Adding upstream version 1.16.10.upstream/1.16.10upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1011 insertions, 0 deletions

diff --git a/src/cmd/api/goapi.go b/src/cmd/api/goapi.go
new file mode 100644
index 0000000..efc2696
--- /dev/null
+++ b/src/cmd/api/goapi.go
@@ -0,0 +1,1011 @@
+// Copyright 2011 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.
+
+// Binary api computes the exported API of a set of Go packages.
+package main
+
+import (
+	"bufio"
+	"bytes"
+	"encoding/json"
+	"flag"
+	"fmt"
+	"go/ast"
+	"go/build"
+	"go/parser"
+	"go/token"
+	"go/types"
+	exec "internal/execabs"
+	"io"
+	"log"
+	"os"
+	"path/filepath"
+	"regexp"
+	"runtime"
+	"sort"
+	"strings"
+	"sync"
+)
+
+func goCmd() string {
+	var exeSuffix string
+	if runtime.GOOS == "windows" {
+		exeSuffix = ".exe"
+	}
+	path := filepath.Join(runtime.GOROOT(), "bin", "go"+exeSuffix)
+	if _, err := os.Stat(path); err == nil {
+		return path
+	}
+	return "go"
+}
+
+// Flags
+var (
+	checkFile  = flag.String("c", "", "optional comma-separated filename(s) to check API against")
+	allowNew   = flag.Bool("allow_new", true, "allow API additions")
+	exceptFile = flag.String("except", "", "optional filename of packages that are allowed to change without triggering a failure in the tool")
+	nextFile   = flag.String("next", "", "optional filename of tentative upcoming API features for the next release. This file can be lazily maintained. It only affects the delta warnings from the -c file printed on success.")
+	verbose    = flag.Bool("v", false, "verbose debugging")
+	forceCtx   = flag.String("contexts", "", "optional comma-separated list of <goos>-<goarch>[-cgo] to override default contexts.")
+)
+
+// contexts are the default contexts which are scanned, unless
+// overridden by the -contexts flag.
+var contexts = []*build.Context{
+	{GOOS: "linux", GOARCH: "386", CgoEnabled: true},
+	{GOOS: "linux", GOARCH: "386"},
+	{GOOS: "linux", GOARCH: "amd64", CgoEnabled: true},
+	{GOOS: "linux", GOARCH: "amd64"},
+	{GOOS: "linux", GOARCH: "arm", CgoEnabled: true},
+	{GOOS: "linux", GOARCH: "arm"},
+	{GOOS: "darwin", GOARCH: "amd64", CgoEnabled: true},
+	{GOOS: "darwin", GOARCH: "amd64"},
+	{GOOS: "windows", GOARCH: "amd64"},
+	{GOOS: "windows", GOARCH: "386"},
+	{GOOS: "freebsd", GOARCH: "386", CgoEnabled: true},
+	{GOOS: "freebsd", GOARCH: "386"},
+	{GOOS: "freebsd", GOARCH: "amd64", CgoEnabled: true},
+	{GOOS: "freebsd", GOARCH: "amd64"},
+	{GOOS: "freebsd", GOARCH: "arm", CgoEnabled: true},
+	{GOOS: "freebsd", GOARCH: "arm"},
+	{GOOS: "netbsd", GOARCH: "386", CgoEnabled: true},
+	{GOOS: "netbsd", GOARCH: "386"},
+	{GOOS: "netbsd", GOARCH: "amd64", CgoEnabled: true},
+	{GOOS: "netbsd", GOARCH: "amd64"},
+	{GOOS: "netbsd", GOARCH: "arm", CgoEnabled: true},
+	{GOOS: "netbsd", GOARCH: "arm"},
+	{GOOS: "netbsd", GOARCH: "arm64", CgoEnabled: true},
+	{GOOS: "netbsd", GOARCH: "arm64"},
+	{GOOS: "openbsd", GOARCH: "386", CgoEnabled: true},
+	{GOOS: "openbsd", GOARCH: "386"},
+	{GOOS: "openbsd", GOARCH: "amd64", CgoEnabled: true},
+	{GOOS: "openbsd", GOARCH: "amd64"},
