form (4) or (5), making it a slightly later prerelease.
+
+package module
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+	"time"
+
+	"golang.org/x/mod/internal/lazyregexp"
+	"golang.org/x/mod/semver"
+)
+
+var pseudoVersionRE = lazyregexp.New(`^v[0-9]+\.(0\.0-|\d+\.\d+-([^+]*\.)?0\.)\d{14}-[A-Za-z0-9]+(\+[0-9A-Za-z-]+(\.[0-9A-Za-z-]+)*)?$`)
+
+const PseudoVersionTimestampFormat = "20060102150405"
+
+// PseudoVersion returns a pseudo-version for the given major version ("v1")
+// preexisting older tagged version ("" or "v1.2.3" or "v1.2.3-pre"), revision time,
+// and revision identifier (usually a 12-byte commit hash prefix).
+func PseudoVersion(major, older string, t time.Time, rev string) string {
+	if major == "" {
+		major = "v0"
+	}
+	segment := fmt.Sprintf("%s-%s", t.UTC().Format(PseudoVersionTimestampFormat), rev)
+	build := semver.Build(older)
+	older = semver.Canonical(older)
+	if older == "" {
+		return major + ".0.0-" + segment // form (1)
+	}
+	if semver.Prerelease(older) != "" {
+		return older + ".0." + segment + build // form (4), (5)
+	}
+
+	// Form (2), (3).
+	// Extract patch from vMAJOR.MINOR.PATCH
+	i := strings.LastIndex(older, ".") + 1
+	v, patch := older[:i], older[i:]
+
+	// Reassemble.
+	return v + incDecimal(patch) + "-0." + segment + build
+}
+
+// ZeroPseudoVersion returns a pseudo-version with a zero timestamp and
+// revision, which may be used as a placeholder.
+func ZeroPseudoVersion(major string) string {
+	return PseudoVersion(major, "", time.Time{}, "000000000000")
+}
+
+// incDecimal returns the decimal string incremented by 1.
+func incDecimal(decimal string) string {
+	// Scan right to left turning 9s to 0s until you find a digit to increment.
+	digits := []byte(decimal)
+	i := len(digits) - 1
+	for ; i >= 0 && digits[i] == '9'; i-- {
+		digits[i] = '0'
+	}
+	if i >= 0 {
+		digits[i]++
+	} else {
+		// digits is all zeros
+		digits[0] = '1'
+		digits = append(digits, '0')
+	}
+	return string(digits)
+}
+
+// decDecimal returns the decimal string decremented by 1, or the empty string
+// if the decimal is all zeroes.
+func decDecimal(decimal string) string {
+	// Scan right to left turning 0s to 9s until you find a digit to decrement.
+	digits := []byte(decimal)
+	i := len(digits) - 1
+	for ; i >= 0 && digits[i] == '0'; i-- {
+		digits[i] = '9'
+	}
+	if i < 0 {
+		// decimal is all zeros
+		return ""
+	}
+	if i == 0 && digits[i] == '1' && len(digits) > 1 {
+		digits = digits[1:]
+	} else {
+		digits[i]--
+	}
+	return string(digits)
+}
+
+// IsPseudoVersion reports whether v is a pseudo-version.
+func IsPseudoVersion(v string) bool {
+	return strings.Count(v, "-") >= 2 && semver.IsValid(v) && pseudoVersionRE.MatchString(v)
+}
+
+// IsZeroPseudoVersion returns whether v is a pseudo-version with a zero base,
+// timestamp, and revision, as returned by ZeroPseudoVersion.
+func IsZeroPseudoVersion(v string) bool {
+	return v == ZeroPseudoVersion(semver.Major(v))
+}
+
+// PseudoVersionTime returns the time stamp of the pseudo-version v.
+// It returns an error if v is not a pseudo-version or if the time stamp
+// embedded in the pseudo-version is not a valid time.
+func PseudoVersionTime(v string) (time.Time, error) {
+	_, timestamp, _, _, err := parsePseudoVersion(v)
+	if err != nil {
+		return time.Time{}, err
+	}
+	t, err := time.Parse("20060102150405", timestamp)
+	if err != nil {
+		return time.Time{}, &InvalidVersionError{
+			Version: v,
+			Pseudo:  true,
+			Err:     fmt.Errorf("malformed time %q", timestamp),
+		}
+	}
+	return t, nil
+}
+
+// PseudoVersionRev returns the revision identifier of the pseudo-version v.
+// It returns an error if v is not a pseudo-version.
+func PseudoVersionRev(v string) (rev string, err error) {
+	_, _, rev, _, err = parsePseudoVersion(v)
+	return
+}
+
+// PseudoVersionBase returns the canonical parent version, if any, upon which
+// the pseudo-version v is based.
+//
+// If v has no parent version (that is, if it is "vX.0.0-[…]"),
+// PseudoVersionBase returns the empty string and a nil error.
+func PseudoVersionBase(v string) (string, error) {
+	base, _, _, build, err := parsePseudoVersion(v)
+	if err != nil {
+		return "", err
+	}
+
+	switch pre := semver.Prerelease(base); pre {
+	case "":
+		// vX.0.0-yyyymmddhhmmss-abcdef123456 → ""
+		if build != "" {
+			// Pseudo-versions of the form vX.0.0-yyyymmddhhmmss-abcdef123456+incompatible
+			// are nonsensical: the "vX.0.0-" prefix implies that there is no parent tag,
+			// but the "+incompatible" suffix implies that the major version of
+			// the parent tag is not compatible with the module's import path.
+			//
+			// There are a few such entries in the index generated by proxy.golang.org,
+			// but we believe those entries were generated by the proxy itself.
+			return "", &InvalidVersionError{
+				Version: v,
+				Pseudo:  true,
+				Err:     fmt.Errorf("lacks base version, but has build metadata %q", build),
+			}
+		}
+		return "", nil
+
+	case "-0":
+		// vX.Y.(Z+1)-0.yyyymmddhhmmss-abcdef123456 → vX.Y.Z
+		// vX.Y.(Z+1)-0.yyyymmddhhmmss-abcdef123456+incompatible → vX.Y.Z+incompatible
+		base = strings.TrimSuffix(base, pre)
+		i := strings.LastIndexByte(base, '.')
+		if i < 0 {
+			panic("base from parsePseudoVersion missing patch number: " + base)
+		}
+		patch := decDecimal(base[i+1:])
+		if patch == "" {
+			// vX.0.0-0 is invalid, but has been observed in the wild in the index
+			// generated by requests to proxy.golang.org.
+			//
+			// NOTE(bcmills): I cannot find a historical bug that accounts for
+			// pseudo-versions of this form, nor have I seen such versions in any
+			// actual go.mod files. If we find actual examples of this form and a
+			// reasonable theory of how they came into existence, it seems fine to
+			// treat them as equivalent to vX.0.0 (especially since the invalid
+			// pseudo-versions have lower precedence than the real ones). For now, we
+			// reject them.
+			return "", &InvalidVersionError{
+				Version: v,
+				Pseudo:  true,
+				Err:     fmt.Errorf("version before %s would have negative patch number", base),
+			}
+		}
+		return base[:i+1] + patch + build, nil
+
+	default:
+		// vX.Y.Z-pre.0.yyyymmddhhmmss-abcdef123456 → vX.Y.Z-pre
+		// vX.Y.Z-pre.0.yyyymmddhhmmss-abcdef123456+incompatible → vX.Y.Z-pre+incompatible
+		if !strings.HasSuffix(base, ".0") {
+			panic(`base from parsePseudoVersion missing ".0" before date: ` + base)
+		}
+		return strings.TrimSuffix(base, ".0") + build, nil
+	}
+}
+
+var errPseudoSyntax = errors.New("syntax error")
+
+func parsePseudoVersion(v string) (base, timestamp, rev, build string, err error) {
+	if !IsPseudoVersion(v) {
+		return "", "", "", "", &InvalidVersionError{
+			Version: v,
+			Pseudo:  true,
+			Err:     errPseudoSyntax,
+		}
+	}
+	build = semver.Build(v)
+	v = strings.TrimSuffix(v, build)
+	j := strings.LastIndex(v, "-")
+	v, rev = v[:j], v[j+1:]
+	i := strings.LastIndex(v, "-")
+	if j := strings.LastIndex(v, "."); j > i {
+		base = v[:j] // "vX.Y.Z-pre.0" or "vX.Y.(Z+1)-0"
+		timestamp = v[j+1:]
+	} else {
+		base = v[:i] // "vX.0.0"
+		timestamp = v[i+1:]
+	}
+	return base, timestamp, rev, build, nil
+}

vendor/golang.org/x/mod/semver/semver.go

@@ -22,6 +22,8 @@
 // as shorthands for vMAJOR.0.0 and vMAJOR.MINOR.0.
 package semver
 
+import "sort"
+
 // parsed returns the parsed form of a semantic version string.
 type parsed struct {
 	major      string
@@ -30,7 +32,6 @@ type parsed struct {
 	short      string
 	prerelease string
 	build      string
-	err        string
 }
 
 // IsValid reports whether v is a valid semantic version string.
@@ -150,14 +151,30 @@ func Max(v, w string) string {
 	return w
 }
 
+// ByVersion implements sort.Interface for sorting semantic version strings.
+type ByVersion []string
+
+func (vs ByVersion) Len() int      { return len(vs) }
+func (vs ByVersion) Swap(i, j int) { vs[i], vs[j] = vs[j], vs[i] }
+func (vs ByVersion) Less(i, j int) bool {
+	cmp := Compare(vs[i], vs[j])
+	if cmp != 0 {
+		return cmp < 0
+	}
+	return vs[i] < vs[j]
+}
+
+// Sort sorts a list of semantic version strings using ByVersion.
+func Sort(list []string) {
+	sort.Sort(ByVersion(list))
+}
+
 func parse(v string) (p parsed, ok bool) {
 	if v == "" || v[0] != 'v' {
-		p.err = "missing v prefix"
 		return
 	}
 	p.major, v, ok = parseInt(v[1:])
 	if !ok {
-		p.err = "bad major version"
 		return
 	}
 	if v == "" {
@@ -167,13 +184,11 @@ func parse(v string) (p parsed, ok bool) {
 		return
 	}
 	if v[0] != '.' {
-		p.err = "bad minor prefix"
 		ok = false
 		return
 	}
 	p.minor, v, ok = parseInt(v[1:])
 	if !ok {
-		p.err = "bad minor version"
 		return
 	}
 	if v == "" {
@@ -182,31 +197,26 @@ func parse(v string) (p parsed, ok bool) {
 		return
 	}
 	if v[0] != '.' {
-		p.err = "bad patch prefix"
 		ok = false
 		return
 	}
 	p.patch, v, ok = parseInt(v[1:])
 	if !ok {
-		p.err = "bad patch version"
 		return
 	}
 	if len(v) > 0 && v[0] == '-' {
 		p.prerelease, v, ok = parsePrerelease(v)
 		if !ok {
-			p.err = "bad prerelease"
 			return
 		}
 	}
 	if len(v) > 0 && v[0] == '+' {
 		p.build, v, ok = parseBuild(v)
 		if !ok {
-			p.err = "bad build"
 			return
 		}
 	}
 	if v != "" {
-		p.err = "junk on end"
 		ok = false
 		return
 	}

vendor/golang.org/x/tools/go/analysis/analysis.go

@@ -0,0 +1,242 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package analysis
+
+import (
+	"flag"
+	"fmt"
+	"go/ast"
+	"go/token"
+	"go/types"
+	"reflect"
+
+	"golang.org/x/tools/internal/analysisinternal"
+)
+
+// An Analyzer describes an analysis function and its options.
+type Analyzer struct {
+	// The Name of the analyzer must be a valid Go identifier
+	// as it may appear in command-line flags, URLs, and so on.
+	Name string
+
+	// Doc is the documentation for the analyzer.
+	// The part before the first "\n\n" is the title
+	// (no capital or period, max ~60 letters).
+	Doc string
+
+	// Flags defines any flags accepted by the analyzer.
+	// The manner in which these flags are exposed to the user
+	// depends on the driver which runs the analyzer.
+	Flags flag.FlagSet
+
+	// Run applies the analyzer to a package.
+	// It returns an error if the analyzer failed.
+	//
+	// On success, the Run function may return a result
+	// computed by the Analyzer; its type must match ResultType.
+	// The driver makes this result available as an input to
+	// another Analyzer that depends directly on this one (see
+	// Requires) when it analyzes the same package.
+	//
+	// To pass analysis results between packages (and thus
+	// potentially between address spaces), use Facts, which are
+	// serializable.
+	Run func(*Pass) (interface{}, error)
+
+	// RunDespiteErrors allows the driver to invoke
+	// the Run method of this analyzer even on a
+	// package that contains parse or type errors.
+	RunDespiteErrors bool
+
+	// Requires is a set of analyzers that must run successfully
+	// before this one on a given package. This analyzer may inspect
+	// the outputs produced by each analyzer in Requires.
+	// The graph over analyzers implied by Requires edges must be acyclic.
+	//
+	// Requires establishes a "horizontal" dependency between
+	// analysis passes (different analyzers, same package).
+	Requires []*Analyzer
+
+	// ResultType is the type of the optional result of the Run function.
+	ResultType reflect.Type
+
+	// FactTypes indicates that this analyzer imports and exports
+	// Facts of the specified concrete types.
+	// An analyzer that uses facts may assume that its import
+	// dependencies have been similarly analyzed before it runs.
+	// Facts must be pointers.
+	//
+	// FactTypes establishes a "vertical" dependency between
+	// analysis passes (same analyzer, different packages).
+	FactTypes []Fact
+}
+
+func (a *Analyzer) String() string { return a.Name }
+
+func init() {
+	// Set the analysisinternal functions to be able to pass type errors
+	// to the Pass type without modifying the go/analysis API.
+	analysisinternal.SetTypeErrors = func(p interface{}, errors []types.Error) {
+		p.(*Pass).typeErrors = errors
+	}
+	analysisinternal.GetTypeErrors = func(p interface{}) []types.Error {
+		return p.(*Pass).typeErrors
+	}
+}
+
+// A Pass provides information to the Run function that
+// applies a specific analyzer to a single Go package.
+//
+// It forms the interface between the analysis logic and the driver
+// program, and has both input and an output components.
+//
+// As in a compiler, one pass may depend on the result computed by another.
+//
+// The Run function should not call any of the Pass functions concurrently.
+type Pass struct {
+	Analyzer *Analyzer // the identity of the current analyzer
+
+	// syntax and type information
+	Fset         *token.FileSet // file position information
+	Files        []*ast.File    // the abstract syntax tree of each file
+	OtherFiles   []string       // names of non-Go files of this package
+	IgnoredFiles []string       // names of ignored source files in this package
+	Pkg          *types.Package // type information about the package
+	TypesInfo    *types.Info    // type information about the syntax trees
+	TypesSizes   types.Sizes    // function for computing sizes of types
+
+	// Report reports a Diagnostic, a finding about a specific location
+	// in the analyzed source code such as a potential mistake.
+	// It may be called by the Run function.
+	Report func(Diagnostic)
+
+	// ResultOf provides the inputs to this analysis pass, which are
+	// the corresponding results of its prerequisite analyzers.
+	// The map keys are the elements of Analysis.Required,
+	// and the type of each corresponding value is the required
+	// analysis's ResultType.
+	ResultOf map[*Analyzer]interface{}
+
+	// -- facts --
+
+	// ImportObjectFact retrieves a fact associated with obj.
+	// Given a value ptr of type *T, where *T satisfies Fact,
+	// ImportObjectFact copies the value to *ptr.
+	//
+	// ImportObjectFact panics if called after the pass is complete.
+	// ImportObjectFact is not concurrency-safe.
+	ImportObjectFact func(obj types.Object, fact Fact) bool
+
+	// ImportPackageFact retrieves a fact associated with package pkg,
+	// which must be this package or one of its dependencies.
+	// See comments for ImportObjectFact.
+	ImportPackageFact func(pkg *types.Package, fact Fact) bool
+
+	// ExportObjectFact associates a fact of type *T with the obj,
+	// replacing any previous fact of that type.
+	//
+	// ExportObjectFact panics if it is called after the pass is
+	// complete, or if obj does not belong to the package being analyzed.
+	// ExportObjectFact is not concurrency-safe.
+	ExportObjectFact func(obj types.Object, fact Fact)
+
+	// ExportPackageFact associates a fact with the current package.
+	// See comments for ExportObjectFact.
+	ExportPackageFact func(fact Fact)
+
+	// AllPackageFacts returns a new slice containing all package facts of the analysis's FactTypes
+	// in unspecified order.
+	// WARNING: This is an experimental API and may change in the future.
+	AllPackageFacts func() []PackageFact
+
+	// AllObjectFacts returns a new slice containing all object facts of the analysis's FactTypes
+	// in unspecified order.
+	// WARNING: This is an experimental API and may change in the future.
+	AllObjectFacts func() []ObjectFact
+
+	// typeErrors contains types.Errors that are associated with the pkg.
+	typeErrors []types.Error
+
+	/* Further fields may be added in future. */
+	// For example, suggested or applied refactorings.
+}
+
+// PackageFact is a package together with an associated fact.
+// WARNING: This is an experimental API and may change in the future.
+type PackageFact struct {
+	Package *types.Package
+	Fact    Fact
+}
+
+// ObjectFact is an object together with an associated fact.
+// WARNING: This is an experimental API and may change in the future.
+type ObjectFact struct {
+	Object types.Object
+	Fact   Fact
+}
+
+// Reportf is a helper function that reports a Diagnostic using the
+// specified position and formatted error message.
+func (pass *Pass) Reportf(pos token.Pos, format string, args ...interface{}) {
+	msg := fmt.Sprintf(format, args...)
+	pass.Report(Diagnostic{Pos: pos, Message: msg})
+}
+
+// The Range interface provides a range. It's equivalent to and satisfied by
+// ast.Node.
+type Range interface {
+	Pos() token.Pos // position of first character belonging to the node
+	End() token.Pos // position of first character immediately after the node
+}
+
+// ReportRangef is a helper function that reports a Diagnostic using the
+// range provided. ast.Node values can be passed in as the range because
+// they satisfy the Range interface.
+func (pass *Pass) ReportRangef(rng Range, format string, args ...interface{}) {
+	msg := fmt.Sprintf(format, args...)
+	pass.Report(Diagnostic{Pos: rng.Pos(), End: rng.End(), Message: msg})
+}
+
+func (pass *Pass) String() string {
+	return fmt.Sprintf("%s@%s", pass.Analyzer.Name, pass.Pkg.Path())
+}
+
+// A Fact is an intermediate fact produced during analysis.
+//
+// Each fact is associated with a named declaration (a types.Object) or
+// with a package as a whole. A single object or package may have
+// multiple associated facts, but only one of any particular fact type.
+//
+// A Fact represents a predicate such as "never returns", but does not
+// represent the subject of the predicate such as "function F" or "package P".
+//
+// Facts may be produced in one analysis pass and consumed by another
+// analysis pass even if these are in different address spaces.
+// If package P imports Q, all facts about Q produced during
+// analysis of that package will be available during later analysis of P.
+// Facts are analogous to type export data in a build system:
+// just as export data enables separate compilation of several passes,
+// facts enable "separate analysis".
+//
+// Each pass (a, p) starts with the set of facts produced by the
+// same analyzer a applied to the packages directly imported by p.
+// The analysis may add facts to the set, and they may be exported in turn.
+// An analysis's Run function may retrieve facts by calling
+// Pass.Import{Object,Package}Fact and update them using
+// Pass.Export{Object,Package}Fact.
+//
+// A fact is logically private to its Analysis. To pass values
+// between different analyzers, use the results mechanism;
+// see Analyzer.Requires, Analyzer.ResultType, and Pass.ResultOf.
+//
+// A Fact type must be a pointer.
+// Facts are encoded and decoded using encoding/gob.
+// A Fact may implement the GobEncoder/GobDecoder interfaces
+// to customize its encoding. Fact encoding should not fail.
+//
+// A Fact should not be modified once exported.
+type Fact interface {
+	AFact() // dummy method to avoid type errors
+}

vendor/golang.org/x/tools/go/analysis/diagnostic.go

@@ -0,0 +1,65 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package analysis
+
+import "go/token"
+
+// A Diagnostic is a message associated with a source location or range.
+//
+// An Analyzer may return a variety of diagnostics; the optional Category,
+// which should be a constant, may be used to classify them.
+// It is primarily intended to make it easy to look up documentation.
+//
+// If End is provided, the diagnostic is specified to apply to the range between
+// Pos and End.
+type Diagnostic struct {
+	Pos      token.Pos
+	End      token.Pos // optional
+	Category string    // optional
+	Message  string
+
+	// SuggestedFixes contains suggested fixes for a diagnostic which can be used to perform
+	// edits to a file that address the diagnostic.
+	// TODO(matloob): Should multiple SuggestedFixes be allowed for a diagnostic?
+	// Diagnostics should not contain SuggestedFixes that overlap.
+	// Experimental: This API is experimental and may change in the future.
+	SuggestedFixes []SuggestedFix // optional
+
+	// Experimental: This API is experimental and may change in the future.
+	Related []RelatedInformation // optional
+}
+
+// RelatedInformation contains information related to a diagnostic.
+// For example, a diagnostic that flags duplicated declarations of a
+// variable may include one RelatedInformation per existing
+// declaration.
+type RelatedInformation struct {
+	Pos     token.Pos
+	End     token.Pos
+	Message string
+}
+
+// A SuggestedFix is a code change associated with a Diagnostic that a user can choose
+// to apply to their code. Usually the SuggestedFix is meant to fix the issue flagged
+// by the diagnostic.
+// TextEdits for a SuggestedFix should not overlap. TextEdits for a SuggestedFix
+// should not contain edits for other packages.
+// Experimental: This API is experimental and may change in the future.
+type SuggestedFix struct {
+	// A description for this suggested fix to be shown to a user deciding
+	// whether to accept it.
+	Message   string
+	TextEdits []TextEdit
+}
+
+// A TextEdit represents the replacement of the code between Pos and End with the new text.
+// Each TextEdit should apply to a single file. End should not be earlier in the file than Pos.
+// Experimental: This API is experimental and may change in the future.
+type TextEdit struct {
+	// For a pure insertion, End can either be set to Pos or token.NoPos.
+	Pos     token.Pos
+	End     token.Pos
+	NewText []byte
+}

vendor/golang.org/x/tools/go/analysis/doc.go

@@ -0,0 +1,321 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+
+Package analysis defines the interface between a modular static
+analysis and an analysis driver program.
+
+
+Background
+
+A static analysis is a function that inspects a package of Go code and
+reports a set of diagnostics (typically mistakes in the code), and
+perhaps produces other results as well, such as suggested refactorings
+or other facts. An analysis that reports mistakes is informally called a
+"checker". For example, the printf checker reports mistakes in
+fmt.Printf format strings.
+
+A "modular" analysis is one that inspects one package at a time but can
+save information from a lower-level package and use it when inspecting a
+higher-level package, analogous to separate compilation in a toolchain.
+The printf checker is modular: when it discovers that a function such as
+log.Fatalf delegates to fmt.Printf, it records this fact, and checks
+calls to that function too, including calls made from another package.
+
+By implementing a common interface, checkers from a variety of sources
+can be easily selected, incorporated, and reused in a wide range of
+driver programs including command-line tools (such as vet), text editors and
+IDEs, build and test systems (such as go build, Bazel, or Buck), test
+frameworks, code review tools, code-base indexers (such as SourceGraph),
+documentation viewers (such as godoc), batch pipelines for large code
+bases, and so on.
+
+
+Analyzer
+
+The primary type in the API is Analyzer. An Analyzer statically
+describes an analysis function: its name, documentation, flags,
+relationship to other analyzers, and of course, its logic.
+
+To define an analysis, a user declares a (logically constant) variable
+of type Analyzer. Here is a typical example from one of the analyzers in
+the go/analysis/passes/ subdirectory:
+
+	package unusedresult
+
+	var Analyzer = &analysis.Analyzer{
+		Name: "unusedresult",
+		Doc:  "check for unused results of calls to some functions",
+		Run:  run,
+		...
+	}
+
+	func run(pass *analysis.Pass) (interface{}, error) {
+		...
+	}
+
+An analysis driver is a program such as vet that runs a set of
+analyses and prints the diagnostics that they report.
+The driver program must import the list of Analyzers it needs.
+Typically each Analyzer resides in a separate package.
+To add a new Analyzer to an existing driver, add another item to the list:
+
+	import ( "unusedresult"; "nilness"; "printf" )
+
+	var analyses = []*analysis.Analyzer{
+		unusedresult.Analyzer,
+		nilness.Analyzer,
+		printf.Analyzer,
+	}
+
+A driver may use the name, flags, and documentation to provide on-line
+help that describes the analyses it performs.
+The doc comment contains a brief one-line summary,
+optionally followed by paragraphs of explanation.
+
+The Analyzer type has more fields besides those shown above:
+
+	type Analyzer struct {
+		Name             string
+		Doc              string
+		Flags            flag.FlagSet
+		Run              func(*Pass) (interface{}, error)
+		RunDespiteErrors bool
+		ResultType       reflect.Type
+		Requires         []*Analyzer
+		FactTypes        []Fact
+	}
+
+The Flags field declares a set of named (global) flag variables that
+control analysis behavior. Unlike vet, analysis flags are not declared
+directly in the command line FlagSet; it is up to the driver to set the
+flag variables. A driver for a single analysis, a, might expose its flag
+f directly on the command line as -f, whereas a driver for multiple
+analyses might prefix the flag name by the analysis name (-a.f) to avoid
+ambiguity. An IDE might expose the flags through a graphical interface,
+and a batch pipeline might configure them from a config file.
+See the "findcall" analyzer for an example of flags in action.
+
+The RunDespiteErrors flag indicates whether the analysis is equipped to
+handle ill-typed code. If not, the driver will skip the analysis if
+there were parse or type errors.
+The optional ResultType field specifies the type of the result value
+computed by this analysis and made available to other analyses.
+The Requires field specifies a list of analyses upon which
+this one depends and whose results it may access, and it constrains the
+order in which a driver may run analyses.
+The FactTypes field is discussed in the section on Modularity.
+The analysis package provides a Validate function to perform basic
+sanity checks on an Analyzer, such as that its Requires graph is
+acyclic, its fact and result types are unique, and so on.
+
+Finally, the Run field contains a function to be called by the driver to
+execute the analysis on a single package. The driver passes it an
+instance of the Pass type.
+
+
+Pass
+
+A Pass describes a single unit of work: the application of a particular
+Analyzer to a particular package of Go code.
+The Pass provides information to the Analyzer's Run function about the
+package being analyzed, and provides operations to the Run function for
+reporting diagnostics and other information back to the driver.
+
+	type Pass struct {
+		Fset         *token.FileSet
+		Files        []*ast.File
+		OtherFiles   []string
+		IgnoredFiles []string
+		Pkg          *types.Package
+		TypesInfo    *types.Info
+		ResultOf     map[*Analyzer]interface{}
+		Report       func(Diagnostic)
+		...
+	}
+
+The Fset, Files, Pkg, and TypesInfo fields provide the syntax trees,
+type information, and source positions for a single package of Go code.
+
+The OtherFiles field provides the names, but not the contents, of non-Go
+files such as assembly that are part of this package. See the "asmdecl"
+or "buildtags" analyzers for examples of loading non-Go files and reporting
+diagnostics against them.
+
+The IgnoredFiles field provides the names, but not the contents,
+of ignored Go and non-Go source files that are not part of this package
+with the current build configuration but may be part of other build
+configurations. See the "buildtags" analyzer for an example of loading
+and checking IgnoredFiles.
+
+The ResultOf field provides the results computed by the analyzers
+required by this one, as expressed in its Analyzer.Requires field. The
+driver runs the required analyzers first and makes their results
+available in this map. Each Analyzer must return a value of the type
+described in its Analyzer.ResultType field.
+For example, the "ctrlflow" analyzer returns a *ctrlflow.CFGs, which
+provides a control-flow graph for each function in the package (see
+golang.org/x/tools/go/cfg); the "inspect" analyzer returns a value that
+enables other Analyzers to traverse the syntax trees of the package more
+efficiently; and the "buildssa" analyzer constructs an SSA-form
+intermediate representation.
+Each of these Analyzers extends the capabilities of later Analyzers
+without adding a dependency to the core API, so an analysis tool pays
+only for the extensions it needs.
+
+The Report function emits a diagnostic, a message associated with a
+source position. For most analyses, diagnostics are their primary
+result.
+For convenience, Pass provides a helper method, Reportf, to report a new
+diagnostic by formatting a string.
+Diagnostic is defined as:
+
+	type Diagnostic struct {
+		Pos      token.Pos
+		Category string // optional
+		Message  string
+	}
+
+The optional Category field is a short identifier that classifies the
+kind of message when an analysis produces several kinds of diagnostic.
+
+Many analyses want to associate diagnostics with a severity level.
+Because Diagnostic does not have a severity level field, an Analyzer's
+diagnostics effectively all have the same severity level. To separate which
+diagnostics are high severity and which are low severity, expose multiple
+Analyzers instead. Analyzers should also be separated when their
+diagnostics belong in different groups, or could be tagged differently
+before being shown to the end user. Analyzers should document their severity
+level to help downstream tools surface diagnostics properly.
+
+Most Analyzers inspect typed Go syntax trees, but a few, such as asmdecl
+and buildtag, inspect the raw text of Go source files or even non-Go
+files such as assembly. To report a diagnostic against a line of a
+raw text file, use the following sequence:
+
+	content, err := ioutil.ReadFile(filename)
+	if err != nil { ... }
+	tf := fset.AddFile(filename, -1, len(content))
+	tf.SetLinesForContent(content)
+	...
+	pass.Reportf(tf.LineStart(line), "oops")
+
+
+Modular analysis with Facts
+
+To improve efficiency and scalability, large programs are routinely
+built using separate compilation: units of the program are compiled
+separately, and recompiled only when one of their dependencies changes;
+independent modules may be compiled in parallel. The same technique may
+be applied to static analyses, for the same benefits. Such analyses are
+described as "modular".
+
+A compiler’s type checker is an example of a modular static analysis.
+Many other checkers we would like to apply to Go programs can be
+understood as alternative or non-standard type systems. For example,
+vet's printf checker infers whether a function has the "printf wrapper"
+type, and it applies stricter checks to calls of such functions. In
+addition, it records which functions are printf wrappers for use by
+later analysis passes to identify other printf wrappers by induction.
+A result such as “f is a printf wrapper” that is not interesting by
+itself but serves as a stepping stone to an interesting result (such as
+a diagnostic) is called a "fact".
+
+The analysis API allows an analysis to define new types of facts, to
+associate facts of these types with objects (named entities) declared
+within the current package, or with the package as a whole, and to query
+for an existing fact of a given type associated with an object or
+package.
+
+An Analyzer that uses facts must declare their types:
+
+	var Analyzer = &analysis.Analyzer{
+		Name:      "printf",
+		FactTypes: []analysis.Fact{new(isWrapper)},
+		...
+	}
+
+	type isWrapper struct{} // => *types.Func f “is a printf wrapper”
+
+The driver program ensures that facts for a pass’s dependencies are
+generated before analyzing the package and is responsible for propagating
+facts from one package to another, possibly across address spaces.
+Consequently, Facts must be serializable. The API requires that drivers
+use the gob encoding, an efficient, robust, self-describing binary
+protocol. A fact type may implement the GobEncoder/GobDecoder interfaces
+if the default encoding is unsuitable. Facts should be stateless.
+
+The Pass type has functions to import and export facts,
+associated either with an object or with a package:
+
+	type Pass struct {
+		...
+		ExportObjectFact func(types.Object, Fact)
+		ImportObjectFact func(types.Object, Fact) bool
+
+		ExportPackageFact func(fact Fact)
+		ImportPackageFact func(*types.Package, Fact) bool
+	}
+
+An Analyzer may only export facts associated with the current package or
+its objects, though it may import facts from any package or object that
+is an import dependency of the current package.
+
+Conceptually, ExportObjectFact(obj, fact) inserts fact into a hidden map keyed by
+the pair (obj, TypeOf(fact)), and the ImportObjectFact function
+retrieves the entry from this map and copies its value into the variable
+pointed to by fact. This scheme assumes that the concrete type of fact
+is a pointer; this assumption is checked by the Validate function.
+See the "printf" analyzer for an example of object facts in action.
+
+Some driver implementations (such as those based on Bazel and Blaze) do
+not currently apply analyzers to packages of the standard library.
+Therefore, for best results, analyzer authors should not rely on
+analysis facts being available for standard packages.
+For example, although the printf checker is capable of deducing during
+analysis of the log package that log.Printf is a printf wrapper,
+this fact is built in to the analyzer so that it correctly checks
+calls to log.Printf even when run in a driver that does not apply
+it to standard packages. We would like to remove this limitation in future.
+
+
+Testing an Analyzer
+
+The analysistest subpackage provides utilities for testing an Analyzer.
+In a few lines of code, it is possible to run an analyzer on a package
+of testdata files and check that it reported all the expected
+diagnostics and facts (and no more). Expectations are expressed using
+"// want ..." comments in the input code.
+
+
+Standalone commands
+
+Analyzers are provided in the form of packages that a driver program is
+expected to import. The vet command imports a set of several analyzers,
+but users may wish to define their own analysis commands that perform
+additional checks. To simplify the task of creating an analysis command,
+either for a single analyzer or for a whole suite, we provide the
+singlechecker and multichecker subpackages.
+
+The singlechecker package provides the main function for a command that
+runs one analyzer. By convention, each analyzer such as
+go/passes/findcall should be accompanied by a singlechecker-based
+command such as go/analysis/passes/findcall/cmd/findcall, defined in its
+entirety as:
+
+	package main
+
+	import (
+		"golang.org/x/tools/go/analysis/passes/findcall"
+		"golang.org/x/tools/go/analysis/singlechecker"
+	)
+
+	func main() { singlechecker.Main(findcall.Analyzer) }
+
+A tool that provides multiple analyzers can use multichecker in a
+similar way, giving it the list of Analyzers.
+
+*/
+package analysis

vendor/golang.org/x/tools/go/analysis/passes/inspect/inspect.go

@@ -0,0 +1,49 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package inspect defines an Analyzer that provides an AST inspector
+// (golang.org/x/tools/go/ast/inspector.Inspector) for the syntax trees
+// of a package. It is only a building block for other analyzers.
+//
+// Example of use in another analysis:
+//
+//	import (
+//		"golang.org/x/tools/go/analysis"
+//		"golang.org/x/tools/go/analysis/passes/inspect"
+//		"golang.org/x/tools/go/ast/inspector"
+//	)
+//
+//	var Analyzer = &analysis.Analyzer{
+//		...
+//		Requires:       []*analysis.Analyzer{inspect.Analyzer},
+//	}
+//
+// 	func run(pass *analysis.Pass) (interface{}, error) {
+// 		inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)
+// 		inspect.Preorder(nil, func(n ast.Node) {
+// 			...
+// 		})
+// 		return nil
+// 	}
+//
+package inspect
+
+import (
+	"reflect"
+
+	"golang.org/x/tools/go/analysis"
+	"golang.org/x/tools/go/ast/inspector"
+)
+
+var Analyzer = &analysis.Analyzer{
+	Name:             "inspect",
+	Doc:              "optimize AST traversal for later passes",
+	Run:              run,
+	RunDespiteErrors: true,
+	ResultType:       reflect.TypeOf(new(inspector.Inspector)),
+}
+
+func run(pass *analysis.Pass) (interface{}, error) {
+	return inspector.New(pass.Files), nil
+}

vendor/golang.org/x/tools/go/analysis/validate.go

@@ -0,0 +1,130 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package analysis
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+	"unicode"
+)
+
+// Validate reports an error if any of the analyzers are misconfigured.
+// Checks include:
+// that the name is a valid identifier;
+// that the Requires graph is acyclic;
+// that analyzer fact types are unique;
+// that each fact type is a pointer.
+func Validate(analyzers []*Analyzer) error {
+	// Map each fact type to its sole generating analyzer.
+	factTypes := make(map[reflect.Type]*Analyzer)
+
+	// Traverse the Requires graph, depth first.
+	const (
+		white = iota
+		grey
+		black
+		finished
+	)
+	color := make(map[*Analyzer]uint8)
+	var visit func(a *Analyzer) error
+	visit = func(a *Analyzer) error {
+		if a == nil {
+			return fmt.Errorf("nil *Analyzer")
+		}
+		if color[a] == white {
+			color[a] = grey
+
+			// names
+			if !validIdent(a.Name) {
+				return fmt.Errorf("invalid analyzer name %q", a)
+			}
+
+			if a.Doc == "" {
+				return fmt.Errorf("analyzer %q is undocumented", a)
+			}
+
+			// fact types
+			for _, f := range a.FactTypes {
+				if f == nil {
+					return fmt.Errorf("analyzer %s has nil FactType", a)
+				}
+				t := reflect.TypeOf(f)
+				if prev := factTypes[t]; prev != nil {
+					return fmt.Errorf("fact type %s registered by two analyzers: %v, %v",
+						t, a, prev)
+				}
+				if t.Kind() != reflect.Ptr {
+					return fmt.Errorf("%s: fact type %s is not a pointer", a, t)
+				}
+				factTypes[t] = a
+			}
+
+			// recursion
+			for _, req := range a.Requires {
+				if err := visit(req); err != nil {
+					return err
+				}
+			}
+			color[a] = black
+		}
+
+		if color[a] == grey {
+			stack := []*Analyzer{a}
+			inCycle := map[string]bool{}
+			for len(stack) > 0 {
+				current := stack[len(stack)-1]
+				stack = stack[:len(stack)-1]
+				if color[current] == grey && !inCycle[current.Name] {
+					inCycle[current.Name] = true
+					stack = append(stack, current.Requires...)
+				}
+			}
+			return &CycleInRequiresGraphError{AnalyzerNames: inCycle}
+		}
+
+		return nil
+	}
+	for _, a := range analyzers {
+		if err := visit(a); err != nil {
+			return err
+		}
+	}
+
+	// Reject duplicates among analyzers.
+	// Precondition:  color[a] == black.
+	// Postcondition: color[a] == finished.
+	for _, a := range analyzers {
+		if color[a] == finished {
+			return fmt.Errorf("duplicate analyzer: %s", a.Name)
+		}
+		color[a] = finished
+	}
+
+	return nil
+}
+
+func validIdent(name string) bool {
+	for i, r := range name {
+		if !(r == '_' || unicode.IsLetter(r) || i > 0 && unicode.IsDigit(r)) {
+			return false
+		}
+	}
+	return name != ""
+}
+
+type CycleInRequiresGraphError struct {
+	AnalyzerNames map[string]bool
+}
+
+func (e *CycleInRequiresGraphError) Error() string {
+	var b strings.Builder
+	b.WriteString("cycle detected involving the following analyzers:")
+	for n := range e.AnalyzerNames {
+		b.WriteByte(' ')
+		b.WriteString(n)
+	}
+	return b.String()
+}

vendor/golang.org/x/tools/go/ast/astutil/enclosing.go

@@ -11,6 +11,8 @@ import (
 	"go/ast"
 	"go/token"
 	"sort"
+
+	"golang.org/x/tools/internal/typeparams"
 )
 
 // PathEnclosingInterval returns the node that encloses the source
@@ -294,8 +296,8 @@ func childrenOf(n ast.Node) []ast.Node {
 
 	case *ast.FieldList:
 		children = append(children,
-			tok(n.Opening, len("(")),
-			tok(n.Closing, len(")")))
+			tok(n.Opening, len("(")), // or len("[")
+			tok(n.Closing, len(")"))) // or len("]")
 
 	case *ast.File:
 		// TODO test: Doc
@@ -322,6 +324,9 @@ func childrenOf(n ast.Node) []ast.Node {
 			children = append(children, n.Recv)
 		}
 		children = append(children, n.Name)
+		if tparams := typeparams.ForFuncType(n.Type); tparams != nil {
+			children = append(children, tparams)
+		}
 		if n.Type.Params != nil {
 			children = append(children, n.Type.Params)
 		}
@@ -371,8 +376,13 @@ func childrenOf(n ast.Node) []ast.Node {
 
 	case *ast.IndexExpr:
 		children = append(children,
-			tok(n.Lbrack, len("{")),
-			tok(n.Rbrack, len("}")))
+			tok(n.Lbrack, len("[")),
+			tok(n.Rbrack, len("]")))
+
+	case *typeparams.IndexListExpr:
+		children = append(children,
+			tok(n.Lbrack, len("[")),
+			tok(n.Rbrack, len("]")))
 
 	case *ast.InterfaceType:
 		children = append(children,
@@ -581,6 +591,8 @@ func NodeDescription(n ast.Node) string {
 		return "decrement statement"
 	case *ast.IndexExpr:
 		return "index expression"
+	case *typeparams.IndexListExpr:
+		return "index list expression"
 	case *ast.InterfaceType:
 		return "interface type"
 	case *ast.KeyValueExpr:

vendor/golang.org/x/tools/go/ast/astutil/rewrite.go

@@ -253,6 +253,10 @@ func (a *application) apply(parent ast.Node, name string, iter *iterator, n ast.
 		a.apply(n, "X", nil, n.X)
 		a.apply(n, "Index", nil, n.Index)
 