+}
+
+func contextName(c *build.Context) string {
+	s := c.GOOS + "-" + c.GOARCH
+	if c.CgoEnabled {
+		s += "-cgo"
+	}
+	if c.Dir != "" {
+		s += fmt.Sprintf(" [%s]", c.Dir)
+	}
+	return s
+}
+
+func parseContext(c string) *build.Context {
+	parts := strings.Split(c, "-")
+	if len(parts) < 2 {
+		log.Fatalf("bad context: %q", c)
+	}
+	bc := &build.Context{
+		GOOS:   parts[0],
+		GOARCH: parts[1],
+	}
+	if len(parts) == 3 {
+		if parts[2] == "cgo" {
+			bc.CgoEnabled = true
+		} else {
+			log.Fatalf("bad context: %q", c)
+		}
+	}
+	return bc
+}
+
+func setContexts() {
+	contexts = []*build.Context{}
+	for _, c := range strings.Split(*forceCtx, ",") {
+		contexts = append(contexts, parseContext(c))
+	}
+}
+
+var internalPkg = regexp.MustCompile(`(^|/)internal($|/)`)
+
+func main() {
+	flag.Parse()
+
+	if !strings.Contains(runtime.Version(), "weekly") && !strings.Contains(runtime.Version(), "devel") {
+		if *nextFile != "" {
+			fmt.Printf("Go version is %q, ignoring -next %s\n", runtime.Version(), *nextFile)
+			*nextFile = ""
+		}
+	}
+
+	if *forceCtx != "" {
+		setContexts()
+	}
+	for _, c := range contexts {
+		c.Compiler = build.Default.Compiler
+	}
+
+	walkers := make([]*Walker, len(contexts))
+	var wg sync.WaitGroup
+	for i, context := range contexts {
+		i, context := i, context
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			walkers[i] = NewWalker(context, filepath.Join(build.Default.GOROOT, "src"))
+		}()
+	}
+	wg.Wait()
+
+	var featureCtx = make(map[string]map[string]bool) // feature -> context name -> true
+	for _, w := range walkers {
+		pkgNames := w.stdPackages
+		if flag.NArg() > 0 {
+			pkgNames = flag.Args()
+		}
+
+		for _, name := range pkgNames {
+			pkg, err := w.Import(name)
+			if _, nogo := err.(*build.NoGoError); nogo {
+				continue
+			}
+			if err != nil {
+				log.Fatalf("Import(%q): %v", name, err)
+			}
+			w.export(pkg)
+		}
+
+		ctxName := contextName(w.context)
+		for _, f := range w.Features() {
+			if featureCtx[f] == nil {
+				featureCtx[f] = make(map[string]bool)
+			}
+			featureCtx[f][ctxName] = true
+		}
+	}
+
+	var features []string
+	for f, cmap := range featureCtx {
+		if len(cmap) == len(contexts) {
+			features = append(features, f)
+			continue
+		}
+		comma := strings.Index(f, ",")
+		for cname := range cmap {
+			f2 := fmt.Sprintf("%s (%s)%s", f[:comma], cname, f[comma:])
+			features = append(features, f2)
+		}
+	}
+
+	fail := false
+	defer func() {
+		if fail {
+			os.Exit(1)
+		}
+	}()
+
+	bw := bufio.NewWriter(os.Stdout)
+	defer bw.Flush()
+
+	if *checkFile == "" {
+		sort.Strings(features)
+		for _, f := range features {
+			fmt.Fprintln(bw, f)
+		}
+		return
+	}
+
+	var required []string
+	for _, file := range strings.Split(*checkFile, ",") {
+		required = append(required, fileFeatures(file)...)
+	}
+	optional := fileFeatures(*nextFile)
+	exception := fileFeatures(*exceptFile)
+	fail = !compareAPI(bw, features, required, optional, exception,
+		*allowNew && strings.Contains(runtime.Version(), "devel"))
+}
+
+// export emits the exported package features.
+func (w *Walker) export(pkg *types.Package) {
+	if *verbose {
+		log.Println(pkg)
+	}
+	pop := w.pushScope("pkg " + pkg.Path())
+	w.current = pkg
+	scope := pkg.Scope()
+	for _, name := range scope.Names() {
+		if token.IsExported(name) {
+			w.emitObj(scope.Lookup(name))
+		}
+	}
+	pop()
+}
+
+func set(items []string) map[string]bool {
+	s := make(map[string]bool)
+	for _, v := range items {
+		s[v] = true
+	}
+	return s
+}
+
+var spaceParensRx = regexp.MustCompile(` \(\S+?\)`)
+
+func featureWithoutContext(f string) string {
+	if !strings.Contains(f, "(") {
+		return f
+	}
+	return spaceParensRx.ReplaceAllString(f, "")
+}
+
+// portRemoved reports whether the given port-specific API feature is
+// okay to no longer exist because its port was removed.
+func portRemoved(feature string) bool {
+	return strings.Contains(feature, "(darwin-386)") ||
+		strings.Contains(feature, "(darwin-386-cgo)")
+}
+
+func compareAPI(w io.Writer, features, required, optional, exception []string, allowAdd bool) (ok bool) {
+	ok = true
+
+	optionalSet := set(optional)
+	exceptionSet := set(exception)
+	featureSet := set(features)
+
+	sort.Strings(features)
+	sort.Strings(required)
+
+	take := func(sl *[]string) string {
+		s := (*sl)[0]
+		*sl = (*sl)[1:]
+		return s
+	}
+
+	for len(required) > 0 || len(features) > 0 {
+		switch {
+		case len(features) == 0 || (len(required) > 0 && required[0] < features[0]):
+			feature := take(&required)
+			if exceptionSet[feature] {
+				// An "unfortunate" case: the feature was once
+				// included in the API (e.g. go1.txt), but was
+				// subsequently removed. These are already
+				// acknowledged by being in the file
+				// "api/except.txt". No need to print them out
+				// here.
+			} else if portRemoved(feature) {
+				// okay.
+			} else if featureSet[featureWithoutContext(feature)] {
+				// okay.
+			} else {
+				fmt.Fprintf(w, "-%s\n", feature)
+				ok = false // broke compatibility
+			}
+		case len(required) == 0 || (len(features) > 0 && required[0] > features[0]):
+			newFeature := take(&features)
+			if optionalSet[newFeature] {
+				// Known added feature to the upcoming release.
+				// Delete it from the map so we can detect any upcoming features
+				// which were never seen.  (so we can clean up the nextFile)
+				delete(optionalSet, newFeature)
+			} else {
+				fmt.Fprintf(w, "+%s\n", newFeature)
+				if !allowAdd {
+					ok = false // we're in lock-down mode for next release
+				}
+			}
+		default:
+			take(&required)
+			take(&features)
+		}
+	}
+
+	// In next file, but not in API.
+	var missing []string
+	for feature := range optionalSet {
+		missing = append(missing, feature)
+	}
+	sort.Strings(missing)
+	for _, feature := range missing {
+		fmt.Fprintf(w, "±%s\n", feature)
+	}
+	return
+}
+
+// aliasReplacer applies type aliases to earlier API files,
+// to avoid misleading negative results.
+// This makes all the references to os.FileInfo in go1.txt
+// be read as if they said fs.FileInfo, since os.FileInfo is now an alias.
+// If there are many of these, we could do a more general solution,
+// but for now the replacer is fine.