+	case *typeparams.IndexListExpr:
+		a.apply(n, "X", nil, n.X)
+		a.applyList(n, "Indices")
+
 	case *ast.SliceExpr:
 		a.apply(n, "X", nil, n.X)
 		a.apply(n, "Low", nil, n.Low)
@@ -439,13 +443,7 @@ func (a *application) apply(parent ast.Node, name string, iter *iterator, n ast.
 		}
 
 	default:
-		if ix := typeparams.GetIndexExprData(n); ix != nil {
-			a.apply(n, "X", nil, ix.X)
-			// *ast.IndexExpr was handled above, so n must be an *ast.MultiIndexExpr.
-			a.applyList(n, "Indices")
-		} else {
-			panic(fmt.Sprintf("Apply: unexpected node type %T", n))
-		}
+		panic(fmt.Sprintf("Apply: unexpected node type %T", n))
 	}
 
 	if a.post != nil && !a.post(&a.cursor) {

vendor/golang.org/x/tools/go/ast/inspector/inspector.go

@@ -0,0 +1,186 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package inspector provides helper functions for traversal over the
+// syntax trees of a package, including node filtering by type, and
+// materialization of the traversal stack.
+//
+// During construction, the inspector does a complete traversal and
+// builds a list of push/pop events and their node type. Subsequent
+// method calls that request a traversal scan this list, rather than walk
+// the AST, and perform type filtering using efficient bit sets.
+//
+// Experiments suggest the inspector's traversals are about 2.5x faster
+// than ast.Inspect, but it may take around 5 traversals for this
+// benefit to amortize the inspector's construction cost.
+// If efficiency is the primary concern, do not use Inspector for
+// one-off traversals.
+package inspector
+
+// There are four orthogonal features in a traversal:
+//  1 type filtering
+//  2 pruning
+//  3 postorder calls to f
+//  4 stack
+// Rather than offer all of them in the API,
+// only a few combinations are exposed:
+// - Preorder is the fastest and has fewest features,
+//   but is the most commonly needed traversal.
+// - Nodes and WithStack both provide pruning and postorder calls,
+//   even though few clients need it, because supporting two versions
+//   is not justified.
+// More combinations could be supported by expressing them as
+// wrappers around a more generic traversal, but this was measured
+// and found to degrade performance significantly (30%).
+
+import (
+	"go/ast"
+)
+
+// An Inspector provides methods for inspecting
+// (traversing) the syntax trees of a package.
+type Inspector struct {
+	events []event
+}
+
+// New returns an Inspector for the specified syntax trees.
+func New(files []*ast.File) *Inspector {
+	return &Inspector{traverse(files)}
+}
+
+// An event represents a push or a pop
+// of an ast.Node during a traversal.
+type event struct {
+	node  ast.Node
+	typ   uint64 // typeOf(node)
+	index int    // 1 + index of corresponding pop event, or 0 if this is a pop
+}
+
+// Preorder visits all the nodes of the files supplied to New in
+// depth-first order. It calls f(n) for each node n before it visits
+// n's children.
+//
+// The types argument, if non-empty, enables type-based filtering of
+// events. The function f if is called only for nodes whose type
+// matches an element of the types slice.
+func (in *Inspector) Preorder(types []ast.Node, f func(ast.Node)) {
+	// Because it avoids postorder calls to f, and the pruning
+	// check, Preorder is almost twice as fast as Nodes. The two
+	// features seem to contribute similar slowdowns (~1.4x each).
+
+	mask := maskOf(types)
+	for i := 0; i < len(in.events); {
+		ev := in.events[i]
+		if ev.typ&mask != 0 {
+			if ev.index > 0 {
+				f(ev.node)
+			}
+		}
+		i++
+	}
+}
+
+// Nodes visits the nodes of the files supplied to New in depth-first
+// order. It calls f(n, true) for each node n before it visits n's
+// children. If f returns true, Nodes invokes f recursively for each
+// of the non-nil children of the node, followed by a call of
+// f(n, false).
+//
+// The types argument, if non-empty, enables type-based filtering of
+// events. The function f if is called only for nodes whose type
+// matches an element of the types slice.
+func (in *Inspector) Nodes(types []ast.Node, f func(n ast.Node, push bool) (proceed bool)) {
+	mask := maskOf(types)
+	for i := 0; i < len(in.events); {
+		ev := in.events[i]
+		if ev.typ&mask != 0 {
+			if ev.index > 0 {
+				// push
+				if !f(ev.node, true) {
+					i = ev.index // jump to corresponding pop + 1
+					continue
+				}
+			} else {
+				// pop
+				f(ev.node, false)
+			}
+		}
+		i++
+	}
+}
+
+// WithStack visits nodes in a similar manner to Nodes, but it
+// supplies each call to f an additional argument, the current
+// traversal stack. The stack's first element is the outermost node,
+// an *ast.File; its last is the innermost, n.
+func (in *Inspector) WithStack(types []ast.Node, f func(n ast.Node, push bool, stack []ast.Node) (proceed bool)) {
+	mask := maskOf(types)
+	var stack []ast.Node
+	for i := 0; i < len(in.events); {
+		ev := in.events[i]
+		if ev.index > 0 {
+			// push
+			stack = append(stack, ev.node)
+			if ev.typ&mask != 0 {
+				if !f(ev.node, true, stack) {
+					i = ev.index
+					stack = stack[:len(stack)-1]
+					continue
+				}
+			}
+		} else {
+			// pop
+			if ev.typ&mask != 0 {
+				f(ev.node, false, stack)
+			}
+			stack = stack[:len(stack)-1]
+		}
+		i++
+	}
+}
+
+// traverse builds the table of events representing a traversal.
+func traverse(files []*ast.File) []event {
+	// Preallocate approximate number of events
+	// based on source file extent.
+	// This makes traverse faster by 4x (!).
+	var extent int
+	for _, f := range files {
+		extent += int(f.End() - f.Pos())
+	}
+	// This estimate is based on the net/http package.
+	capacity := extent * 33 / 100
+	if capacity > 1e6 {
+		capacity = 1e6 // impose some reasonable maximum
+	}
+	events := make([]event, 0, capacity)
+
+	var stack []event
+	for _, f := range files {
+		ast.Inspect(f, func(n ast.Node) bool {
+			if n != nil {
+				// push
+				ev := event{
+					node:  n,
+					typ:   typeOf(n),
+					index: len(events), // push event temporarily holds own index
+				}
+				stack = append(stack, ev)
+				events = append(events, ev)
+			} else {
+				// pop
+				ev := stack[len(stack)-1]
+				stack = stack[:len(stack)-1]
+
+				events[ev.index].index = len(events) + 1 // make push refer to pop
+
+				ev.index = 0 // turn ev into a pop event
+				events = append(events, ev)
+			}
+			return true
+		})
+	}
+
+	return events
+}

vendor/golang.org/x/tools/go/ast/inspector/typeof.go

@@ -0,0 +1,227 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package inspector
+
+// This file defines func typeOf(ast.Node) uint64.
+//
+// The initial map-based implementation was too slow;
+// see https://go-review.googlesource.com/c/tools/+/135655/1/go/ast/inspector/inspector.go#196
+
+import (
+	"go/ast"
+
+	"golang.org/x/tools/internal/typeparams"
+)
+
+const (
+	nArrayType = iota
+	nAssignStmt
+	nBadDecl
+	nBadExpr
+	nBadStmt
+	nBasicLit
+	nBinaryExpr
+	nBlockStmt
+	nBranchStmt
+	nCallExpr
+	nCaseClause
+	nChanType
+	nCommClause
+	nComment
+	nCommentGroup
+	nCompositeLit
+	nDeclStmt
+	nDeferStmt
+	nEllipsis
+	nEmptyStmt
+	nExprStmt
+	nField
+	nFieldList
+	nFile
+	nForStmt
+	nFuncDecl
+	nFuncLit
+	nFuncType
+	nGenDecl
+	nGoStmt
+	nIdent
+	nIfStmt
+	nImportSpec
+	nIncDecStmt
+	nIndexExpr
+	nIndexListExpr
+	nInterfaceType
+	nKeyValueExpr
+	nLabeledStmt
+	nMapType
+	nPackage
+	nParenExpr
+	nRangeStmt
+	nReturnStmt
+	nSelectStmt
+	nSelectorExpr
+	nSendStmt
+	nSliceExpr
+	nStarExpr
+	nStructType
+	nSwitchStmt
+	nTypeAssertExpr
+	nTypeSpec
+	nTypeSwitchStmt
+	nUnaryExpr
+	nValueSpec
+)
+
+// typeOf returns a distinct single-bit value that represents the type of n.
+//
+// Various implementations were benchmarked with BenchmarkNewInspector:
+//								GOGC=off
+// - type switch				4.9-5.5ms	2.1ms
+// - binary search over a sorted list of types  5.5-5.9ms	2.5ms
+// - linear scan, frequency-ordered list 	5.9-6.1ms	2.7ms
+// - linear scan, unordered list		6.4ms		2.7ms
+// - hash table					6.5ms		3.1ms
+// A perfect hash seemed like overkill.
+//
+// The compiler's switch statement is the clear winner
+// as it produces a binary tree in code,
+// with constant conditions and good branch prediction.
+// (Sadly it is the most verbose in source code.)
+// Binary search suffered from poor branch prediction.
+//
+func typeOf(n ast.Node) uint64 {
+	// Fast path: nearly half of all nodes are identifiers.
+	if _, ok := n.(*ast.Ident); ok {
+		return 1 << nIdent
+	}
+
+	// These cases include all nodes encountered by ast.Inspect.
+	switch n.(type) {
+	case *ast.ArrayType:
+		return 1 << nArrayType
+	case *ast.AssignStmt:
+		return 1 << nAssignStmt
+	case *ast.BadDecl:
+		return 1 << nBadDecl
+	case *ast.BadExpr:
+		return 1 << nBadExpr
+	case *ast.BadStmt:
+		return 1 << nBadStmt
+	case *ast.BasicLit:
+		return 1 << nBasicLit
+	case *ast.BinaryExpr:
+		return 1 << nBinaryExpr
+	case *ast.BlockStmt:
+		return 1 << nBlockStmt
+	case *ast.BranchStmt:
+		return 1 << nBranchStmt
+	case *ast.CallExpr:
+		return 1 << nCallExpr
+	case *ast.CaseClause:
+		return 1 << nCaseClause
+	case *ast.ChanType:
+		return 1 << nChanType
+	case *ast.CommClause:
+		return 1 << nCommClause
+	case *ast.Comment:
+		return 1 << nComment
+	case *ast.CommentGroup:
+		return 1 << nCommentGroup
+	case *ast.CompositeLit:
+		return 1 << nCompositeLit
+	case *ast.DeclStmt:
+		return 1 << nDeclStmt
+	case *ast.DeferStmt:
+		return 1 << nDeferStmt
+	case *ast.Ellipsis:
+		return 1 << nEllipsis
+	case *ast.EmptyStmt:
+		return 1 << nEmptyStmt
+	case *ast.ExprStmt:
+		return 1 << nExprStmt
+	case *ast.Field:
+		return 1 << nField
+	case *ast.FieldList:
+		return 1 << nFieldList
+	case *ast.File:
+		return 1 << nFile
+	case *ast.ForStmt:
+		return 1 << nForStmt
+	case *ast.FuncDecl:
+		return 1 << nFuncDecl
+	case *ast.FuncLit:
+		return 1 << nFuncLit
+	case *ast.FuncType:
+		return 1 << nFuncType
+	case *ast.GenDecl:
+		return 1 << nGenDecl
+	case *ast.GoStmt:
+		return 1 << nGoStmt
+	case *ast.Ident:
+		return 1 << nIdent
+	case *ast.IfStmt:
+		return 1 << nIfStmt
+	case *ast.ImportSpec:
+		return 1 << nImportSpec
+	case *ast.IncDecStmt:
+		return 1 << nIncDecStmt
+	case *ast.IndexExpr:
+		return 1 << nIndexExpr
+	case *typeparams.IndexListExpr:
+		return 1 << nIndexListExpr
+	case *ast.InterfaceType:
+		return 1 << nInterfaceType
+	case *ast.KeyValueExpr:
+		return 1 << nKeyValueExpr
+	case *ast.LabeledStmt:
+		return 1 << nLabeledStmt
+	case *ast.MapType:
+		return 1 << nMapType
+	case *ast.Package:
+		return 1 << nPackage
+	case *ast.ParenExpr:
+		return 1 << nParenExpr
+	case *ast.RangeStmt:
+		return 1 << nRangeStmt
+	case *ast.ReturnStmt:
+		return 1 << nReturnStmt
+	case *ast.SelectStmt:
+		return 1 << nSelectStmt
+	case *ast.SelectorExpr:
+		return 1 << nSelectorExpr
+	case *ast.SendStmt:
+		return 1 << nSendStmt
+	case *ast.SliceExpr:
+		return 1 << nSliceExpr
+	case *ast.StarExpr:
+		return 1 << nStarExpr
+	case *ast.StructType:
+		return 1 << nStructType
+	case *ast.SwitchStmt:
+		return 1 << nSwitchStmt
+	case *ast.TypeAssertExpr:
+		return 1 << nTypeAssertExpr
+	case *ast.TypeSpec:
+		return 1 << nTypeSpec
+	case *ast.TypeSwitchStmt:
+		return 1 << nTypeSwitchStmt
+	case *ast.UnaryExpr:
+		return 1 << nUnaryExpr
+	case *ast.ValueSpec:
+		return 1 << nValueSpec
+	}
+	return 0
+}
+
+func maskOf(nodes []ast.Node) uint64 {
+	if nodes == nil {
+		return 1<<64 - 1 // match all node types
+	}
+	var mask uint64
+	for _, n := range nodes {
+		mask |= typeOf(n)
+	}
+	return mask
+}

vendor/golang.org/x/tools/go/buildutil/allpackages.go

@@ -0,0 +1,198 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package buildutil provides utilities related to the go/build
+// package in the standard library.
+//
+// All I/O is done via the build.Context file system interface, which must
+// be concurrency-safe.
+package buildutil // import "golang.org/x/tools/go/buildutil"
+
+import (
+	"go/build"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+	"sync"
+)
+
+// AllPackages returns the package path of each Go package in any source
+// directory of the specified build context (e.g. $GOROOT or an element
+// of $GOPATH).  Errors are ignored.  The results are sorted.
+// All package paths are canonical, and thus may contain "/vendor/".
+//
+// The result may include import paths for directories that contain no
+// *.go files, such as "archive" (in $GOROOT/src).
+//
+// All I/O is done via the build.Context file system interface,
+// which must be concurrency-safe.
+//
+func AllPackages(ctxt *build.Context) []string {
+	var list []string
+	ForEachPackage(ctxt, func(pkg string, _ error) {
+		list = append(list, pkg)
+	})
+	sort.Strings(list)
+	return list
+}
+
+// ForEachPackage calls the found function with the package path of
+// each Go package it finds in any source directory of the specified
+// build context (e.g. $GOROOT or an element of $GOPATH).
+// All package paths are canonical, and thus may contain "/vendor/".
+//
+// If the package directory exists but could not be read, the second
+// argument to the found function provides the error.
+//
+// All I/O is done via the build.Context file system interface,
+// which must be concurrency-safe.
+//
+func ForEachPackage(ctxt *build.Context, found func(importPath string, err error)) {
+	ch := make(chan item)
+
+	var wg sync.WaitGroup
+	for _, root := range ctxt.SrcDirs() {
+		root := root
+		wg.Add(1)
+		go func() {
+			allPackages(ctxt, root, ch)
+			wg.Done()
+		}()
+	}
+	go func() {
+		wg.Wait()
+		close(ch)
+	}()
+
+	// All calls to found occur in the caller's goroutine.
+	for i := range ch {
+		found(i.importPath, i.err)
+	}
+}
+
+type item struct {
+	importPath string
+	err        error // (optional)
+}
+
+// We use a process-wide counting semaphore to limit
+// the number of parallel calls to ReadDir.
+var ioLimit = make(chan bool, 20)
+
+func allPackages(ctxt *build.Context, root string, ch chan<- item) {
+	root = filepath.Clean(root) + string(os.PathSeparator)
+
+	var wg sync.WaitGroup
+
+	var walkDir func(dir string)
+	walkDir = func(dir string) {
+		// Avoid .foo, _foo, and testdata directory trees.
+		base := filepath.Base(dir)
+		if base == "" || base[0] == '.' || base[0] == '_' || base == "testdata" {
+			return
+		}
+
+		pkg := filepath.ToSlash(strings.TrimPrefix(dir, root))
+
+		// Prune search if we encounter any of these import paths.
+		switch pkg {
+		case "builtin":
+			return
+		}
+
+		ioLimit <- true
+		files, err := ReadDir(ctxt, dir)
+		<-ioLimit
+		if pkg != "" || err != nil {
+			ch <- item{pkg, err}
+		}
+		for _, fi := range files {
+			fi := fi
+			if fi.IsDir() {
+				wg.Add(1)
+				go func() {
+					walkDir(filepath.Join(dir, fi.Name()))
+					wg.Done()
+				}()
+			}
+		}
+	}
+
+	walkDir(root)
+	wg.Wait()
+}
+
+// ExpandPatterns returns the set of packages matched by patterns,
+// which may have the following forms:
+//
+//		golang.org/x/tools/cmd/guru     # a single package
+//		golang.org/x/tools/...          # all packages beneath dir
+//		...                             # the entire workspace.
+//
+// Order is significant: a pattern preceded by '-' removes matching
+// packages from the set.  For example, these patterns match all encoding
+// packages except encoding/xml:
+//
+// 	encoding/... -encoding/xml
+//
+// A trailing slash in a pattern is ignored.  (Path components of Go
+// package names are separated by slash, not the platform's path separator.)
+//
+func ExpandPatterns(ctxt *build.Context, patterns []string) map[string]bool {
+	// TODO(adonovan): support other features of 'go list':
+	// - "std"/"cmd"/"all" meta-packages
+	// - "..." not at the end of a pattern
+	// - relative patterns using "./" or "../" prefix
+
+	pkgs := make(map[string]bool)
+	doPkg := func(pkg string, neg bool) {
+		if neg {
+			delete(pkgs, pkg)
+		} else {
+			pkgs[pkg] = true
+		}
+	}
+
+	// Scan entire workspace if wildcards are present.
+	// TODO(adonovan): opt: scan only the necessary subtrees of the workspace.
+	var all []string
+	for _, arg := range patterns {
+		if strings.HasSuffix(arg, "...") {
+			all = AllPackages(ctxt)
+			break
+		}
+	}
+
+	for _, arg := range patterns {
+		if arg == "" {
+			continue
+		}
+
+		neg := arg[0] == '-'
+		if neg {
+			arg = arg[1:]
+		}
+
+		if arg == "..." {
+			// ... matches all packages
+			for _, pkg := range all {
+				doPkg(pkg, neg)
+			}
+		} else if dir := strings.TrimSuffix(arg, "/..."); dir != arg {
+			// dir/... matches all packages beneath dir
+			for _, pkg := range all {
+				if strings.HasPrefix(pkg, dir) &&
+					(len(pkg) == len(dir) || pkg[len(dir)] == '/') {
+					doPkg(pkg, neg)
+				}
+			}
+		} else {
+			// single package
+			doPkg(strings.TrimSuffix(arg, "/"), neg)
+		}
+	}
+
+	return pkgs
+}

vendor/golang.org/x/tools/go/buildutil/fakecontext.go

@@ -0,0 +1,113 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package buildutil
+
+import (
+	"fmt"
+	"go/build"
+	"io"
+	"io/ioutil"
+	"os"
+	"path"
+	"path/filepath"
+	"sort"
+	"strings"
+	"time"
+)
+
+// FakeContext returns a build.Context for the fake file tree specified
+// by pkgs, which maps package import paths to a mapping from file base
+// names to contents.
+//
+// The fake Context has a GOROOT of "/go" and no GOPATH, and overrides
+// the necessary file access methods to read from memory instead of the
+// real file system.
+//
+// Unlike a real file tree, the fake one has only two levels---packages
+// and files---so ReadDir("/go/src/") returns all packages under
+// /go/src/ including, for instance, "math" and "math/big".
+// ReadDir("/go/src/math/big") would return all the files in the
+// "math/big" package.
+//
+func FakeContext(pkgs map[string]map[string]string) *build.Context {
+	clean := func(filename string) string {
+		f := path.Clean(filepath.ToSlash(filename))
+		// Removing "/go/src" while respecting segment
+		// boundaries has this unfortunate corner case:
+		if f == "/go/src" {
+			return ""
+		}
+		return strings.TrimPrefix(f, "/go/src/")
+	}
+
+	ctxt := build.Default // copy
+	ctxt.GOROOT = "/go"
+	ctxt.GOPATH = ""
+	ctxt.Compiler = "gc"
+	ctxt.IsDir = func(dir string) bool {
+		dir = clean(dir)
+		if dir == "" {
+			return true // needed by (*build.Context).SrcDirs
+		}
+		return pkgs[dir] != nil
+	}
+	ctxt.ReadDir = func(dir string) ([]os.FileInfo, error) {
+		dir = clean(dir)
+		var fis []os.FileInfo
+		if dir == "" {
+			// enumerate packages
+			for importPath := range pkgs {
+				fis = append(fis, fakeDirInfo(importPath))
+			}
+		} else {
+			// enumerate files of package
+			for basename := range pkgs[dir] {
+				fis = append(fis, fakeFileInfo(basename))
+			}
+		}
+		sort.Sort(byName(fis))
+		return fis, nil
+	}
+	ctxt.OpenFile = func(filename string) (io.ReadCloser, error) {
+		filename = clean(filename)
+		dir, base := path.Split(filename)
+		content, ok := pkgs[path.Clean(dir)][base]
+		if !ok {
+			return nil, fmt.Errorf("file not found: %s", filename)
+		}
+		return ioutil.NopCloser(strings.NewReader(content)), nil
+	}
+	ctxt.IsAbsPath = func(path string) bool {
+		path = filepath.ToSlash(path)
+		// Don't rely on the default (filepath.Path) since on
+		// Windows, it reports virtual paths as non-absolute.
+		return strings.HasPrefix(path, "/")
+	}
+	return &ctxt
+}
+
+type byName []os.FileInfo
+
+func (s byName) Len() int           { return len(s) }
+func (s byName) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
+func (s byName) Less(i, j int) bool { return s[i].Name() < s[j].Name() }
+
+type fakeFileInfo string
+
+func (fi fakeFileInfo) Name() string    { return string(fi) }
+func (fakeFileInfo) Sys() interface{}   { return nil }
+func (fakeFileInfo) ModTime() time.Time { return time.Time{} }
+func (fakeFileInfo) IsDir() bool        { return false }
+func (fakeFileInfo) Size() int64        { return 0 }
+func (fakeFileInfo) Mode() os.FileMode  { return 0644 }
+
+type fakeDirInfo string
+
+func (fd fakeDirInfo) Name() string    { return string(fd) }
+func (fakeDirInfo) Sys() interface{}   { return nil }
+func (fakeDirInfo) ModTime() time.Time { return time.Time{} }
+func (fakeDirInfo) IsDir() bool        { return true }
+func (fakeDirInfo) Size() int64        { return 0 }
+func (fakeDirInfo) Mode() os.FileMode  { return 0755 }

vendor/golang.org/x/tools/go/buildutil/overlay.go

@@ -0,0 +1,103 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package buildutil
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"go/build"
+	"io"
+	"io/ioutil"
+	"path/filepath"
+	"strconv"
+	"strings"
+)
+
+// OverlayContext overlays a build.Context with additional files from
+// a map. Files in the map take precedence over other files.
+//
+// In addition to plain string comparison, two file names are
+// considered equal if their base names match and their directory
+// components point at the same directory on the file system. That is,
+// symbolic links are followed for directories, but not files.
+//
+// A common use case for OverlayContext is to allow editors to pass in
+// a set of unsaved, modified files.
+//
+// Currently, only the Context.OpenFile function will respect the
+// overlay. This may change in the future.
+func OverlayContext(orig *build.Context, overlay map[string][]byte) *build.Context {
+	// TODO(dominikh): Implement IsDir, HasSubdir and ReadDir
+
+	rc := func(data []byte) (io.ReadCloser, error) {
+		return ioutil.NopCloser(bytes.NewBuffer(data)), nil
+	}
+
+	copy := *orig // make a copy
+	ctxt := &copy
+	ctxt.OpenFile = func(path string) (io.ReadCloser, error) {
+		// Fast path: names match exactly.
+		if content, ok := overlay[path]; ok {
+			return rc(content)
+		}
+
+		// Slow path: check for same file under a different
+		// alias, perhaps due to a symbolic link.
+		for filename, content := range overlay {
+			if sameFile(path, filename) {
+				return rc(content)
+			}
+		}
+
+		return OpenFile(orig, path)
+	}
+	return ctxt
+}
+
+// ParseOverlayArchive parses an archive containing Go files and their
+// contents. The result is intended to be used with OverlayContext.
+//
+//
+// Archive format
+//
+// The archive consists of a series of files. Each file consists of a
+// name, a decimal file size and the file contents, separated by
+// newlines. No newline follows after the file contents.
+func ParseOverlayArchive(archive io.Reader) (map[string][]byte, error) {
+	overlay := make(map[string][]byte)
+	r := bufio.NewReader(archive)
+	for {
+		// Read file name.
+		filename, err := r.ReadString('\n')
+		if err != nil {
+			if err == io.EOF {
+				break // OK
+			}
+			return nil, fmt.Errorf("reading archive file name: %v", err)
+		}
+		filename = filepath.Clean(strings.TrimSpace(filename))
+
+		// Read file size.
+		sz, err := r.ReadString('\n')
+		if err != nil {
+			return nil, fmt.Errorf("reading size of archive file %s: %v", filename, err)
+		}
+		sz = strings.TrimSpace(sz)
+		size, err := strconv.ParseUint(sz, 10, 32)
+		if err != nil {
+			return nil, fmt.Errorf("parsing size of archive file %s: %v", filename, err)
+		}
+
+		// Read file content.
+		content := make([]byte, size)
+		if _, err := io.ReadFull(r, content); err != nil {
+			return nil, fmt.Errorf("reading archive file %s: %v", filename, err)
+		}
+		overlay[filename] = content
+	}
+
+	return overlay, nil
+}

vendor/golang.org/x/tools/go/buildutil/tags.go

@@ -0,0 +1,79 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package buildutil
+
+// This logic was copied from stringsFlag from $GOROOT/src/cmd/go/build.go.
+
+import "fmt"
+
+const TagsFlagDoc = "a list of `build tags` to consider satisfied during the build. " +
+	"For more information about build tags, see the description of " +
+	"build constraints in the documentation for the go/build package"
+
+// TagsFlag is an implementation of the flag.Value and flag.Getter interfaces that parses
+// a flag value in the same manner as go build's -tags flag and
+// populates a []string slice.
+//
+// See $GOROOT/src/go/build/doc.go for description of build tags.
+// See $GOROOT/src/cmd/go/doc.go for description of 'go build -tags' flag.
+//
+// Example:
+// 	flag.Var((*buildutil.TagsFlag)(&build.Default.BuildTags), "tags", buildutil.TagsFlagDoc)
+type TagsFlag []string
+
+func (v *TagsFlag) Set(s string) error {
+	var err error
+	*v, err = splitQuotedFields(s)
+	if *v == nil {
+		*v = []string{}
+	}
+	return err
+}
+
+func (v *TagsFlag) Get() interface{} { return *v }
+
+func splitQuotedFields(s string) ([]string, error) {
+	// Split fields allowing '' or "" around elements.
+	// Quotes further inside the string do not count.
+	var f []string
+	for len(s) > 0 {
+		for len(s) > 0 && isSpaceByte(s[0]) {
+			s = s[1:]
+		}
+		if len(s) == 0 {
+			break
+		}
+		// Accepted quoted string. No unescaping inside.
+		if s[0] == '"' || s[0] == '\'' {
+			quote := s[0]
+			s = s[1:]
+			i := 0
+			for i < len(s) && s[i] != quote {
+				i++
+			}
+			if i >= len(s) {
+				return nil, fmt.Errorf("unterminated %c string", quote)
+			}
+			f = append(f, s[:i])
+			s = s[i+1:]
+			continue
+		}
+		i := 0
+		for i < len(s) && !isSpaceByte(s[i]) {
+			i++
+		}
+		f = append(f, s[:i])
+		s = s[i:]
+	}
+	return f, nil
+}
+
+func (v *TagsFlag) String() string {
+	return "<tagsFlag>"
+}
+
+func isSpaceByte(c byte) bool {
+	return c == ' ' || c == '\t' || c == '\n' || c == '\r'
+}

vendor/golang.org/x/tools/go/buildutil/util.go

@@ -0,0 +1,212 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package buildutil
+
+import (
+	"fmt"
+	"go/ast"
+	"go/build"
+	"go/parser"
+	"go/token"
+	"io"
+	"io/ioutil"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+)
+
+// ParseFile behaves like parser.ParseFile,
+// but uses the build context's file system interface, if any.
+//
+// If file is not absolute (as defined by IsAbsPath), the (dir, file)
+// components are joined using JoinPath; dir must be absolute.
+//
+// The displayPath function, if provided, is used to transform the
+// filename that will be attached to the ASTs.
+//
+// TODO(adonovan): call this from go/loader.parseFiles when the tree thaws.
+//
+func ParseFile(fset *token.FileSet, ctxt *build.Context, displayPath func(string) string, dir string, file string, mode parser.Mode) (*ast.File, error) {
+	if !IsAbsPath(ctxt, file) {
+		file = JoinPath(ctxt, dir, file)
+	}
+	rd, err := OpenFile(ctxt, file)
+	if err != nil {
+		return nil, err
+	}
+	defer rd.Close() // ignore error
+	if displayPath != nil {
+		file = displayPath(file)
+	}
+	return parser.ParseFile(fset, file, rd, mode)
+}
+
+// ContainingPackage returns the package containing filename.
+//
+// If filename is not absolute, it is interpreted relative to working directory dir.
+// All I/O is via the build context's file system interface, if any.
+//
+// The '...Files []string' fields of the resulting build.Package are not
+// populated (build.FindOnly mode).
+//
+func ContainingPackage(ctxt *build.Context, dir, filename string) (*build.Package, error) {
+	if !IsAbsPath(ctxt, filename) {
+		filename = JoinPath(ctxt, dir, filename)
+	}
+
+	// We must not assume the file tree uses
+	// "/" always,
+	// `\` always,
+	// or os.PathSeparator (which varies by platform),
+	// but to make any progress, we are forced to assume that
+	// paths will not use `\` unless the PathSeparator
+	// is also `\`, thus we can rely on filepath.ToSlash for some sanity.
+
+	dirSlash := path.Dir(filepath.ToSlash(filename)) + "/"
+
+	// We assume that no source root (GOPATH[i] or GOROOT) contains any other.
+	for _, srcdir := range ctxt.SrcDirs() {
+		srcdirSlash := filepath.ToSlash(srcdir) + "/"
+		if importPath, ok := HasSubdir(ctxt, srcdirSlash, dirSlash); ok {
+			return ctxt.Import(importPath, dir, build.FindOnly)
+		}
+	}
+
+	return nil, fmt.Errorf("can't find package containing %s", filename)
+}
+
+// -- Effective methods of file system interface -------------------------
+
+// (go/build.Context defines these as methods, but does not export them.)
+
+// hasSubdir calls ctxt.HasSubdir (if not nil) or else uses
+// the local file system to answer the question.
+func HasSubdir(ctxt *build.Context, root, dir string) (rel string, ok bool) {
+	if f := ctxt.HasSubdir; f != nil {
+		return f(root, dir)
+	}
+
+	// Try using paths we received.
+	if rel, ok = hasSubdir(root, dir); ok {
+		return
+	}
+
+	// Try expanding symlinks and comparing
+	// expanded against unexpanded and
+	// expanded against expanded.
+	rootSym, _ := filepath.EvalSymlinks(root)
+	dirSym, _ := filepath.EvalSymlinks(dir)
+
+	if rel, ok = hasSubdir(rootSym, dir); ok {
+		return
+	}
+	if rel, ok = hasSubdir(root, dirSym); ok {
+		return
+	}
+	return hasSubdir(rootSym, dirSym)
+}
+
+func hasSubdir(root, dir string) (rel string, ok bool) {
+	const sep = string(filepath.Separator)
+	root = filepath.Clean(root)
+	if !strings.HasSuffix(root, sep) {
+		root += sep
+	}
+
+	dir = filepath.Clean(dir)
+	if !strings.HasPrefix(dir, root) {
+		return "", false
+	}
+
+	return filepath.ToSlash(dir[len(root):]), true
+}
+
+// FileExists returns true if the specified file exists,
+// using the build context's file system interface.
+func FileExists(ctxt *build.Context, path string) bool {
+	if ctxt.OpenFile != nil {
+		r, err := ctxt.OpenFile(path)
+		if err != nil {
+			return false
+		}
+		r.Close() // ignore error
+		return true
+	}
+	_, err := os.Stat(path)
+	return err == nil
+}
+
+// OpenFile behaves like os.Open,
+// but uses the build context's file system interface, if any.
+func OpenFile(ctxt *build.Context, path string) (io.ReadCloser, error) {
+	if ctxt.OpenFile != nil {
+		return ctxt.OpenFile(path)
+	}
+	return os.Open(path)
+}
+
+// IsAbsPath behaves like filepath.IsAbs,
+// but uses the build context's file system interface, if any.
+func IsAbsPath(ctxt *build.Context, path string) bool {
+	if ctxt.IsAbsPath != nil {
+		return ctxt.IsAbsPath(path)
+	}
+	return filepath.IsAbs(path)
+}
+
+// JoinPath behaves like filepath.Join,
+// but uses the build context's file system interface, if any.
+func JoinPath(ctxt *build.Context, path ...string) string {
+	if ctxt.JoinPath != nil {
+		return ctxt.JoinPath(path...)
+	}
+	return filepath.Join(path...)
+}
+
+// IsDir behaves like os.Stat plus IsDir,
+// but uses the build context's file system interface, if any.
+func IsDir(ctxt *build.Context, path string) bool {
+	if ctxt.IsDir != nil {
+		return ctxt.IsDir(path)
+	}
+	fi, err := os.Stat(path)
+	return err == nil && fi.IsDir()
+}
+
+// ReadDir behaves like ioutil.ReadDir,
+// but uses the build context's file system interface, if any.
+func ReadDir(ctxt *build.Context, path string) ([]os.FileInfo, error) {
+	if ctxt.ReadDir != nil {
+		return ctxt.ReadDir(path)
+	}
+	return ioutil.ReadDir(path)
+}
+
+// SplitPathList behaves like filepath.SplitList,
+// but uses the build context's file system interface, if any.
+func SplitPathList(ctxt *build.Context, s string) []string {
+	if ctxt.SplitPathList != nil {
+		return ctxt.SplitPathList(s)
+	}
+	return filepath.SplitList(s)
+}
+
+// sameFile returns true if x and y have the same basename and denote
+// the same file.
+//
+func sameFile(x, y string) bool {
+	if path.Clean(x) == path.Clean(y) {
+		return true
+	}
+	if filepath.Base(x) == filepath.Base(y) { // (optimisation)
+		if xi, err := os.Stat(x); err == nil {
+			if yi, err := os.Stat(y); err == nil {
+				return os.SameFile(xi, yi)
+			}
+		}
+	}
+	return false
+}

vendor/golang.org/x/tools/go/gcexportdata/gcexportdata.go

@@ -50,11 +50,24 @@ func Find(importPath, srcDir string) (filename, path string) {
 // additional trailing data beyond the end of the export data.
 func NewReader(r io.Reader) (io.Reader, error) {
 	buf := bufio.NewReader(r)
-	_, err := gcimporter.FindExportData(buf)
-	// If we ever switch to a zip-like archive format with the ToC
-	// at the end, we can return the correct portion of export data,
-	// but for now we must return the entire rest of the file.
-	return buf, err
+	_, size, err := gcimporter.FindExportData(buf)
+	if err != nil {
+		return nil, err
+	}
+
+	if size >= 0 {
+		// We were given an archive and found the __.PKGDEF in it.
+		// This tells us the size of the export data, and we don't
+		// need to return the entire file.
+		return &io.LimitedReader{
+			R: buf,
+			N: size,
+		}, nil
+	} else {
+		// We were given an object file. As such, we don't know how large
+		// the export data is and must return the entire file.
+		return buf, nil
+	}
 }
 