+var aliasReplacer = strings.NewReplacer(
+	"os.FileInfo", "fs.FileInfo",
+	"os.FileMode", "fs.FileMode",
+	"os.PathError", "fs.PathError",
+)
+
+func fileFeatures(filename string) []string {
+	if filename == "" {
+		return nil
+	}
+	bs, err := os.ReadFile(filename)
+	if err != nil {
+		log.Fatalf("Error reading file %s: %v", filename, err)
+	}
+	s := string(bs)
+	s = aliasReplacer.Replace(s)
+	lines := strings.Split(s, "\n")
+	var nonblank []string
+	for _, line := range lines {
+		line = strings.TrimSpace(line)
+		if line != "" && !strings.HasPrefix(line, "#") {
+			nonblank = append(nonblank, line)
+		}
+	}
+	return nonblank
+}
+
+var fset = token.NewFileSet()
+
+type Walker struct {
+	context     *build.Context
+	root        string
+	scope       []string
+	current     *types.Package
+	features    map[string]bool              // set
+	imported    map[string]*types.Package    // packages already imported
+	stdPackages []string                     // names, omitting "unsafe", internal, and vendored packages
+	importMap   map[string]map[string]string // importer dir -> import path -> canonical path
+	importDir   map[string]string            // canonical import path -> dir
+
+}
+
+func NewWalker(context *build.Context, root string) *Walker {
+	w := &Walker{
+		context:  context,
+		root:     root,
+		features: map[string]bool{},
+		imported: map[string]*types.Package{"unsafe": types.Unsafe},
+	}
+	w.loadImports()
+	return w
+}
+
+func (w *Walker) Features() (fs []string) {
+	for f := range w.features {
+		fs = append(fs, f)
+	}
+	sort.Strings(fs)
+	return
+}
+
+var parsedFileCache = make(map[string]*ast.File)
+
+func (w *Walker) parseFile(dir, file string) (*ast.File, error) {
+	filename := filepath.Join(dir, file)
+	if f := parsedFileCache[filename]; f != nil {
+		return f, nil
+	}
+
+	f, err := parser.ParseFile(fset, filename, nil, 0)
+	if err != nil {
+		return nil, err
+	}
+	parsedFileCache[filename] = f
+
+	return f, nil
+}
+
+// Disable before debugging non-obvious errors from the type-checker.
+const usePkgCache = true
+
+var (
+	pkgCache = map[string]*types.Package{} // map tagKey to package
+	pkgTags  = map[string][]string{}       // map import dir to list of relevant tags
+)
+
+// tagKey returns the tag-based key to use in the pkgCache.
+// It is a comma-separated string; the first part is dir, the rest tags.
+// The satisfied tags are derived from context but only those that
+// matter (the ones listed in the tags argument plus GOOS and GOARCH) are used.
+// The tags list, which came from go/build's Package.AllTags,
+// is known to be sorted.
+func tagKey(dir string, context *build.Context, tags []string) string {
+	ctags := map[string]bool{
+		context.GOOS:   true,
+		context.GOARCH: true,
+	}
+	if context.CgoEnabled {
+		ctags["cgo"] = true
+	}
+	for _, tag := range context.BuildTags {
+		ctags[tag] = true
+	}
+	// TODO: ReleaseTags (need to load default)
+	key := dir
+
+	// explicit on GOOS and GOARCH as global cache will use "all" cached packages for
+	// an indirect imported package. See https://github.com/golang/go/issues/21181
+	// for more detail.
+	tags = append(tags, context.GOOS, context.GOARCH)
+	sort.Strings(tags)
+
+	for _, tag := range tags {
+		if ctags[tag] {
+			key += "," + tag
+			ctags[tag] = false
+		}
+	}
+	return key
+}
+
+type listImports struct {
+	stdPackages []string                     // names, omitting "unsafe", internal, and vendored packages
+	importDir   map[string]string            // canonical import path → directory
+	importMap   map[string]map[string]string // import path → canonical import path
+}
+
+var listCache sync.Map // map[string]listImports, keyed by contextName
+
+// listSem is a semaphore restricting concurrent invocations of 'go list'.
+var listSem = make(chan semToken, runtime.GOMAXPROCS(0))
+
+type semToken struct{}
+
+// loadImports populates w with information about the packages in the standard
+// library and the packages they themselves import in w's build context.
+//
+// The source import path and expanded import path are identical except for vendored packages.
+// For example, on return:
+//
+//	w.importMap["math"] = "math"
+//	w.importDir["math"] = "<goroot>/src/math"
+//
+//	w.importMap["golang.org/x/net/route"] = "vendor/golang.org/x/net/route"
+//	w.importDir["vendor/golang.org/x/net/route"] = "<goroot>/src/vendor/golang.org/x/net/route"
+//
+// Since the set of packages that exist depends on context, the result of
+// loadImports also depends on context. However, to improve test running time
+// the configuration for each environment is cached across runs.
+func (w *Walker) loadImports() {
+	if w.context == nil {
+		return // test-only Walker; does not use the import map
+	}
+
+	name := contextName(w.context)
+
+	imports, ok := listCache.Load(name)
+	if !ok {
+		listSem <- semToken{}
+		defer func() { <-listSem }()
+
+		cmd := exec.Command(goCmd(), "list", "-e", "-deps", "-json", "std")
+		cmd.Env = listEnv(w.context)
+		if w.context.Dir != "" {
+			cmd.Dir = w.context.Dir
+		}
+		out, err := cmd.CombinedOutput()
+		if err != nil {
+			log.Fatalf("loading imports: %v\n%s", err, out)
+		}
+
+		var stdPackages []string
+		importMap := make(map[string]map[string]string)
+		importDir := make(map[string]string)
+		dec := json.NewDecoder(bytes.NewReader(out))
+		for {
+			var pkg struct {
+				ImportPath, Dir string
+				ImportMap       map[string]string
+				Standard        bool
+			}
+			err := dec.Decode(&pkg)
+			if err == io.EOF {
+				break
+			}
+			if err != nil {
+				log.Fatalf("go list: invalid output: %v", err)
+			}
+
+			// - Package "unsafe" contains special signatures requiring
+			//   extra care when printing them - ignore since it is not
+			//   going to change w/o a language change.
+			// - Internal and vendored packages do not contribute to our
+			//   API surface. (If we are running within the "std" module,
+			//   vendored dependencies appear as themselves instead of
+			//   their "vendor/" standard-library copies.)
+			// - 'go list std' does not include commands, which cannot be
+			//   imported anyway.
+			if ip := pkg.ImportPath; pkg.Standard && ip != "unsafe" && !strings.HasPrefix(ip, "vendor/") && !internalPkg.MatchString(ip) {
+				stdPackages = append(stdPackages, ip)
+			}
+			importDir[pkg.ImportPath] = pkg.Dir
+			if len(pkg.ImportMap) > 0 {
+				importMap[pkg.Dir] = make(map[string]string, len(pkg.ImportMap))
+			}
+			for k, v := range pkg.ImportMap {
+				importMap[pkg.Dir][k] = v
+			}
+		}
+
+		sort.Strings(stdPackages)
+		imports = listImports{
+			stdPackages: stdPackages,
+			importMap:   importMap,
+			importDir:   importDir,
+		}
+		imports, _ = listCache.LoadOrStore(name, imports)
+	}
+
+	li := imports.(listImports)
+	w.stdPackages = li.stdPackages
+	w.importDir = li.importDir
+	w.importMap = li.importMap
+}
+
+// listEnv returns the process environment to use when invoking 'go list' for
+// the given context.
+func listEnv(c *build.Context) []string {
+	if c == nil {
+		return os.Environ()
+	}
+
+	environ := append(os.Environ(),
+		"GOOS="+c.GOOS,
+		"GOARCH="+c.GOARCH)
+	if c.CgoEnabled {
+		environ = append(environ, "CGO_ENABLED=1")
+	} else {
+		environ = append(environ, "CGO_ENABLED=0")
+	}
+	return environ
+}
+
+// Importing is a sentinel taking the place in Walker.imported
+// for a package that is in the process of being imported.
+var importing types.Package
+
+func (w *Walker) Import(name string) (*types.Package, error) {
+	return w.ImportFrom(name, "", 0)
+}
+
+func (w *Walker) ImportFrom(fromPath, fromDir string, mode types.ImportMode) (*types.Package, error) {
+	name := fromPath
+	if canonical, ok := w.importMap[fromDir][fromPath]; ok {
+		name = canonical
+	}
+
+	pkg := w.imported[name]
+	if pkg != nil {
+		if pkg == &importing {
+			log.Fatalf("cycle importing package %q", name)
+		}
+		return pkg, nil
+	}
+	w.imported[name] = &importing
+
+	// Determine package files.
+	dir := w.importDir[name]
+	if dir == "" {
+		dir = filepath.Join(w.root, filepath.FromSlash(name))
+	}
+	if fi, err := os.Stat(dir); err != nil || !fi.IsDir() {
+		log.Panicf("no source in tree for import %q (from import %s in %s): %v", name, fromPath, fromDir, err)
+	}
+
+	context := w.context
+	if context == nil {
+		context = &build.Default
+	}
+
+	// Look in cache.
+	// If we've already done an import with the same set
+	// of relevant tags, reuse the result.