 // Read reads export data from in, decodes it, and returns type

vendor/golang.org/x/tools/go/internal/cgo/cgo.go

@@ -0,0 +1,222 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package cgo handles cgo preprocessing of files containing `import "C"`.
+//
+// DESIGN
+//
+// The approach taken is to run the cgo processor on the package's
+// CgoFiles and parse the output, faking the filenames of the
+// resulting ASTs so that the synthetic file containing the C types is
+// called "C" (e.g. "~/go/src/net/C") and the preprocessed files
+// have their original names (e.g. "~/go/src/net/cgo_unix.go"),
+// not the names of the actual temporary files.
+//
+// The advantage of this approach is its fidelity to 'go build'.  The
+// downside is that the token.Position.Offset for each AST node is
+// incorrect, being an offset within the temporary file.  Line numbers
+// should still be correct because of the //line comments.
+//
+// The logic of this file is mostly plundered from the 'go build'
+// tool, which also invokes the cgo preprocessor.
+//
+//
+// REJECTED ALTERNATIVE
+//
+// An alternative approach that we explored is to extend go/types'
+// Importer mechanism to provide the identity of the importing package
+// so that each time `import "C"` appears it resolves to a different
+// synthetic package containing just the objects needed in that case.
+// The loader would invoke cgo but parse only the cgo_types.go file
+// defining the package-level objects, discarding the other files
+// resulting from preprocessing.
+//
+// The benefit of this approach would have been that source-level
+// syntax information would correspond exactly to the original cgo
+// file, with no preprocessing involved, making source tools like
+// godoc, guru, and eg happy.  However, the approach was rejected
+// due to the additional complexity it would impose on go/types.  (It
+// made for a beautiful demo, though.)
+//
+// cgo files, despite their *.go extension, are not legal Go source
+// files per the specification since they may refer to unexported
+// members of package "C" such as C.int.  Also, a function such as
+// C.getpwent has in effect two types, one matching its C type and one
+// which additionally returns (errno C.int).  The cgo preprocessor
+// uses name mangling to distinguish these two functions in the
+// processed code, but go/types would need to duplicate this logic in
+// its handling of function calls, analogous to the treatment of map
+// lookups in which y=m[k] and y,ok=m[k] are both legal.
+
+package cgo
+
+import (
+	"fmt"
+	"go/ast"
+	"go/build"
+	"go/parser"
+	"go/token"
+	"io/ioutil"
+	"log"
+	"os"
+	"path/filepath"
+	"regexp"
+	"strings"
+
+	exec "golang.org/x/sys/execabs"
+)
+
+// ProcessFiles invokes the cgo preprocessor on bp.CgoFiles, parses
+// the output and returns the resulting ASTs.
+//
+func ProcessFiles(bp *build.Package, fset *token.FileSet, DisplayPath func(path string) string, mode parser.Mode) ([]*ast.File, error) {
+	tmpdir, err := ioutil.TempDir("", strings.Replace(bp.ImportPath, "/", "_", -1)+"_C")
+	if err != nil {
+		return nil, err
+	}
+	defer os.RemoveAll(tmpdir)
+
+	pkgdir := bp.Dir
+	if DisplayPath != nil {
+		pkgdir = DisplayPath(pkgdir)
+	}
+
+	cgoFiles, cgoDisplayFiles, err := Run(bp, pkgdir, tmpdir, false)
+	if err != nil {
+		return nil, err
+	}
+	var files []*ast.File
+	for i := range cgoFiles {
+		rd, err := os.Open(cgoFiles[i])
+		if err != nil {
+			return nil, err
+		}
+		display := filepath.Join(bp.Dir, cgoDisplayFiles[i])
+		f, err := parser.ParseFile(fset, display, rd, mode)
+		rd.Close()
+		if err != nil {
+			return nil, err
+		}
+		files = append(files, f)
+	}
+	return files, nil
+}
+
+var cgoRe = regexp.MustCompile(`[/\\:]`)
+
+// Run invokes the cgo preprocessor on bp.CgoFiles and returns two
+// lists of files: the resulting processed files (in temporary
+// directory tmpdir) and the corresponding names of the unprocessed files.
+//
+// Run is adapted from (*builder).cgo in
+// $GOROOT/src/cmd/go/build.go, but these features are unsupported:
+// Objective C, CGOPKGPATH, CGO_FLAGS.
+//
+// If useabs is set to true, absolute paths of the bp.CgoFiles will be passed in
+// to the cgo preprocessor. This in turn will set the // line comments
+// referring to those files to use absolute paths. This is needed for
+// go/packages using the legacy go list support so it is able to find
+// the original files.
+func Run(bp *build.Package, pkgdir, tmpdir string, useabs bool) (files, displayFiles []string, err error) {
+	cgoCPPFLAGS, _, _, _ := cflags(bp, true)
+	_, cgoexeCFLAGS, _, _ := cflags(bp, false)
+
+	if len(bp.CgoPkgConfig) > 0 {
+		pcCFLAGS, err := pkgConfigFlags(bp)
+		if err != nil {
+			return nil, nil, err
+		}
+		cgoCPPFLAGS = append(cgoCPPFLAGS, pcCFLAGS...)
+	}
+
+	// Allows including _cgo_export.h from .[ch] files in the package.
+	cgoCPPFLAGS = append(cgoCPPFLAGS, "-I", tmpdir)
+
+	// _cgo_gotypes.go (displayed "C") contains the type definitions.
+	files = append(files, filepath.Join(tmpdir, "_cgo_gotypes.go"))
+	displayFiles = append(displayFiles, "C")
+	for _, fn := range bp.CgoFiles {
+		// "foo.cgo1.go" (displayed "foo.go") is the processed Go source.
+		f := cgoRe.ReplaceAllString(fn[:len(fn)-len("go")], "_")
+		files = append(files, filepath.Join(tmpdir, f+"cgo1.go"))
+		displayFiles = append(displayFiles, fn)
+	}
+
+	var cgoflags []string
+	if bp.Goroot && bp.ImportPath == "runtime/cgo" {
+		cgoflags = append(cgoflags, "-import_runtime_cgo=false")
+	}
+	if bp.Goroot && bp.ImportPath == "runtime/race" || bp.ImportPath == "runtime/cgo" {
+		cgoflags = append(cgoflags, "-import_syscall=false")
+	}
+
+	var cgoFiles []string = bp.CgoFiles
+	if useabs {
+		cgoFiles = make([]string, len(bp.CgoFiles))
+		for i := range cgoFiles {
+			cgoFiles[i] = filepath.Join(pkgdir, bp.CgoFiles[i])
+		}
+	}
+
+	args := stringList(
+		"go", "tool", "cgo", "-objdir", tmpdir, cgoflags, "--",
+		cgoCPPFLAGS, cgoexeCFLAGS, cgoFiles,
+	)
+	if false {
+		log.Printf("Running cgo for package %q: %s (dir=%s)", bp.ImportPath, args, pkgdir)
+	}
+	cmd := exec.Command(args[0], args[1:]...)
+	cmd.Dir = pkgdir
+	cmd.Env = append(os.Environ(), "PWD="+pkgdir)
+	cmd.Stdout = os.Stderr
+	cmd.Stderr = os.Stderr
+	if err := cmd.Run(); err != nil {
+		return nil, nil, fmt.Errorf("cgo failed: %s: %s", args, err)
+	}
+
+	return files, displayFiles, nil
+}
+
+// -- unmodified from 'go build' ---------------------------------------
+
+// Return the flags to use when invoking the C or C++ compilers, or cgo.
+func cflags(p *build.Package, def bool) (cppflags, cflags, cxxflags, ldflags []string) {
+	var defaults string
+	if def {
+		defaults = "-g -O2"
+	}
+
+	cppflags = stringList(envList("CGO_CPPFLAGS", ""), p.CgoCPPFLAGS)
+	cflags = stringList(envList("CGO_CFLAGS", defaults), p.CgoCFLAGS)
+	cxxflags = stringList(envList("CGO_CXXFLAGS", defaults), p.CgoCXXFLAGS)
+	ldflags = stringList(envList("CGO_LDFLAGS", defaults), p.CgoLDFLAGS)
+	return
+}
+
+// envList returns the value of the given environment variable broken
+// into fields, using the default value when the variable is empty.
+func envList(key, def string) []string {
+	v := os.Getenv(key)
+	if v == "" {
+		v = def
+	}
+	return strings.Fields(v)
+}
+
+// stringList's arguments should be a sequence of string or []string values.
+// stringList flattens them into a single []string.
+func stringList(args ...interface{}) []string {
+	var x []string
+	for _, arg := range args {
+		switch arg := arg.(type) {
+		case []string:
+			x = append(x, arg...)
+		case string:
+			x = append(x, arg)
+		default:
+			panic("stringList: invalid argument")
+		}
+	}
+	return x
+}

vendor/golang.org/x/tools/go/internal/cgo/cgo_pkgconfig.go

@@ -0,0 +1,39 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package cgo
+
+import (
+	"errors"
+	"fmt"
+	"go/build"
+	exec "golang.org/x/sys/execabs"
+	"strings"
+)
+
+// pkgConfig runs pkg-config with the specified arguments and returns the flags it prints.
+func pkgConfig(mode string, pkgs []string) (flags []string, err error) {
+	cmd := exec.Command("pkg-config", append([]string{mode}, pkgs...)...)
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		s := fmt.Sprintf("%s failed: %v", strings.Join(cmd.Args, " "), err)
+		if len(out) > 0 {
+			s = fmt.Sprintf("%s: %s", s, out)
+		}
+		return nil, errors.New(s)
+	}
+	if len(out) > 0 {
+		flags = strings.Fields(string(out))
+	}
+	return
+}
+
+// pkgConfigFlags calls pkg-config if needed and returns the cflags
+// needed to build the package.
+func pkgConfigFlags(p *build.Package) (cflags []string, err error) {
+	if len(p.CgoPkgConfig) == 0 {
+		return nil, nil
+	}
+	return pkgConfig("--cflags", p.CgoPkgConfig)
+}

vendor/golang.org/x/tools/go/internal/gcimporter/bexport.go

@@ -34,9 +34,6 @@ import (
 // (suspected) format errors, and whenever a change is made to the format.
 const debugFormat = false // default: false
 
-// If trace is set, debugging output is printed to std out.
-const trace = false // default: false
-
 // Current export format version. Increase with each format change.
 // Note: The latest binary (non-indexed) export format is at version 6.
 //       This exporter is still at level 4, but it doesn't matter since
@@ -92,16 +89,18 @@ func internalErrorf(format string, args ...interface{}) error {
 // BExportData returns binary export data for pkg.
 // If no file set is provided, position info will be missing.
 func BExportData(fset *token.FileSet, pkg *types.Package) (b []byte, err error) {
-	defer func() {
-		if e := recover(); e != nil {
-			if ierr, ok := e.(internalError); ok {
-				err = ierr
-				return
+	if !debug {
+		defer func() {
+			if e := recover(); e != nil {
+				if ierr, ok := e.(internalError); ok {
+					err = ierr
+					return
+				}
+				// Not an internal error; panic again.
+				panic(e)
 			}
-			// Not an internal error; panic again.
-			panic(e)
-		}
-	}()
+		}()
+	}
 
 	p := exporter{
 		fset:          fset,

vendor/golang.org/x/tools/go/internal/gcimporter/bimport.go

@@ -74,9 +74,10 @@ func BImportData(fset *token.FileSet, imports map[string]*types.Package, data []
 		pathList:   []string{""}, // empty string is mapped to 0
 		fake: fakeFileSet{
 			fset:  fset,
-			files: make(map[string]*token.File),
+			files: make(map[string]*fileInfo),
 		},
 	}
+	defer p.fake.setLines() // set lines for files in fset
 
 	// read version info
 	var versionstr string
@@ -338,37 +339,49 @@ func (p *importer) pos() token.Pos {
 // Synthesize a token.Pos
 type fakeFileSet struct {
 	fset  *token.FileSet
-	files map[string]*token.File
+	files map[string]*fileInfo
 }
 
+type fileInfo struct {
+	file     *token.File
+	lastline int
+}
+
+const maxlines = 64 * 1024
+
 func (s *fakeFileSet) pos(file string, line, column int) token.Pos {
 	// TODO(mdempsky): Make use of column.
 
-	// Since we don't know the set of needed file positions, we
-	// reserve maxlines positions per file.
-	const maxlines = 64 * 1024
+	// Since we don't know the set of needed file positions, we reserve maxlines
+	// positions per file. We delay calling token.File.SetLines until all
+	// positions have been calculated (by way of fakeFileSet.setLines), so that
+	// we can avoid setting unnecessary lines. See also golang/go#46586.
 	f := s.files[file]
 	if f == nil {
-		f = s.fset.AddFile(file, -1, maxlines)
+		f = &fileInfo{file: s.fset.AddFile(file, -1, maxlines)}
 		s.files[file] = f
-		// Allocate the fake linebreak indices on first use.
-		// TODO(adonovan): opt: save ~512KB using a more complex scheme?
-		fakeLinesOnce.Do(func() {
-			fakeLines = make([]int, maxlines)
-			for i := range fakeLines {
-				fakeLines[i] = i
-			}
-		})
-		f.SetLines(fakeLines)
 	}
-
 	if line > maxlines {
 		line = 1
 	}
+	if line > f.lastline {
+		f.lastline = line
+	}
 
-	// Treat the file as if it contained only newlines
-	// and column=1: use the line number as the offset.
-	return f.Pos(line - 1)
+	// Return a fake position assuming that f.file consists only of newlines.
+	return token.Pos(f.file.Base() + line - 1)
+}
+
+func (s *fakeFileSet) setLines() {
+	fakeLinesOnce.Do(func() {
+		fakeLines = make([]int, maxlines)
+		for i := range fakeLines {
+			fakeLines[i] = i
+		}
+	})
+	for _, f := range s.files {
+		f.file.SetLines(fakeLines[:f.lastline])
+	}
 }
 
 var (
@@ -1029,6 +1042,7 @@ func predeclared() []types.Type {
 			// used internally by gc; never used by this package or in .a files
 			anyType{},
 		}
+		predecl = append(predecl, additionalPredeclared()...)
 	})
 	return predecl
 }

vendor/golang.org/x/tools/go/internal/gcimporter/exportdata.go

@@ -16,7 +16,7 @@ import (
 	"strings"
 )
 
-func readGopackHeader(r *bufio.Reader) (name string, size int, err error) {
+func readGopackHeader(r *bufio.Reader) (name string, size int64, err error) {
 	// See $GOROOT/include/ar.h.
 	hdr := make([]byte, 16+12+6+6+8+10+2)
 	_, err = io.ReadFull(r, hdr)
@@ -28,7 +28,8 @@ func readGopackHeader(r *bufio.Reader) (name string, size int, err error) {
 		fmt.Printf("header: %s", hdr)
 	}
 	s := strings.TrimSpace(string(hdr[16+12+6+6+8:][:10]))
-	size, err = strconv.Atoi(s)
+	length, err := strconv.Atoi(s)
+	size = int64(length)
 	if err != nil || hdr[len(hdr)-2] != '`' || hdr[len(hdr)-1] != '\n' {
 		err = fmt.Errorf("invalid archive header")
 		return
@@ -42,8 +43,8 @@ func readGopackHeader(r *bufio.Reader) (name string, size int, err error) {
 // file by reading from it. The reader must be positioned at the
 // start of the file before calling this function. The hdr result
 // is the string before the export data, either "$$" or "$$B".
-//
-func FindExportData(r *bufio.Reader) (hdr string, err error) {
+// The size result is the length of the export data in bytes, or -1 if not known.
+func FindExportData(r *bufio.Reader) (hdr string, size int64, err error) {
 	// Read first line to make sure this is an object file.
 	line, err := r.ReadSlice('\n')
 	if err != nil {
@@ -54,7 +55,7 @@ func FindExportData(r *bufio.Reader) (hdr string, err error) {
 	if string(line) == "!<arch>\n" {
 		// Archive file. Scan to __.PKGDEF.
 		var name string
-		if name, _, err = readGopackHeader(r); err != nil {
+		if name, size, err = readGopackHeader(r); err != nil {
 			return
 		}
 
@@ -70,6 +71,7 @@ func FindExportData(r *bufio.Reader) (hdr string, err error) {
 			err = fmt.Errorf("can't find export data (%v)", err)
 			return
 		}
+		size -= int64(len(line))
 	}
 
 	// Now at __.PKGDEF in archive or still at beginning of file.
@@ -86,8 +88,12 @@ func FindExportData(r *bufio.Reader) (hdr string, err error) {
 			err = fmt.Errorf("can't find export data (%v)", err)
 			return
 		}
+		size -= int64(len(line))
 	}
 	hdr = string(line)
+	if size < 0 {
+		size = -1
+	}
 
 	return
 }

vendor/golang.org/x/tools/go/internal/gcimporter/gcimporter.go

@@ -29,8 +29,14 @@ import (
 	"text/scanner"
 )
 
-// debugging/development support
-const debug = false
+const (
+	// Enable debug during development: it adds some additional checks, and
+	// prevents errors from being recovered.
+	debug = false
+
+	// If trace is set, debugging output is printed to std out.
+	trace = false
+)
 
 var pkgExts = [...]string{".a", ".o"}
 
@@ -179,7 +185,7 @@ func Import(packages map[string]*types.Package, path, srcDir string, lookup func
 
 	var hdr string
 	buf := bufio.NewReader(rc)
-	if hdr, err = FindExportData(buf); err != nil {
+	if hdr, _, err = FindExportData(buf); err != nil {
 		return
 	}
 

vendor/golang.org/x/tools/go/internal/gcimporter/iexport.go

@@ -11,6 +11,7 @@ package gcimporter
 import (
 	"bytes"
 	"encoding/binary"
+	"fmt"
 	"go/ast"
 	"go/constant"
 	"go/token"
@@ -19,11 +20,11 @@ import (
 	"math/big"
 	"reflect"
 	"sort"
-)
+	"strconv"
+	"strings"
 
-// Current indexed export format version. Increase with each format change.
-// 0: Go1.11 encoding
-const iexportVersion = 0
+	"golang.org/x/tools/internal/typeparams"
+)
 
 // Current bundled export format version. Increase with each format change.
 // 0: initial implementation
@@ -35,31 +36,35 @@ const bundleVersion = 0
 // The package path of the top-level package will not be recorded,
 // so that calls to IImportData can override with a provided package path.
 func IExportData(out io.Writer, fset *token.FileSet, pkg *types.Package) error {
-	return iexportCommon(out, fset, false, []*types.Package{pkg})
+	return iexportCommon(out, fset, false, iexportVersion, []*types.Package{pkg})
 }
 
 // IExportBundle writes an indexed export bundle for pkgs to out.
 func IExportBundle(out io.Writer, fset *token.FileSet, pkgs []*types.Package) error {
-	return iexportCommon(out, fset, true, pkgs)
-}
-
-func iexportCommon(out io.Writer, fset *token.FileSet, bundle bool, pkgs []*types.Package) (err error) {
-	defer func() {
-		if e := recover(); e != nil {
-			if ierr, ok := e.(internalError); ok {
-				err = ierr
-				return
+	return iexportCommon(out, fset, true, iexportVersion, pkgs)
+}
+
+func iexportCommon(out io.Writer, fset *token.FileSet, bundle bool, version int, pkgs []*types.Package) (err error) {
+	if !debug {
+		defer func() {
+			if e := recover(); e != nil {
+				if ierr, ok := e.(internalError); ok {
+					err = ierr
+					return
+				}
+				// Not an internal error; panic again.
+				panic(e)
 			}
-			// Not an internal error; panic again.
-			panic(e)
-		}
-	}()
+		}()
+	}
 
 	p := iexporter{
 		fset:        fset,
+		version:     version,
 		allPkgs:     map[*types.Package]bool{},
 		stringIndex: map[string]uint64{},
 		declIndex:   map[types.Object]uint64{},
+		tparamNames: map[types.Object]string{},
 		typIndex:    map[types.Type]uint64{},
 	}
 	if !bundle {
@@ -119,7 +124,7 @@ func iexportCommon(out io.Writer, fset *token.FileSet, bundle bool, pkgs []*type
 	if bundle {
 		hdr.uint64(bundleVersion)
 	}
-	hdr.uint64(iexportVersion)
+	hdr.uint64(uint64(p.version))
 	hdr.uint64(uint64(p.strings.Len()))
 	hdr.uint64(dataLen)
 
@@ -136,8 +141,12 @@ func iexportCommon(out io.Writer, fset *token.FileSet, bundle bool, pkgs []*type
 // non-compiler tools and includes a complete package description
 // (i.e., name and height).
 func (w *exportWriter) writeIndex(index map[types.Object]uint64) {
+	type pkgObj struct {
+		obj  types.Object
+		name string // qualified name; differs from obj.Name for type params
+	}
 	// Build a map from packages to objects from that package.
-	pkgObjs := map[*types.Package][]types.Object{}
+	pkgObjs := map[*types.Package][]pkgObj{}
 
 	// For the main index, make sure to include every package that
 	// we reference, even if we're not exporting (or reexporting)
@@ -150,7 +159,8 @@ func (w *exportWriter) writeIndex(index map[types.Object]uint64) {
 	}
 
 	for obj := range index {
-		pkgObjs[obj.Pkg()] = append(pkgObjs[obj.Pkg()], obj)
+		name := w.p.exportName(obj)
+		pkgObjs[obj.Pkg()] = append(pkgObjs[obj.Pkg()], pkgObj{obj, name})
 	}
 
 	var pkgs []*types.Package
@@ -158,7 +168,7 @@ func (w *exportWriter) writeIndex(index map[types.Object]uint64) {
 		pkgs = append(pkgs, pkg)
 
 		sort.Slice(objs, func(i, j int) bool {
-			return objs[i].Name() < objs[j].Name()
+			return objs[i].name < objs[j].name
 		})
 	}
 
@@ -175,15 +185,25 @@ func (w *exportWriter) writeIndex(index map[types.Object]uint64) {
 		objs := pkgObjs[pkg]
 		w.uint64(uint64(len(objs)))
 		for _, obj := range objs {
-			w.string(obj.Name())
-			w.uint64(index[obj])
+			w.string(obj.name)
+			w.uint64(index[obj.obj])
 		}
 	}
 }
 
+// exportName returns the 'exported' name of an object. It differs from
+// obj.Name() only for type parameters (see tparamExportName for details).
+func (p *iexporter) exportName(obj types.Object) (res string) {
+	if name := p.tparamNames[obj]; name != "" {
+		return name
+	}
+	return obj.Name()
+}
+
 type iexporter struct {
-	fset *token.FileSet
-	out  *bytes.Buffer
+	fset    *token.FileSet
+	out     *bytes.Buffer
+	version int
 
 	localpkg *types.Package
 
@@ -197,9 +217,21 @@ type iexporter struct {
 	strings     intWriter
 	stringIndex map[string]uint64
 
-	data0     intWriter
-	declIndex map[types.Object]uint64
-	typIndex  map[types.Type]uint64
+	data0       intWriter
+	declIndex   map[types.Object]uint64
+	tparamNames map[types.Object]string // typeparam->exported name
+	typIndex    map[types.Type]uint64
+
+	indent int // for tracing support
+}
+
+func (p *iexporter) trace(format string, args ...interface{}) {
+	if !trace {
+		// Call sites should also be guarded, but having this check here allows
+		// easily enabling/disabling debug trace statements.
+		return
+	}
+	fmt.Printf(strings.Repeat("..", p.indent)+format+"\n", args...)
 }
 
 // stringOff returns the offset of s within the string section.
@@ -225,7 +257,7 @@ func (p *iexporter) pushDecl(obj types.Object) {
 		return
 	}
 
-	p.declIndex[obj] = ^uint64(0) // mark n present in work queue
+	p.declIndex[obj] = ^uint64(0) // mark obj present in work queue
 	p.declTodo.pushTail(obj)
 }
 
@@ -233,10 +265,11 @@ func (p *iexporter) pushDecl(obj types.Object) {
 type exportWriter struct {
 	p *iexporter
 
-	data     intWriter
-	currPkg  *types.Package
-	prevFile string
-	prevLine int64
+	data       intWriter
+	currPkg    *types.Package
+	prevFile   string
+	prevLine   int64
+	prevColumn int64
 }
 
 func (w *exportWriter) exportPath(pkg *types.Package) string {
@@ -247,6 +280,14 @@ func (w *exportWriter) exportPath(pkg *types.Package) string {
 }
 
 func (p *iexporter) doDecl(obj types.Object) {
+	if trace {
+		p.trace("exporting decl %v (%T)", obj, obj)
+		p.indent++
+		defer func() {
+			p.indent--
+			p.trace("=> %s", obj)
+		}()
+	}
 	w := p.newWriter()
 	w.setPkg(obj.Pkg(), false)
 
@@ -261,8 +302,24 @@ func (p *iexporter) doDecl(obj types.Object) {
 		if sig.Recv() != nil {
 			panic(internalErrorf("unexpected method: %v", sig))
 		}
-		w.tag('F')
+
+		// Function.
+		if typeparams.ForSignature(sig).Len() == 0 {
+			w.tag('F')
+		} else {
+			w.tag('G')
+		}
 		w.pos(obj.Pos())
+		// The tparam list of the function type is the declaration of the type
+		// params. So, write out the type params right now. Then those type params
+		// will be referenced via their type offset (via typOff) in all other
+		// places in the signature and function where they are used.
+		//
+		// While importing the type parameters, tparamList computes and records
+		// their export name, so that it can be later used when writing the index.
+		if tparams := typeparams.ForSignature(sig); tparams.Len() > 0 {
+			w.tparamList(obj.Name(), tparams, obj.Pkg())
+		}
 		w.signature(sig)
 
 	case *types.Const:
@@ -271,30 +328,56 @@ func (p *iexporter) doDecl(obj types.Object) {
 		w.value(obj.Type(), obj.Val())
 
 	case *types.TypeName:
+		t := obj.Type()
+
+		if tparam, ok := t.(*typeparams.TypeParam); ok {
+			w.tag('P')
+			w.pos(obj.Pos())
+			constraint := tparam.Constraint()
+			if p.version >= iexportVersionGo1_18 {
+				implicit := false
+				if iface, _ := constraint.(*types.Interface); iface != nil {
+					implicit = typeparams.IsImplicit(iface)
+				}
+				w.bool(implicit)
+			}
+			w.typ(constraint, obj.Pkg())
+			break
+		}
+
 		if obj.IsAlias() {
 			w.tag('A')
 			w.pos(obj.Pos())
-			w.typ(obj.Type(), obj.Pkg())
+			w.typ(t, obj.Pkg())
 			break
 		}
 
 		// Defined type.
-		w.tag('T')
+		named, ok := t.(*types.Named)
+		if !ok {
+			panic(internalErrorf("%s is not a defined type", t))
+		}
+
+		if typeparams.ForNamed(named).Len() == 0 {
+			w.tag('T')
+		} else {
+			w.tag('U')
+		}
 		w.pos(obj.Pos())
 
+		if typeparams.ForNamed(named).Len() > 0 {
+			// While importing the type parameters, tparamList computes and records
+			// their export name, so that it can be later used when writing the index.
+			w.tparamList(obj.Name(), typeparams.ForNamed(named), obj.Pkg())
+		}
+
 		underlying := obj.Type().Underlying()
 		w.typ(underlying, obj.Pkg())
 
-		t := obj.Type()
 		if types.IsInterface(t) {
 			break
 		}
 
-		named, ok := t.(*types.Named)
-		if !ok {
-			panic(internalErrorf("%s is not a defined type", t))
-		}
-
 		n := named.NumMethods()
 		w.uint64(uint64(n))
 		for i := 0; i < n; i++ {
@@ -302,6 +385,17 @@ func (p *iexporter) doDecl(obj types.Object) {
 			w.pos(m.Pos())
 			w.string(m.Name())
 			sig, _ := m.Type().(*types.Signature)
+
+			// Receiver type parameters are type arguments of the receiver type, so
+			// their name must be qualified before exporting recv.
+			if rparams := typeparams.RecvTypeParams(sig); rparams.Len() > 0 {
+				prefix := obj.Name() + "." + m.Name()
+				for i := 0; i < rparams.Len(); i++ {
+					rparam := rparams.At(i)
+					name := tparamExportName(prefix, rparam)
+					w.p.tparamNames[rparam.Obj()] = name
+				}
+			}
 			w.param(sig.Recv())
 			w.signature(sig)
 		}
@@ -318,6 +412,48 @@ func (w *exportWriter) tag(tag byte) {
 }
 
 func (w *exportWriter) pos(pos token.Pos) {
+	if w.p.version >= iexportVersionPosCol {
+		w.posV1(pos)
+	} else {
+		w.posV0(pos)
+	}
+}
+
+func (w *exportWriter) posV1(pos token.Pos) {
+	if w.p.fset == nil {
+		w.int64(0)
+		return
+	}
+
+	p := w.p.fset.Position(pos)
+	file := p.Filename
+	line := int64(p.Line)
+	column := int64(p.Column)
+
+	deltaColumn := (column - w.prevColumn) << 1
+	deltaLine := (line - w.prevLine) << 1
+
+	if file != w.prevFile {
+		deltaLine |= 1
+	}
+	if deltaLine != 0 {
+		deltaColumn |= 1
+	}
+
+	w.int64(deltaColumn)
+	if deltaColumn&1 != 0 {
+		w.int64(deltaLine)
+		if deltaLine&1 != 0 {
+			w.string(file)
+		}
+	}
+
+	w.prevFile = file
+	w.prevLine = line
+	w.prevColumn = column
+}
+
+func (w *exportWriter) posV0(pos token.Pos) {
 	if w.p.fset == nil {
 		w.int64(0)
 		return
@@ -359,10 +495,11 @@ func (w *exportWriter) pkg(pkg *types.Package) {
 }
 
 func (w *exportWriter) qualifiedIdent(obj types.Object) {
+	name := w.p.exportName(obj)
+
 	// Ensure any referenced declarations are written out too.
 	w.p.pushDecl(obj)
-
-	w.string(obj.Name())
+	w.string(name)
 	w.pkg(obj.Pkg())
 }
 
@@ -396,11 +533,32 @@ func (w *exportWriter) startType(k itag) {
 }
 
 func (w *exportWriter) doTyp(t types.Type, pkg *types.Package) {
+	if trace {
+		w.p.trace("exporting type %s (%T)", t, t)
+		w.p.indent++
+		defer func() {
+			w.p.indent--
+			w.p.trace("=> %s", t)
+		}()
+	}
 	switch t := t.(type) {
 	case *types.Named:
+		if targs := typeparams.NamedTypeArgs(t); targs.Len() > 0 {
+			w.startType(instanceType)
+			// TODO(rfindley): investigate if this position is correct, and if it
+			// matters.
+			w.pos(t.Obj().Pos())
+			w.typeList(targs, pkg)
+			w.typ(typeparams.NamedTypeOrigin(t), pkg)
+			return
+		}
 		w.startType(definedType)
 		w.qualifiedIdent(t.Obj())
 
+	case *typeparams.TypeParam:
+		w.startType(typeParamType)
+		w.qualifiedIdent(t.Obj())
+
 	case *types.Pointer:
 		w.startType(pointerType)
 		w.typ(t.Elem(), pkg)
@@ -461,9 +619,14 @@ func (w *exportWriter) doTyp(t types.Type, pkg *types.Package) {
 		n := t.NumEmbeddeds()
 		w.uint64(uint64(n))
 		for i := 0; i < n; i++ {
-			f := t.Embedded(i)
-			w.pos(f.Obj().Pos())
-			w.typ(f.Obj().Type(), f.Obj().Pkg())
+			ft := t.EmbeddedType(i)
+			tPkg := pkg
+			if named, _ := ft.(*types.Named); named != nil {
+				w.pos(named.Obj().Pos())
+			} else {
+				w.pos(token.NoPos)
+			}
+			w.typ(ft, tPkg)
 		}
 
 		n = t.NumExplicitMethods()
@@ -476,6 +639,16 @@ func (w *exportWriter) doTyp(t types.Type, pkg *types.Package) {
 			w.signature(sig)
 		}
 
+	case *typeparams.Union:
+		w.startType(unionType)
+		nt := t.Len()
+		w.uint64(uint64(nt))
+		for i := 0; i < nt; i++ {
+			term := t.Term(i)
+			w.bool(term.Tilde())
+			w.typ(term.Type(), pkg)
+		}
+
 	default:
 		panic(internalErrorf("unexpected type: %v, %v", t, reflect.TypeOf(t)))
 	}
@@ -497,6 +670,56 @@ func (w *exportWriter) signature(sig *types.Signature) {
 	}
 }
 
+func (w *exportWriter) typeList(ts *typeparams.TypeList, pkg *types.Package) {
+	w.uint64(uint64(ts.Len()))
+	for i := 0; i < ts.Len(); i++ {
+		w.typ(ts.At(i), pkg)
+	}
+}
+
+func (w *exportWriter) tparamList(prefix string, list *typeparams.TypeParamList, pkg *types.Package) {
+	ll := uint64(list.Len())
+	w.uint64(ll)
+	for i := 0; i < list.Len(); i++ {
+		tparam := list.At(i)
+		// Set the type parameter exportName before exporting its type.
+		exportName := tparamExportName(prefix, tparam)
+		w.p.tparamNames[tparam.Obj()] = exportName
+		w.typ(list.At(i), pkg)
+	}
+}
+
+const blankMarker = "$"
+
+// tparamExportName returns the 'exported' name of a type parameter, which
+// differs from its actual object name: it is prefixed with a qualifier, and
+// blank type parameter names are disambiguated by their index in the type
+// parameter list.
+func tparamExportName(prefix string, tparam *typeparams.TypeParam) string {
+	assert(prefix != "")
+	name := tparam.Obj().Name()
+	if name == "_" {
+		name = blankMarker + strconv.Itoa(tparam.Index())
+	}
+	return prefix + "." + name
+}
+
+// tparamName returns the real name of a type parameter, after stripping its
+// qualifying prefix and reverting blank-name encoding. See tparamExportName
+// for details.
+func tparamName(exportName string) string {
+	// Remove the "path" from the type param name that makes it unique.
+	ix := strings.LastIndex(exportName, ".")
+	if ix < 0 {
+		errorf("malformed type parameter export name %s: missing prefix", exportName)
+	}
+	name := exportName[ix+1:]
+	if strings.HasPrefix(name, blankMarker) {
+		return "_"
+	}
+	return name
+}
+
 func (w *exportWriter) paramList(tup *types.Tuple) {
 	n := tup.Len()
 	w.uint64(uint64(n))
@@ -513,6 +736,9 @@ func (w *exportWriter) param(obj types.Object) {
 
 func (w *exportWriter) value(typ types.Type, v constant.Value) {
 	w.typ(typ, nil)
+	if w.p.version >= iexportVersionGo1_18 {
+		w.int64(int64(v.Kind()))
+	}
 
 	switch b := typ.Underlying().(*types.Basic); b.Info() & types.IsConstType {
 	case types.IsBoolean:

vendor/golang.org/x/tools/go/internal/gcimporter/iimport.go

@@ -18,6 +18,9 @@ import (
 	"go/types"
 	"io"
 	"sort"
+	"strings"
+
+	"golang.org/x/tools/internal/typeparams"
 )
 
 type intReader struct {
@@ -41,6 +44,19 @@ func (r *intReader) uint64() uint64 {
 	return i
 }
 
+// Keep this in sync with constants in iexport.go.
+const (
+	iexportVersionGo1_11   = 0
+	iexportVersionPosCol   = 1
+	iexportVersionGo1_18   = 2
+	iexportVersionGenerics = 2
+)
+
+type ident struct {
+	pkg  string
+	name string
+}
+
 const predeclReserved = 32
 
 type itag uint64
@@ -56,6 +72,9 @@ const (
 	signatureType
 	structType
 	interfaceType
+	typeParamType
+	instanceType
+	unionType
 )
 
 // IImportData imports a package from the serialized package data
@@ -78,15 +97,17 @@ func IImportBundle(fset *token.FileSet, imports map[string]*types.Package, data
 func iimportCommon(fset *token.FileSet, imports map[string]*types.Package, data []byte, bundle bool, path string) (pkgs []*types.Package, err error) {
 	const currentVersion = 1
 	version := int64(-1)
-	defer func() {
-		if e := recover(); e != nil {
-			if version > currentVersion {
-				err = fmt.Errorf("cannot import %q (%v), export data is newer version - update tool", path, e)
-			} else {
-				err = fmt.Errorf("cannot import %q (%v), possibly version skew - reinstall package", path, e)
+	if !debug {
+		defer func() {
+			if e := recover(); e != nil {
+				if version > currentVersion {
+					err = fmt.Errorf("cannot import %q (%v), export data is newer version - update tool", path, e)
+				} else {
+					err = fmt.Errorf("cannot import %q (%v), possibly version skew - reinstall package", path, e)
+				}
 			}
-		}
-	}()
+		}()
+	}
 
 	r := &intReader{bytes.NewReader(data), path}
 
@@ -101,9 +122,13 @@ func iimportCommon(fset *token.FileSet, imports map[string]*types.Package, data
 
 	version = int64(r.uint64())
 	switch version {
-	case currentVersion, 0:
+	case iexportVersionGo1_18, iexportVersionPosCol, iexportVersionGo1_11:
 	default:
-		errorf("unknown iexport format version %d", version)
+		if version > iexportVersionGo1_18 {
+			errorf("unstable iexport format version %d, just rebuild compiler and std library", version)
+		} else {
+			errorf("unknown iexport format version %d", version)
+		}
 	}
 
 	sLen := int64(r.uint64())
@@ -115,8 +140,8 @@ func iimportCommon(fset *token.FileSet, imports map[string]*types.Package, data
 	r.Seek(sLen+dLen, io.SeekCurrent)
 
 	p := iimporter{
-		ipath:   path,
 		version: int(version),
+		ipath:   path,
 
 		stringData:  stringData,
 		stringCache: make(map[uint64]string),
@@ -125,12 +150,16 @@ func iimportCommon(fset *token.FileSet, imports map[string]*types.Package, data
 		declData: declData,
 		pkgIndex: make(map[*types.Package]map[string]uint64),
 		typCache: make(map[uint64]types.Type),
+		// Separate map for typeparams, keyed by their package and unique
+		// name.
+		tparamIndex: make(map[ident]types.Type),
 
 		fake: fakeFileSet{
 			fset:  fset,
-			files: make(map[string]*token.File),
+			files: make(map[string]*fileInfo),
 		},
 	}
+	defer p.fake.setLines() // set lines for files in fset
 
 	for i, pt := range predeclared() {
 		p.typCache[uint64(i)] = pt
@@ -208,6 +237,15 @@ func iimportCommon(fset *token.FileSet, imports map[string]*types.Package, data
 		pkg.MarkComplete()
 	}
 
+	// SetConstraint can't be called if the constraint type is not yet complete.
+	// When type params are created in the 'P' case of (*importReader).obj(),
+	// the associated constraint type may not be complete due to recursion.
+	// Therefore, we defer calling SetConstraint there, and call it here instead
+	// after all types are complete.
+	for _, d := range p.later {
+		typeparams.SetTypeParamConstraint(d.t, d.constraint)
+	}
+
 	for _, typ := range p.interfaceList {
 		typ.Complete()
 	}
@@ -215,23 +253,51 @@ func iimportCommon(fset *token.FileSet, imports map[string]*types.Package, data
 	return pkgs, nil
 }
 
+type setConstraintArgs struct {
+	t          *typeparams.TypeParam
+	constraint types.Type
+}
+
 type iimporter struct {
-	ipath   string
 	version int
+	ipath   string
 
 	stringData  []byte
 	stringCache map[uint64]string
 	pkgCache    map[uint64]*types.Package
 
-	declData []byte
-	pkgIndex map[*types.Package]map[string]uint64
-	typCache map[uint64]types.Type
+	declData    []byte
+	pkgIndex    map[*types.Package]map[string]uint64
+	typCache    map[uint64]types.Type
+	tparamIndex map[ident]types.Type
 
 	fake          fakeFileSet
 	interfaceList []*types.Interface
+
+	// Arguments for calls to SetConstraint that are deferred due to recursive types
+	later []setConstraintArgs
+
+	indent int // for tracing support
+}
+
+func (p *iimporter) trace(format string, args ...interface{}) {
+	if !trace {
+		// Call sites should also be guarded, but having this check here allows
+		// easily enabling/disabling debug trace statements.
+		return
+	}
+	fmt.Printf(strings.Repeat("..", p.indent)+format+"\n", args...)
 }
 
 func (p *iimporter) doDecl(pkg *types.Package, name string) {
+	if debug {
+		p.trace("import decl %s", name)
+		p.indent++
+		defer func() {
+			p.indent--
+			p.trace("=> %s", name)
+		}()
+	}
 	// See if we've already imported this declaration.
 	if obj := pkg.Scope().Lookup(name); obj != nil {
 		return
@@ -273,7 +339,7 @@ func (p *iimporter) pkgAt(off uint64) *types.Package {
 }
 
 func (p *iimporter) typAt(off uint64, base *types.Named) types.Type {
-	if t, ok := p.typCache[off]; ok && (base == nil || !isInterface(t)) {
+	if t, ok := p.typCache[off]; ok && canReuse(base, t) {
 		return t
 	}
 
@@ -285,12 +351,30 @@ func (p *iimporter) typAt(off uint64, base *types.Named) types.Type {
 	r.declReader.Reset(p.declData[off-predeclReserved:])
 	t := r.doType(base)
 
-	if base == nil || !isInterface(t) {
+	if canReuse(base, t) {
 		p.typCache[off] = t
 	}
 	return t
 }
 
+// canReuse reports whether the type rhs on the RHS of the declaration for def
+// may be re-used.
+//
+// Specifically, if def is non-nil and rhs is an interface type with methods, it
+// may not be re-used because we have a convention of setting the receiver type
+// for interface methods to def.
+func canReuse(def *types.Named, rhs types.Type) bool {
+	if def == nil {
+		return true
+	}
+	iface, _ := rhs.(*types.Interface)
+	if iface == nil {
+		return true
+	}
+	// Don't use iface.Empty() here as iface may not be complete.
+	return iface.NumEmbeddeds() == 0 && iface.NumExplicitMethods() == 0
+}
+
 type importReader struct {
 	p          *iimporter
 	declReader bytes.Reader
@@ -315,17 +399,26 @@ func (r *importReader) obj(name string) {
 
 		r.declare(types.NewConst(pos, r.currPkg, name, typ, val))
 
-	case 'F':
-		sig := r.signature(nil)
-
+	case 'F', 'G':
+		var tparams []*typeparams.TypeParam
+		if tag == 'G' {
+			tparams = r.tparamList()
+		}
+		sig := r.signature(nil, nil, tparams)
 		r.declare(types.NewFunc(pos, r.currPkg, name, sig))
 