+	var key string
+	if usePkgCache {
+		if tags, ok := pkgTags[dir]; ok {
+			key = tagKey(dir, context, tags)
+			if pkg := pkgCache[key]; pkg != nil {
+				w.imported[name] = pkg
+				return pkg, nil
+			}
+		}
+	}
+
+	info, err := context.ImportDir(dir, 0)
+	if err != nil {
+		if _, nogo := err.(*build.NoGoError); nogo {
+			return nil, err
+		}
+		log.Fatalf("pkg %q, dir %q: ScanDir: %v", name, dir, err)
+	}
+
+	// Save tags list first time we see a directory.
+	if usePkgCache {
+		if _, ok := pkgTags[dir]; !ok {
+			pkgTags[dir] = info.AllTags
+			key = tagKey(dir, context, info.AllTags)
+		}
+	}
+
+	filenames := append(append([]string{}, info.GoFiles...), info.CgoFiles...)
+
+	// Parse package files.
+	var files []*ast.File
+	for _, file := range filenames {
+		f, err := w.parseFile(dir, file)
+		if err != nil {
+			log.Fatalf("error parsing package %s: %s", name, err)
+		}
+		files = append(files, f)
+	}
+
+	// Type-check package files.
+	conf := types.Config{
+		IgnoreFuncBodies: true,
+		FakeImportC:      true,
+		Importer:         w,
+	}
+	pkg, err = conf.Check(name, fset, files, nil)
+	if err != nil {
+		ctxt := "<no context>"
+		if w.context != nil {
+			ctxt = fmt.Sprintf("%s-%s", w.context.GOOS, w.context.GOARCH)
+		}
+		log.Fatalf("error typechecking package %s: %s (%s)", name, err, ctxt)
+	}
+
+	if usePkgCache {
+		pkgCache[key] = pkg
+	}
+
+	w.imported[name] = pkg
+	return pkg, nil
+}
+
+// pushScope enters a new scope (walking a package, type, node, etc)
+// and returns a function that will leave the scope (with sanity checking
+// for mismatched pushes & pops)
+func (w *Walker) pushScope(name string) (popFunc func()) {
+	w.scope = append(w.scope, name)
+	return func() {
+		if len(w.scope) == 0 {
+			log.Fatalf("attempt to leave scope %q with empty scope list", name)
+		}
+		if w.scope[len(w.scope)-1] != name {
+			log.Fatalf("attempt to leave scope %q, but scope is currently %#v", name, w.scope)
+		}
+		w.scope = w.scope[:len(w.scope)-1]
+	}
+}
+
+func sortedMethodNames(typ *types.Interface) []string {
+	n := typ.NumMethods()
+	list := make([]string, n)
+	for i := range list {
+		list[i] = typ.Method(i).Name()
+	}
+	sort.Strings(list)
+	return list
+}
+
+func (w *Walker) writeType(buf *bytes.Buffer, typ types.Type) {
+	switch typ := typ.(type) {
+	case *types.Basic:
+		s := typ.Name()
+		switch typ.Kind() {
+		case types.UnsafePointer:
+			s = "unsafe.Pointer"
+		case types.UntypedBool:
+			s = "ideal-bool"
+		case types.UntypedInt:
+			s = "ideal-int"
+		case types.UntypedRune:
+			// "ideal-char" for compatibility with old tool
+			// TODO(gri) change to "ideal-rune"
+			s = "ideal-char"
+		case types.UntypedFloat:
+			s = "ideal-float"
+		case types.UntypedComplex:
+			s = "ideal-complex"
+		case types.UntypedString:
+			s = "ideal-string"
+		case types.UntypedNil:
+			panic("should never see untyped nil type")
+		default:
+			switch s {
+			case "byte":
+				s = "uint8"
+			case "rune":
+				s = "int32"
+			}
+		}
+		buf.WriteString(s)
+
+	case *types.Array:
+		fmt.Fprintf(buf, "[%d]", typ.Len())
+		w.writeType(buf, typ.Elem())
+
+	case *types.Slice:
+		buf.WriteString("[]")
+		w.writeType(buf, typ.Elem())
+
+	case *types.Struct:
+		buf.WriteString("struct")
+
+	case *types.Pointer:
+		buf.WriteByte('*')
+		w.writeType(buf, typ.Elem())
+
+	case *types.Tuple:
+		panic("should never see a tuple type")
+
+	case *types.Signature:
+		buf.WriteString("func")
+		w.writeSignature(buf, typ)
+
+	case *types.Interface:
+		buf.WriteString("interface{")
+		if typ.NumMethods() > 0 {
+			buf.WriteByte(' ')
+			buf.WriteString(strings.Join(sortedMethodNames(typ), ", "))
+			buf.WriteByte(' ')
+		}
+		buf.WriteString("}")
+
+	case *types.Map:
+		buf.WriteString("map[")
+		w.writeType(buf, typ.Key())
+		buf.WriteByte(']')
+		w.writeType(buf, typ.Elem())
+
+	case *types.Chan:
+		var s string
+		switch typ.Dir() {
+		case types.SendOnly:
+			s = "chan<- "
+		case types.RecvOnly:
+			s = "<-chan "
+		case types.SendRecv:
+			s = "chan "
+		default:
+			panic("unreachable")
+		}
+		buf.WriteString(s)
+		w.writeType(buf, typ.Elem())
+
+	case *types.Named:
+		obj := typ.Obj()
+		pkg := obj.Pkg()
+		if pkg != nil && pkg != w.current {
+			buf.WriteString(pkg.Name())
+			buf.WriteByte('.')
+		}
+		buf.WriteString(typ.Obj().Name())
+
+	default:
+		panic(fmt.Sprintf("unknown type %T", typ))
+	}
+}
+
+func (w *Walker) writeSignature(buf *bytes.Buffer, sig *types.Signature) {
+	w.writeParams(buf, sig.Params(), sig.Variadic())
+	switch res := sig.Results(); res.Len() {
+	case 0:
+		// nothing to do
+	case 1:
+		buf.WriteByte(' ')
+		w.writeType(buf, res.At(0).Type())
+	default:
+		buf.WriteByte(' ')
+		w.writeParams(buf, res, false)
+	}
+}
+
+func (w *Walker) writeParams(buf *bytes.Buffer, t *types.Tuple, variadic bool) {
+	buf.WriteByte('(')
+	for i, n := 0, t.Len(); i < n; i++ {
+		if i > 0 {
+			buf.WriteString(", ")
+		}
+		typ := t.At(i).Type()
+		if variadic && i+1 == n {
+			buf.WriteString("...")
+			typ = typ.(*types.Slice).Elem()
+		}
+		w.writeType(buf, typ)
+	}
+	buf.WriteByte(')')
+}
+
+func (w *Walker) typeString(typ types.Type) string {
+	var buf bytes.Buffer
+	w.writeType(&buf, typ)
+	return buf.String()
+}
+
+func (w *Walker) signatureString(sig *types.Signature) string {
+	var buf bytes.Buffer
+	w.writeSignature(&buf, sig)
+	return buf.String()
+}
+
+func (w *Walker) emitObj(obj types.Object) {
+	switch obj := obj.(type) {
+	case *types.Const:
+		w.emitf("const %s %s", obj.Name(), w.typeString(obj.Type()))
+		x := obj.Val()
+		short := x.String()
+		exact := x.ExactString()
+		if short == exact {
+			w.emitf("const %s = %s", obj.Name(), short)
+		} else {
+			w.emitf("const %s = %s  // %s", obj.Name(), short, exact)
+		}
+	case *types.Var:
+		w.emitf("var %s %s", obj.Name(), w.typeString(obj.Type()))
+	case *types.TypeName:
+		w.emitType(obj)
+	case *types.Func:
+		w.emitFunc(obj)
+	default:
+		panic("unknown object: " + obj.String())
+	}
+}
+
+func (w *Walker) emitType(obj *types.TypeName) {
+	name := obj.Name()
+	typ := obj.Type()
+	if obj.IsAlias() {
+		w.emitf("type %s = %s", name, w.typeString(typ))
+		return
+	}
+	switch typ := typ.Underlying().(type) {
+	case *types.Struct:
+		w.emitStructType(name, typ)
+	case *types.Interface:
+		w.emitIfaceType(name, typ)
+		return // methods are handled by emitIfaceType
+	default:
+		w.emitf("type %s %s", name, w.typeString(typ.Underlying()))
+	}
+
+	// emit methods with value receiver
+	var methodNames map[string]bool
+	vset := types.NewMethodSet(typ)
+	for i, n := 0, vset.Len(); i < n; i++ {