-	case 'T':
+	case 'T', 'U':
 		// Types can be recursive. We need to setup a stub
 		// declaration before recursing.
 		obj := types.NewTypeName(pos, r.currPkg, name, nil)
 		named := types.NewNamed(obj, nil, nil)
+		// Declare obj before calling r.tparamList, so the new type name is recognized
+		// if used in the constraint of one of its own typeparams (see #48280).
 		r.declare(obj)
+		if tag == 'U' {
+			tparams := r.tparamList()
+			typeparams.SetForNamed(named, tparams)
+		}
 
 		underlying := r.p.typAt(r.uint64(), named).Underlying()
 		named.SetUnderlying(underlying)
@@ -335,12 +428,59 @@ func (r *importReader) obj(name string) {
 				mpos := r.pos()
 				mname := r.ident()
 				recv := r.param()
-				msig := r.signature(recv)
+
+				// If the receiver has any targs, set those as the
+				// rparams of the method (since those are the
+				// typeparams being used in the method sig/body).
+				base := baseType(recv.Type())
+				assert(base != nil)
+				targs := typeparams.NamedTypeArgs(base)
+				var rparams []*typeparams.TypeParam
+				if targs.Len() > 0 {
+					rparams = make([]*typeparams.TypeParam, targs.Len())
+					for i := range rparams {
+						rparams[i] = targs.At(i).(*typeparams.TypeParam)
+					}
+				}
+				msig := r.signature(recv, rparams, nil)
 
 				named.AddMethod(types.NewFunc(mpos, r.currPkg, mname, msig))
 			}
 		}
 
+	case 'P':
+		// We need to "declare" a typeparam in order to have a name that
+		// can be referenced recursively (if needed) in the type param's
+		// bound.
+		if r.p.version < iexportVersionGenerics {
+			errorf("unexpected type param type")
+		}
+		name0 := tparamName(name)
+		tn := types.NewTypeName(pos, r.currPkg, name0, nil)
+		t := typeparams.NewTypeParam(tn, nil)
+
+		// To handle recursive references to the typeparam within its
+		// bound, save the partial type in tparamIndex before reading the bounds.
+		id := ident{r.currPkg.Name(), name}
+		r.p.tparamIndex[id] = t
+		var implicit bool
+		if r.p.version >= iexportVersionGo1_18 {
+			implicit = r.bool()
+		}
+		constraint := r.typ()
+		if implicit {
+			iface, _ := constraint.(*types.Interface)
+			if iface == nil {
+				errorf("non-interface constraint marked implicit")
+			}
+			typeparams.MarkImplicit(iface)
+		}
+		// The constraint type may not be complete, if we
+		// are in the middle of a type recursion involving type
+		// constraints. So, we defer SetConstraint until we have
+		// completely set up all types in ImportData.
+		r.p.later = append(r.p.later, setConstraintArgs{t: t, constraint: constraint})
+
 	case 'V':
 		typ := r.typ()
 
@@ -357,6 +497,10 @@ func (r *importReader) declare(obj types.Object) {
 
 func (r *importReader) value() (typ types.Type, val constant.Value) {
 	typ = r.typ()
+	if r.p.version >= iexportVersionGo1_18 {
+		// TODO: add support for using the kind.
+		_ = constant.Kind(r.int64())
+	}
 
 	switch b := typ.Underlying().(*types.Basic); b.Info() & types.IsConstType {
 	case types.IsBoolean:
@@ -499,7 +643,7 @@ func (r *importReader) qualifiedIdent() (*types.Package, string) {
 }
 
 func (r *importReader) pos() token.Pos {
-	if r.p.version >= 1 {
+	if r.p.version >= iexportVersionPosCol {
 		r.posv1()
 	} else {
 		r.posv0()
@@ -547,8 +691,17 @@ func isInterface(t types.Type) bool {
 func (r *importReader) pkg() *types.Package { return r.p.pkgAt(r.uint64()) }
 func (r *importReader) string() string      { return r.p.stringAt(r.uint64()) }
 
-func (r *importReader) doType(base *types.Named) types.Type {
-	switch k := r.kind(); k {
+func (r *importReader) doType(base *types.Named) (res types.Type) {
+	k := r.kind()
+	if debug {
+		r.p.trace("importing type %d (base: %s)", k, base)
+		r.p.indent++
+		defer func() {
+			r.p.indent--
+			r.p.trace("=> %s", res)
+		}()
+	}
+	switch k {
 	default:
 		errorf("unexpected kind tag in %q: %v", r.p.ipath, k)
 		return nil
@@ -571,7 +724,7 @@ func (r *importReader) doType(base *types.Named) types.Type {
 		return types.NewMap(r.typ(), r.typ())
 	case signatureType:
 		r.currPkg = r.pkg()
-		return r.signature(nil)
+		return r.signature(nil, nil, nil)
 
 	case structType:
 		r.currPkg = r.pkg()
@@ -611,13 +764,56 @@ func (r *importReader) doType(base *types.Named) types.Type {
 				recv = types.NewVar(token.NoPos, r.currPkg, "", base)
 			}
 
-			msig := r.signature(recv)
+			msig := r.signature(recv, nil, nil)
 			methods[i] = types.NewFunc(mpos, r.currPkg, mname, msig)
 		}
 
 		typ := newInterface(methods, embeddeds)
 		r.p.interfaceList = append(r.p.interfaceList, typ)
 		return typ
+
+	case typeParamType:
+		if r.p.version < iexportVersionGenerics {
+			errorf("unexpected type param type")
+		}
+		pkg, name := r.qualifiedIdent()
+		id := ident{pkg.Name(), name}
+		if t, ok := r.p.tparamIndex[id]; ok {
+			// We're already in the process of importing this typeparam.
+			return t
+		}
+		// Otherwise, import the definition of the typeparam now.
+		r.p.doDecl(pkg, name)
+		return r.p.tparamIndex[id]
+
+	case instanceType:
+		if r.p.version < iexportVersionGenerics {
+			errorf("unexpected instantiation type")
+		}
+		// pos does not matter for instances: they are positioned on the original
+		// type.
+		_ = r.pos()
+		len := r.uint64()
+		targs := make([]types.Type, len)
+		for i := range targs {
+			targs[i] = r.typ()
+		}
+		baseType := r.typ()
+		// The imported instantiated type doesn't include any methods, so
+		// we must always use the methods of the base (orig) type.
+		// TODO provide a non-nil *Environment
+		t, _ := typeparams.Instantiate(nil, baseType, targs, false)
+		return t
+
+	case unionType:
+		if r.p.version < iexportVersionGenerics {
+			errorf("unexpected instantiation type")
+		}
+		terms := make([]*typeparams.Term, r.uint64())
+		for i := range terms {
+			terms[i] = typeparams.NewTerm(r.bool(), r.typ())
+		}
+		return typeparams.NewUnion(terms)
 	}
 }
 
@@ -625,11 +821,25 @@ func (r *importReader) kind() itag {
 	return itag(r.uint64())
 }
 
-func (r *importReader) signature(recv *types.Var) *types.Signature {
+func (r *importReader) signature(recv *types.Var, rparams []*typeparams.TypeParam, tparams []*typeparams.TypeParam) *types.Signature {
 	params := r.paramList()
 	results := r.paramList()
 	variadic := params.Len() > 0 && r.bool()
-	return types.NewSignature(recv, params, results, variadic)
+	return typeparams.NewSignatureType(recv, rparams, tparams, params, results, variadic)
+}
+
+func (r *importReader) tparamList() []*typeparams.TypeParam {
+	n := r.uint64()
+	if n == 0 {
+		return nil
+	}
+	xs := make([]*typeparams.TypeParam, n)
+	for i := range xs {
+		// Note: the standard library importer is tolerant of nil types here,
+		// though would panic in SetTypeParams.
+		xs[i] = r.typ().(*typeparams.TypeParam)
+	}
+	return xs
 }
 
 func (r *importReader) paramList() *types.Tuple {
@@ -674,3 +884,13 @@ func (r *importReader) byte() byte {
 	}
 	return x
 }
+
+func baseType(typ types.Type) *types.Named {
+	// pointer receivers are never types.Named types
+	if p, _ := typ.(*types.Pointer); p != nil {
+		typ = p.Elem()
+	}
+	// receiver base types are always (possibly generic) types.Named types
+	n, _ := typ.(*types.Named)
+	return n
+}

vendor/golang.org/x/tools/go/internal/gcimporter/support_go117.go

@@ -0,0 +1,16 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build !go1.18
+// +build !go1.18
+
+package gcimporter
+
+import "go/types"
+
+const iexportVersion = iexportVersionGo1_11
+
+func additionalPredeclared() []types.Type {
+	return nil
+}

vendor/golang.org/x/tools/go/internal/gcimporter/support_go118.go

@@ -0,0 +1,23 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build go1.18
+// +build go1.18
+
+package gcimporter
+
+import "go/types"
+
+const iexportVersion = iexportVersionGenerics
+
+// additionalPredeclared returns additional predeclared types in go.1.18.
+func additionalPredeclared() []types.Type {
+	return []types.Type{
+		// comparable
+		types.Universe.Lookup("comparable").Type(),
+
+		// any
+		types.Universe.Lookup("any").Type(),
+	}
+}

vendor/golang.org/x/tools/go/loader/doc.go

@@ -0,0 +1,204 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package loader loads a complete Go program from source code, parsing
+// and type-checking the initial packages plus their transitive closure
+// of dependencies.  The ASTs and the derived facts are retained for
+// later use.
+//
+// Deprecated: This is an older API and does not have support
+// for modules. Use golang.org/x/tools/go/packages instead.
+//
+// The package defines two primary types: Config, which specifies a
+// set of initial packages to load and various other options; and
+// Program, which is the result of successfully loading the packages
+// specified by a configuration.
+//
+// The configuration can be set directly, but *Config provides various
+// convenience methods to simplify the common cases, each of which can
+// be called any number of times.  Finally, these are followed by a
+// call to Load() to actually load and type-check the program.
+//
+//      var conf loader.Config
+//
+//      // Use the command-line arguments to specify
+//      // a set of initial packages to load from source.
+//      // See FromArgsUsage for help.
+//      rest, err := conf.FromArgs(os.Args[1:], wantTests)
+//
+//      // Parse the specified files and create an ad hoc package with path "foo".
+//      // All files must have the same 'package' declaration.
+//      conf.CreateFromFilenames("foo", "foo.go", "bar.go")
+//
+//      // Create an ad hoc package with path "foo" from
+//      // the specified already-parsed files.
+//      // All ASTs must have the same 'package' declaration.
+//      conf.CreateFromFiles("foo", parsedFiles)
+//
+//      // Add "runtime" to the set of packages to be loaded.
+//      conf.Import("runtime")
+//
+//      // Adds "fmt" and "fmt_test" to the set of packages
+//      // to be loaded.  "fmt" will include *_test.go files.
+//      conf.ImportWithTests("fmt")
+//
+//      // Finally, load all the packages specified by the configuration.
+//      prog, err := conf.Load()
+//
+// See examples_test.go for examples of API usage.
+//
+//
+// CONCEPTS AND TERMINOLOGY
+//
+// The WORKSPACE is the set of packages accessible to the loader.  The
+// workspace is defined by Config.Build, a *build.Context.  The
+// default context treats subdirectories of $GOROOT and $GOPATH as
+// packages, but this behavior may be overridden.
+//
+// An AD HOC package is one specified as a set of source files on the
+// command line.  In the simplest case, it may consist of a single file
+// such as $GOROOT/src/net/http/triv.go.
+//
+// EXTERNAL TEST packages are those comprised of a set of *_test.go
+// files all with the same 'package foo_test' declaration, all in the
+// same directory.  (go/build.Package calls these files XTestFiles.)
+//
+// An IMPORTABLE package is one that can be referred to by some import
+// spec.  Every importable package is uniquely identified by its
+// PACKAGE PATH or just PATH, a string such as "fmt", "encoding/json",
+// or "cmd/vendor/golang.org/x/arch/x86/x86asm".  A package path
+// typically denotes a subdirectory of the workspace.
+//
+// An import declaration uses an IMPORT PATH to refer to a package.
+// Most import declarations use the package path as the import path.
+//
+// Due to VENDORING (https://golang.org/s/go15vendor), the
+// interpretation of an import path may depend on the directory in which
+// it appears.  To resolve an import path to a package path, go/build
+// must search the enclosing directories for a subdirectory named
+// "vendor".
+//
+// ad hoc packages and external test packages are NON-IMPORTABLE.  The
+// path of an ad hoc package is inferred from the package
+// declarations of its files and is therefore not a unique package key.
+// For example, Config.CreatePkgs may specify two initial ad hoc
+// packages, both with path "main".
+//
+// An AUGMENTED package is an importable package P plus all the
+// *_test.go files with same 'package foo' declaration as P.
+// (go/build.Package calls these files TestFiles.)
+//
+// The INITIAL packages are those specified in the configuration.  A
+// DEPENDENCY is a package loaded to satisfy an import in an initial
+// package or another dependency.
+//
+package loader
+
+// IMPLEMENTATION NOTES
+//
+// 'go test', in-package test files, and import cycles
+// ---------------------------------------------------
+//
+// An external test package may depend upon members of the augmented
+// package that are not in the unaugmented package, such as functions
+// that expose internals.  (See bufio/export_test.go for an example.)
+// So, the loader must ensure that for each external test package
+// it loads, it also augments the corresponding non-test package.
+//
+// The import graph over n unaugmented packages must be acyclic; the
+// import graph over n-1 unaugmented packages plus one augmented
+// package must also be acyclic.  ('go test' relies on this.)  But the
+// import graph over n augmented packages may contain cycles.
+//
+// First, all the (unaugmented) non-test packages and their
+// dependencies are imported in the usual way; the loader reports an
+// error if it detects an import cycle.
+//
+// Then, each package P for which testing is desired is augmented by
+// the list P' of its in-package test files, by calling
+// (*types.Checker).Files.  This arrangement ensures that P' may
+// reference definitions within P, but P may not reference definitions
+// within P'.  Furthermore, P' may import any other package, including
+// ones that depend upon P, without an import cycle error.
+//
+// Consider two packages A and B, both of which have lists of
+// in-package test files we'll call A' and B', and which have the
+// following import graph edges:
+//    B  imports A
+//    B' imports A
+//    A' imports B
+// This last edge would be expected to create an error were it not
+// for the special type-checking discipline above.
+// Cycles of size greater than two are possible.  For example:
+//   compress/bzip2/bzip2_test.go (package bzip2)  imports "io/ioutil"
+//   io/ioutil/tempfile_test.go   (package ioutil) imports "regexp"
+//   regexp/exec_test.go          (package regexp) imports "compress/bzip2"
+//
+//
+// Concurrency
+// -----------
+//
+// Let us define the import dependency graph as follows.  Each node is a
+// list of files passed to (Checker).Files at once.  Many of these lists
+// are the production code of an importable Go package, so those nodes
+// are labelled by the package's path.  The remaining nodes are
+// ad hoc packages and lists of in-package *_test.go files that augment
+// an importable package; those nodes have no label.
+//
+// The edges of the graph represent import statements appearing within a
+// file.  An edge connects a node (a list of files) to the node it
+// imports, which is importable and thus always labelled.
+//
+// Loading is controlled by this dependency graph.
+//
+// To reduce I/O latency, we start loading a package's dependencies
+// asynchronously as soon as we've parsed its files and enumerated its
+// imports (scanImports).  This performs a preorder traversal of the
+// import dependency graph.
+//
+// To exploit hardware parallelism, we type-check unrelated packages in
+// parallel, where "unrelated" means not ordered by the partial order of
+// the import dependency graph.
+//
+// We use a concurrency-safe non-blocking cache (importer.imported) to
+// record the results of type-checking, whether success or failure.  An
+// entry is created in this cache by startLoad the first time the
+// package is imported.  The first goroutine to request an entry becomes
+// responsible for completing the task and broadcasting completion to
+// subsequent requestors, which block until then.
+//
+// Type checking occurs in (parallel) postorder: we cannot type-check a
+// set of files until we have loaded and type-checked all of their
+// immediate dependencies (and thus all of their transitive
+// dependencies). If the input were guaranteed free of import cycles,
+// this would be trivial: we could simply wait for completion of the
+// dependencies and then invoke the typechecker.
+//
+// But as we saw in the 'go test' section above, some cycles in the
+// import graph over packages are actually legal, so long as the
+// cycle-forming edge originates in the in-package test files that
+// augment the package.  This explains why the nodes of the import
+// dependency graph are not packages, but lists of files: the unlabelled
+// nodes avoid the cycles.  Consider packages A and B where B imports A
+// and A's in-package tests AT import B.  The naively constructed import
+// graph over packages would contain a cycle (A+AT) --> B --> (A+AT) but
+// the graph over lists of files is AT --> B --> A, where AT is an
+// unlabelled node.
+//
+// Awaiting completion of the dependencies in a cyclic graph would
+// deadlock, so we must materialize the import dependency graph (as
+// importer.graph) and check whether each import edge forms a cycle.  If
+// x imports y, and the graph already contains a path from y to x, then
+// there is an import cycle, in which case the processing of x must not
+// wait for the completion of processing of y.
+//
+// When the type-checker makes a callback (doImport) to the loader for a
+// given import edge, there are two possible cases.  In the normal case,
+// the dependency has already been completely type-checked; doImport
+// does a cache lookup and returns it.  In the cyclic case, the entry in
+// the cache is still necessarily incomplete, indicating a cycle.  We
+// perform the cycle check again to obtain the error message, and return
+// the error.
+//
+// The result of using concurrency is about a 2.5x speedup for stdlib_test.

vendor/golang.org/x/tools/go/loader/loader.go

@@ -0,0 +1,1080 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package loader
+
+// See doc.go for package documentation and implementation notes.
+
+import (
+	"errors"
+	"fmt"
+	"go/ast"
+	"go/build"
+	"go/parser"
+	"go/token"
+	"go/types"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+	"sync"
+	"time"
+
+	"golang.org/x/tools/go/ast/astutil"
+	"golang.org/x/tools/go/internal/cgo"
+	"golang.org/x/tools/internal/typeparams"
+)
+
+var ignoreVendor build.ImportMode
+
+const trace = false // show timing info for type-checking
+
+// Config specifies the configuration for loading a whole program from
+// Go source code.
+// The zero value for Config is a ready-to-use default configuration.
+type Config struct {
+	// Fset is the file set for the parser to use when loading the
+	// program.  If nil, it may be lazily initialized by any
+	// method of Config.
+	Fset *token.FileSet
+
+	// ParserMode specifies the mode to be used by the parser when
+	// loading source packages.
+	ParserMode parser.Mode
+
+	// TypeChecker contains options relating to the type checker.
+	//
+	// The supplied IgnoreFuncBodies is not used; the effective
+	// value comes from the TypeCheckFuncBodies func below.
+	// The supplied Import function is not used either.
+	TypeChecker types.Config
+
+	// TypeCheckFuncBodies is a predicate over package paths.
+	// A package for which the predicate is false will
+	// have its package-level declarations type checked, but not
+	// its function bodies; this can be used to quickly load
+	// dependencies from source.  If nil, all func bodies are type
+	// checked.
+	TypeCheckFuncBodies func(path string) bool
+
+	// If Build is non-nil, it is used to locate source packages.
+	// Otherwise &build.Default is used.
+	//
+	// By default, cgo is invoked to preprocess Go files that
+	// import the fake package "C".  This behaviour can be
+	// disabled by setting CGO_ENABLED=0 in the environment prior
+	// to startup, or by setting Build.CgoEnabled=false.
+	Build *build.Context
+
+	// The current directory, used for resolving relative package
+	// references such as "./go/loader".  If empty, os.Getwd will be
+	// used instead.
+	Cwd string
+
+	// If DisplayPath is non-nil, it is used to transform each
+	// file name obtained from Build.Import().  This can be used
+	// to prevent a virtualized build.Config's file names from
+	// leaking into the user interface.
+	DisplayPath func(path string) string
+
+	// If AllowErrors is true, Load will return a Program even
+	// if some of the its packages contained I/O, parser or type
+	// errors; such errors are accessible via PackageInfo.Errors.  If
+	// false, Load will fail if any package had an error.
+	AllowErrors bool
+
+	// CreatePkgs specifies a list of non-importable initial
+	// packages to create.  The resulting packages will appear in
+	// the corresponding elements of the Program.Created slice.
+	CreatePkgs []PkgSpec
+
+	// ImportPkgs specifies a set of initial packages to load.
+	// The map keys are package paths.
+	//
+	// The map value indicates whether to load tests.  If true, Load
+	// will add and type-check two lists of files to the package:
+	// non-test files followed by in-package *_test.go files.  In
+	// addition, it will append the external test package (if any)
+	// to Program.Created.
+	ImportPkgs map[string]bool
+
+	// FindPackage is called during Load to create the build.Package
+	// for a given import path from a given directory.
+	// If FindPackage is nil, (*build.Context).Import is used.
+	// A client may use this hook to adapt to a proprietary build
+	// system that does not follow the "go build" layout
+	// conventions, for example.
+	//
+	// It must be safe to call concurrently from multiple goroutines.
+	FindPackage func(ctxt *build.Context, importPath, fromDir string, mode build.ImportMode) (*build.Package, error)
+
+	// AfterTypeCheck is called immediately after a list of files
+	// has been type-checked and appended to info.Files.
+	//
+	// This optional hook function is the earliest opportunity for
+	// the client to observe the output of the type checker,
+	// which may be useful to reduce analysis latency when loading
+	// a large program.
+	//
+	// The function is permitted to modify info.Info, for instance
+	// to clear data structures that are no longer needed, which can
+	// dramatically reduce peak memory consumption.
+	//
+	// The function may be called twice for the same PackageInfo:
+	// once for the files of the package and again for the
+	// in-package test files.
+	//
+	// It must be safe to call concurrently from multiple goroutines.
+	AfterTypeCheck func(info *PackageInfo, files []*ast.File)
+}
+
+// A PkgSpec specifies a non-importable package to be created by Load.
+// Files are processed first, but typically only one of Files and
+// Filenames is provided.  The path needn't be globally unique.
+//
+// For vendoring purposes, the package's directory is the one that
+// contains the first file.
+type PkgSpec struct {
+	Path      string      // package path ("" => use package declaration)
+	Files     []*ast.File // ASTs of already-parsed files
+	Filenames []string    // names of files to be parsed
+}
+
+// A Program is a Go program loaded from source as specified by a Config.
+type Program struct {
+	Fset *token.FileSet // the file set for this program
+
+	// Created[i] contains the initial package whose ASTs or
+	// filenames were supplied by Config.CreatePkgs[i], followed by
+	// the external test package, if any, of each package in
+	// Config.ImportPkgs ordered by ImportPath.
+	//
+	// NOTE: these files must not import "C".  Cgo preprocessing is
+	// only performed on imported packages, not ad hoc packages.
+	//
+	// TODO(adonovan): we need to copy and adapt the logic of
+	// goFilesPackage (from $GOROOT/src/cmd/go/build.go) and make
+	// Config.Import and Config.Create methods return the same kind
+	// of entity, essentially a build.Package.
+	// Perhaps we can even reuse that type directly.
+	Created []*PackageInfo
+
+	// Imported contains the initially imported packages,
+	// as specified by Config.ImportPkgs.
+	Imported map[string]*PackageInfo
+
+	// AllPackages contains the PackageInfo of every package
+	// encountered by Load: all initial packages and all
+	// dependencies, including incomplete ones.
+	AllPackages map[*types.Package]*PackageInfo
+
+	// importMap is the canonical mapping of package paths to
+	// packages.  It contains all Imported initial packages, but not
+	// Created ones, and all imported dependencies.
+	importMap map[string]*types.Package
+}
+
+// PackageInfo holds the ASTs and facts derived by the type-checker
+// for a single package.
+//
+// Not mutated once exposed via the API.
+//
+type PackageInfo struct {
+	Pkg                   *types.Package
+	Importable            bool        // true if 'import "Pkg.Path()"' would resolve to this
+	TransitivelyErrorFree bool        // true if Pkg and all its dependencies are free of errors
+	Files                 []*ast.File // syntax trees for the package's files
+	Errors                []error     // non-nil if the package had errors
+	types.Info                        // type-checker deductions.
+	dir                   string      // package directory
+
+	checker   *types.Checker // transient type-checker state
+	errorFunc func(error)
+}
+
+func (info *PackageInfo) String() string { return info.Pkg.Path() }
+
+func (info *PackageInfo) appendError(err error) {
+	if info.errorFunc != nil {
+		info.errorFunc(err)
+	} else {
+		fmt.Fprintln(os.Stderr, err)
+	}
+	info.Errors = append(info.Errors, err)
+}
+
+func (conf *Config) fset() *token.FileSet {
+	if conf.Fset == nil {
+		conf.Fset = token.NewFileSet()
+	}
+	return conf.Fset
+}
+
+// ParseFile is a convenience function (intended for testing) that invokes
+// the parser using the Config's FileSet, which is initialized if nil.
+//
+// src specifies the parser input as a string, []byte, or io.Reader, and
+// filename is its apparent name.  If src is nil, the contents of
+// filename are read from the file system.
+//
+func (conf *Config) ParseFile(filename string, src interface{}) (*ast.File, error) {
+	// TODO(adonovan): use conf.build() etc like parseFiles does.
+	return parser.ParseFile(conf.fset(), filename, src, conf.ParserMode)
+}
+
+// FromArgsUsage is a partial usage message that applications calling
+// FromArgs may wish to include in their -help output.
+const FromArgsUsage = `
+<args> is a list of arguments denoting a set of initial packages.
+It may take one of two forms:
+
+1. A list of *.go source files.
+
+   All of the specified files are loaded, parsed and type-checked
+   as a single package.  All the files must belong to the same directory.
+
+2. A list of import paths, each denoting a package.
+
+   The package's directory is found relative to the $GOROOT and
+   $GOPATH using similar logic to 'go build', and the *.go files in
+   that directory are loaded, parsed and type-checked as a single
+   package.
+
+   In addition, all *_test.go files in the directory are then loaded
+   and parsed.  Those files whose package declaration equals that of
+   the non-*_test.go files are included in the primary package.  Test
+   files whose package declaration ends with "_test" are type-checked
+   as another package, the 'external' test package, so that a single
+   import path may denote two packages.  (Whether this behaviour is
+   enabled is tool-specific, and may depend on additional flags.)
+
+A '--' argument terminates the list of packages.
+`
+
+// FromArgs interprets args as a set of initial packages to load from
+// source and updates the configuration.  It returns the list of
+// unconsumed arguments.
+//
+// It is intended for use in command-line interfaces that require a
+// set of initial packages to be specified; see FromArgsUsage message
+// for details.
+//
+// Only superficial errors are reported at this stage; errors dependent
+// on I/O are detected during Load.
+//
+func (conf *Config) FromArgs(args []string, xtest bool) ([]string, error) {
+	var rest []string
+	for i, arg := range args {
+		if arg == "--" {
+			rest = args[i+1:]
+			args = args[:i]
+			break // consume "--" and return the remaining args
+		}
+	}
+
+	if len(args) > 0 && strings.HasSuffix(args[0], ".go") {
+		// Assume args is a list of a *.go files
+		// denoting a single ad hoc package.
+		for _, arg := range args {
+			if !strings.HasSuffix(arg, ".go") {
+				return nil, fmt.Errorf("named files must be .go files: %s", arg)
+			}
+		}
+		conf.CreateFromFilenames("", args...)
+	} else {
+		// Assume args are directories each denoting a
+		// package and (perhaps) an external test, iff xtest.
+		for _, arg := range args {
+			if xtest {
+				conf.ImportWithTests(arg)
+			} else {
+				conf.Import(arg)
+			}
+		}
+	}
+
+	return rest, nil
+}
+
+// CreateFromFilenames is a convenience function that adds
+// a conf.CreatePkgs entry to create a package of the specified *.go
+// files.
+//
+func (conf *Config) CreateFromFilenames(path string, filenames ...string) {
+	conf.CreatePkgs = append(conf.CreatePkgs, PkgSpec{Path: path, Filenames: filenames})
+}
+
+// CreateFromFiles is a convenience function that adds a conf.CreatePkgs
+// entry to create package of the specified path and parsed files.
+//
+func (conf *Config) CreateFromFiles(path string, files ...*ast.File) {
+	conf.CreatePkgs = append(conf.CreatePkgs, PkgSpec{Path: path, Files: files})
+}
+
+// ImportWithTests is a convenience function that adds path to
+// ImportPkgs, the set of initial source packages located relative to
+// $GOPATH.  The package will be augmented by any *_test.go files in
+// its directory that contain a "package x" (not "package x_test")
+// declaration.
+//
+// In addition, if any *_test.go files contain a "package x_test"
+// declaration, an additional package comprising just those files will
+// be added to CreatePkgs.
+//
+func (conf *Config) ImportWithTests(path string) { conf.addImport(path, true) }
+
+// Import is a convenience function that adds path to ImportPkgs, the
+// set of initial packages that will be imported from source.
+//
+func (conf *Config) Import(path string) { conf.addImport(path, false) }
+
+func (conf *Config) addImport(path string, tests bool) {
+	if path == "C" {
+		return // ignore; not a real package
+	}
+	if conf.ImportPkgs == nil {
+		conf.ImportPkgs = make(map[string]bool)
+	}
+	conf.ImportPkgs[path] = conf.ImportPkgs[path] || tests
+}
+
+// PathEnclosingInterval returns the PackageInfo and ast.Node that
+// contain source interval [start, end), and all the node's ancestors
+// up to the AST root.  It searches all ast.Files of all packages in prog.
+// exact is defined as for astutil.PathEnclosingInterval.
+//
+// The zero value is returned if not found.
+//
+func (prog *Program) PathEnclosingInterval(start, end token.Pos) (pkg *PackageInfo, path []ast.Node, exact bool) {
+	for _, info := range prog.AllPackages {
+		for _, f := range info.Files {
+			if f.Pos() == token.NoPos {
+				// This can happen if the parser saw
+				// too many errors and bailed out.
+				// (Use parser.AllErrors to prevent that.)
+				continue
+			}
+			if !tokenFileContainsPos(prog.Fset.File(f.Pos()), start) {
+				continue
+			}
+			if path, exact := astutil.PathEnclosingInterval(f, start, end); path != nil {
+				return info, path, exact
+			}
+		}
+	}
+	return nil, nil, false
+}
+
+// InitialPackages returns a new slice containing the set of initial
+// packages (Created + Imported) in unspecified order.
+//
+func (prog *Program) InitialPackages() []*PackageInfo {
+	infos := make([]*PackageInfo, 0, len(prog.Created)+len(prog.Imported))
+	infos = append(infos, prog.Created...)
+	for _, info := range prog.Imported {
+		infos = append(infos, info)
+	}
+	return infos
+}
+
+// Package returns the ASTs and results of type checking for the
+// specified package.
+func (prog *Program) Package(path string) *PackageInfo {
+	if info, ok := prog.AllPackages[prog.importMap[path]]; ok {
+		return info
+	}
+	for _, info := range prog.Created {
+		if path == info.Pkg.Path() {
+			return info
+		}
+	}
+	return nil
+}
+
+// ---------- Implementation ----------
+
+// importer holds the working state of the algorithm.
+type importer struct {
+	conf  *Config   // the client configuration
+	start time.Time // for logging
+
+	progMu sync.Mutex // guards prog
+	prog   *Program   // the resulting program
+
+	// findpkg is a memoization of FindPackage.
+	findpkgMu sync.Mutex // guards findpkg
+	findpkg   map[findpkgKey]*findpkgValue
+
+	importedMu sync.Mutex             // guards imported
+	imported   map[string]*importInfo // all imported packages (incl. failures) by import path
+
+	// import dependency graph: graph[x][y] => x imports y
+	//
+	// Since non-importable packages cannot be cyclic, we ignore
+	// their imports, thus we only need the subgraph over importable
+	// packages.  Nodes are identified by their import paths.
+	graphMu sync.Mutex
+	graph   map[string]map[string]bool
+}
+
+type findpkgKey struct {
+	importPath string
+	fromDir    string
+	mode       build.ImportMode
+}
+
+type findpkgValue struct {
+	ready chan struct{} // closed to broadcast readiness
+	bp    *build.Package
+	err   error
+}
+
+// importInfo tracks the success or failure of a single import.
+//
+// Upon completion, exactly one of info and err is non-nil:
+// info on successful creation of a package, err otherwise.
+// A successful package may still contain type errors.
+//
+type importInfo struct {
+	path     string        // import path
+	info     *PackageInfo  // results of typechecking (including errors)
+	complete chan struct{} // closed to broadcast that info is set.
+}
+
+// awaitCompletion blocks until ii is complete,
+// i.e. the info field is safe to inspect.
+func (ii *importInfo) awaitCompletion() {
+	<-ii.complete // wait for close
+}
+
+// Complete marks ii as complete.
+// Its info and err fields will not be subsequently updated.
+func (ii *importInfo) Complete(info *PackageInfo) {
+	if info == nil {
+		panic("info == nil")
+	}
+	ii.info = info
+	close(ii.complete)
+}
+
+type importError struct {
+	path string // import path
+	err  error  // reason for failure to create a package
+}
+
+// Load creates the initial packages specified by conf.{Create,Import}Pkgs,
+// loading their dependencies packages as needed.
+//
+// On success, Load returns a Program containing a PackageInfo for
+// each package.  On failure, it returns an error.
+//
+// If AllowErrors is true, Load will return a Program even if some
+// packages contained I/O, parser or type errors, or if dependencies
+// were missing.  (Such errors are accessible via PackageInfo.Errors.  If
+// false, Load will fail if any package had an error.
+//
+// It is an error if no packages were loaded.
+//
+func (conf *Config) Load() (*Program, error) {
+	// Create a simple default error handler for parse/type errors.
+	if conf.TypeChecker.Error == nil {
+		conf.TypeChecker.Error = func(e error) { fmt.Fprintln(os.Stderr, e) }
+	}
+
+	// Set default working directory for relative package references.
+	if conf.Cwd == "" {
+		var err error
+		conf.Cwd, err = os.Getwd()
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	// Install default FindPackage hook using go/build logic.
+	if conf.FindPackage == nil {
+		conf.FindPackage = (*build.Context).Import
+	}
+
+	prog := &Program{
+		Fset:        conf.fset(),
+		Imported:    make(map[string]*PackageInfo),
+		importMap:   make(map[string]*types.Package),
+		AllPackages: make(map[*types.Package]*PackageInfo),
+	}
+
+	imp := importer{
+		conf:     conf,
+		prog:     prog,
+		findpkg:  make(map[findpkgKey]*findpkgValue),
+		imported: make(map[string]*importInfo),
+		start:    time.Now(),
+		graph:    make(map[string]map[string]bool),
+	}
+
+	// -- loading proper (concurrent phase) --------------------------------
+
+	var errpkgs []string // packages that contained errors
+
+	// Load the initially imported packages and their dependencies,
+	// in parallel.
+	// No vendor check on packages imported from the command line.
+	infos, importErrors := imp.importAll("", conf.Cwd, conf.ImportPkgs, ignoreVendor)
+	for _, ie := range importErrors {
+		conf.TypeChecker.Error(ie.err) // failed to create package
+		errpkgs = append(errpkgs, ie.path)
+	}
+	for _, info := range infos {
+		prog.Imported[info.Pkg.Path()] = info
+	}
+
+	// Augment the designated initial packages by their tests.
+	// Dependencies are loaded in parallel.
+	var xtestPkgs []*build.Package
+	for importPath, augment := range conf.ImportPkgs {
+		if !augment {
+			continue
+		}
+
+		// No vendor check on packages imported from command line.
+		bp, err := imp.findPackage(importPath, conf.Cwd, ignoreVendor)
+		if err != nil {
+			// Package not found, or can't even parse package declaration.
+			// Already reported by previous loop; ignore it.
+			continue
+		}
+
+		// Needs external test package?
+		if len(bp.XTestGoFiles) > 0 {
+			xtestPkgs = append(xtestPkgs, bp)
+		}
+
+		// Consult the cache using the canonical package path.
+		path := bp.ImportPath
+		imp.importedMu.Lock() // (unnecessary, we're sequential here)
+		ii, ok := imp.imported[path]
+		// Paranoid checks added due to issue #11012.
+		if !ok {
+			// Unreachable.
+			// The previous loop called importAll and thus
+			// startLoad for each path in ImportPkgs, which
+			// populates imp.imported[path] with a non-zero value.
+			panic(fmt.Sprintf("imported[%q] not found", path))
+		}
+		if ii == nil {
+			// Unreachable.
+			// The ii values in this loop are the same as in
+			// the previous loop, which enforced the invariant
+			// that at least one of ii.err and ii.info is non-nil.
+			panic(fmt.Sprintf("imported[%q] == nil", path))
+		}
+		if ii.info == nil {
+			// Unreachable.
+			// awaitCompletion has the postcondition
+			// ii.info != nil.
+			panic(fmt.Sprintf("imported[%q].info = nil", path))
+		}
+		info := ii.info
+		imp.importedMu.Unlock()
+
+		// Parse the in-package test files.
+		files, errs := imp.conf.parsePackageFiles(bp, 't')
+		for _, err := range errs {
+			info.appendError(err)
+		}
+
+		// The test files augmenting package P cannot be imported,
+		// but may import packages that import P,
+		// so we must disable the cycle check.
+		imp.addFiles(info, files, false)
+	}
+
+	createPkg := func(path, dir string, files []*ast.File, errs []error) {
+		info := imp.newPackageInfo(path, dir)
+		for _, err := range errs {
+			info.appendError(err)
+		}
+
+		// Ad hoc packages are non-importable,
+		// so no cycle check is needed.
+		// addFiles loads dependencies in parallel.
+		imp.addFiles(info, files, false)
+		prog.Created = append(prog.Created, info)
+	}
+
+	// Create packages specified by conf.CreatePkgs.
+	for _, cp := range conf.CreatePkgs {
+		files, errs := parseFiles(conf.fset(), conf.build(), nil, conf.Cwd, cp.Filenames, conf.ParserMode)
+		files = append(files, cp.Files...)
+
+		path := cp.Path
+		if path == "" {
+			if len(files) > 0 {
+				path = files[0].Name.Name
+			} else {
+				path = "(unnamed)"
+			}
+		}
+
+		dir := conf.Cwd
+		if len(files) > 0 && files[0].Pos().IsValid() {
+			dir = filepath.Dir(conf.fset().File(files[0].Pos()).Name())
+		}
+		createPkg(path, dir, files, errs)
+	}
+
+	// Create external test packages.
+	sort.Sort(byImportPath(xtestPkgs))
+	for _, bp := range xtestPkgs {
+		files, errs := imp.conf.parsePackageFiles(bp, 'x')
+		createPkg(bp.ImportPath+"_test", bp.Dir, files, errs)
+	}
+
+	// -- finishing up (sequential) ----------------------------------------
+
+	if len(prog.Imported)+len(prog.Created) == 0 {
+		return nil, errors.New("no initial packages were loaded")
+	}
+
+	// Create infos for indirectly imported packages.
+	// e.g. incomplete packages without syntax, loaded from export data.
+	for _, obj := range prog.importMap {
+		info := prog.AllPackages[obj]
+		if info == nil {
+			prog.AllPackages[obj] = &PackageInfo{Pkg: obj, Importable: true}
+		} else {
+			// finished
+			info.checker = nil
+			info.errorFunc = nil
+		}
+	}
+
+	if !conf.AllowErrors {
+		// Report errors in indirectly imported packages.
+		for _, info := range prog.AllPackages {
+			if len(info.Errors) > 0 {
+				errpkgs = append(errpkgs, info.Pkg.Path())
+			}
+		}
+		if errpkgs != nil {
+			var more string
+			if len(errpkgs) > 3 {
+				more = fmt.Sprintf(" and %d more", len(errpkgs)-3)
+				errpkgs = errpkgs[:3]
+			}
+			return nil, fmt.Errorf("couldn't load packages due to errors: %s%s",
+				strings.Join(errpkgs, ", "), more)
+		}
+	}
+
+	markErrorFreePackages(prog.AllPackages)
+
+	return prog, nil
+}
+
+type byImportPath []*build.Package
+
+func (b byImportPath) Len() int           { return len(b) }
+func (b byImportPath) Less(i, j int) bool { return b[i].ImportPath < b[j].ImportPath }
+func (b byImportPath) Swap(i, j int)      { b[i], b[j] = b[j], b[i] }
+
+// markErrorFreePackages sets the TransitivelyErrorFree flag on all
+// applicable packages.
+func markErrorFreePackages(allPackages map[*types.Package]*PackageInfo) {
+	// Build the transpose of the import graph.
+	importedBy := make(map[*types.Package]map[*types.Package]bool)
+	for P := range allPackages {
+		for _, Q := range P.Imports() {
+			clients, ok := importedBy[Q]
+			if !ok {
+				clients = make(map[*types.Package]bool)
+				importedBy[Q] = clients
+			}
+			clients[P] = true
+		}
+	}
+
+	// Find all packages reachable from some error package.
+	reachable := make(map[*types.Package]bool)
+	var visit func(*types.Package)
+	visit = func(p *types.Package) {
+		if !reachable[p] {
+			reachable[p] = true
+			for q := range importedBy[p] {
+				visit(q)
+			}
+		}
+	}
+	for _, info := range allPackages {
+		if len(info.Errors) > 0 {
+			visit(info.Pkg)
+		}
+	}
+
+	// Mark the others as "transitively error-free".
+	for _, info := range allPackages {
+		if !reachable[info.Pkg] {
+			info.TransitivelyErrorFree = true
+		}
+	}
+}
+
+// build returns the effective build context.
+func (conf *Config) build() *build.Context {
+	if conf.Build != nil {
+		return conf.Build
+	}
+	return &build.Default
+}
+
+// parsePackageFiles enumerates the files belonging to package path,
+// then loads, parses and returns them, plus a list of I/O or parse
+// errors that were encountered.
+//
+// 'which' indicates which files to include:
+//    'g': include non-test *.go source files (GoFiles + processed CgoFiles)
+//    't': include in-package *_test.go source files (TestGoFiles)
+//    'x': include external *_test.go source files. (XTestGoFiles)
+//
+func (conf *Config) parsePackageFiles(bp *build.Package, which rune) ([]*ast.File, []error) {
+	if bp.ImportPath == "unsafe" {
+		return nil, nil
+	}
+	var filenames []string
+	switch which {
+	case 'g':
+		filenames = bp.GoFiles
+	case 't':
+		filenames = bp.TestGoFiles
+	case 'x':
+		filenames = bp.XTestGoFiles
+	default:
+		panic(which)
+	}
+
+	files, errs := parseFiles(conf.fset(), conf.build(), conf.DisplayPath, bp.Dir, filenames, conf.ParserMode)
+
+	// Preprocess CgoFiles and parse the outputs (sequentially).
+	if which == 'g' && bp.CgoFiles != nil {
+		cgofiles, err := cgo.ProcessFiles(bp, conf.fset(), conf.DisplayPath, conf.ParserMode)
+		if err != nil {
+			errs = append(errs, err)
+		} else {
+			files = append(files, cgofiles...)
+		}
+	}
+
+	return files, errs
+}
+
+// doImport imports the package denoted by path.
+// It implements the types.Importer signature.
+//
+// It returns an error if a package could not be created
+// (e.g. go/build or parse error), but type errors are reported via
+// the types.Config.Error callback (the first of which is also saved
+// in the package's PackageInfo).
+//
+// Idempotent.
+//
+func (imp *importer) doImport(from *PackageInfo, to string) (*types.Package, error) {
+	if to == "C" {
+		// This should be unreachable, but ad hoc packages are
+		// not currently subject to cgo preprocessing.
+		// See https://golang.org/issue/11627.
+		return nil, fmt.Errorf(`the loader doesn't cgo-process ad hoc packages like %q; see Go issue 11627`,
+			from.Pkg.Path())
+	}
+
+	bp, err := imp.findPackage(to, from.dir, 0)
+	if err != nil {
+		return nil, err
+	}
+
+	// The standard unsafe package is handled specially,
+	// and has no PackageInfo.
+	if bp.ImportPath == "unsafe" {
+		return types.Unsafe, nil
+	}
+
+	// Look for the package in the cache using its canonical path.
+	path := bp.ImportPath
+	imp.importedMu.Lock()
+	ii := imp.imported[path]
+	imp.importedMu.Unlock()
+	if ii == nil {
+		panic("internal error: unexpected import: " + path)
+	}
+	if ii.info != nil {
+		return ii.info.Pkg, nil
+	}
+
+	// Import of incomplete package: this indicates a cycle.
+	fromPath := from.Pkg.Path()
+	if cycle := imp.findPath(path, fromPath); cycle != nil {
+		// Normalize cycle: start from alphabetically largest node.
+		pos, start := -1, ""
+		for i, s := range cycle {
+			if pos < 0 || s > start {
+				pos, start = i, s
+			}
+		}
+		cycle = append(cycle, cycle[:pos]...)[pos:] // rotate cycle to start from largest
+		cycle = append(cycle, cycle[0])             // add start node to end to show cycliness
+		return nil, fmt.Errorf("import cycle: %s", strings.Join(cycle, " -> "))
+	}
+
+	panic("internal error: import of incomplete (yet acyclic) package: " + fromPath)
+}
+
+// findPackage locates the package denoted by the importPath in the
+// specified directory.
+func (imp *importer) findPackage(importPath, fromDir string, mode build.ImportMode) (*build.Package, error) {
+	// We use a non-blocking duplicate-suppressing cache (gopl.io §9.7)
+	// to avoid holding the lock around FindPackage.
+	key := findpkgKey{importPath, fromDir, mode}
+	imp.findpkgMu.Lock()
+	v, ok := imp.findpkg[key]
+	if ok {
+		// cache hit
+		imp.findpkgMu.Unlock()
+
+		<-v.ready // wait for entry to become ready
+	} else {
+		// Cache miss: this goroutine becomes responsible for
+		// populating the map entry and broadcasting its readiness.
+		v = &findpkgValue{ready: make(chan struct{})}
+		imp.findpkg[key] = v
+		imp.findpkgMu.Unlock()
+
+		ioLimit <- true
+		v.bp, v.err = imp.conf.FindPackage(imp.conf.build(), importPath, fromDir, mode)
+		<-ioLimit
+
+		if _, ok := v.err.(*build.NoGoError); ok {
+			v.err = nil // empty directory is not an error
+		}
+
+		close(v.ready) // broadcast ready condition
+	}
+	return v.bp, v.err
+}
+
+// importAll loads, parses, and type-checks the specified packages in
+// parallel and returns their completed importInfos in unspecified order.
+//
+// fromPath is the package path of the importing package, if it is
+// importable, "" otherwise.  It is used for cycle detection.
+//
+// fromDir is the directory containing the import declaration that
+// caused these imports.
+//
+func (imp *importer) importAll(fromPath, fromDir string, imports map[string]bool, mode build.ImportMode) (infos []*PackageInfo, errors []importError) {
+	if fromPath != "" {
+		// We're loading a set of imports.
+		//
+		// We must record graph edges from the importing package
+		// to its dependencies, and check for cycles.
+		imp.graphMu.Lock()
+		deps, ok := imp.graph[fromPath]
+		if !ok {
+			deps = make(map[string]bool)
+			imp.graph[fromPath] = deps
+		}
+		for importPath := range imports {
+			deps[importPath] = true
+		}
+		imp.graphMu.Unlock()
+	}
+
+	var pending []*importInfo
+	for importPath := range imports {
+		if fromPath != "" {
+			if cycle := imp.findPath(importPath, fromPath); cycle != nil {
+				// Cycle-forming import: we must not check it
+				// since it would deadlock.
+				if trace {
+					fmt.Fprintf(os.Stderr, "import cycle: %q\n", cycle)
+				}
+				continue
+			}
+		}
+		bp, err := imp.findPackage(importPath, fromDir, mode)
+		if err != nil {
+			errors = append(errors, importError{
+				path: importPath,
+				err:  err,
+			})
+			continue
+		}
+		pending = append(pending, imp.startLoad(bp))
+	}
+
+	for _, ii := range pending {
+		ii.awaitCompletion()
+		infos = append(infos, ii.info)
+	}
+
+	return infos, errors
+}
+
+// findPath returns an arbitrary path from 'from' to 'to' in the import
+// graph, or nil if there was none.
+func (imp *importer) findPath(from, to string) []string {
+	imp.graphMu.Lock()
+	defer imp.graphMu.Unlock()
+
+	seen := make(map[string]bool)
+	var search func(stack []string, importPath string) []string
+	search = func(stack []string, importPath string) []string {
+		if !seen[importPath] {
+			seen[importPath] = true
+			stack = append(stack, importPath)
+			if importPath == to {
+				return stack
+			}
+			for x := range imp.graph[importPath] {
+				if p := search(stack, x); p != nil {
+					return p
+				}
+			}
+		}
+		return nil
+	}
+	return search(make([]string, 0, 20), from)
+}
+
+// startLoad initiates the loading, parsing and type-checking of the
+// specified package and its dependencies, if it has not already begun.
+//
+// It returns an importInfo, not necessarily in a completed state.  The
+// caller must call awaitCompletion() before accessing its info field.
+//
+// startLoad is concurrency-safe and idempotent.
+//
+func (imp *importer) startLoad(bp *build.Package) *importInfo {
+	path := bp.ImportPath
+	imp.importedMu.Lock()
+	ii, ok := imp.imported[path]
+	if !ok {
+		ii = &importInfo{path: path, complete: make(chan struct{})}
+		imp.imported[path] = ii
+		go func() {
+			info := imp.load(bp)
+			ii.Complete(info)
+		}()
+	}
+	imp.importedMu.Unlock()
+
+	return ii
+}
+
+// load implements package loading by parsing Go source files
+// located by go/build.
+func (imp *importer) load(bp *build.Package) *PackageInfo {
+	info := imp.newPackageInfo(bp.ImportPath, bp.Dir)
+	info.Importable = true
+	files, errs := imp.conf.parsePackageFiles(bp, 'g')
+	for _, err := range errs {
+		info.appendError(err)
+	}
+
+	imp.addFiles(info, files, true)
+
+	imp.progMu.Lock()
+	imp.prog.importMap[bp.ImportPath] = info.Pkg
+	imp.progMu.Unlock()
+
+	return info
+}
+
+// addFiles adds and type-checks the specified files to info, loading
+// their dependencies if needed.  The order of files determines the
+// package initialization order.  It may be called multiple times on the
+// same package.  Errors are appended to the info.Errors field.
+//
+// cycleCheck determines whether the imports within files create
+// dependency edges that should be checked for potential cycles.
+//
+func (imp *importer) addFiles(info *PackageInfo, files []*ast.File, cycleCheck bool) {
+	// Ensure the dependencies are loaded, in parallel.
+	var fromPath string
+	if cycleCheck {
+		fromPath = info.Pkg.Path()
+	}
+	// TODO(adonovan): opt: make the caller do scanImports.
+	// Callers with a build.Package can skip it.
+	imp.importAll(fromPath, info.dir, scanImports(files), 0)
+
+	if trace {
+		fmt.Fprintf(os.Stderr, "%s: start %q (%d)\n",
+			time.Since(imp.start), info.Pkg.Path(), len(files))
+	}
+
+	// Don't call checker.Files on Unsafe, even with zero files,
+	// because it would mutate the package, which is a global.
+	if info.Pkg == types.Unsafe {
+		if len(files) > 0 {
+			panic(`"unsafe" package contains unexpected files`)
+		}
+	} else {
+		// Ignore the returned (first) error since we
+		// already collect them all in the PackageInfo.
+		info.checker.Files(files)
+		info.Files = append(info.Files, files...)
+	}
+
+	if imp.conf.AfterTypeCheck != nil {
+		imp.conf.AfterTypeCheck(info, files)
+	}
+
+	if trace {
+		fmt.Fprintf(os.Stderr, "%s: stop %q\n",
+			time.Since(imp.start), info.Pkg.Path())
+	}
+}
+
+func (imp *importer) newPackageInfo(path, dir string) *PackageInfo {
+	var pkg *types.Package
+	if path == "unsafe" {
+		pkg = types.Unsafe
+	} else {
+		pkg = types.NewPackage(path, "")
+	}
+	info := &PackageInfo{
+		Pkg: pkg,
+		Info: types.Info{
+			Types:      make(map[ast.Expr]types.TypeAndValue),
+			Defs:       make(map[*ast.Ident]types.Object),
+			Uses:       make(map[*ast.Ident]types.Object),
+			Implicits:  make(map[ast.Node]types.Object),
+			Scopes:     make(map[ast.Node]*types.Scope),
+			Selections: make(map[*ast.SelectorExpr]*types.Selection),
+		},
+		errorFunc: imp.conf.TypeChecker.Error,
+		dir:       dir,
+	}
+	typeparams.InitInstanceInfo(&info.Info)
+
+	// Copy the types.Config so we can vary it across PackageInfos.
+	tc := imp.conf.TypeChecker
+	tc.IgnoreFuncBodies = false
+	if f := imp.conf.TypeCheckFuncBodies; f != nil {
+		tc.IgnoreFuncBodies = !f(path)
+	}
+	tc.Importer = closure{imp, info}
+	tc.Error = info.appendError // appendError wraps the user's Error function
+
+	info.checker = types.NewChecker(&tc, imp.conf.fset(), pkg, &info.Info)
+	imp.progMu.Lock()
+	imp.prog.AllPackages[pkg] = info
+	imp.progMu.Unlock()
+	return info
+}
+
+type closure struct {
+	imp  *importer
+	info *PackageInfo
+}
+
+func (c closure) Import(to string) (*types.Package, error) { return c.imp.doImport(c.info, to) }

vendor/golang.org/x/tools/go/loader/util.go

@@ -0,0 +1,124 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package loader
+
+import (
+	"go/ast"
+	"go/build"
+	"go/parser"
+	"go/token"
+	"io"
+	"os"
+	"strconv"
+	"sync"
+
+	"golang.org/x/tools/go/buildutil"
+)
+
+// We use a counting semaphore to limit
+// the number of parallel I/O calls per process.
+var ioLimit = make(chan bool, 10)
+
+// parseFiles parses the Go source files within directory dir and
+// returns the ASTs of the ones that could be at least partially parsed,
+// along with a list of I/O and parse errors encountered.
+//
+// I/O is done via ctxt, which may specify a virtual file system.
+// displayPath is used to transform the filenames attached to the ASTs.
+//
+func parseFiles(fset *token.FileSet, ctxt *build.Context, displayPath func(string) string, dir string, files []string, mode parser.Mode) ([]*ast.File, []error) {
+	if displayPath == nil {
+		displayPath = func(path string) string { return path }
+	}
+	var wg sync.WaitGroup
+	n := len(files)
+	parsed := make([]*ast.File, n)
+	errors := make([]error, n)
+	for i, file := range files {
+		if !buildutil.IsAbsPath(ctxt, file) {
+			file = buildutil.JoinPath(ctxt, dir, file)
+		}
+		wg.Add(1)
+		go func(i int, file string) {
+			ioLimit <- true // wait
+			defer func() {
+				wg.Done()
+				<-ioLimit // signal
+			}()
+			var rd io.ReadCloser
+			var err error
+			if ctxt.OpenFile != nil {
+				rd, err = ctxt.OpenFile(file)
+			} else {
+				rd, err = os.Open(file)
+			}
+			if err != nil {
+				errors[i] = err // open failed
+				return
+			}
+
+			// ParseFile may return both an AST and an error.
+			parsed[i], errors[i] = parser.ParseFile(fset, displayPath(file), rd, mode)
+			rd.Close()
+		}(i, file)
+	}
+	wg.Wait()
+
+	// Eliminate nils, preserving order.
+	var o int
+	for _, f := range parsed {
+		if f != nil {
+			parsed[o] = f
+			o++
+		}
+	}
+	parsed = parsed[:o]
+
+	o = 0
+	for _, err := range errors {
+		if err != nil {
+			errors[o] = err
+			o++
+		}
+	}
+	errors = errors[:o]
+
+	return parsed, errors
+}
+
+// scanImports returns the set of all import paths from all
+// import specs in the specified files.
+func scanImports(files []*ast.File) map[string]bool {
+	imports := make(map[string]bool)
+	for _, f := range files {
+		for _, decl := range f.Decls {
+			if decl, ok := decl.(*ast.GenDecl); ok && decl.Tok == token.IMPORT {
+				for _, spec := range decl.Specs {
+					spec := spec.(*ast.ImportSpec)
+
+					// NB: do not assume the program is well-formed!
+					path, err := strconv.Unquote(spec.Path.Value)
+					if err != nil {
+						continue // quietly ignore the error
+					}
+					if path == "C" {
+						continue // skip pseudopackage
+					}
+					imports[path] = true
+				}
+			}
+		}
+	}
+	return imports
+}
+
+// ---------- Internal helpers ----------
+
+// TODO(adonovan): make this a method: func (*token.File) Contains(token.Pos)
+func tokenFileContainsPos(f *token.File, pos token.Pos) bool {
+	p := int(pos)
+	base := f.Base()
+	return base <= p && p < base+f.Size()
+}

vendor/golang.org/x/tools/go/packages/packages.go

@@ -26,6 +26,7 @@ import (
 	"golang.org/x/tools/go/gcexportdata"
 	"golang.org/x/tools/internal/gocommand"
 	"golang.org/x/tools/internal/packagesinternal"
+	"golang.org/x/tools/internal/typeparams"
 	"golang.org/x/tools/internal/typesinternal"
 )
 
@@ -327,6 +328,9 @@ type Package struct {
 	// The NeedSyntax LoadMode bit populates this field for packages matching the patterns.
 	// If NeedDeps and NeedImports are also set, this field will also be populated
 	// for dependencies.
+	//
+	// Syntax is kept in the same order as CompiledGoFiles, with the caveat that nils are
+	// removed.  If parsing returned nil, Syntax may be shorter than CompiledGoFiles.
 	Syntax []*ast.File
 
 	// TypesInfo provides type information about the package's syntax trees.
@@ -910,6 +914,7 @@ func (ld *loader) loadPackage(lpkg *loaderPackage) {
 		Scopes:     make(map[ast.Node]*types.Scope),
 		Selections: make(map[*ast.SelectorExpr]*types.Selection),
 	}
+	typeparams.InitInstanceInfo(lpkg.TypesInfo)
 	lpkg.TypesSizes = ld.sizes
 
 	importer := importerFunc(func(path string) (*types.Package, error) {

vendor/golang.org/x/tools/go/types/objectpath/objectpath.go

@@ -0,0 +1,617 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package objectpath defines a naming scheme for types.Objects
+// (that is, named entities in Go programs) relative to their enclosing
+// package.
+//
+// Type-checker objects are canonical, so they are usually identified by
+// their address in memory (a pointer), but a pointer has meaning only
+// within one address space. By contrast, objectpath names allow the
+// identity of an object to be sent from one program to another,
+// establishing a correspondence between types.Object variables that are
+// distinct but logically equivalent.
+//
+// A single object may have multiple paths. In this example,
+//     type A struct{ X int }
+//     type B A
+// the field X has two paths due to its membership of both A and B.
+// The For(obj) function always returns one of these paths, arbitrarily
+// but consistently.
+package objectpath
+
+import (
+	"fmt"
+	"go/types"
+	"sort"
+	"strconv"
+	"strings"
+
+	"golang.org/x/tools/internal/typeparams"
+)
+
+// A Path is an opaque name that identifies a types.Object
+// relative to its package. Conceptually, the name consists of a
+// sequence of destructuring operations applied to the package scope
+// to obtain the original object.
+// The name does not include the package itself.
+type Path string
+
+// Encoding
+//
+// An object path is a textual and (with training) human-readable encoding
+// of a sequence of destructuring operators, starting from a types.Package.
+// The sequences represent a path through the package/object/type graph.
+// We classify these operators by their type:
+//
+//   PO package->object	Package.Scope.Lookup
+//   OT  object->type 	Object.Type
+//   TT    type->type 	Type.{Elem,Key,Params,Results,Underlying} [EKPRU]
+//   TO   type->object	Type.{At,Field,Method,Obj} [AFMO]
+//
+// All valid paths start with a package and end at an object
+// and thus may be defined by the regular language:
+//
+//   objectpath = PO (OT TT* TO)*
+//
+// The concrete encoding follows directly:
+// - The only PO operator is Package.Scope.Lookup, which requires an identifier.
+// - The only OT operator is Object.Type,
+//   which we encode as '.' because dot cannot appear in an identifier.
+// - The TT operators are encoded as [EKPRUTC];
+//   one of these (TypeParam) requires an integer operand,
+//   which is encoded as a string of decimal digits.
+// - The TO operators are encoded as [AFMO];
+//   three of these (At,Field,Method) require an integer operand,
+//   which is encoded as a string of decimal digits.
+//   These indices are stable across different representations
+//   of the same package, even source and export data.
+//   The indices used are implementation specific and may not correspond to
+//   the argument to the go/types function.
+//
+// In the example below,
+//
+//	package p
+//
+//	type T interface {
+//		f() (a string, b struct{ X int })
+//	}
+//
+// field X has the path "T.UM0.RA1.F0",
+// representing the following sequence of operations:
+//
+//    p.Lookup("T")					T
+//    .Type().Underlying().Method(0).			f
+//    .Type().Results().At(1)				b
+//    .Type().Field(0)					X
+//
+// The encoding is not maximally compact---every R or P is
+// followed by an A, for example---but this simplifies the
+// encoder and decoder.
+//
+const (
+	// object->type operators
+	opType = '.' // .Type()		  (Object)
+
+	// type->type operators
+	opElem       = 'E' // .Elem()		        (Pointer, Slice, Array, Chan, Map)
+	opKey        = 'K' // .Key()		        (Map)
+	opParams     = 'P' // .Params()		      (Signature)
+	opResults    = 'R' // .Results()	      (Signature)
+	opUnderlying = 'U' // .Underlying()	    (Named)
+	opTypeParam  = 'T' // .TypeParams.At(i) (Named, Signature)
+	opConstraint = 'C' // .Constraint()     (TypeParam)
+
+	// type->object operators
+	opAt     = 'A' // .At(i)		 (Tuple)
+	opField  = 'F' // .Field(i)	 (Struct)
+	opMethod = 'M' // .Method(i) (Named or Interface; not Struct: "promoted" names are ignored)
+	opObj    = 'O' // .Obj()		 (Named, TypeParam)
+)
+
+// The For function returns the path to an object relative to its package,
+// or an error if the object is not accessible from the package's Scope.
+//
+// The For function guarantees to return a path only for the following objects:
+// - package-level types
+// - exported package-level non-types
+// - methods
+// - parameter and result variables
+// - struct fields
+// These objects are sufficient to define the API of their package.
+// The objects described by a package's export data are drawn from this set.
+//
+// For does not return a path for predeclared names, imported package
+// names, local names, and unexported package-level names (except
+// types).
+//
+// Example: given this definition,
+//
+//	package p
+//
+//	type T interface {
+//		f() (a string, b struct{ X int })
+//	}
+//
+// For(X) would return a path that denotes the following sequence of operations:
+//
+//    p.Scope().Lookup("T")				(TypeName T)
+//    .Type().Underlying().Method(0).			(method Func f)
+//    .Type().Results().At(1)				(field Var b)
+//    .Type().Field(0)					(field Var X)
+//
+// where p is the package (*types.Package) to which X belongs.
+func For(obj types.Object) (Path, error) {
+	pkg := obj.Pkg()
+
+	// This table lists the cases of interest.
+	//
+	// Object				Action
+	// ------                               ------
+	// nil					reject
+	// builtin				reject
+	// pkgname				reject
+	// label				reject
+	// var
+	//    package-level			accept
+	//    func param/result			accept
+	//    local				reject
+	//    struct field			accept
+	// const
+	//    package-level			accept
+	//    local				reject
+	// func
+	//    package-level			accept
+	//    init functions			reject
+	//    concrete method			accept
+	//    interface method			accept
+	// type
+	//    package-level			accept
+	//    local				reject
+	//
+	// The only accessible package-level objects are members of pkg itself.
+	//
+	// The cases are handled in four steps:
+	//
+	// 1. reject nil and builtin
+	// 2. accept package-level objects
+	// 3. reject obviously invalid objects
+	// 4. search the API for the path to the param/result/field/method.
+
+	// 1. reference to nil or builtin?
+	if pkg == nil {
+		return "", fmt.Errorf("predeclared %s has no path", obj)
+	}
+	scope := pkg.Scope()
+
+	// 2. package-level object?
+	if scope.Lookup(obj.Name()) == obj {
+		// Only exported objects (and non-exported types) have a path.
+		// Non-exported types may be referenced by other objects.
+		if _, ok := obj.(*types.TypeName); !ok && !obj.Exported() {
+			return "", fmt.Errorf("no path for non-exported %v", obj)
+		}
+		return Path(obj.Name()), nil
+	}
+
+	// 3. Not a package-level object.
+	//    Reject obviously non-viable cases.
+	switch obj := obj.(type) {
+	case *types.TypeName:
+		if _, ok := obj.Type().(*typeparams.TypeParam); !ok {
+			// With the exception of type parameters, only package-level type names
+			// have a path.
+			return "", fmt.Errorf("no path for %v", obj)
+		}
+	case *types.Const, // Only package-level constants have a path.
+		*types.Label,   // Labels are function-local.
+		*types.PkgName: // PkgNames are file-local.
+		return "", fmt.Errorf("no path for %v", obj)
+
+	case *types.Var:
+		// Could be:
+		// - a field (obj.IsField())
+		// - a func parameter or result
+		// - a local var.
+		// Sadly there is no way to distinguish
+		// a param/result from a local
+		// so we must proceed to the find.
+
+	case *types.Func:
+		// A func, if not package-level, must be a method.
+		if recv := obj.Type().(*types.Signature).Recv(); recv == nil {
+			return "", fmt.Errorf("func is not a method: %v", obj)
+		}
+		// TODO(adonovan): opt: if the method is concrete,
+		// do a specialized version of the rest of this function so
+		// that it's O(1) not O(|scope|).  Basically 'find' is needed
+		// only for struct fields and interface methods.
+
+	default:
+		panic(obj)
+	}
+
+	// 4. Search the API for the path to the var (field/param/result) or method.
+
+	// First inspect package-level named types.
+	// In the presence of path aliases, these give
+	// the best paths because non-types may
+	// refer to types, but not the reverse.
+	empty := make([]byte, 0, 48) // initial space
+	names := scope.Names()
+	for _, name := range names {
+		o := scope.Lookup(name)
+		tname, ok := o.(*types.TypeName)
+		if !ok {
+			continue // handle non-types in second pass
+		}
+
+		path := append(empty, name...)
+		path = append(path, opType)
+
+		T := o.Type()
+
+		if tname.IsAlias() {
+			// type alias
+			if r := find(obj, T, path); r != nil {
+				return Path(r), nil
+			}
+		} else {
+			if named, _ := T.(*types.Named); named != nil {
+				if r := findTypeParam(obj, typeparams.ForNamed(named), path); r != nil {
+					// generic named type
+					return Path(r), nil
+				}
+			}
+			// defined (named) type
+			if r := find(obj, T.Underlying(), append(path, opUnderlying)); r != nil {
+				return Path(r), nil
+			}
+		}
+	}
+
+	// Then inspect everything else:
+	// non-types, and declared methods of defined types.
+	for _, name := range names {
+		o := scope.Lookup(name)
+		path := append(empty, name...)
+		if _, ok := o.(*types.TypeName); !ok {
+			if o.Exported() {
+				// exported non-type (const, var, func)
+				if r := find(obj, o.Type(), append(path, opType)); r != nil {
+					return Path(r), nil
+				}
+			}
+			continue
+		}
+
+		// Inspect declared methods of defined types.
+		if T, ok := o.Type().(*types.Named); ok {
+			path = append(path, opType)
+			// Note that method index here is always with respect
+			// to canonical ordering of methods, regardless of how
+			// they appear in the underlying type.
+			canonical := canonicalize(T)
+			for i := 0; i < len(canonical); i++ {
+				m := canonical[i]
+				path2 := appendOpArg(path, opMethod, i)
+				if m == obj {
+					return Path(path2), nil // found declared method
+				}
+				if r := find(obj, m.Type(), append(path2, opType)); r != nil {
+					return Path(r), nil
+				}
+			}
+		}
+	}
+
+	return "", fmt.Errorf("can't find path for %v in %s", obj, pkg.Path())
+}
+
+func appendOpArg(path []byte, op byte, arg int) []byte {
+	path = append(path, op)
+	path = strconv.AppendInt(path, int64(arg), 10)
+	return path
+}
+
+// find finds obj within type T, returning the path to it, or nil if not found.
+func find(obj types.Object, T types.Type, path []byte) []byte {
+	switch T := T.(type) {
+	case *types.Basic, *types.Named:
+		// Named types belonging to pkg were handled already,
+		// so T must belong to another package. No path.
+		return nil
+	case *types.Pointer:
+		return find(obj, T.Elem(), append(path, opElem))
+	case *types.Slice:
+		return find(obj, T.Elem(), append(path, opElem))
+	case *types.Array:
+		return find(obj, T.Elem(), append(path, opElem))
+	case *types.Chan:
+		return find(obj, T.Elem(), append(path, opElem))
+	case *types.Map:
+		if r := find(obj, T.Key(), append(path, opKey)); r != nil {
+			return r
+		}
+		return find(obj, T.Elem(), append(path, opElem))
+	case *types.Signature:
+		if r := findTypeParam(obj, typeparams.ForSignature(T), path); r != nil {
+			return r
+		}
+		if r := find(obj, T.Params(), append(path, opParams)); r != nil {
+			return r
+		}
+		return find(obj, T.Results(), append(path, opResults))
+	case *types.Struct:
+		for i := 0; i < T.NumFields(); i++ {
+			f := T.Field(i)
+			path2 := appendOpArg(path, opField, i)
+			if f == obj {
+				return path2 // found field var
+			}
+			if r := find(obj, f.Type(), append(path2, opType)); r != nil {
+				return r
+			}
+		}
+		return nil
+	case *types.Tuple:
+		for i := 0; i < T.Len(); i++ {
+			v := T.At(i)
+			path2 := appendOpArg(path, opAt, i)
+			if v == obj {
+				return path2 // found param/result var
+			}
+			if r := find(obj, v.Type(), append(path2, opType)); r != nil {
+				return r
+			}
+		}
+		return nil
+	case *types.Interface:
+		for i := 0; i < T.NumMethods(); i++ {
+			m := T.Method(i)
+			path2 := appendOpArg(path, opMethod, i)
+			if m == obj {
+				return path2 // found interface method
+			}
+			if r := find(obj, m.Type(), append(path2, opType)); r != nil {
+				return r
+			}
+		}
+		return nil
+	case *typeparams.TypeParam:
+		name := T.Obj()
+		if name == obj {
+			return append(path, opObj)
+		}
+		if r := find(obj, T.Constraint(), append(path, opConstraint)); r != nil {
+			return r
+		}
+		return nil
+	}
+	panic(T)
+}
+
+func findTypeParam(obj types.Object, list *typeparams.TypeParamList, path []byte) []byte {
+	for i := 0; i < list.Len(); i++ {
+		tparam := list.At(i)
+		path2 := appendOpArg(path, opTypeParam, i)
+		if r := find(obj, tparam, path2); r != nil {
+			return r
+		}
+	}
+	return nil
+}
+
+// Object returns the object denoted by path p within the package pkg.
+func Object(pkg *types.Package, p Path) (types.Object, error) {
+	if p == "" {
+		return nil, fmt.Errorf("empty path")
+	}
+
+	pathstr := string(p)
+	var pkgobj, suffix string
+	if dot := strings.IndexByte(pathstr, opType); dot < 0 {
+		pkgobj = pathstr
+	} else {
+		pkgobj = pathstr[:dot]
+		suffix = pathstr[dot:] // suffix starts with "."
+	}
+
+	obj := pkg.Scope().Lookup(pkgobj)
+	if obj == nil {
+		return nil, fmt.Errorf("package %s does not contain %q", pkg.Path(), pkgobj)
+	}
+
+	// abstraction of *types.{Pointer,Slice,Array,Chan,Map}
+	type hasElem interface {
+		Elem() types.Type
+	}
+	// abstraction of *types.{Named,Signature}
+	type hasTypeParams interface {
+		TypeParams() *typeparams.TypeParamList
+	}
+	// abstraction of *types.{Named,TypeParam}
+	type hasObj interface {
+		Obj() *types.TypeName
+	}
+
+	// The loop state is the pair (t, obj),
+	// exactly one of which is non-nil, initially obj.
+	// All suffixes start with '.' (the only object->type operation),
+	// followed by optional type->type operations,
+	// then a type->object operation.
+	// The cycle then repeats.
+	var t types.Type
+	for suffix != "" {
+		code := suffix[0]
+		suffix = suffix[1:]
+
+		// Codes [AFM] have an integer operand.
+		var index int
+		switch code {
+		case opAt, opField, opMethod, opTypeParam:
+			rest := strings.TrimLeft(suffix, "0123456789")
+			numerals := suffix[:len(suffix)-len(rest)]
+			suffix = rest
+			i, err := strconv.Atoi(numerals)
+			if err != nil {
+				return nil, fmt.Errorf("invalid path: bad numeric operand %q for code %q", numerals, code)
+			}
+			index = int(i)
+		case opObj:
+			// no operand
+		default:
+			// The suffix must end with a type->object operation.
+			if suffix == "" {
+				return nil, fmt.Errorf("invalid path: ends with %q, want [AFMO]", code)
+			}
+		}
+
+		if code == opType {
+			if t != nil {
+				return nil, fmt.Errorf("invalid path: unexpected %q in type context", opType)
+			}
+			t = obj.Type()
+			obj = nil
+			continue
+		}
+
+		if t == nil {
+			return nil, fmt.Errorf("invalid path: code %q in object context", code)
+		}
+
+		// Inv: t != nil, obj == nil
+
+		switch code {
+		case opElem:
+			hasElem, ok := t.(hasElem) // Pointer, Slice, Array, Chan, Map
+			if !ok {
+				return nil, fmt.Errorf("cannot apply %q to %s (got %T, want pointer, slice, array, chan or map)", code, t, t)
+			}
+			t = hasElem.Elem()
+
+		case opKey:
+			mapType, ok := t.(*types.Map)
+			if !ok {
+				return nil, fmt.Errorf("cannot apply %q to %s (got %T, want map)", code, t, t)
+			}
+			t = mapType.Key()
+
+		case opParams:
+			sig, ok := t.(*types.Signature)
+			if !ok {
+				return nil, fmt.Errorf("cannot apply %q to %s (got %T, want signature)", code, t, t)
+			}
+			t = sig.Params()
+
+		case opResults:
+			sig, ok := t.(*types.Signature)
+			if !ok {
+				return nil, fmt.Errorf("cannot apply %q to %s (got %T, want signature)", code, t, t)
+			}
+			t = sig.Results()
+
+		case opUnderlying:
+			named, ok := t.(*types.Named)
+			if !ok {
+				return nil, fmt.Errorf("cannot apply %q to %s (got %T, want named)", code, t, t)
+			}
+			t = named.Underlying()
+
+		case opTypeParam:
+			hasTypeParams, ok := t.(hasTypeParams) // Named, Signature
+			if !ok {
+				return nil, fmt.Errorf("cannot apply %q to %s (got %T, want named or signature)", code, t, t)
+			}
+			tparams := hasTypeParams.TypeParams()
+			if n := tparams.Len(); index >= n {
+				return nil, fmt.Errorf("tuple index %d out of range [0-%d)", index, n)
+			}
+			t = tparams.At(index)
+
+		case opConstraint:
+			tparam, ok := t.(*typeparams.TypeParam)
+			if !ok {
+				return nil, fmt.Errorf("cannot apply %q to %s (got %T, want type parameter)", code, t, t)
+			}
+			t = tparam.Constraint()
+
+		case opAt:
+			tuple, ok := t.(*types.Tuple)
+			if !ok {
+				return nil, fmt.Errorf("cannot apply %q to %s (got %T, want tuple)", code, t, t)
+			}
+			if n := tuple.Len(); index >= n {
+				return nil, fmt.Errorf("tuple index %d out of range [0-%d)", index, n)
+			}
+			obj = tuple.At(index)
+			t = nil
+
+		case opField:
+			structType, ok := t.(*types.Struct)
+			if !ok {
+				return nil, fmt.Errorf("cannot apply %q to %s (got %T, want struct)", code, t, t)
+			}
+			if n := structType.NumFields(); index >= n {
+				return nil, fmt.Errorf("field index %d out of range [0-%d)", index, n)
+			}
+			obj = structType.Field(index)
+			t = nil
+
+		case opMethod:
+			hasMethods, ok := t.(hasMethods) // Interface or Named
+			if !ok {
+				return nil, fmt.Errorf("cannot apply %q to %s (got %T, want interface or named)", code, t, t)
+			}
+			canonical := canonicalize(hasMethods)
+			if n := len(canonical); index >= n {
+				return nil, fmt.Errorf("method index %d out of range [0-%d)", index, n)
+			}
+			obj = canonical[index]
+			t = nil
+
+		case opObj:
+			hasObj, ok := t.(hasObj)
+			if !ok {
+				return nil, fmt.Errorf("cannot apply %q to %s (got %T, want named or type param)", code, t, t)
+			}
+			obj = hasObj.Obj()
+			t = nil
+
+		default:
+			return nil, fmt.Errorf("invalid path: unknown code %q", code)
+		}
+	}
+
+	if obj.Pkg() != pkg {
+		return nil, fmt.Errorf("path denotes %s, which belongs to a different package", obj)
+	}
+
+	return obj, nil // success
+}
+
+// hasMethods is an abstraction of *types.{Interface,Named}. This is pulled up
+// because it is used by methodOrdering, which is in turn used by both encoding
+// and decoding.
+type hasMethods interface {
+	Method(int) *types.Func
+	NumMethods() int
+}
+
+// canonicalize returns a canonical order for the methods in a hasMethod.
+func canonicalize(hm hasMethods) []*types.Func {
+	count := hm.NumMethods()
+	if count <= 0 {
+		return nil
+	}
+	canon := make([]*types.Func, count)
+	for i := 0; i < count; i++ {
+		canon[i] = hm.Method(i)
+	}
+	less := func(i, j int) bool {
+		return canon[i].Id() < canon[j].Id()
+	}
+	sort.Slice(canon, less)
+	return canon
+}

vendor/golang.org/x/tools/go/types/typeutil/callee.go

@@ -0,0 +1,69 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package typeutil
+
+import (
+	"go/ast"
+	"go/types"
+
+	"golang.org/x/tools/go/ast/astutil"
+	"golang.org/x/tools/internal/typeparams"
+)
+
+// Callee returns the named target of a function call, if any:
+// a function, method, builtin, or variable.
+//
+// Functions and methods may potentially have type parameters.
+func Callee(info *types.Info, call *ast.CallExpr) types.Object {
+	fun := astutil.Unparen(call.Fun)
+
+	// Look through type instantiation if necessary.
+	isInstance := false
+	switch fun.(type) {
+	case *ast.IndexExpr, *typeparams.IndexListExpr:
+		// When extracting the callee from an *IndexExpr, we need to check that
+		// it is a *types.Func and not a *types.Var.
+		// Example: Don't match a slice m within the expression `m[0]()`.
+		isInstance = true
+		fun, _, _, _ = typeparams.UnpackIndexExpr(fun)
+	}
+
+	var obj types.Object
+	switch fun := fun.(type) {
+	case *ast.Ident:
+		obj = info.Uses[fun] // type, var, builtin, or declared func
+	case *ast.SelectorExpr:
+		if sel, ok := info.Selections[fun]; ok {
+			obj = sel.Obj() // method or field
+		} else {
+			obj = info.Uses[fun.Sel] // qualified identifier?
+		}
+	}
+	if _, ok := obj.(*types.TypeName); ok {
+		return nil // T(x) is a conversion, not a call
+	}
+	// A Func is required to match instantiations.
+	if _, ok := obj.(*types.Func); isInstance && !ok {
+		return nil // Was not a Func.
+	}
+	return obj
+}
+
+// StaticCallee returns the target (function or method) of a static function
+// call, if any. It returns nil for calls to builtins.
+//
+// Note: for calls of instantiated functions and methods, StaticCallee returns
+// the corresponding generic function or method on the generic type.
+func StaticCallee(info *types.Info, call *ast.CallExpr) *types.Func {
+	if f, ok := Callee(info, call).(*types.Func); ok && !interfaceMethod(f) {
+		return f
+	}
+	return nil
+}
+
+func interfaceMethod(f *types.Func) bool {
+	recv := f.Type().(*types.Signature).Recv()
+	return recv != nil && types.IsInterface(recv.Type())
+}