+		m := vset.At(i)
+		if m.Obj().Exported() {
+			w.emitMethod(m)
+			if methodNames == nil {
+				methodNames = make(map[string]bool)
+			}
+			methodNames[m.Obj().Name()] = true
+		}
+	}
+
+	// emit methods with pointer receiver; exclude
+	// methods that we have emitted already
+	// (the method set of *T includes the methods of T)
+	pset := types.NewMethodSet(types.NewPointer(typ))
+	for i, n := 0, pset.Len(); i < n; i++ {
+		m := pset.At(i)
+		if m.Obj().Exported() && !methodNames[m.Obj().Name()] {
+			w.emitMethod(m)
+		}
+	}
+}
+
+func (w *Walker) emitStructType(name string, typ *types.Struct) {
+	typeStruct := fmt.Sprintf("type %s struct", name)
+	w.emitf(typeStruct)
+	defer w.pushScope(typeStruct)()
+
+	for i := 0; i < typ.NumFields(); i++ {
+		f := typ.Field(i)
+		if !f.Exported() {
+			continue
+		}
+		typ := f.Type()
+		if f.Anonymous() {
+			w.emitf("embedded %s", w.typeString(typ))
+			continue
+		}
+		w.emitf("%s %s", f.Name(), w.typeString(typ))
+	}
+}
+
+func (w *Walker) emitIfaceType(name string, typ *types.Interface) {
+	pop := w.pushScope("type " + name + " interface")
+
+	var methodNames []string
+	complete := true
+	mset := types.NewMethodSet(typ)
+	for i, n := 0, mset.Len(); i < n; i++ {
+		m := mset.At(i).Obj().(*types.Func)
+		if !m.Exported() {
+			complete = false
+			continue
+		}
+		methodNames = append(methodNames, m.Name())
+		w.emitf("%s%s", m.Name(), w.signatureString(m.Type().(*types.Signature)))
+	}
+
+	if !complete {
+		// The method set has unexported methods, so all the
+		// implementations are provided by the same package,
+		// so the method set can be extended. Instead of recording
+		// the full set of names (below), record only that there were
+		// unexported methods. (If the interface shrinks, we will notice
+		// because a method signature emitted during the last loop
+		// will disappear.)
+		w.emitf("unexported methods")
+	}
+
+	pop()
+
+	if !complete {
+		return
+	}
+
+	if len(methodNames) == 0 {
+		w.emitf("type %s interface {}", name)
+		return
+	}
+
+	sort.Strings(methodNames)
+	w.emitf("type %s interface { %s }", name, strings.Join(methodNames, ", "))
+}
+
+func (w *Walker) emitFunc(f *types.Func) {
+	sig := f.Type().(*types.Signature)
+	if sig.Recv() != nil {
+		panic("method considered a regular function: " + f.String())
+	}
+	w.emitf("func %s%s", f.Name(), w.signatureString(sig))
+}
+
+func (w *Walker) emitMethod(m *types.Selection) {
+	sig := m.Type().(*types.Signature)
+	recv := sig.Recv().Type()
+	// report exported methods with unexported receiver base type
+	if true {
+		base := recv
+		if p, _ := recv.(*types.Pointer); p != nil {
+			base = p.Elem()
+		}
+		if obj := base.(*types.Named).Obj(); !obj.Exported() {
+			log.Fatalf("exported method with unexported receiver base type: %s", m)
+		}
+	}
+	w.emitf("method (%s) %s%s", w.typeString(recv), m.Obj().Name(), w.signatureString(sig))
+}
+
+func (w *Walker) emitf(format string, args ...interface{}) {
+	f := strings.Join(w.scope, ", ") + ", " + fmt.Sprintf(format, args...)
+	if strings.Contains(f, "\n") {
+		panic("feature contains newlines: " + f)
+	}
+
+	if _, dup := w.features[f]; dup {
+		panic("duplicate feature inserted: " + f)
+	}
+	w.features[f] = true
+
+	if *verbose {
+		log.Printf("feature: %s", f)
+	}
+}