vendor/golang.org/x/tools/go/types/typeutil/imports.go

@@ -0,0 +1,31 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package typeutil
+
+import "go/types"
+
+// Dependencies returns all dependencies of the specified packages.
+//
+// Dependent packages appear in topological order: if package P imports
+// package Q, Q appears earlier than P in the result.
+// The algorithm follows import statements in the order they
+// appear in the source code, so the result is a total order.
+//
+func Dependencies(pkgs ...*types.Package) []*types.Package {
+	var result []*types.Package
+	seen := make(map[*types.Package]bool)
+	var visit func(pkgs []*types.Package)
+	visit = func(pkgs []*types.Package) {
+		for _, p := range pkgs {
+			if !seen[p] {
+				seen[p] = true
+				visit(p.Imports())
+				result = append(result, p)
+			}
+		}
+	}
+	visit(pkgs)
+	return result
+}

vendor/golang.org/x/tools/go/types/typeutil/map.go

@@ -0,0 +1,443 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package typeutil defines various utilities for types, such as Map,
+// a mapping from types.Type to interface{} values.
+package typeutil // import "golang.org/x/tools/go/types/typeutil"
+
+import (
+	"bytes"
+	"fmt"
+	"go/types"
+	"reflect"
+
+	"golang.org/x/tools/internal/typeparams"
+)
+
+// Map is a hash-table-based mapping from types (types.Type) to
+// arbitrary interface{} values.  The concrete types that implement
+// the Type interface are pointers.  Since they are not canonicalized,
+// == cannot be used to check for equivalence, and thus we cannot
+// simply use a Go map.
+//
+// Just as with map[K]V, a nil *Map is a valid empty map.
+//
+// Not thread-safe.
+//
+type Map struct {
+	hasher Hasher             // shared by many Maps
+	table  map[uint32][]entry // maps hash to bucket; entry.key==nil means unused
+	length int                // number of map entries
+}
+
+// entry is an entry (key/value association) in a hash bucket.
+type entry struct {
+	key   types.Type
+	value interface{}
+}
+
+// SetHasher sets the hasher used by Map.
+//
+// All Hashers are functionally equivalent but contain internal state
+// used to cache the results of hashing previously seen types.
+//
+// A single Hasher created by MakeHasher() may be shared among many
+// Maps.  This is recommended if the instances have many keys in
+// common, as it will amortize the cost of hash computation.
+//
+// A Hasher may grow without bound as new types are seen.  Even when a
+// type is deleted from the map, the Hasher never shrinks, since other
+// types in the map may reference the deleted type indirectly.
+//
+// Hashers are not thread-safe, and read-only operations such as
+// Map.Lookup require updates to the hasher, so a full Mutex lock (not a
+// read-lock) is require around all Map operations if a shared
+// hasher is accessed from multiple threads.
+//
+// If SetHasher is not called, the Map will create a private hasher at
+// the first call to Insert.
+//
+func (m *Map) SetHasher(hasher Hasher) {
+	m.hasher = hasher
+}
+
+// Delete removes the entry with the given key, if any.
+// It returns true if the entry was found.
+//
+func (m *Map) Delete(key types.Type) bool {
+	if m != nil && m.table != nil {
+		hash := m.hasher.Hash(key)
+		bucket := m.table[hash]
+		for i, e := range bucket {
+			if e.key != nil && types.Identical(key, e.key) {
+				// We can't compact the bucket as it
+				// would disturb iterators.
+				bucket[i] = entry{}
+				m.length--
+				return true
+			}
+		}
+	}
+	return false
+}
+
+// At returns the map entry for the given key.
+// The result is nil if the entry is not present.
+//
+func (m *Map) At(key types.Type) interface{} {
+	if m != nil && m.table != nil {
+		for _, e := range m.table[m.hasher.Hash(key)] {
+			if e.key != nil && types.Identical(key, e.key) {
+				return e.value
+			}
+		}
+	}
+	return nil
+}
+
+// Set sets the map entry for key to val,
+// and returns the previous entry, if any.
+func (m *Map) Set(key types.Type, value interface{}) (prev interface{}) {
+	if m.table != nil {
+		hash := m.hasher.Hash(key)
+		bucket := m.table[hash]
+		var hole *entry
+		for i, e := range bucket {
+			if e.key == nil {
+				hole = &bucket[i]
+			} else if types.Identical(key, e.key) {
+				prev = e.value
+				bucket[i].value = value
+				return
+			}
+		}
+
+		if hole != nil {
+			*hole = entry{key, value} // overwrite deleted entry
+		} else {
+			m.table[hash] = append(bucket, entry{key, value})
+		}
+	} else {
+		if m.hasher.memo == nil {
+			m.hasher = MakeHasher()
+		}
+		hash := m.hasher.Hash(key)
+		m.table = map[uint32][]entry{hash: {entry{key, value}}}
+	}
+
+	m.length++
+	return
+}
+
+// Len returns the number of map entries.
+func (m *Map) Len() int {
+	if m != nil {
+		return m.length
+	}
+	return 0
+}
+
+// Iterate calls function f on each entry in the map in unspecified order.
+//
+// If f should mutate the map, Iterate provides the same guarantees as
+// Go maps: if f deletes a map entry that Iterate has not yet reached,
+// f will not be invoked for it, but if f inserts a map entry that
+// Iterate has not yet reached, whether or not f will be invoked for
+// it is unspecified.
+//
+func (m *Map) Iterate(f func(key types.Type, value interface{})) {
+	if m != nil {
+		for _, bucket := range m.table {
+			for _, e := range bucket {
+				if e.key != nil {
+					f(e.key, e.value)
+				}
+			}
+		}
+	}
+}
+
+// Keys returns a new slice containing the set of map keys.
+// The order is unspecified.
+func (m *Map) Keys() []types.Type {
+	keys := make([]types.Type, 0, m.Len())
+	m.Iterate(func(key types.Type, _ interface{}) {
+		keys = append(keys, key)
+	})
+	return keys
+}
+
+func (m *Map) toString(values bool) string {
+	if m == nil {
+		return "{}"
+	}
+	var buf bytes.Buffer
+	fmt.Fprint(&buf, "{")
+	sep := ""
+	m.Iterate(func(key types.Type, value interface{}) {
+		fmt.Fprint(&buf, sep)
+		sep = ", "
+		fmt.Fprint(&buf, key)
+		if values {
+			fmt.Fprintf(&buf, ": %q", value)
+		}
+	})
+	fmt.Fprint(&buf, "}")
+	return buf.String()
+}
+
+// String returns a string representation of the map's entries.
+// Values are printed using fmt.Sprintf("%v", v).
+// Order is unspecified.
+//
+func (m *Map) String() string {
+	return m.toString(true)
+}
+
+// KeysString returns a string representation of the map's key set.
+// Order is unspecified.
+//
+func (m *Map) KeysString() string {
+	return m.toString(false)
+}
+
+////////////////////////////////////////////////////////////////////////
+// Hasher
+
+// A Hasher maps each type to its hash value.
+// For efficiency, a hasher uses memoization; thus its memory
+// footprint grows monotonically over time.
+// Hashers are not thread-safe.
+// Hashers have reference semantics.
+// Call MakeHasher to create a Hasher.
+type Hasher struct {
+	memo map[types.Type]uint32
+
+	// ptrMap records pointer identity.
+	ptrMap map[interface{}]uint32
+
+	// sigTParams holds type parameters from the signature being hashed.
+	// Signatures are considered identical modulo renaming of type parameters, so
+	// within the scope of a signature type the identity of the signature's type
+	// parameters is just their index.
+	//
+	// Since the language does not currently support referring to uninstantiated
+	// generic types or functions, and instantiated signatures do not have type
+	// parameter lists, we should never encounter a second non-empty type
+	// parameter list when hashing a generic signature.
+	sigTParams *typeparams.TypeParamList
+}
+
+// MakeHasher returns a new Hasher instance.
+func MakeHasher() Hasher {
+	return Hasher{
+		memo:       make(map[types.Type]uint32),
+		ptrMap:     make(map[interface{}]uint32),
+		sigTParams: nil,
+	}
+}
+
+// Hash computes a hash value for the given type t such that
+// Identical(t, t') => Hash(t) == Hash(t').
+func (h Hasher) Hash(t types.Type) uint32 {
+	hash, ok := h.memo[t]
+	if !ok {
+		hash = h.hashFor(t)
+		h.memo[t] = hash
+	}
+	return hash
+}
+
+// hashString computes the Fowler–Noll–Vo hash of s.
+func hashString(s string) uint32 {
+	var h uint32
+	for i := 0; i < len(s); i++ {
+		h ^= uint32(s[i])
+		h *= 16777619
+	}
+	return h
+}
+
+// hashFor computes the hash of t.
+func (h Hasher) hashFor(t types.Type) uint32 {
+	// See Identical for rationale.
+	switch t := t.(type) {
+	case *types.Basic:
+		return uint32(t.Kind())
+
+	case *types.Array:
+		return 9043 + 2*uint32(t.Len()) + 3*h.Hash(t.Elem())
+
+	case *types.Slice:
+		return 9049 + 2*h.Hash(t.Elem())
+
+	case *types.Struct:
+		var hash uint32 = 9059
+		for i, n := 0, t.NumFields(); i < n; i++ {
+			f := t.Field(i)
+			if f.Anonymous() {
+				hash += 8861
+			}
+			hash += hashString(t.Tag(i))
+			hash += hashString(f.Name()) // (ignore f.Pkg)
+			hash += h.Hash(f.Type())
+		}
+		return hash
+
+	case *types.Pointer:
+		return 9067 + 2*h.Hash(t.Elem())
+
+	case *types.Signature:
+		var hash uint32 = 9091
+		if t.Variadic() {
+			hash *= 8863
+		}
+
+		// Use a separate hasher for types inside of the signature, where type
+		// parameter identity is modified to be (index, constraint). We must use a
+		// new memo for this hasher as type identity may be affected by this
+		// masking. For example, in func[T any](*T), the identity of *T depends on
+		// whether we are mapping the argument in isolation, or recursively as part
+		// of hashing the signature.
+		//
+		// We should never encounter a generic signature while hashing another
+		// generic signature, but defensively set sigTParams only if h.mask is
+		// unset.
+		tparams := typeparams.ForSignature(t)
+		if h.sigTParams == nil && tparams.Len() != 0 {
+			h = Hasher{
+				// There may be something more efficient than discarding the existing
+				// memo, but it would require detecting whether types are 'tainted' by
+				// references to type parameters.
+				memo: make(map[types.Type]uint32),
+				// Re-using ptrMap ensures that pointer identity is preserved in this
+				// hasher.
+				ptrMap:     h.ptrMap,
+				sigTParams: tparams,
+			}
+		}
+
+		for i := 0; i < tparams.Len(); i++ {
+			tparam := tparams.At(i)
+			hash += 7 * h.Hash(tparam.Constraint())
+		}
+
+		return hash + 3*h.hashTuple(t.Params()) + 5*h.hashTuple(t.Results())
+
+	case *typeparams.Union:
+		return h.hashUnion(t)
+
+	case *types.Interface:
+		// Interfaces are identical if they have the same set of methods, with
+		// identical names and types, and they have the same set of type
+		// restrictions. See go/types.identical for more details.
+		var hash uint32 = 9103
+
+		// Hash methods.
+		for i, n := 0, t.NumMethods(); i < n; i++ {
+			// Method order is not significant.
+			// Ignore m.Pkg().
+			m := t.Method(i)
+			hash += 3*hashString(m.Name()) + 5*h.Hash(m.Type())
+		}
+
+		// Hash type restrictions.
+		terms, err := typeparams.InterfaceTermSet(t)
+		// if err != nil t has invalid type restrictions.
+		if err == nil {
+			hash += h.hashTermSet(terms)
+		}
+
+		return hash
+
+	case *types.Map:
+		return 9109 + 2*h.Hash(t.Key()) + 3*h.Hash(t.Elem())
+
+	case *types.Chan:
+		return 9127 + 2*uint32(t.Dir()) + 3*h.Hash(t.Elem())
+
+	case *types.Named:
+		hash := h.hashPtr(t.Obj())
+		targs := typeparams.NamedTypeArgs(t)
+		for i := 0; i < targs.Len(); i++ {
+			targ := targs.At(i)
+			hash += 2 * h.Hash(targ)
+		}
+		return hash
+
+	case *typeparams.TypeParam:
+		return h.hashTypeParam(t)
+
+	case *types.Tuple:
+		return h.hashTuple(t)
+	}
+
+	panic(fmt.Sprintf("%T: %v", t, t))
+}
+
+func (h Hasher) hashTuple(tuple *types.Tuple) uint32 {
+	// See go/types.identicalTypes for rationale.
+	n := tuple.Len()
+	hash := 9137 + 2*uint32(n)
+	for i := 0; i < n; i++ {
+		hash += 3 * h.Hash(tuple.At(i).Type())
+	}
+	return hash
+}
+
+func (h Hasher) hashUnion(t *typeparams.Union) uint32 {
+	// Hash type restrictions.
+	terms, err := typeparams.UnionTermSet(t)
+	// if err != nil t has invalid type restrictions. Fall back on a non-zero
+	// hash.
+	if err != nil {
+		return 9151
+	}
+	return h.hashTermSet(terms)
+}
+
+func (h Hasher) hashTermSet(terms []*typeparams.Term) uint32 {
+	hash := 9157 + 2*uint32(len(terms))
+	for _, term := range terms {
+		// term order is not significant.
+		termHash := h.Hash(term.Type())
+		if term.Tilde() {
+			termHash *= 9161
+		}
+		hash += 3 * termHash
+	}
+	return hash
+}
+
+// hashTypeParam returns a hash of the type parameter t, with a hash value
+// depending on whether t is contained in h.sigTParams.
+//
+// If h.sigTParams is set and contains t, then we are in the process of hashing
+// a signature, and the hash value of t must depend only on t's index and
+// constraint: signatures are considered identical modulo type parameter
+// renaming. To avoid infinite recursion, we only hash the type parameter
+// index, and rely on types.Identical to handle signatures where constraints
+// are not identical.
+//
+// Otherwise the hash of t depends only on t's pointer identity.
+func (h Hasher) hashTypeParam(t *typeparams.TypeParam) uint32 {
+	if h.sigTParams != nil {
+		i := t.Index()
+		if i >= 0 && i < h.sigTParams.Len() && t == h.sigTParams.At(i) {
+			return 9173 + 3*uint32(i)
+		}
+	}
+	return h.hashPtr(t.Obj())
+}
+
+// hashPtr hashes the pointer identity of ptr. It uses h.ptrMap to ensure that
+// pointers values are not dependent on the GC.
+func (h Hasher) hashPtr(ptr interface{}) uint32 {
+	if hash, ok := h.ptrMap[ptr]; ok {
+		return hash
+	}
+	hash := uint32(reflect.ValueOf(ptr).Pointer())
+	h.ptrMap[ptr] = hash
+	return hash
+}

vendor/golang.org/x/tools/go/types/typeutil/methodsetcache.go

@@ -0,0 +1,72 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements a cache of method sets.
+
+package typeutil
+
+import (
+	"go/types"
+	"sync"
+)
+
+// A MethodSetCache records the method set of each type T for which
+// MethodSet(T) is called so that repeat queries are fast.
+// The zero value is a ready-to-use cache instance.
+type MethodSetCache struct {
+	mu     sync.Mutex
+	named  map[*types.Named]struct{ value, pointer *types.MethodSet } // method sets for named N and *N
+	others map[types.Type]*types.MethodSet                            // all other types
+}
+
+// MethodSet returns the method set of type T.  It is thread-safe.
+//
+// If cache is nil, this function is equivalent to types.NewMethodSet(T).
+// Utility functions can thus expose an optional *MethodSetCache
+// parameter to clients that care about performance.
+//
+func (cache *MethodSetCache) MethodSet(T types.Type) *types.MethodSet {
+	if cache == nil {
+		return types.NewMethodSet(T)
+	}
+	cache.mu.Lock()
+	defer cache.mu.Unlock()
+
+	switch T := T.(type) {
+	case *types.Named:
+		return cache.lookupNamed(T).value
+
+	case *types.Pointer:
+		if N, ok := T.Elem().(*types.Named); ok {
+			return cache.lookupNamed(N).pointer
+		}
+	}
+
+	// all other types
+	// (The map uses pointer equivalence, not type identity.)
+	mset := cache.others[T]
+	if mset == nil {
+		mset = types.NewMethodSet(T)
+		if cache.others == nil {
+			cache.others = make(map[types.Type]*types.MethodSet)
+		}
+		cache.others[T] = mset
+	}
+	return mset
+}
+
+func (cache *MethodSetCache) lookupNamed(named *types.Named) struct{ value, pointer *types.MethodSet } {
+	if cache.named == nil {
+		cache.named = make(map[*types.Named]struct{ value, pointer *types.MethodSet })
+	}
+	// Avoid recomputing mset(*T) for each distinct Pointer
+	// instance whose underlying type is a named type.
+	msets, ok := cache.named[named]
+	if !ok {
+		msets.value = types.NewMethodSet(named)
+		msets.pointer = types.NewMethodSet(types.NewPointer(named))
+		cache.named[named] = msets
+	}
+	return msets
+}

vendor/golang.org/x/tools/go/types/typeutil/ui.go

@@ -0,0 +1,52 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package typeutil
+
+// This file defines utilities for user interfaces that display types.
+
+import "go/types"
+
+// IntuitiveMethodSet returns the intuitive method set of a type T,
+// which is the set of methods you can call on an addressable value of
+// that type.
+//
+// The result always contains MethodSet(T), and is exactly MethodSet(T)
+// for interface types and for pointer-to-concrete types.
+// For all other concrete types T, the result additionally
+// contains each method belonging to *T if there is no identically
+// named method on T itself.
+//
+// This corresponds to user intuition about method sets;
+// this function is intended only for user interfaces.
+//
+// The order of the result is as for types.MethodSet(T).
+//
+func IntuitiveMethodSet(T types.Type, msets *MethodSetCache) []*types.Selection {
+	isPointerToConcrete := func(T types.Type) bool {
+		ptr, ok := T.(*types.Pointer)
+		return ok && !types.IsInterface(ptr.Elem())
+	}
+
+	var result []*types.Selection
+	mset := msets.MethodSet(T)
+	if types.IsInterface(T) || isPointerToConcrete(T) {
+		for i, n := 0, mset.Len(); i < n; i++ {
+			result = append(result, mset.At(i))
+		}
+	} else {
+		// T is some other concrete type.
+		// Report methods of T and *T, preferring those of T.
+		pmset := msets.MethodSet(types.NewPointer(T))
+		for i, n := 0, pmset.Len(); i < n; i++ {
+			meth := pmset.At(i)
+			if m := mset.Lookup(meth.Obj().Pkg(), meth.Obj().Name()); m != nil {
+				meth = m
+			}
+			result = append(result, meth)
+		}
+
+	}
+	return result
+}

vendor/golang.org/x/tools/internal/analysisinternal/analysis.go

@@ -0,0 +1,428 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package analysisinternal exposes internal-only fields from go/analysis.
+package analysisinternal
+
+import (
+	"bytes"
+	"fmt"
+	"go/ast"
+	"go/token"
+	"go/types"
+	"strings"
+
+	"golang.org/x/tools/go/ast/astutil"
+	"golang.org/x/tools/internal/lsp/fuzzy"
+)
+
+// Flag to gate diagnostics for fuzz tests in 1.18.
+var DiagnoseFuzzTests bool = false
+
+var (
+	GetTypeErrors func(p interface{}) []types.Error
+	SetTypeErrors func(p interface{}, errors []types.Error)
+)
+
+func TypeErrorEndPos(fset *token.FileSet, src []byte, start token.Pos) token.Pos {
+	// Get the end position for the type error.
+	offset, end := fset.PositionFor(start, false).Offset, start
+	if offset >= len(src) {
+		return end
+	}
+	if width := bytes.IndexAny(src[offset:], " \n,():;[]+-*"); width > 0 {
+		end = start + token.Pos(width)
+	}
+	return end
+}
+
+func ZeroValue(fset *token.FileSet, f *ast.File, pkg *types.Package, typ types.Type) ast.Expr {
+	under := typ
+	if n, ok := typ.(*types.Named); ok {
+		under = n.Underlying()
+	}
+	switch u := under.(type) {
+	case *types.Basic:
+		switch {
+		case u.Info()&types.IsNumeric != 0:
+			return &ast.BasicLit{Kind: token.INT, Value: "0"}
+		case u.Info()&types.IsBoolean != 0:
+			return &ast.Ident{Name: "false"}
+		case u.Info()&types.IsString != 0:
+			return &ast.BasicLit{Kind: token.STRING, Value: `""`}
+		default:
+			panic("unknown basic type")
+		}
+	case *types.Chan, *types.Interface, *types.Map, *types.Pointer, *types.Signature, *types.Slice, *types.Array:
+		return ast.NewIdent("nil")
+	case *types.Struct:
+		texpr := TypeExpr(fset, f, pkg, typ) // typ because we want the name here.
+		if texpr == nil {
+			return nil
+		}
+		return &ast.CompositeLit{
+			Type: texpr,
+		}
+	}
+	return nil
+}
+
+// IsZeroValue checks whether the given expression is a 'zero value' (as determined by output of
+// analysisinternal.ZeroValue)
+func IsZeroValue(expr ast.Expr) bool {
+	switch e := expr.(type) {
+	case *ast.BasicLit:
+		return e.Value == "0" || e.Value == `""`
+	case *ast.Ident:
+		return e.Name == "nil" || e.Name == "false"
+	default:
+		return false
+	}
+}
+
+func TypeExpr(fset *token.FileSet, f *ast.File, pkg *types.Package, typ types.Type) ast.Expr {
+	switch t := typ.(type) {
+	case *types.Basic:
+		switch t.Kind() {
+		case types.UnsafePointer:
+			return &ast.SelectorExpr{X: ast.NewIdent("unsafe"), Sel: ast.NewIdent("Pointer")}
+		default:
+			return ast.NewIdent(t.Name())
+		}
+	case *types.Pointer:
+		x := TypeExpr(fset, f, pkg, t.Elem())
+		if x == nil {
+			return nil
+		}
+		return &ast.UnaryExpr{
+			Op: token.MUL,
+			X:  x,
+		}
+	case *types.Array:
+		elt := TypeExpr(fset, f, pkg, t.Elem())
+		if elt == nil {
+			return nil
+		}
+		return &ast.ArrayType{
+			Len: &ast.BasicLit{
+				Kind:  token.INT,
+				Value: fmt.Sprintf("%d", t.Len()),
+			},
+			Elt: elt,
+		}
+	case *types.Slice:
+		elt := TypeExpr(fset, f, pkg, t.Elem())
+		if elt == nil {
+			return nil
+		}
+		return &ast.ArrayType{
+			Elt: elt,
+		}
+	case *types.Map:
+		key := TypeExpr(fset, f, pkg, t.Key())
+		value := TypeExpr(fset, f, pkg, t.Elem())
+		if key == nil || value == nil {
+			return nil
+		}
+		return &ast.MapType{
+			Key:   key,
+			Value: value,
+		}
+	case *types.Chan:
+		dir := ast.ChanDir(t.Dir())
+		if t.Dir() == types.SendRecv {
+			dir = ast.SEND | ast.RECV
+		}
+		value := TypeExpr(fset, f, pkg, t.Elem())
+		if value == nil {
+			return nil
+		}
+		return &ast.ChanType{
+			Dir:   dir,
+			Value: value,
+		}
+	case *types.Signature:
+		var params []*ast.Field
+		for i := 0; i < t.Params().Len(); i++ {
+			p := TypeExpr(fset, f, pkg, t.Params().At(i).Type())
+			if p == nil {
+				return nil
+			}
+			params = append(params, &ast.Field{
+				Type: p,
+				Names: []*ast.Ident{
+					{
+						Name: t.Params().At(i).Name(),
+					},
+				},
+			})
+		}
+		var returns []*ast.Field
+		for i := 0; i < t.Results().Len(); i++ {
+			r := TypeExpr(fset, f, pkg, t.Results().At(i).Type())
+			if r == nil {
+				return nil
+			}
+			returns = append(returns, &ast.Field{
+				Type: r,
+			})
+		}
+		return &ast.FuncType{
+			Params: &ast.FieldList{
+				List: params,
+			},
+			Results: &ast.FieldList{
+				List: returns,
+			},
+		}
+	case *types.Named:
+		if t.Obj().Pkg() == nil {
+			return ast.NewIdent(t.Obj().Name())
+		}
+		if t.Obj().Pkg() == pkg {
+			return ast.NewIdent(t.Obj().Name())
+		}
+		pkgName := t.Obj().Pkg().Name()
+		// If the file already imports the package under another name, use that.
+		for _, group := range astutil.Imports(fset, f) {
+			for _, cand := range group {
+				if strings.Trim(cand.Path.Value, `"`) == t.Obj().Pkg().Path() {
+					if cand.Name != nil && cand.Name.Name != "" {
+						pkgName = cand.Name.Name
+					}
+				}
+			}
+		}
+		if pkgName == "." {
+			return ast.NewIdent(t.Obj().Name())
+		}
+		return &ast.SelectorExpr{
+			X:   ast.NewIdent(pkgName),
+			Sel: ast.NewIdent(t.Obj().Name()),
+		}
+	case *types.Struct:
+		return ast.NewIdent(t.String())
+	case *types.Interface:
+		return ast.NewIdent(t.String())
+	default:
+		return nil
+	}
+}
+
+type TypeErrorPass string
+
+const (
+	NoNewVars      TypeErrorPass = "nonewvars"
+	NoResultValues TypeErrorPass = "noresultvalues"
+	UndeclaredName TypeErrorPass = "undeclaredname"
+)
+
+// StmtToInsertVarBefore returns the ast.Stmt before which we can safely insert a new variable.
+// Some examples:
+//
+// Basic Example:
+// z := 1
+// y := z + x
+// If x is undeclared, then this function would return `y := z + x`, so that we
+// can insert `x := ` on the line before `y := z + x`.
+//
+// If stmt example:
+// if z == 1 {
+// } else if z == y {}
+// If y is undeclared, then this function would return `if z == 1 {`, because we cannot
+// insert a statement between an if and an else if statement. As a result, we need to find
+// the top of the if chain to insert `y := ` before.
+func StmtToInsertVarBefore(path []ast.Node) ast.Stmt {
+	enclosingIndex := -1
+	for i, p := range path {
+		if _, ok := p.(ast.Stmt); ok {
+			enclosingIndex = i
+			break
+		}
+	}
+	if enclosingIndex == -1 {
+		return nil
+	}
+	enclosingStmt := path[enclosingIndex]
+	switch enclosingStmt.(type) {
+	case *ast.IfStmt:
+		// The enclosingStmt is inside of the if declaration,
+		// We need to check if we are in an else-if stmt and
+		// get the base if statement.
+		return baseIfStmt(path, enclosingIndex)
+	case *ast.CaseClause:
+		// Get the enclosing switch stmt if the enclosingStmt is
+		// inside of the case statement.
+		for i := enclosingIndex + 1; i < len(path); i++ {
+			if node, ok := path[i].(*ast.SwitchStmt); ok {
+				return node
+			} else if node, ok := path[i].(*ast.TypeSwitchStmt); ok {
+				return node
+			}
+		}
+	}
+	if len(path) <= enclosingIndex+1 {
+		return enclosingStmt.(ast.Stmt)
+	}
+	// Check if the enclosing statement is inside another node.
+	switch expr := path[enclosingIndex+1].(type) {
+	case *ast.IfStmt:
+		// Get the base if statement.
+		return baseIfStmt(path, enclosingIndex+1)
+	case *ast.ForStmt:
+		if expr.Init == enclosingStmt || expr.Post == enclosingStmt {
+			return expr
+		}
+	}
+	return enclosingStmt.(ast.Stmt)
+}
+
+// baseIfStmt walks up the if/else-if chain until we get to
+// the top of the current if chain.
+func baseIfStmt(path []ast.Node, index int) ast.Stmt {
+	stmt := path[index]
+	for i := index + 1; i < len(path); i++ {
+		if node, ok := path[i].(*ast.IfStmt); ok && node.Else == stmt {
+			stmt = node
+			continue
+		}
+		break
+	}
+	return stmt.(ast.Stmt)
+}
+
+// WalkASTWithParent walks the AST rooted at n. The semantics are
+// similar to ast.Inspect except it does not call f(nil).
+func WalkASTWithParent(n ast.Node, f func(n ast.Node, parent ast.Node) bool) {
+	var ancestors []ast.Node
+	ast.Inspect(n, func(n ast.Node) (recurse bool) {
+		if n == nil {
+			ancestors = ancestors[:len(ancestors)-1]
+			return false
+		}
+
+		var parent ast.Node
+		if len(ancestors) > 0 {
+			parent = ancestors[len(ancestors)-1]
+		}
+		ancestors = append(ancestors, n)
+		return f(n, parent)
+	})
+}
+
+// FindMatchingIdents finds all identifiers in 'node' that match any of the given types.
+// 'pos' represents the position at which the identifiers may be inserted. 'pos' must be within
+// the scope of each of identifier we select. Otherwise, we will insert a variable at 'pos' that
+// is unrecognized.
+func FindMatchingIdents(typs []types.Type, node ast.Node, pos token.Pos, info *types.Info, pkg *types.Package) map[types.Type][]*ast.Ident {
+	matches := map[types.Type][]*ast.Ident{}
+	// Initialize matches to contain the variable types we are searching for.
+	for _, typ := range typs {
+		if typ == nil {
+			continue
+		}
+		matches[typ] = []*ast.Ident{}
+	}
+	seen := map[types.Object]struct{}{}
+	ast.Inspect(node, func(n ast.Node) bool {
+		if n == nil {
+			return false
+		}
+		// Prevent circular definitions. If 'pos' is within an assignment statement, do not
+		// allow any identifiers in that assignment statement to be selected. Otherwise,
+		// we could do the following, where 'x' satisfies the type of 'f0':
+		//
+		// x := fakeStruct{f0: x}
+		//
+		assignment, ok := n.(*ast.AssignStmt)
+		if ok && pos > assignment.Pos() && pos <= assignment.End() {
+			return false
+		}
+		if n.End() > pos {
+			return n.Pos() <= pos
+		}
+		ident, ok := n.(*ast.Ident)
+		if !ok || ident.Name == "_" {
+			return true
+		}
+		obj := info.Defs[ident]
+		if obj == nil || obj.Type() == nil {
+			return true
+		}
+		if _, ok := obj.(*types.TypeName); ok {
+			return true
+		}
+		// Prevent duplicates in matches' values.
+		if _, ok = seen[obj]; ok {
+			return true
+		}
+		seen[obj] = struct{}{}
+		// Find the scope for the given position. Then, check whether the object
+		// exists within the scope.
+		innerScope := pkg.Scope().Innermost(pos)
+		if innerScope == nil {
+			return true
+		}
+		_, foundObj := innerScope.LookupParent(ident.Name, pos)
+		if foundObj != obj {
+			return true
+		}
+		// The object must match one of the types that we are searching for.
+		if idents, ok := matches[obj.Type()]; ok {
+			matches[obj.Type()] = append(idents, ast.NewIdent(ident.Name))
+		}
+		// If the object type does not exactly match any of the target types, greedily
+		// find the first target type that the object type can satisfy.
+		for typ := range matches {
+			if obj.Type() == typ {
+				continue
+			}
+			if equivalentTypes(obj.Type(), typ) {
+				matches[typ] = append(matches[typ], ast.NewIdent(ident.Name))
+			}
+		}
+		return true
+	})
+	return matches
+}
+
+func equivalentTypes(want, got types.Type) bool {
+	if want == got || types.Identical(want, got) {
+		return true
+	}
+	// Code segment to help check for untyped equality from (golang/go#32146).
+	if rhs, ok := want.(*types.Basic); ok && rhs.Info()&types.IsUntyped > 0 {
+		if lhs, ok := got.Underlying().(*types.Basic); ok {
+			return rhs.Info()&types.IsConstType == lhs.Info()&types.IsConstType
+		}
+	}
+	return types.AssignableTo(want, got)
+}
+
+// FindBestMatch employs fuzzy matching to evaluate the similarity of each given identifier to the
+// given pattern. We return the identifier whose name is most similar to the pattern.
+func FindBestMatch(pattern string, idents []*ast.Ident) ast.Expr {
+	fuzz := fuzzy.NewMatcher(pattern)
+	var bestFuzz ast.Expr
+	highScore := float32(0) // minimum score is 0 (no match)
+	for _, ident := range idents {
+		// TODO: Improve scoring algorithm.
+		score := fuzz.Score(ident.Name)
+		if score > highScore {
+			highScore = score
+			bestFuzz = ident
+		} else if score == 0 {
+			// Order matters in the fuzzy matching algorithm. If we find no match
+			// when matching the target to the identifier, try matching the identifier
+			// to the target.
+			revFuzz := fuzzy.NewMatcher(ident.Name)
+			revScore := revFuzz.Score(pattern)
+			if revScore > highScore {
+				highScore = revScore
+				bestFuzz = ident
+			}
+		}
+	}
+	return bestFuzz
+}

vendor/golang.org/x/tools/internal/gocommand/invoke.go

@@ -9,7 +9,6 @@ import (
 	"bytes"
 	"context"
 	"fmt"
-	exec "golang.org/x/sys/execabs"
 	"io"
 	"os"
 	"regexp"
@@ -18,6 +17,8 @@ import (
 	"sync"
 	"time"
 
+	exec "golang.org/x/sys/execabs"
+
 	"golang.org/x/tools/internal/event"
 )
 
@@ -131,9 +132,16 @@ type Invocation struct {
 	Verb       string
 	Args       []string
 	BuildFlags []string
-	ModFlag    string
-	ModFile    string
-	Overlay    string
+
+	// If ModFlag is set, the go command is invoked with -mod=ModFlag.
+	ModFlag string
+
+	// If ModFile is set, the go command is invoked with -modfile=ModFile.
+	ModFile string
+
+	// If Overlay is set, the go command is invoked with -overlay=Overlay.
+	Overlay string
+
 	// If CleanEnv is set, the invocation will run only with the environment
 	// in Env, not starting with os.Environ.
 	CleanEnv   bool

vendor/golang.org/x/tools/internal/gocommand/vendor.go

@@ -38,10 +38,10 @@ var modFlagRegexp = regexp.MustCompile(`-mod[ =](\w+)`)
 // with the supplied context.Context and Invocation. The Invocation can contain pre-defined fields,
 // of which only Verb and Args are modified to run the appropriate Go command.
 // Inspired by setDefaultBuildMod in modload/init.go
-func VendorEnabled(ctx context.Context, inv Invocation, r *Runner) (*ModuleJSON, bool, error) {
+func VendorEnabled(ctx context.Context, inv Invocation, r *Runner) (bool, *ModuleJSON, error) {
 	mainMod, go114, err := getMainModuleAnd114(ctx, inv, r)
 	if err != nil {
-		return nil, false, err
+		return false, nil, err
 	}
 
 	// We check the GOFLAGS to see if there is anything overridden or not.
@@ -49,7 +49,7 @@ func VendorEnabled(ctx context.Context, inv Invocation, r *Runner) (*ModuleJSON,
 	inv.Args = []string{"GOFLAGS"}
 	stdout, err := r.Run(ctx, inv)
 	if err != nil {
-		return nil, false, err
+		return false, nil, err
 	}
 	goflags := string(bytes.TrimSpace(stdout.Bytes()))
 	matches := modFlagRegexp.FindStringSubmatch(goflags)
@@ -57,25 +57,27 @@ func VendorEnabled(ctx context.Context, inv Invocation, r *Runner) (*ModuleJSON,
 	if len(matches) != 0 {
 		modFlag = matches[1]
 	}
-	if modFlag != "" {
-		// Don't override an explicit '-mod=' argument.
-		return mainMod, modFlag == "vendor", nil
+	// Don't override an explicit '-mod=' argument.
+	if modFlag == "vendor" {
+		return true, mainMod, nil
+	} else if modFlag != "" {
+		return false, nil, nil
 	}
 	if mainMod == nil || !go114 {
-		return mainMod, false, nil
+		return false, nil, nil
 	}
 	// Check 1.14's automatic vendor mode.
 	if fi, err := os.Stat(filepath.Join(mainMod.Dir, "vendor")); err == nil && fi.IsDir() {
 		if mainMod.GoVersion != "" && semver.Compare("v"+mainMod.GoVersion, "v1.14") >= 0 {
 			// The Go version is at least 1.14, and a vendor directory exists.
 			// Set -mod=vendor by default.
-			return mainMod, true, nil
+			return true, mainMod, nil
 		}
 	}
-	return mainMod, false, nil
+	return false, nil, nil
 }
 
-// getMainModuleAnd114 gets the main module's information and whether the
+// getMainModuleAnd114 gets one of the main modules' information and whether the
 // go command in use is 1.14+. This is the information needed to figure out
 // if vendoring should be enabled.
 func getMainModuleAnd114(ctx context.Context, inv Invocation, r *Runner) (*ModuleJSON, bool, error) {

vendor/golang.org/x/tools/internal/imports/imports.go

@@ -306,7 +306,7 @@ func matchSpace(orig []byte, src []byte) []byte {
 	return b.Bytes()
 }
 
-var impLine = regexp.MustCompile(`^\s+(?:[\w\.]+\s+)?"(.+)"`)
+var impLine = regexp.MustCompile(`^\s+(?:[\w\.]+\s+)?"(.+?)"`)
 
 func addImportSpaces(r io.Reader, breaks []string) ([]byte, error) {
 	var out bytes.Buffer

vendor/golang.org/x/tools/internal/imports/mod.go

@@ -34,7 +34,8 @@ type ModuleResolver struct {
 	scannedRoots   map[gopathwalk.Root]bool
 
 	initialized   bool
-	main          *gocommand.ModuleJSON
+	mains         []*gocommand.ModuleJSON
+	mainByDir     map[string]*gocommand.ModuleJSON
 	modsByModPath []*gocommand.ModuleJSON // All modules, ordered by # of path components in module Path...
 	modsByDir     []*gocommand.ModuleJSON // ...or Dir.
 
@@ -69,21 +70,21 @@ func (r *ModuleResolver) init() error {
 		Logf:       r.env.Logf,
 		WorkingDir: r.env.WorkingDir,
 	}
-	mainMod, vendorEnabled, err := gocommand.VendorEnabled(context.TODO(), inv, r.env.GocmdRunner)
+	vendorEnabled, mainModVendor, err := gocommand.VendorEnabled(context.TODO(), inv, r.env.GocmdRunner)
 	if err != nil {
 		return err
 	}
 
-	if mainMod != nil && vendorEnabled {
+	if mainModVendor != nil && vendorEnabled {
 		// Vendor mode is on, so all the non-Main modules are irrelevant,
 		// and we need to search /vendor for everything.
-		r.main = mainMod
+		r.mains = []*gocommand.ModuleJSON{mainModVendor}
 		r.dummyVendorMod = &gocommand.ModuleJSON{
 			Path: "",
-			Dir:  filepath.Join(mainMod.Dir, "vendor"),
+			Dir:  filepath.Join(mainModVendor.Dir, "vendor"),
 		}
-		r.modsByModPath = []*gocommand.ModuleJSON{mainMod, r.dummyVendorMod}
-		r.modsByDir = []*gocommand.ModuleJSON{mainMod, r.dummyVendorMod}
+		r.modsByModPath = []*gocommand.ModuleJSON{mainModVendor, r.dummyVendorMod}
+		r.modsByDir = []*gocommand.ModuleJSON{mainModVendor, r.dummyVendorMod}
 	} else {
 		// Vendor mode is off, so run go list -m ... to find everything.
 		err := r.initAllMods()
@@ -122,8 +123,10 @@ func (r *ModuleResolver) init() error {
 	r.roots = []gopathwalk.Root{
 		{filepath.Join(goenv["GOROOT"], "/src"), gopathwalk.RootGOROOT},
 	}
-	if r.main != nil {
-		r.roots = append(r.roots, gopathwalk.Root{r.main.Dir, gopathwalk.RootCurrentModule})
+	r.mainByDir = make(map[string]*gocommand.ModuleJSON)
+	for _, main := range r.mains {
+		r.roots = append(r.roots, gopathwalk.Root{main.Dir, gopathwalk.RootCurrentModule})
+		r.mainByDir[main.Dir] = main
 	}
 	if vendorEnabled {
 		r.roots = append(r.roots, gopathwalk.Root{r.dummyVendorMod.Dir, gopathwalk.RootOther})
@@ -189,7 +192,7 @@ func (r *ModuleResolver) initAllMods() error {
 		r.modsByModPath = append(r.modsByModPath, mod)
 		r.modsByDir = append(r.modsByDir, mod)
 		if mod.Main {
-			r.main = mod
+			r.mains = append(r.mains, mod)
 		}
 	}
 	return nil
@@ -609,7 +612,7 @@ func (r *ModuleResolver) scanDirForPackage(root gopathwalk.Root, dir string) dir
 	}
 	switch root.Type {
 	case gopathwalk.RootCurrentModule:
-		importPath = path.Join(r.main.Path, filepath.ToSlash(subdir))
+		importPath = path.Join(r.mainByDir[root.Path].Path, filepath.ToSlash(subdir))
 	case gopathwalk.RootModuleCache:
 		matches := modCacheRegexp.FindStringSubmatch(subdir)
 		if len(matches) == 0 {

vendor/golang.org/x/tools/internal/imports/sortimports.go

@@ -9,6 +9,7 @@ package imports
 import (
 	"go/ast"
 	"go/token"
+	"log"
 	"sort"
 	"strconv"
 )
@@ -60,6 +61,7 @@ func sortImports(localPrefix string, fset *token.FileSet, f *ast.File) {
 
 // mergeImports merges all the import declarations into the first one.
 // Taken from golang.org/x/tools/ast/astutil.
+// This does not adjust line numbers properly
 func mergeImports(fset *token.FileSet, f *ast.File) {
 	if len(f.Decls) <= 1 {
 		return
@@ -237,8 +239,17 @@ func sortSpecs(localPrefix string, fset *token.FileSet, f *ast.File, specs []ast
 		p := s.Pos()
 		line := fset.File(p).Line(p)
 		for previousLine := line - 1; previousLine >= firstSpecLine; {
-			fset.File(p).MergeLine(previousLine)
-			previousLine--
+			// MergeLine can panic. Avoid the panic at the cost of not removing the blank line
+			// golang/go#50329
+			if previousLine > 0 && previousLine < fset.File(p).LineCount() {
+				fset.File(p).MergeLine(previousLine)
+				previousLine--
+			} else {
+				// try to gather some data to diagnose how this could happen
+				req := "Please report what the imports section of your go file looked like."
+				log.Printf("panic avoided: first:%d line:%d previous:%d max:%d. %s",
+					firstSpecLine, line, previousLine, fset.File(p).LineCount(), req)
+			}
 		}
 	}
 	return specs

vendor/golang.org/x/tools/internal/imports/zstdlib.go

@@ -180,6 +180,8 @@ var stdlib = map[string][]string{
 		"NewReader",
 		"NewWriter",
 		"Order",
+		"Reader",
+		"Writer",
 	},
 	"compress/zlib": []string{
 		"BestCompression",
@@ -641,7 +643,9 @@ var stdlib = map[string][]string{
 		"Named",
 		"NamedArg",
 		"NullBool",
+		"NullByte",
 		"NullFloat64",
+		"NullInt16",
 		"NullInt32",
 		"NullInt64",
 		"NullString",
@@ -2248,6 +2252,7 @@ var stdlib = map[string][]string{
 		"SHT_LOOS",
 		"SHT_LOPROC",
 		"SHT_LOUSER",
+		"SHT_MIPS_ABIFLAGS",
 		"SHT_NOBITS",
 		"SHT_NOTE",
 		"SHT_NULL",
@@ -3061,6 +3066,7 @@ var stdlib = map[string][]string{
 		"ParseExpr",
 		"ParseExprFrom",
 		"ParseFile",
+		"SkipObjectResolution",
 		"SpuriousErrors",
 		"Trace",
 	},
@@ -3441,6 +3447,7 @@ var stdlib = map[string][]string{
 		"Pt",
 		"RGBA",
 		"RGBA64",
+		"RGBA64Image",
 		"Rect",
 		"Rectangle",
 		"RegisterFormat",
@@ -3507,6 +3514,7 @@ var stdlib = map[string][]string{
 		"Op",
 		"Over",
 		"Quantizer",
+		"RGBA64Image",
 		"Src",
 	},
 	"image/gif": []string{
@@ -3612,6 +3620,7 @@ var stdlib = map[string][]string{
 		"FS",
 		"File",
 		"FileInfo",
+		"FileInfoToDirEntry",
 		"FileMode",
 		"Glob",
 		"GlobFS",
@@ -3772,15 +3781,18 @@ var stdlib = map[string][]string{
 		"Max",
 		"MaxFloat32",
 		"MaxFloat64",
+		"MaxInt",
 		"MaxInt16",
 		"MaxInt32",
 		"MaxInt64",
 		"MaxInt8",
+		"MaxUint",
 		"MaxUint16",
 		"MaxUint32",
 		"MaxUint64",
 		"MaxUint8",
 		"Min",
+		"MinInt",
 		"MinInt16",
 		"MinInt32",
 		"MinInt64",
@@ -4078,6 +4090,7 @@ var stdlib = map[string][]string{
 		"UnknownNetworkError",
 	},
 	"net/http": []string{
+		"AllowQuerySemicolons",
 		"CanonicalHeaderKey",
 		"Client",
 		"CloseNotifier",
@@ -4660,6 +4673,7 @@ var stdlib = map[string][]string{
 		"Value",
 		"ValueError",
 		"ValueOf",
+		"VisibleFields",
 		"Zero",
 	},
 	"regexp": []string{
@@ -4799,6 +4813,10 @@ var stdlib = map[string][]string{
 		"UnlockOSThread",
 		"Version",
 	},
+	"runtime/cgo": []string{
+		"Handle",
+		"NewHandle",
+	},
 	"runtime/debug": []string{
 		"BuildInfo",
 		"FreeOSMemory",
@@ -4915,6 +4933,7 @@ var stdlib = map[string][]string{
 		"QuoteRuneToGraphic",
 		"QuoteToASCII",
 		"QuoteToGraphic",
+		"QuotedPrefix",
 		"Unquote",
 		"UnquoteChar",
 	},
@@ -10334,6 +10353,7 @@ var stdlib = map[string][]string{
 		"PipeNode",
 		"Pos",
 		"RangeNode",
+		"SkipFuncCheck",
 		"StringNode",
 		"TemplateNode",
 		"TextNode",
@@ -10358,6 +10378,7 @@ var stdlib = map[string][]string{
 		"July",
 		"June",
 		"Kitchen",
+		"Layout",
 		"LoadLocation",
 		"LoadLocationFromTZData",
 		"Local",
@@ -10406,6 +10427,8 @@ var stdlib = map[string][]string{
 		"UTC",
 		"Unix",
 		"UnixDate",
+		"UnixMicro",
+		"UnixMilli",
 		"Until",
 		"Wednesday",
 		"Weekday",

vendor/golang.org/x/tools/internal/lsp/fuzzy/input.go

@@ -0,0 +1,183 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package fuzzy
+
+import (
+	"unicode"
+)
+
+// RuneRole specifies the role of a rune in the context of an input.
+type RuneRole byte
+
+const (
+	// RNone specifies a rune without any role in the input (i.e., whitespace/non-ASCII).
+	RNone RuneRole = iota
+	// RSep specifies a rune with the role of segment separator.
+	RSep
+	// RTail specifies a rune which is a lower-case tail in a word in the input.
+	RTail
+	// RUCTail specifies a rune which is an upper-case tail in a word in the input.
+	RUCTail
+	// RHead specifies a rune which is the first character in a word in the input.
+	RHead
+)
+
+// RuneRoles detects the roles of each byte rune in an input string and stores it in the output
+// slice. The rune role depends on the input type. Stops when it parsed all the runes in the string
+// or when it filled the output. If output is nil, then it gets created.
+func RuneRoles(candidate []byte, reuse []RuneRole) []RuneRole {
+	var output []RuneRole
+	if cap(reuse) < len(candidate) {
+		output = make([]RuneRole, 0, len(candidate))
+	} else {
+		output = reuse[:0]
+	}
+
+	prev, prev2 := rtNone, rtNone
+	for i := 0; i < len(candidate); i++ {
+		r := rune(candidate[i])
+
+		role := RNone
+
+		curr := rtLower
+		if candidate[i] <= unicode.MaxASCII {
+			curr = runeType(rt[candidate[i]] - '0')
+		}
+
+		if curr == rtLower {
+			if prev == rtNone || prev == rtPunct {
+				role = RHead
+			} else {
+				role = RTail
+			}
+		} else if curr == rtUpper {
+			role = RHead
+
+			if prev == rtUpper {
+				// This and previous characters are both upper case.
+
+				if i+1 == len(candidate) {
+					// This is last character, previous was also uppercase -> this is UCTail
+					// i.e., (current char is C): aBC / BC / ABC
+					role = RUCTail
+				}
+			}
+		} else if curr == rtPunct {
+			switch r {
+			case '.', ':':
+				role = RSep
+			}
+		}
+		if curr != rtLower {
+			if i > 1 && output[i-1] == RHead && prev2 == rtUpper && (output[i-2] == RHead || output[i-2] == RUCTail) {
+				// The previous two characters were uppercase. The current one is not a lower case, so the
+				// previous one can't be a HEAD. Make it a UCTail.
+				// i.e., (last char is current char - B must be a UCTail): ABC / ZABC / AB.
+				output[i-1] = RUCTail
+			}
+		}
+
+		output = append(output, role)
+		prev2 = prev
+		prev = curr
+	}
+	return output
+}
+
+type runeType byte
+
+const (
+	rtNone runeType = iota
+	rtPunct
+	rtLower
+	rtUpper
+)
+
+const rt = "00000000000000000000000000000000000000000000001122222222221000000333333333333333333333333330000002222222222222222222222222200000"
+
+// LastSegment returns the substring representing the last segment from the input, where each
+// byte has an associated RuneRole in the roles slice. This makes sense only for inputs of Symbol
+// or Filename type.
+func LastSegment(input string, roles []RuneRole) string {
+	// Exclude ending separators.
+	end := len(input) - 1
+	for end >= 0 && roles[end] == RSep {
+		end--
+	}
+	if end < 0 {
+		return ""
+	}
+
+	start := end - 1
+	for start >= 0 && roles[start] != RSep {
+		start--
+	}
+
+	return input[start+1 : end+1]
+}
+
+// fromChunks copies string chunks into the given buffer.
+func fromChunks(chunks []string, buffer []byte) []byte {
+	ii := 0
+	for _, chunk := range chunks {
+		for i := 0; i < len(chunk); i++ {
+			if ii >= cap(buffer) {
+				break
+			}
+			buffer[ii] = chunk[i]
+			ii++
+		}
+	}
+	return buffer[:ii]
+}
+
+// toLower transforms the input string to lower case, which is stored in the output byte slice.
+// The lower casing considers only ASCII values - non ASCII values are left unmodified.
+// Stops when parsed all input or when it filled the output slice. If output is nil, then it gets
+// created.
+func toLower(input []byte, reuse []byte) []byte {
+	output := reuse
+	if cap(reuse) < len(input) {
+		output = make([]byte, len(input))
+	}
+
+	for i := 0; i < len(input); i++ {
+		r := rune(input[i])
+		if input[i] <= unicode.MaxASCII {
+			if 'A' <= r && r <= 'Z' {
+				r += 'a' - 'A'
+			}
+		}
+		output[i] = byte(r)
+	}
+	return output[:len(input)]
+}
+
+// WordConsumer defines a consumer for a word delimited by the [start,end) byte offsets in an input
+// (start is inclusive, end is exclusive).
+type WordConsumer func(start, end int)
+
+// Words find word delimiters in an input based on its bytes' mappings to rune roles. The offset
+// delimiters for each word are fed to the provided consumer function.
+func Words(roles []RuneRole, consume WordConsumer) {
+	var wordStart int
+	for i, r := range roles {
+		switch r {
+		case RUCTail, RTail:
+		case RHead, RNone, RSep:
+			if i != wordStart {
+				consume(wordStart, i)
+			}
+			wordStart = i
+			if r != RHead {
+				// Skip this character.
+				wordStart = i + 1
+			}
+		}
+	}
+	if wordStart != len(roles) {
+		consume(wordStart, len(roles))
+	}
+}

vendor/golang.org/x/tools/internal/lsp/fuzzy/matcher.go

@@ -0,0 +1,407 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package fuzzy implements a fuzzy matching algorithm.
+package fuzzy
+
+import (
+	"bytes"
+	"fmt"
+)
+
+const (
+	// MaxInputSize is the maximum size of the input scored against the fuzzy matcher. Longer inputs
+	// will be truncated to this size.
+	MaxInputSize = 127
+	// MaxPatternSize is the maximum size of the pattern used to construct the fuzzy matcher. Longer
+	// inputs are truncated to this size.
+	MaxPatternSize = 63
+)
+
+type scoreVal int
+
+func (s scoreVal) val() int {
+	return int(s) >> 1
+}
+
+func (s scoreVal) prevK() int {
+	return int(s) & 1
+}
+
+func score(val int, prevK int /*0 or 1*/) scoreVal {
+	return scoreVal(val<<1 + prevK)
+}
+
+// Matcher implements a fuzzy matching algorithm for scoring candidates against a pattern.
+// The matcher does not support parallel usage.
+type Matcher struct {
+	pattern       string
+	patternLower  []byte // lower-case version of the pattern
+	patternShort  []byte // first characters of the pattern
+	caseSensitive bool   // set if the pattern is mix-cased
+
+	patternRoles []RuneRole // the role of each character in the pattern
+	roles        []RuneRole // the role of each character in the tested string
+
+	scores [MaxInputSize + 1][MaxPatternSize + 1][2]scoreVal
+
+	scoreScale float32
+
+	lastCandidateLen     int // in bytes
+	lastCandidateMatched bool
+
+	// Reusable buffers to avoid allocating for every candidate.
+	//  - inputBuf stores the concatenated input chunks
+	//  - lowerBuf stores the last candidate in lower-case
+	//  - rolesBuf stores the calculated roles for each rune in the last
+	//    candidate.
+	inputBuf [MaxInputSize]byte
+	lowerBuf [MaxInputSize]byte
+	rolesBuf [MaxInputSize]RuneRole
+}
+
+func (m *Matcher) bestK(i, j int) int {
+	if m.scores[i][j][0].val() < m.scores[i][j][1].val() {
+		return 1
+	}
+	return 0
+}
+
+// NewMatcher returns a new fuzzy matcher for scoring candidates against the provided pattern.
+func NewMatcher(pattern string) *Matcher {
+	if len(pattern) > MaxPatternSize {
+		pattern = pattern[:MaxPatternSize]
+	}
+
+	m := &Matcher{
+		pattern:      pattern,
+		patternLower: toLower([]byte(pattern), nil),
+	}
+
+	for i, c := range m.patternLower {
+		if pattern[i] != c {
+			m.caseSensitive = true
+			break
+		}
+	}
+
+	if len(pattern) > 3 {
+		m.patternShort = m.patternLower[:3]
+	} else {
+		m.patternShort = m.patternLower
+	}
+
+	m.patternRoles = RuneRoles([]byte(pattern), nil)
+
+	if len(pattern) > 0 {
+		maxCharScore := 4
+		m.scoreScale = 1 / float32(maxCharScore*len(pattern))
+	}
+
+	return m
+}
+
+// Score returns the score returned by matching the candidate to the pattern.
+// This is not designed for parallel use. Multiple candidates must be scored sequentially.
+// Returns a score between 0 and 1 (0 - no match, 1 - perfect match).
+func (m *Matcher) Score(candidate string) float32 {
+	return m.ScoreChunks([]string{candidate})
+}
+
+func (m *Matcher) ScoreChunks(chunks []string) float32 {
+	candidate := fromChunks(chunks, m.inputBuf[:])
+	if len(candidate) > MaxInputSize {
+		candidate = candidate[:MaxInputSize]
+	}
+	lower := toLower(candidate, m.lowerBuf[:])
+	m.lastCandidateLen = len(candidate)
+
+	if len(m.pattern) == 0 {
+		// Empty patterns perfectly match candidates.
+		return 1
+	}
+
+	if m.match(candidate, lower) {
+		sc := m.computeScore(candidate, lower)
+		if sc > minScore/2 && !m.poorMatch() {
+			m.lastCandidateMatched = true
+			if len(m.pattern) == len(candidate) {
+				// Perfect match.
+				return 1
+			}
+
+			if sc < 0 {
+				sc = 0
+			}
+			normalizedScore := float32(sc) * m.scoreScale
+			if normalizedScore > 1 {
+				normalizedScore = 1
+			}
+
+			return normalizedScore
+		}
+	}
+
+	m.lastCandidateMatched = false
+	return 0
+}
+
+const minScore = -10000
+
+// MatchedRanges returns matches ranges for the last scored string as a flattened array of
+// [begin, end) byte offset pairs.
+func (m *Matcher) MatchedRanges() []int {
+	if len(m.pattern) == 0 || !m.lastCandidateMatched {
+		return nil
+	}
+	i, j := m.lastCandidateLen, len(m.pattern)
+	if m.scores[i][j][0].val() < minScore/2 && m.scores[i][j][1].val() < minScore/2 {
+		return nil
+	}
+
+	var ret []int
+	k := m.bestK(i, j)
+	for i > 0 {
+		take := (k == 1)
+		k = m.scores[i][j][k].prevK()
+		if take {
+			if len(ret) == 0 || ret[len(ret)-1] != i {
+				ret = append(ret, i)
+				ret = append(ret, i-1)
+			} else {
+				ret[len(ret)-1] = i - 1
+			}
+			j--
+		}
+		i--
+	}
+	// Reverse slice.
+	for i := 0; i < len(ret)/2; i++ {
+		ret[i], ret[len(ret)-1-i] = ret[len(ret)-1-i], ret[i]
+	}
+	return ret
+}
+
+func (m *Matcher) match(candidate []byte, candidateLower []byte) bool {
+	i, j := 0, 0
+	for ; i < len(candidateLower) && j < len(m.patternLower); i++ {
+		if candidateLower[i] == m.patternLower[j] {
+			j++
+		}
+	}
+	if j != len(m.patternLower) {
+		return false
+	}
+
+	// The input passes the simple test against pattern, so it is time to classify its characters.
+	// Character roles are used below to find the last segment.
+	m.roles = RuneRoles(candidate, m.rolesBuf[:])
+
+	return true
+}
+
+func (m *Matcher) computeScore(candidate []byte, candidateLower []byte) int {
+	pattLen, candLen := len(m.pattern), len(candidate)
+
+	for j := 0; j <= len(m.pattern); j++ {
+		m.scores[0][j][0] = minScore << 1
+		m.scores[0][j][1] = minScore << 1
+	}
+	m.scores[0][0][0] = score(0, 0) // Start with 0.
+
+	segmentsLeft, lastSegStart := 1, 0
+	for i := 0; i < candLen; i++ {
+		if m.roles[i] == RSep {
+			segmentsLeft++
+			lastSegStart = i + 1
+		}
+	}
+
+	// A per-character bonus for a consecutive match.
+	consecutiveBonus := 2
+	wordIdx := 0 // Word count within segment.
+	for i := 1; i <= candLen; i++ {
+
+		role := m.roles[i-1]
+		isHead := role == RHead
+
+		if isHead {
+			wordIdx++
+		} else if role == RSep && segmentsLeft > 1 {
+			wordIdx = 0
+			segmentsLeft--
+		}
+
+		var skipPenalty int
+		if i == 1 || (i-1) == lastSegStart {
+			// Skipping the start of first or last segment.
+			skipPenalty++
+		}
+
+		for j := 0; j <= pattLen; j++ {
+			// By default, we don't have a match. Fill in the skip data.
+			m.scores[i][j][1] = minScore << 1
+
+			// Compute the skip score.
+			k := 0
+			if m.scores[i-1][j][0].val() < m.scores[i-1][j][1].val() {
+				k = 1
+			}
+
+			skipScore := m.scores[i-1][j][k].val()
+			// Do not penalize missing characters after the last matched segment.
+			if j != pattLen {
+				skipScore -= skipPenalty
+			}
+			m.scores[i][j][0] = score(skipScore, k)
+
+			if j == 0 || candidateLower[i-1] != m.patternLower[j-1] {
+				// Not a match.
+				continue
+			}
+			pRole := m.patternRoles[j-1]
+
+			if role == RTail && pRole == RHead {
+				if j > 1 {
+					// Not a match: a head in the pattern matches a tail character in the candidate.
+					continue
+				}
+				// Special treatment for the first character of the pattern. We allow
+				// matches in the middle of a word if they are long enough, at least
+				// min(3, pattern.length) characters.
+				if !bytes.HasPrefix(candidateLower[i-1:], m.patternShort) {
+					continue
+				}
+			}
+
+			// Compute the char score.
+			var charScore int
+			// Bonus 1: the char is in the candidate's last segment.
+			if segmentsLeft <= 1 {
+				charScore++
+			}
+			// Bonus 2: Case match or a Head in the pattern aligns with one in the word.
+			// Single-case patterns lack segmentation signals and we assume any character
+			// can be a head of a segment.
+			if candidate[i-1] == m.pattern[j-1] || role == RHead && (!m.caseSensitive || pRole == RHead) {
+				charScore++
+			}
+
+			// Penalty 1: pattern char is Head, candidate char is Tail.
+			if role == RTail && pRole == RHead {
+				charScore--
+			}
+			// Penalty 2: first pattern character matched in the middle of a word.
+			if j == 1 && role == RTail {
+				charScore -= 4
+			}
+
+			// Third dimension encodes whether there is a gap between the previous match and the current
+			// one.
+			for k := 0; k < 2; k++ {
+				sc := m.scores[i-1][j-1][k].val() + charScore
+
+				isConsecutive := k == 1 || i-1 == 0 || i-1 == lastSegStart
+				if isConsecutive {
+					// Bonus 3: a consecutive match. First character match also gets a bonus to
+					// ensure prefix final match score normalizes to 1.0.
+					// Logically, this is a part of charScore, but we have to compute it here because it
+					// only applies for consecutive matches (k == 1).
+					sc += consecutiveBonus
+				}
+				if k == 0 {
+					// Penalty 3: Matching inside a segment (and previous char wasn't matched). Penalize for the lack
+					// of alignment.
+					if role == RTail || role == RUCTail {
+						sc -= 3
+					}
+				}
+
+				if sc > m.scores[i][j][1].val() {
+					m.scores[i][j][1] = score(sc, k)
+				}
+			}
+		}
+	}
+
+	result := m.scores[len(candidate)][len(m.pattern)][m.bestK(len(candidate), len(m.pattern))].val()
+
+	return result
+}
+
+// ScoreTable returns the score table computed for the provided candidate. Used only for debugging.
+func (m *Matcher) ScoreTable(candidate string) string {
+	var buf bytes.Buffer
+
+	var line1, line2, separator bytes.Buffer
+	line1.WriteString("\t")
+	line2.WriteString("\t")
+	for j := 0; j < len(m.pattern); j++ {
+		line1.WriteString(fmt.Sprintf("%c\t\t", m.pattern[j]))
+		separator.WriteString("----------------")
+	}
+
+	buf.WriteString(line1.String())
+	buf.WriteString("\n")
+	buf.WriteString(separator.String())
+	buf.WriteString("\n")
+
+	for i := 1; i <= len(candidate); i++ {
+		line1.Reset()
+		line2.Reset()
+
+		line1.WriteString(fmt.Sprintf("%c\t", candidate[i-1]))
+		line2.WriteString("\t")
+
+		for j := 1; j <= len(m.pattern); j++ {
+			line1.WriteString(fmt.Sprintf("M%6d(%c)\t", m.scores[i][j][0].val(), dir(m.scores[i][j][0].prevK())))
+			line2.WriteString(fmt.Sprintf("H%6d(%c)\t", m.scores[i][j][1].val(), dir(m.scores[i][j][1].prevK())))
+		}
+		buf.WriteString(line1.String())
+		buf.WriteString("\n")
+		buf.WriteString(line2.String())
+		buf.WriteString("\n")
+		buf.WriteString(separator.String())
+		buf.WriteString("\n")
+	}
+
+	return buf.String()
+}
+
+func dir(prevK int) rune {
+	if prevK == 0 {
+		return 'M'
+	}
+	return 'H'
+}
+
+func (m *Matcher) poorMatch() bool {
+	if len(m.pattern) < 2 {
+		return false
+	}
+
+	i, j := m.lastCandidateLen, len(m.pattern)
+	k := m.bestK(i, j)
+
+	var counter, len int
+	for i > 0 {
+		take := (k == 1)
+		k = m.scores[i][j][k].prevK()
+		if take {
+			len++
+			if k == 0 && len < 3 && m.roles[i-1] == RTail {
+				// Short match in the middle of a word
+				counter++
+				if counter > 1 {
+					return true
+				}
+			}
+			j--
+		} else {
+			len = 0
+		}
+		i--
+	}
+	return false
+}

vendor/golang.org/x/tools/internal/lsp/fuzzy/symbol.go

@@ -0,0 +1,236 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package fuzzy
+
+import (
+	"unicode"
+)
+
+// SymbolMatcher implements a fuzzy matching algorithm optimized for Go symbols
+// of the form:
+//  example.com/path/to/package.object.field
+//
+// Knowing that we are matching symbols like this allows us to make the
+// following optimizations:
+//  - We can incorporate right-to-left relevance directly into the score
+//    calculation.
+//  - We can match from right to left, discarding leading bytes if the input is
+//    too long.
+//  - We just take the right-most match without losing too much precision. This
+//    allows us to use an O(n) algorithm.
+//  - We can operate directly on chunked strings; in many cases we will
+//    be storing the package path and/or package name separately from the
+//    symbol or identifiers, so doing this avoids allocating strings.
+//  - We can return the index of the right-most match, allowing us to trim
+//    irrelevant qualification.
+//
+// This implementation is experimental, serving as a reference fast algorithm
+// to compare to the fuzzy algorithm implemented by Matcher.
+type SymbolMatcher struct {
+	// Using buffers of length 256 is both a reasonable size for most qualified
+	// symbols, and makes it easy to avoid bounds checks by using uint8 indexes.
+	pattern     [256]rune
+	patternLen  uint8
+	inputBuffer [256]rune   // avoid allocating when considering chunks
+	roles       [256]uint32 // which roles does a rune play (word start, etc.)
+	segments    [256]uint8  // how many segments from the right is each rune
+}
+
+const (
+	segmentStart uint32 = 1 << iota
+	wordStart
+	separator
+)
+
+// NewSymbolMatcher creates a SymbolMatcher that may be used to match the given
+// search pattern.
+//
+// Currently this matcher only accepts case-insensitive fuzzy patterns.
+//
+// An empty pattern matches no input.
+func NewSymbolMatcher(pattern string) *SymbolMatcher {
+	m := &SymbolMatcher{}
+	for _, p := range pattern {
+		m.pattern[m.patternLen] = unicode.ToLower(p)
+		m.patternLen++
+		if m.patternLen == 255 || int(m.patternLen) == len(pattern) {
+			// break at 255 so that we can represent patternLen with a uint8.
+			break
+		}
+	}
+	return m
+}
+
+// Match looks for the right-most match of the search pattern within the symbol
+// represented by concatenating the given chunks, returning its offset and
+// score.
+//
+// If a match is found, the first return value will hold the absolute byte
+// offset within all chunks for the start of the symbol. In other words, the
+// index of the match within strings.Join(chunks, ""). If no match is found,
+// the first return value will be -1.
+//
+// The second return value will be the score of the match, which is always
+// between 0 and 1, inclusive. A score of 0 indicates no match.
+func (m *SymbolMatcher) Match(chunks []string) (int, float64) {
+	// Explicit behavior for an empty pattern.
+	//
+	// As a minor optimization, this also avoids nilness checks later on, since
+	// the compiler can prove that m != nil.
+	if m.patternLen == 0 {
+		return -1, 0
+	}
+
+	// First phase: populate the input buffer with lower-cased runes.
+	//
+	// We could also check for a forward match here, but since we'd have to write
+	// the entire input anyway this has negligible impact on performance.
+
+	var (
+		inputLen  = uint8(0)
+		modifiers = wordStart | segmentStart
+	)
+
+input:
+	for _, chunk := range chunks {
+		for _, r := range chunk {
+			if r == '.' || r == '/' {
+				modifiers |= separator
+			}
+			// optimization: avoid calls to unicode.ToLower, which can't be inlined.
+			l := r
+			if r <= unicode.MaxASCII {
+				if 'A' <= r && r <= 'Z' {
+					l = r + 'a' - 'A'
+				}
+			} else {
+				l = unicode.ToLower(r)
+			}
+			if l != r {
+				modifiers |= wordStart
+			}
+			m.inputBuffer[inputLen] = l
+			m.roles[inputLen] = modifiers
+			inputLen++
+			if m.roles[inputLen-1]&separator != 0 {
+				modifiers = wordStart | segmentStart
+			} else {
+				modifiers = 0
+			}
+			// TODO: we should prefer the right-most input if it overflows, rather
+			//       than the left-most as we're doing here.
+			if inputLen == 255 {
+				break input
+			}
+		}
+	}
+
+	// Second phase: find the right-most match, and count segments from the
+	// right.
+
+	var (
+		pi    = uint8(m.patternLen - 1) // pattern index
+		p     = m.pattern[pi]           // pattern rune
+		start = -1                      // start offset of match
+		rseg  = uint8(0)
+	)
+	const maxSeg = 3 // maximum number of segments from the right to count, for scoring purposes.
+
+	for ii := inputLen - 1; ; ii-- {
+		r := m.inputBuffer[ii]
+		if rseg < maxSeg && m.roles[ii]&separator != 0 {
+			rseg++
+		}
+		m.segments[ii] = rseg
+		if p == r {
+			if pi == 0 {
+				start = int(ii)
+				break
+			}
+			pi--
+			p = m.pattern[pi]
+		}
+		// Don't check ii >= 0 in the loop condition: ii is a uint8.
+		if ii == 0 {
+			break
+		}
+	}
+
+	if start < 0 {
+		// no match: skip scoring
+		return -1, 0
+	}
+
+	// Third phase: find the shortest match, and compute the score.
+
+	// Score is the average score for each character.
+	//
+	// A character score is the multiple of:
+	//   1. 1.0 if the character starts a segment, .8 if the character start a
+	//      mid-segment word, otherwise 0.6. This carries over to immediately
+	//      following characters.
+	//   2. For the final character match, the multiplier from (1) is reduced to
+	//     .8 if the next character in the input is a mid-segment word, or 0.6 if
+	//      the next character in the input is not a word or segment start. This
+	//      ensures that we favor whole-word or whole-segment matches over prefix
+	//      matches.
+	//   3. 1.0 if the character is part of the last segment, otherwise
+	//      1.0-.2*<segments from the right>, with a max segment count of 3.
+	//
+	// This is a very naive algorithm, but it is fast. There's lots of prior art
+	// here, and we should leverage it. For example, we could explicitly consider
+	// character distance, and exact matches of words or segments.
+	//
+	// Also note that this might not actually find the highest scoring match, as
+	// doing so could require a non-linear algorithm, depending on how the score
+	// is calculated.
+
+	pi = 0
+	p = m.pattern[pi]
+
+	const (
+		segStreak  = 1.0
+		wordStreak = 0.8
+		noStreak   = 0.6
+		perSegment = 0.2 // we count at most 3 segments above
+	)
+
+	streakBonus := noStreak
+	totScore := 0.0
+	for ii := uint8(start); ii < inputLen; ii++ {
+		r := m.inputBuffer[ii]
+		if r == p {
+			pi++
+			p = m.pattern[pi]
+			// Note: this could be optimized with some bit operations.
+			switch {
+			case m.roles[ii]&segmentStart != 0 && segStreak > streakBonus:
+				streakBonus = segStreak
+			case m.roles[ii]&wordStart != 0 && wordStreak > streakBonus:
+				streakBonus = wordStreak
+			}
+			finalChar := pi >= m.patternLen
+			// finalCost := 1.0
+			if finalChar && streakBonus > noStreak {
+				switch {
+				case ii == inputLen-1 || m.roles[ii+1]&segmentStart != 0:
+					// Full segment: no reduction
+				case m.roles[ii+1]&wordStart != 0:
+					streakBonus = wordStreak
+				default:
+					streakBonus = noStreak
+				}
+			}
+			totScore += streakBonus * (1.0 - float64(m.segments[ii])*perSegment)
+			if finalChar {
+				break
+			}
+		} else {
+			streakBonus = noStreak
+		}
+	}
+
+	return start, totScore / float64(m.patternLen)
+}

vendor/golang.org/x/tools/internal/typeparams/common.go

@@ -2,24 +2,179 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Package typeparams provides functions to work indirectly with type parameter
-// data stored in go/ast and go/types objects, while these API are guarded by a
-// build constraint.
+// Package typeparams contains common utilities for writing tools that interact
+// with generic Go code, as introduced with Go 1.18.
 //
-// This package exists to make it easier for tools to work with generic code,
-// while also compiling against older Go versions.
+// Many of the types and functions in this package are proxies for the new APIs
+// introduced in the standard library with Go 1.18. For example, the
+// typeparams.Union type is an alias for go/types.Union, and the ForTypeSpec
+// function returns the value of the go/ast.TypeSpec.TypeParams field. At Go
+// versions older than 1.18 these helpers are implemented as stubs, allowing
+// users of this package to write code that handles generic constructs inline,
+// even if the Go version being used to compile does not support generics.
+//
+// Additionally, this package contains common utilities for working with the
+// new generic constructs, to supplement the standard library APIs. Notably,
+// the StructuralTerms API computes a minimal representation of the structural
+// restrictions on a type parameter. In the future, this API may be available
+// from go/types.
+//
+// See the example/README.md for a more detailed guide on how to update tools
+// to support generics.
 package typeparams
 
 import (
 	"go/ast"
 	"go/token"
+	"go/types"
 )
 
-// A IndexExprData holds data from both ast.IndexExpr and the new
-// ast.MultiIndexExpr, which was introduced in Go 1.18.
-type IndexExprData struct {
-	X       ast.Expr   // expression
-	Lbrack  token.Pos  // position of "["
-	Indices []ast.Expr // index expressions
-	Rbrack  token.Pos  // position of "]"
+// UnpackIndexExpr extracts data from AST nodes that represent index
+// expressions.
+//
+// For an ast.IndexExpr, the resulting indices slice will contain exactly one
+// index expression. For an ast.IndexListExpr (go1.18+), it may have a variable
+// number of index expressions.
+//
+// For nodes that don't represent index expressions, the first return value of
+// UnpackIndexExpr will be nil.
+func UnpackIndexExpr(n ast.Node) (x ast.Expr, lbrack token.Pos, indices []ast.Expr, rbrack token.Pos) {
+	switch e := n.(type) {
+	case *ast.IndexExpr:
+		return e.X, e.Lbrack, []ast.Expr{e.Index}, e.Rbrack
+	case *IndexListExpr:
+		return e.X, e.Lbrack, e.Indices, e.Rbrack
+	}
+	return nil, token.NoPos, nil, token.NoPos
+}
+
+// PackIndexExpr returns an *ast.IndexExpr or *ast.IndexListExpr, depending on
+// the cardinality of indices. Calling PackIndexExpr with len(indices) == 0
+// will panic.
+func PackIndexExpr(x ast.Expr, lbrack token.Pos, indices []ast.Expr, rbrack token.Pos) ast.Expr {
+	switch len(indices) {
+	case 0:
+		panic("empty indices")
+	case 1:
+		return &ast.IndexExpr{
+			X:      x,
+			Lbrack: lbrack,
+			Index:  indices[0],
+			Rbrack: rbrack,
+		}
+	default:
+		return &IndexListExpr{
+			X:       x,
+			Lbrack:  lbrack,
+			Indices: indices,
+			Rbrack:  rbrack,
+		}
+	}
+}
+
+// IsTypeParam reports whether t is a type parameter.
+func IsTypeParam(t types.Type) bool {
+	_, ok := t.(*TypeParam)
+	return ok
+}
+
+// OriginMethod returns the origin method associated with the method fn.
+// For methods on a non-generic receiver base type, this is just
+// fn. However, for methods with a generic receiver, OriginMethod returns the
+// corresponding method in the method set of the origin type.
+//
+// As a special case, if fn is not a method (has no receiver), OriginMethod
+// returns fn.
+func OriginMethod(fn *types.Func) *types.Func {
+	recv := fn.Type().(*types.Signature).Recv()
+	if recv == nil {
+
+		return fn
+	}
+	base := recv.Type()
+	p, isPtr := base.(*types.Pointer)
+	if isPtr {
+		base = p.Elem()
+	}
+	named, isNamed := base.(*types.Named)
+	if !isNamed {
+		// Receiver is a *types.Interface.
+		return fn
+	}
+	if ForNamed(named).Len() == 0 {
+		// Receiver base has no type parameters, so we can avoid the lookup below.
+		return fn
+	}
+	orig := NamedTypeOrigin(named)
+	gfn, _, _ := types.LookupFieldOrMethod(orig, true, fn.Pkg(), fn.Name())
+	return gfn.(*types.Func)
+}
+
+// GenericAssignableTo is a generalization of types.AssignableTo that
+// implements the following rule for uninstantiated generic types:
+//
+// If V and T are generic named types, then V is considered assignable to T if,
+// for every possible instantation of V[A_1, ..., A_N], the instantiation
+// T[A_1, ..., A_N] is valid and V[A_1, ..., A_N] implements T[A_1, ..., A_N].
+//
+// If T has structural constraints, they must be satisfied by V.
+//
+// For example, consider the following type declarations:
+//
+//  type Interface[T any] interface {
+//  	Accept(T)
+//  }
+//
+//  type Container[T any] struct {
+//  	Element T
+//  }
+//
+//  func (c Container[T]) Accept(t T) { c.Element = t }
+//
+// In this case, GenericAssignableTo reports that instantiations of Container
+// are assignable to the corresponding instantiation of Interface.
+func GenericAssignableTo(ctxt *Context, V, T types.Type) bool {
+	// If V and T are not both named, or do not have matching non-empty type
+	// parameter lists, fall back on types.AssignableTo.
+
+	VN, Vnamed := V.(*types.Named)
+	TN, Tnamed := T.(*types.Named)
+	if !Vnamed || !Tnamed {
+		return types.AssignableTo(V, T)
+	}
+
+	vtparams := ForNamed(VN)
+	ttparams := ForNamed(TN)
+	if vtparams.Len() == 0 || vtparams.Len() != ttparams.Len() || NamedTypeArgs(VN).Len() != 0 || NamedTypeArgs(TN).Len() != 0 {
+		return types.AssignableTo(V, T)
+	}
+
+	// V and T have the same (non-zero) number of type params. Instantiate both
+	// with the type parameters of V. This must always succeed for V, and will
+	// succeed for T if and only if the type set of each type parameter of V is a
+	// subset of the type set of the corresponding type parameter of T, meaning
+	// that every instantiation of V corresponds to a valid instantiation of T.
+
+	// Minor optimization: ensure we share a context across the two
+	// instantiations below.
+	if ctxt == nil {
+		ctxt = NewContext()
+	}
+
+	var targs []types.Type
+	for i := 0; i < vtparams.Len(); i++ {
+		targs = append(targs, vtparams.At(i))
+	}
+
+	vinst, err := Instantiate(ctxt, V, targs, true)
+	if err != nil {
+		panic("type parameters should satisfy their own constraints")
+	}
+
+	tinst, err := Instantiate(ctxt, T, targs, true)
+	if err != nil {
+		return false
+	}
+
+	return types.AssignableTo(vinst, tinst)
 }

vendor/golang.org/x/tools/internal/typeparams/enabled_go117.go

@@ -0,0 +1,12 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build !go1.18
+// +build !go1.18
+
+package typeparams
+
+// Enabled reports whether type parameters are enabled in the current build
+// environment.
+const Enabled = false

vendor/golang.org/x/tools/internal/typeparams/enabled_go118.go

@@ -0,0 +1,15 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build go1.18
+// +build go1.18
+
+package typeparams
+
+// Note: this constant is in a separate file as this is the only acceptable
+// diff between the <1.18 API of this package and the 1.18 API.
+
+// Enabled reports whether type parameters are enabled in the current build
+// environment.
+const Enabled = true

vendor/golang.org/x/tools/internal/typeparams/normalize.go

@@ -0,0 +1,216 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package typeparams
+
+import (
+	"errors"
+	"fmt"
+	"go/types"
+	"os"
+	"strings"
+)
+
+//go:generate go run copytermlist.go
+
+const debug = false
+
+var ErrEmptyTypeSet = errors.New("empty type set")
+
+// StructuralTerms returns a slice of terms representing the normalized
+// structural type restrictions of a type parameter, if any.
+//
+// Structural type restrictions of a type parameter are created via
+// non-interface types embedded in its constraint interface (directly, or via a
+// chain of interface embeddings). For example, in the declaration
+//  type T[P interface{~int; m()}] int
+// the structural restriction of the type parameter P is ~int.
+//
+// With interface embedding and unions, the specification of structural type
+// restrictions may be arbitrarily complex. For example, consider the
+// following:
+//
+//  type A interface{ ~string|~[]byte }
+//
+//  type B interface{ int|string }
+//
+//  type C interface { ~string|~int }
+//
+//  type T[P interface{ A|B; C }] int
+//
+// In this example, the structural type restriction of P is ~string|int: A|B
+// expands to ~string|~[]byte|int|string, which reduces to ~string|~[]byte|int,
+// which when intersected with C (~string|~int) yields ~string|int.
+//
+// StructuralTerms computes these expansions and reductions, producing a
+// "normalized" form of the embeddings. A structural restriction is normalized
+// if it is a single union containing no interface terms, and is minimal in the
+// sense that removing any term changes the set of types satisfying the
+// constraint. It is left as a proof for the reader that, modulo sorting, there
+// is exactly one such normalized form.
+//
+// Because the minimal representation always takes this form, StructuralTerms
+// returns a slice of tilde terms corresponding to the terms of the union in
+// the normalized structural restriction. An error is returned if the
+// constraint interface is invalid, exceeds complexity bounds, or has an empty
+// type set. In the latter case, StructuralTerms returns ErrEmptyTypeSet.
+//
+// StructuralTerms makes no guarantees about the order of terms, except that it
+// is deterministic.
+func StructuralTerms(tparam *TypeParam) ([]*Term, error) {
+	constraint := tparam.Constraint()
+	if constraint == nil {
+		return nil, fmt.Errorf("%s has nil constraint", tparam)
+	}
+	iface, _ := constraint.Underlying().(*types.Interface)
+	if iface == nil {
+		return nil, fmt.Errorf("constraint is %T, not *types.Interface", constraint.Underlying())
+	}
+	return InterfaceTermSet(iface)
+}
+
+// InterfaceTermSet computes the normalized terms for a constraint interface,
+// returning an error if the term set cannot be computed or is empty. In the
+// latter case, the error will be ErrEmptyTypeSet.
+//
+// See the documentation of StructuralTerms for more information on
+// normalization.
+func InterfaceTermSet(iface *types.Interface) ([]*Term, error) {
+	return computeTermSet(iface)
+}
+
+// UnionTermSet computes the normalized terms for a union, returning an error
+// if the term set cannot be computed or is empty. In the latter case, the
+// error will be ErrEmptyTypeSet.
+//
+// See the documentation of StructuralTerms for more information on
+// normalization.
+func UnionTermSet(union *Union) ([]*Term, error) {
+	return computeTermSet(union)
+}
+
+func computeTermSet(typ types.Type) ([]*Term, error) {
+	tset, err := computeTermSetInternal(typ, make(map[types.Type]*termSet), 0)
+	if err != nil {
+		return nil, err
+	}
+	if tset.terms.isEmpty() {
+		return nil, ErrEmptyTypeSet
+	}
+	if tset.terms.isAll() {
+		return nil, nil
+	}
+	var terms []*Term
+	for _, term := range tset.terms {
+		terms = append(terms, NewTerm(term.tilde, term.typ))
+	}
+	return terms, nil
+}
+
+// A termSet holds the normalized set of terms for a given type.
+//
+// The name termSet is intentionally distinct from 'type set': a type set is
+// all types that implement a type (and includes method restrictions), whereas
+// a term set just represents the structural restrictions on a type.
+type termSet struct {
+	complete bool
+	terms    termlist
+}
+
+func indentf(depth int, format string, args ...interface{}) {
+	fmt.Fprintf(os.Stderr, strings.Repeat(".", depth)+format+"\n", args...)
+}
+
+func computeTermSetInternal(t types.Type, seen map[types.Type]*termSet, depth int) (res *termSet, err error) {
+	if t == nil {
+		panic("nil type")
+	}
+
+	if debug {
+		indentf(depth, "%s", t.String())
+		defer func() {
+			if err != nil {
+				indentf(depth, "=> %s", err)
+			} else {
+				indentf(depth, "=> %s", res.terms.String())
+			}
+		}()
+	}
+
+	const maxTermCount = 100
+	if tset, ok := seen[t]; ok {
+		if !tset.complete {
+			return nil, fmt.Errorf("cycle detected in the declaration of %s", t)
+		}
+		return tset, nil
+	}
+
+	// Mark the current type as seen to avoid infinite recursion.
+	tset := new(termSet)
+	defer func() {
+		tset.complete = true
+	}()
+	seen[t] = tset
+
+	switch u := t.Underlying().(type) {
+	case *types.Interface:
+		// The term set of an interface is the intersection of the term sets of its
+		// embedded types.
+		tset.terms = allTermlist
+		for i := 0; i < u.NumEmbeddeds(); i++ {
+			embedded := u.EmbeddedType(i)
+			if _, ok := embedded.Underlying().(*TypeParam); ok {
+				return nil, fmt.Errorf("invalid embedded type %T", embedded)
+			}
+			tset2, err := computeTermSetInternal(embedded, seen, depth+1)
+			if err != nil {
+				return nil, err
+			}
+			tset.terms = tset.terms.intersect(tset2.terms)
+		}
+	case *Union:
+		// The term set of a union is the union of term sets of its terms.
+		tset.terms = nil
+		for i := 0; i < u.Len(); i++ {
+			t := u.Term(i)
+			var terms termlist
+			switch t.Type().Underlying().(type) {
+			case *types.Interface:
+				tset2, err := computeTermSetInternal(t.Type(), seen, depth+1)
+				if err != nil {
+					return nil, err
+				}
+				terms = tset2.terms
+			case *TypeParam, *Union:
+				// A stand-alone type parameter or union is not permitted as union
+				// term.
+				return nil, fmt.Errorf("invalid union term %T", t)
+			default:
+				if t.Type() == types.Typ[types.Invalid] {
+					continue
+				}
+				terms = termlist{{t.Tilde(), t.Type()}}
+			}
+			tset.terms = tset.terms.union(terms)
+			if len(tset.terms) > maxTermCount {
+				return nil, fmt.Errorf("exceeded max term count %d", maxTermCount)
+			}
+		}
+	case *TypeParam:
+		panic("unreachable")
+	default:
+		// For all other types, the term set is just a single non-tilde term
+		// holding the type itself.
+		if u != types.Typ[types.Invalid] {
+			tset.terms = termlist{{false, t}}
+		}
+	}
+	return tset, nil
+}
+
+// under is a facade for the go/types internal function of the same name. It is
+// used by typeterm.go.
+func under(t types.Type) types.Type {
+	return t.Underlying()
+}

vendor/golang.org/x/tools/internal/typeparams/notypeparams.go

@@ -1,93 +0,0 @@
-// Copyright 2021 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build !typeparams || !go1.18
-// +build !typeparams !go1.18
-
-package typeparams
-
-import (
-	"go/ast"
-	"go/types"
-)
-
-// NOTE: doc comments must be kept in sync with typeparams.go.
-
-// Enabled reports whether type parameters are enabled in the current build
-// environment.
-const Enabled = false
-
-// GetIndexExprData extracts data from AST nodes that represent index
-// expressions.
-//
-// For an ast.IndexExpr, the resulting IndexExprData will have exactly one
-// index expression. For an ast.MultiIndexExpr (go1.18+), it may have a
-// variable number of index expressions.
-//
-// For nodes that don't represent index expressions, GetIndexExprData returns
-// nil.
-func GetIndexExprData(n ast.Node) *IndexExprData {
-	if e, _ := n.(*ast.IndexExpr); e != nil {
-		return &IndexExprData{
-			X:       e.X,
-			Lbrack:  e.Lbrack,
-			Indices: []ast.Expr{e.Index},
-			Rbrack:  e.Rbrack,
-		}
-	}
-	return nil
-}
-
-// ForTypeDecl extracts the (possibly nil) type parameter node list from n.
-func ForTypeDecl(*ast.TypeSpec) *ast.FieldList {
-	return nil
-}
-
-// ForFuncDecl extracts the (possibly nil) type parameter node list from n.
-func ForFuncDecl(*ast.FuncDecl) *ast.FieldList {
-	return nil
-}
-
-// ForSignature extracts the (possibly empty) type parameter object list from
-// sig.
-func ForSignature(*types.Signature) []*types.TypeName {
-	return nil
-}
-
-// IsComparable reports if iface is the comparable interface.
-func IsComparable(*types.Interface) bool {
-	return false
-}
-
-// IsConstraint reports whether iface may only be used as a type parameter
-// constraint (i.e. has a type set or is the comparable interface).
-func IsConstraint(*types.Interface) bool {
-	return false
-}
-
-// ForNamed extracts the (possibly empty) type parameter object list from
-// named.
-func ForNamed(*types.Named) []*types.TypeName {
-	return nil
-}
-
-// NamedTArgs extracts the (possibly empty) type argument list from named.
-func NamedTArgs(*types.Named) []types.Type {
-	return nil
-}
-
-// InitInferred initializes info to record inferred type information.
-func InitInferred(*types.Info) {
-}
-
-// GetInferred extracts inferred type information from info for e.
-//
-// The expression e may have an inferred type if it is an *ast.IndexExpr
-// representing partial instantiation of a generic function type for which type
-// arguments have been inferred using constraint type inference, or if it is an
-// *ast.CallExpr for which type type arguments have be inferred using both
-// constraint type inference and function argument inference.
-func GetInferred(*types.Info, ast.Expr) ([]types.Type, *types.Signature) {
-	return nil, nil
-}

vendor/golang.org/x/tools/internal/typeparams/termlist.go

@@ -0,0 +1,172 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Code generated by copytermlist.go DO NOT EDIT.
+
+package typeparams
+
+import (
+	"bytes"
+	"go/types"
+)
+
+// A termlist represents the type set represented by the union
+// t1 ∪ y2 ∪ ... tn of the type sets of the terms t1 to tn.
+// A termlist is in normal form if all terms are disjoint.
+// termlist operations don't require the operands to be in
+// normal form.
+type termlist []*term
+
+// allTermlist represents the set of all types.
+// It is in normal form.
+var allTermlist = termlist{new(term)}
+
+// String prints the termlist exactly (without normalization).
+func (xl termlist) String() string {
+	if len(xl) == 0 {
+		return "∅"
+	}
+	var buf bytes.Buffer
+	for i, x := range xl {
+		if i > 0 {
+			buf.WriteString(" ∪ ")
+		}
+		buf.WriteString(x.String())
+	}
+	return buf.String()
+}
+
+// isEmpty reports whether the termlist xl represents the empty set of types.
+func (xl termlist) isEmpty() bool {
+	// If there's a non-nil term, the entire list is not empty.
+	// If the termlist is in normal form, this requires at most
+	// one iteration.
+	for _, x := range xl {
+		if x != nil {
+			return false
+		}
+	}
+	return true
+}
+
+// isAll reports whether the termlist xl represents the set of all types.
+func (xl termlist) isAll() bool {
+	// If there's a 𝓤 term, the entire list is 𝓤.
+	// If the termlist is in normal form, this requires at most
+	// one iteration.
+	for _, x := range xl {
+		if x != nil && x.typ == nil {
+			return true
+		}
+	}
+	return false
+}
+
+// norm returns the normal form of xl.
+func (xl termlist) norm() termlist {
+	// Quadratic algorithm, but good enough for now.
+	// TODO(gri) fix asymptotic performance
+	used := make([]bool, len(xl))
+	var rl termlist
+	for i, xi := range xl {
+		if xi == nil || used[i] {
+			continue
+		}
+		for j := i + 1; j < len(xl); j++ {
+			xj := xl[j]
+			if xj == nil || used[j] {
+				continue
+			}
+			if u1, u2 := xi.union(xj); u2 == nil {
+				// If we encounter a 𝓤 term, the entire list is 𝓤.
+				// Exit early.
+				// (Note that this is not just an optimization;
+				// if we continue, we may end up with a 𝓤 term
+				// and other terms and the result would not be
+				// in normal form.)
+				if u1.typ == nil {
+					return allTermlist
+				}
+				xi = u1
+				used[j] = true // xj is now unioned into xi - ignore it in future iterations
+			}
+		}
+		rl = append(rl, xi)
+	}
+	return rl
+}
+
+// If the type set represented by xl is specified by a single (non-𝓤) term,
+// structuralType returns that type. Otherwise it returns nil.
+func (xl termlist) structuralType() types.Type {
+	if nl := xl.norm(); len(nl) == 1 {
+		return nl[0].typ // if nl.isAll() then typ is nil, which is ok
+	}
+	return nil
+}
+
+// union returns the union xl ∪ yl.
+func (xl termlist) union(yl termlist) termlist {
+	return append(xl, yl...).norm()
+}
+
+// intersect returns the intersection xl ∩ yl.
+func (xl termlist) intersect(yl termlist) termlist {
+	if xl.isEmpty() || yl.isEmpty() {
+		return nil
+	}
+
+	// Quadratic algorithm, but good enough for now.
+	// TODO(gri) fix asymptotic performance
+	var rl termlist
+	for _, x := range xl {
+		for _, y := range yl {
+			if r := x.intersect(y); r != nil {
+				rl = append(rl, r)
+			}
+		}
+	}
+	return rl.norm()
+}
+
+// equal reports whether xl and yl represent the same type set.
+func (xl termlist) equal(yl termlist) bool {
+	// TODO(gri) this should be more efficient
+	return xl.subsetOf(yl) && yl.subsetOf(xl)
+}
+
+// includes reports whether t ∈ xl.
+func (xl termlist) includes(t types.Type) bool {
+	for _, x := range xl {
+		if x.includes(t) {
+			return true
+		}
+	}
+	return false
+}
+
+// supersetOf reports whether y ⊆ xl.
+func (xl termlist) supersetOf(y *term) bool {
+	for _, x := range xl {
+		if y.subsetOf(x) {
+			return true
+		}
+	}
+	return false
+}
+
+// subsetOf reports whether xl ⊆ yl.
+func (xl termlist) subsetOf(yl termlist) bool {
+	if yl.isEmpty() {
+		return xl.isEmpty()
+	}
+
+	// each term x of xl must be a subset of yl
+	for _, x := range xl {
+		if !yl.supersetOf(x) {
+			return false // x is not a subset yl
+		}
+	}
+	return true
+}

vendor/golang.org/x/tools/internal/typeparams/typeparams.go

@@ -1,125 +0,0 @@
-// Copyright 2021 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build typeparams && go1.18
-// +build typeparams,go1.18
-
-package typeparams
-
-import (
-	"go/ast"
-	"go/types"
-)
-
-// NOTE: doc comments must be kept in sync with notypeparams.go.
-
-// Enabled reports whether type parameters are enabled in the current build
-// environment.
-const Enabled = true
-
-// GetIndexExprData extracts data from AST nodes that represent index
-// expressions.
-//
-// For an ast.IndexExpr, the resulting IndexExprData will have exactly one
-// index expression. For an ast.MultiIndexExpr (go1.18+), it may have a
-// variable number of index expressions.
-//
-// For nodes that don't represent index expressions, GetIndexExprData returns
-// nil.
-func GetIndexExprData(n ast.Node) *IndexExprData {
-	switch e := n.(type) {
-	case *ast.IndexExpr:
-		return &IndexExprData{
-			X:       e.X,
-			Lbrack:  e.Lbrack,
-			Indices: []ast.Expr{e.Index},
-			Rbrack:  e.Rbrack,
-		}
-	case *ast.MultiIndexExpr:
-		return (*IndexExprData)(e)
-	}
-	return nil
-}
-
-// ForTypeDecl extracts the (possibly nil) type parameter node list from n.
-func ForTypeDecl(n *ast.TypeSpec) *ast.FieldList {
-	return n.TParams
-}
-
-// ForFuncDecl extracts the (possibly nil) type parameter node list from n.
-func ForFuncDecl(n *ast.FuncDecl) *ast.FieldList {
-	if n.Type != nil {
-		return n.Type.TParams
-	}
-	return nil
-}
-
-// ForSignature extracts the (possibly empty) type parameter object list from
-// sig.
-func ForSignature(sig *types.Signature) []*types.TypeName {
-	return tparamsSlice(sig.TParams())
-}
-
-// IsComparable reports if iface is the comparable interface.
-func IsComparable(iface *types.Interface) bool {
-	return iface.IsComparable()
-}
-
-// IsConstraint reports whether iface may only be used as a type parameter
-// constraint (i.e. has a type set or is the comparable interface).
-func IsConstraint(iface *types.Interface) bool {
-	return iface.IsConstraint()
-}
-
-// ForNamed extracts the (possibly empty) type parameter object list from
-// named.
-func ForNamed(named *types.Named) []*types.TypeName {
-	return tparamsSlice(named.TParams())
-}
-
-func tparamsSlice(tparams *types.TypeParams) []*types.TypeName {
-	if tparams.Len() == 0 {
-		return nil
-	}
-	result := make([]*types.TypeName, tparams.Len())
-	for i := 0; i < tparams.Len(); i++ {
-		result[i] = tparams.At(i)
-	}
-	return result
-}
-
-// NamedTArgs extracts the (possibly empty) type argument list from named.
-func NamedTArgs(named *types.Named) []types.Type {
-	ntargs := named.NumTArgs()
-	if ntargs == 0 {
-		return nil
-	}
-
-	targs := make([]types.Type, ntargs)
-	for i := 0; i < ntargs; i++ {
-		targs[i] = named.TArg(i)
-	}
-
-	return targs
-}
-
-// InitInferred initializes info to record inferred type information.
-func InitInferred(info *types.Info) {
-	info.Inferred = make(map[ast.Expr]types.Inferred)
-}
-
-// GetInferred extracts inferred type information from info for e.
-//
-// The expression e may have an inferred type if it is an *ast.IndexExpr
-// representing partial instantiation of a generic function type for which type
-// arguments have been inferred using constraint type inference, or if it is an
-// *ast.CallExpr for which type type arguments have be inferred using both
-// constraint type inference and function argument inference.
-func GetInferred(info *types.Info, e ast.Expr) ([]types.Type, *types.Signature) {
-	if info.Inferred == nil {
-		return nil, nil
-	}
-	inf := info.Inferred[e]
-	return inf.TArgs, inf.Sig
-}

vendor/golang.org/x/tools/internal/typeparams/typeparams_go117.go

@@ -0,0 +1,197 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build !go1.18
+// +build !go1.18
+
+package typeparams
+
+import (
+	"go/ast"
+	"go/token"
+	"go/types"
+)
+
+func unsupported() {
+	panic("type parameters are unsupported at this go version")
+}
+
+// IndexListExpr is a placeholder type, as type parameters are not supported at
+// this Go version. Its methods panic on use.
+type IndexListExpr struct {
+	ast.Expr
+	X       ast.Expr   // expression
+	Lbrack  token.Pos  // position of "["
+	Indices []ast.Expr // index expressions
+	Rbrack  token.Pos  // position of "]"
+}
+
+// ForTypeSpec returns an empty field list, as type parameters on not supported
+// at this Go version.
+func ForTypeSpec(*ast.TypeSpec) *ast.FieldList {
+	return nil
+}
+
+// ForFuncType returns an empty field list, as type parameters are not
+// supported at this Go version.
+func ForFuncType(*ast.FuncType) *ast.FieldList {
+	return nil
+}
+
+// TypeParam is a placeholder type, as type parameters are not supported at
+// this Go version. Its methods panic on use.
+type TypeParam struct{ types.Type }
+
+func (*TypeParam) Index() int             { unsupported(); return 0 }
+func (*TypeParam) Constraint() types.Type { unsupported(); return nil }
+func (*TypeParam) Obj() *types.TypeName   { unsupported(); return nil }
+
+// TypeParamList is a placeholder for an empty type parameter list.
+type TypeParamList struct{}
+
+func (*TypeParamList) Len() int          { return 0 }
+func (*TypeParamList) At(int) *TypeParam { unsupported(); return nil }
+
+// TypeList is a placeholder for an empty type list.
+type TypeList struct{}
+
+func (*TypeList) Len() int          { return 0 }
+func (*TypeList) At(int) types.Type { unsupported(); return nil }
+
+// NewTypeParam is unsupported at this Go version, and panics.
+func NewTypeParam(name *types.TypeName, constraint types.Type) *TypeParam {
+	unsupported()
+	return nil
+}
+
+// SetTypeParamConstraint is unsupported at this Go version, and panics.
+func SetTypeParamConstraint(tparam *TypeParam, constraint types.Type) {
+	unsupported()
+}
+
+// NewSignatureType calls types.NewSignature, panicking if recvTypeParams or
+// typeParams is non-empty.
+func NewSignatureType(recv *types.Var, recvTypeParams, typeParams []*TypeParam, params, results *types.Tuple, variadic bool) *types.Signature {
+	if len(recvTypeParams) != 0 || len(typeParams) != 0 {
+		panic("signatures cannot have type parameters at this Go version")
+	}
+	return types.NewSignature(recv, params, results, variadic)
+}
+
+// ForSignature returns an empty slice.
+func ForSignature(*types.Signature) *TypeParamList {
+	return nil
+}
+
+// RecvTypeParams returns a nil slice.
+func RecvTypeParams(sig *types.Signature) *TypeParamList {
+	return nil
+}
+
+// IsComparable returns false, as no interfaces are type-restricted at this Go
+// version.
+func IsComparable(*types.Interface) bool {
+	return false
+}
+
+// IsMethodSet returns true, as no interfaces are type-restricted at this Go
+// version.
+func IsMethodSet(*types.Interface) bool {
+	return true
+}
+
+// IsImplicit returns false, as no interfaces are implicit at this Go version.
+func IsImplicit(*types.Interface) bool {
+	return false
+}
+
+// MarkImplicit does nothing, because this Go version does not have implicit
+// interfaces.
+func MarkImplicit(*types.Interface) {}
+
+// ForNamed returns an empty type parameter list, as type parameters are not
+// supported at this Go version.
+func ForNamed(*types.Named) *TypeParamList {
+	return nil
+}
+
+// SetForNamed panics if tparams is non-empty.
+func SetForNamed(_ *types.Named, tparams []*TypeParam) {
+	if len(tparams) > 0 {
+		unsupported()
+	}
+}
+
+// NamedTypeArgs returns nil.
+func NamedTypeArgs(*types.Named) *TypeList {
+	return nil
+}
+
+// NamedTypeOrigin is the identity method at this Go version.
+func NamedTypeOrigin(named *types.Named) types.Type {
+	return named
+}
+
+// Term holds information about a structural type restriction.
+type Term struct {
+	tilde bool
+	typ   types.Type
+}
+
+func (m *Term) Tilde() bool      { return m.tilde }
+func (m *Term) Type() types.Type { return m.typ }
+func (m *Term) String() string {
+	pre := ""
+	if m.tilde {
+		pre = "~"
+	}
+	return pre + m.typ.String()
+}
+
+// NewTerm is unsupported at this Go version, and panics.
+func NewTerm(tilde bool, typ types.Type) *Term {
+	return &Term{tilde, typ}
+}
+
+// Union is a placeholder type, as type parameters are not supported at this Go
+// version. Its methods panic on use.
+type Union struct{ types.Type }
+
+func (*Union) Len() int         { return 0 }
+func (*Union) Term(i int) *Term { unsupported(); return nil }
+
+// NewUnion is unsupported at this Go version, and panics.
+func NewUnion(terms []*Term) *Union {
+	unsupported()
+	return nil
+}
+
+// InitInstanceInfo is a noop at this Go version.
+func InitInstanceInfo(*types.Info) {}
+
+// Instance is a placeholder type, as type parameters are not supported at this
+// Go version.
+type Instance struct {
+	TypeArgs *TypeList
+	Type     types.Type
+}
+
+// GetInstances returns a nil map, as type parameters are not supported at this
+// Go version.
+func GetInstances(info *types.Info) map[*ast.Ident]Instance { return nil }
+
+// Context is a placeholder type, as type parameters are not supported at
+// this Go version.
+type Context struct{}
+
+// NewContext returns a placeholder Context instance.
+func NewContext() *Context {
+	return &Context{}
+}
+
+// Instantiate is unsupported on this Go version, and panics.
+func Instantiate(ctxt *Context, typ types.Type, targs []types.Type, validate bool) (types.Type, error) {
+	unsupported()
+	return nil, nil
+}

vendor/golang.org/x/tools/internal/typeparams/typeparams_go118.go

@@ -0,0 +1,151 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build go1.18
+// +build go1.18
+
+package typeparams
+
+import (
+	"go/ast"
+	"go/types"
+)
+
+// IndexListExpr is an alias for ast.IndexListExpr.
+type IndexListExpr = ast.IndexListExpr
+
+// ForTypeSpec returns n.TypeParams.
+func ForTypeSpec(n *ast.TypeSpec) *ast.FieldList {
+	if n == nil {
+		return nil
+	}
+	return n.TypeParams
+}
+
+// ForFuncType returns n.TypeParams.
+func ForFuncType(n *ast.FuncType) *ast.FieldList {
+	if n == nil {
+		return nil
+	}
+	return n.TypeParams
+}
+
+// TypeParam is an alias for types.TypeParam
+type TypeParam = types.TypeParam
+
+// TypeParamList is an alias for types.TypeParamList
+type TypeParamList = types.TypeParamList
+
+// TypeList is an alias for types.TypeList
+type TypeList = types.TypeList
+
+// NewTypeParam calls types.NewTypeParam.
+func NewTypeParam(name *types.TypeName, constraint types.Type) *TypeParam {
+	return types.NewTypeParam(name, constraint)
+}
+
+// SetTypeParamConstraint calls tparam.SetConstraint(constraint).
+func SetTypeParamConstraint(tparam *TypeParam, constraint types.Type) {
+	tparam.SetConstraint(constraint)
+}
+
+// NewSignatureType calls types.NewSignatureType.
+func NewSignatureType(recv *types.Var, recvTypeParams, typeParams []*TypeParam, params, results *types.Tuple, variadic bool) *types.Signature {
+	return types.NewSignatureType(recv, recvTypeParams, typeParams, params, results, variadic)
+}
+
+// ForSignature returns sig.TypeParams()
+func ForSignature(sig *types.Signature) *TypeParamList {
+	return sig.TypeParams()
+}
+
+// RecvTypeParams returns sig.RecvTypeParams().
+func RecvTypeParams(sig *types.Signature) *TypeParamList {
+	return sig.RecvTypeParams()
+}
+
+// IsComparable calls iface.IsComparable().
+func IsComparable(iface *types.Interface) bool {
+	return iface.IsComparable()
+}
+
+// IsMethodSet calls iface.IsMethodSet().
+func IsMethodSet(iface *types.Interface) bool {
+	return iface.IsMethodSet()
+}
+
+// IsImplicit calls iface.IsImplicit().
+func IsImplicit(iface *types.Interface) bool {
+	return iface.IsImplicit()
+}
+
+// MarkImplicit calls iface.MarkImplicit().
+func MarkImplicit(iface *types.Interface) {
+	iface.MarkImplicit()
+}
+
+// ForNamed extracts the (possibly empty) type parameter object list from
+// named.
+func ForNamed(named *types.Named) *TypeParamList {
+	return named.TypeParams()
+}
+
+// SetForNamed sets the type params tparams on n. Each tparam must be of
+// dynamic type *types.TypeParam.
+func SetForNamed(n *types.Named, tparams []*TypeParam) {
+	n.SetTypeParams(tparams)
+}
+
+// NamedTypeArgs returns named.TypeArgs().
+func NamedTypeArgs(named *types.Named) *TypeList {
+	return named.TypeArgs()
+}
+
+// NamedTypeOrigin returns named.Orig().
+func NamedTypeOrigin(named *types.Named) types.Type {
+	return named.Origin()
+}
+
+// Term is an alias for types.Term.
+type Term = types.Term
+
+// NewTerm calls types.NewTerm.
+func NewTerm(tilde bool, typ types.Type) *Term {
+	return types.NewTerm(tilde, typ)
+}
+
+// Union is an alias for types.Union
+type Union = types.Union
+
+// NewUnion calls types.NewUnion.
+func NewUnion(terms []*Term) *Union {
+	return types.NewUnion(terms)
+}
+
+// InitInstanceInfo initializes info to record information about type and
+// function instances.
+func InitInstanceInfo(info *types.Info) {
+	info.Instances = make(map[*ast.Ident]types.Instance)
+}
+
+// Instance is an alias for types.Instance.
+type Instance = types.Instance
+
+// GetInstances returns info.Instances.
+func GetInstances(info *types.Info) map[*ast.Ident]Instance {
+	return info.Instances
+}
+
+// Context is an alias for types.Context.
+type Context = types.Context
+
+// NewContext calls types.NewContext.
+func NewContext() *Context {
+	return types.NewContext()
+}
+
+// Instantiate calls types.Instantiate.
+func Instantiate(ctxt *Context, typ types.Type, targs []types.Type, validate bool) (types.Type, error) {
+	return types.Instantiate(ctxt, typ, targs, validate)
+}

vendor/golang.org/x/tools/internal/typeparams/typeterm.go

@@ -0,0 +1,170 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Code generated by copytermlist.go DO NOT EDIT.
+
+package typeparams
+
+import "go/types"
+
+// A term describes elementary type sets:
+//
+//   ∅:  (*term)(nil)     == ∅                      // set of no types (empty set)
+//   𝓤:  &term{}          == 𝓤                      // set of all types (𝓤niverse)
+//   T:  &term{false, T}  == {T}                    // set of type T
+//  ~t:  &term{true, t}   == {t' | under(t') == t}  // set of types with underlying type t
+//
+type term struct {
+	tilde bool // valid if typ != nil
+	typ   types.Type
+}
+
+func (x *term) String() string {
+	switch {
+	case x == nil:
+		return "∅"
+	case x.typ == nil:
+		return "𝓤"
+	case x.tilde:
+		return "~" + x.typ.String()
+	default:
+		return x.typ.String()
+	}
+}
+
+// equal reports whether x and y represent the same type set.
+func (x *term) equal(y *term) bool {
+	// easy cases
+	switch {
+	case x == nil || y == nil:
+		return x == y
+	case x.typ == nil || y.typ == nil:
+		return x.typ == y.typ
+	}
+	// ∅ ⊂ x, y ⊂ 𝓤
+
+	return x.tilde == y.tilde && types.Identical(x.typ, y.typ)
+}
+
+// union returns the union x ∪ y: zero, one, or two non-nil terms.
+func (x *term) union(y *term) (_, _ *term) {
+	// easy cases
+	switch {
+	case x == nil && y == nil:
+		return nil, nil // ∅ ∪ ∅ == ∅
+	case x == nil:
+		return y, nil // ∅ ∪ y == y
+	case y == nil:
+		return x, nil // x ∪ ∅ == x
+	case x.typ == nil:
+		return x, nil // 𝓤 ∪ y == 𝓤
+	case y.typ == nil:
+		return y, nil // x ∪ 𝓤 == 𝓤
+	}
+	// ∅ ⊂ x, y ⊂ 𝓤
+
+	if x.disjoint(y) {
+		return x, y // x ∪ y == (x, y) if x ∩ y == ∅
+	}
+	// x.typ == y.typ
+
+	// ~t ∪ ~t == ~t
+	// ~t ∪  T == ~t
+	//  T ∪ ~t == ~t
+	//  T ∪  T ==  T
+	if x.tilde || !y.tilde {
+		return x, nil
+	}
+	return y, nil
+}
+
+// intersect returns the intersection x ∩ y.
+func (x *term) intersect(y *term) *term {
+	// easy cases
+	switch {
+	case x == nil || y == nil:
+		return nil // ∅ ∩ y == ∅ and ∩ ∅ == ∅
+	case x.typ == nil:
+		return y // 𝓤 ∩ y == y
+	case y.typ == nil:
+		return x // x ∩ 𝓤 == x
+	}
+	// ∅ ⊂ x, y ⊂ 𝓤
+
+	if x.disjoint(y) {
+		return nil // x ∩ y == ∅ if x ∩ y == ∅
+	}
+	// x.typ == y.typ
+
+	// ~t ∩ ~t == ~t
+	// ~t ∩  T ==  T
+	//  T ∩ ~t ==  T
+	//  T ∩  T ==  T
+	if !x.tilde || y.tilde {
+		return x
+	}
+	return y
+}
+
+// includes reports whether t ∈ x.
+func (x *term) includes(t types.Type) bool {
+	// easy cases
+	switch {
+	case x == nil:
+		return false // t ∈ ∅ == false
+	case x.typ == nil:
+		return true // t ∈ 𝓤 == true
+	}
+	// ∅ ⊂ x ⊂ 𝓤
+
+	u := t
+	if x.tilde {
+		u = under(u)
+	}
+	return types.Identical(x.typ, u)
+}
+
+// subsetOf reports whether x ⊆ y.
+func (x *term) subsetOf(y *term) bool {
+	// easy cases
+	switch {
+	case x == nil:
+		return true // ∅ ⊆ y == true
+	case y == nil:
+		return false // x ⊆ ∅ == false since x != ∅
+	case y.typ == nil:
+		return true // x ⊆ 𝓤 == true
+	case x.typ == nil:
+		return false // 𝓤 ⊆ y == false since y != 𝓤
+	}
+	// ∅ ⊂ x, y ⊂ 𝓤
+
+	if x.disjoint(y) {
+		return false // x ⊆ y == false if x ∩ y == ∅
+	}
+	// x.typ == y.typ
+
+	// ~t ⊆ ~t == true
+	// ~t ⊆ T == false
+	//  T ⊆ ~t == true
+	//  T ⊆  T == true
+	return !x.tilde || y.tilde
+}
+
+// disjoint reports whether x ∩ y == ∅.
+// x.typ and y.typ must not be nil.
+func (x *term) disjoint(y *term) bool {
+	if debug && (x.typ == nil || y.typ == nil) {
+		panic("invalid argument(s)")
+	}
+	ux := x.typ
+	if y.tilde {
+		ux = under(ux)
+	}
+	uy := y.typ
+	if x.tilde {
+		uy = under(uy)
+	}
+	return !types.Identical(ux, uy)
+}

vendor/golang.org/x/tools/internal/typesinternal/errorcode.go

@@ -1365,4 +1365,162 @@ const (
 	//  	return i
 	//  }
 	InvalidGo
+
+	// All codes below were added in Go 1.17.
+
+	/* decl */
+
+	// BadDecl occurs when a declaration has invalid syntax.
+	BadDecl
+
+	// RepeatedDecl occurs when an identifier occurs more than once on the left
+	// hand side of a short variable declaration.
+	//
+	// Example:
+	//  func _() {
+	//  	x, y, y := 1, 2, 3
+	//  }
+	RepeatedDecl
+
+	/* unsafe */
+
+	// InvalidUnsafeAdd occurs when unsafe.Add is called with a
+	// length argument that is not of integer type.
+	//
+	// Example:
+	//  import "unsafe"
+	//
+	//  var p unsafe.Pointer
+	//  var _ = unsafe.Add(p, float64(1))
+	InvalidUnsafeAdd
+
+	// InvalidUnsafeSlice occurs when unsafe.Slice is called with a
+	// pointer argument that is not of pointer type or a length argument
+	// that is not of integer type, negative, or out of bounds.
+	//
+	// Example:
+	//  import "unsafe"
+	//
+	//  var x int
+	//  var _ = unsafe.Slice(x, 1)
+	//
+	// Example:
+	//  import "unsafe"
+	//
+	//  var x int
+	//  var _ = unsafe.Slice(&x, float64(1))
+	//
+	// Example:
+	//  import "unsafe"
+	//
+	//  var x int
+	//  var _ = unsafe.Slice(&x, -1)
+	//
+	// Example:
+	//  import "unsafe"
+	//
+	//  var x int
+	//  var _ = unsafe.Slice(&x, uint64(1) << 63)
+	InvalidUnsafeSlice
+
+	// All codes below were added in Go 1.18.
+
+	/* features */
+
+	// UnsupportedFeature occurs when a language feature is used that is not
+	// supported at this Go version.
+	UnsupportedFeature
+
+	/* type params */
+
+	// NotAGenericType occurs when a non-generic type is used where a generic
+	// type is expected: in type or function instantiation.
+	//
+	// Example:
+	//  type T int
+	//
+	//  var _ T[int]
+	NotAGenericType
+
+	// WrongTypeArgCount occurs when a type or function is instantiated with an
+	// incorrent number of type arguments, including when a generic type or
+	// function is used without instantiation.
+	//
+	// Errors inolving failed type inference are assigned other error codes.
+	//
+	// Example:
+	//  type T[p any] int
+	//
+	//  var _ T[int, string]
+	//
+	// Example:
+	//  func f[T any]() {}
+	//
+	//  var x = f
+	WrongTypeArgCount
+
+	// CannotInferTypeArgs occurs when type or function type argument inference
+	// fails to infer all type arguments.
+	//
+	// Example:
+	//  func f[T any]() {}
+	//
+	//  func _() {
+	//  	f()
+	//  }
+	//
+	// Example:
+	//   type N[P, Q any] struct{}
+	//
+	//   var _ N[int]
+	CannotInferTypeArgs
+
+	// InvalidTypeArg occurs when a type argument does not satisfy its
+	// corresponding type parameter constraints.
+	//
+	// Example:
+	//  type T[P ~int] struct{}
+	//
+	//  var _ T[string]
+	InvalidTypeArg // arguments? InferenceFailed
+
+	// InvalidInstanceCycle occurs when an invalid cycle is detected
+	// within the instantiation graph.
+	//
+	// Example:
+	//  func f[T any]() { f[*T]() }
+	InvalidInstanceCycle
+
+	// InvalidUnion occurs when an embedded union or approximation element is
+	// not valid.
+	//
+	// Example:
+	//  type _ interface {
+	//   	~int | interface{ m() }
+	//  }
+	InvalidUnion
+
+	// MisplacedConstraintIface occurs when a constraint-type interface is used
+	// outside of constraint position.
+	//
+	// Example:
+	//   type I interface { ~int }
+	//
+	//   var _ I
+	MisplacedConstraintIface
+
+	// InvalidMethodTypeParams occurs when methods have type parameters.
+	//
+	// It cannot be encountered with an AST parsed using go/parser.
+	InvalidMethodTypeParams
+
+	// MisplacedTypeParam occurs when a type parameter is used in a place where
+	// it is not permitted.
+	//
+	// Example:
+	//  type T[P any] P
+	//
+	// Example:
+	//  type T[P any] struct{ *P }
+	MisplacedTypeParam
 )

vendor/golang.org/x/tools/internal/typesinternal/types.go

@@ -30,10 +30,15 @@ func SetUsesCgo(conf *types.Config) bool {
 	return true
 }
 
-func ReadGo116ErrorData(terr types.Error) (ErrorCode, token.Pos, token.Pos, bool) {
+// ReadGo116ErrorData extracts additional information from types.Error values
+// generated by Go version 1.16 and later: the error code, start position, and
+// end position. If all positions are valid, start <= err.Pos <= end.
+//
+// If the data could not be read, the final result parameter will be false.
+func ReadGo116ErrorData(err types.Error) (code ErrorCode, start, end token.Pos, ok bool) {
 	var data [3]int
 	// By coincidence all of these fields are ints, which simplifies things.
-	v := reflect.ValueOf(terr)
+	v := reflect.ValueOf(err)
 	for i, name := range []string{"go116code", "go116start", "go116end"} {
 		f := v.FieldByName(name)
 		if !f.IsValid() {
@@ -43,3 +48,5 @@ func ReadGo116ErrorData(terr types.Error) (ErrorCode, token.Pos, token.Pos, bool
 	}
 	return ErrorCode(data[0]), token.Pos(data[1]), token.Pos(data[2]), true
 }
+
+var SetGoVersion = func(conf *types.Config, version string) bool { return false }

vendor/golang.org/x/tools/internal/typesinternal/types_118.go

@@ -0,0 +1,19 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build go1.18
+// +build go1.18
+
+package typesinternal
+
+import (
+	"go/types"
+)
+
+func init() {
+	SetGoVersion = func(conf *types.Config, version string) bool {
+		conf.GoVersion = version
+		return true
+	}
+}