Source file src/cmd/api/goapi.go

Documentation: cmd/api

     1  // Copyright 2011 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Binary api computes the exported API of a set of Go packages.
     6  package main
     7  
     8  import (
     9  	"bufio"
    10  	"bytes"
    11  	"encoding/json"
    12  	"flag"
    13  	"fmt"
    14  	"go/ast"
    15  	"go/build"
    16  	"go/parser"
    17  	"go/token"
    18  	"go/types"
    19  	exec "internal/execabs"
    20  	"io"
    21  	"log"
    22  	"os"
    23  	"path/filepath"
    24  	"regexp"
    25  	"runtime"
    26  	"sort"
    27  	"strings"
    28  	"sync"
    29  )
    30  
    31  func goCmd() string {
    32  	var exeSuffix string
    33  	if runtime.GOOS == "windows" {
    34  		exeSuffix = ".exe"
    35  	}
    36  	path := filepath.Join(runtime.GOROOT(), "bin", "go"+exeSuffix)
    37  	if _, err := os.Stat(path); err == nil {
    38  		return path
    39  	}
    40  	return "go"
    41  }
    42  
    43  // Flags
    44  var (
    45  	checkFile  = flag.String("c", "", "optional comma-separated filename(s) to check API against")
    46  	allowNew   = flag.Bool("allow_new", true, "allow API additions")
    47  	exceptFile = flag.String("except", "", "optional filename of packages that are allowed to change without triggering a failure in the tool")
    48  	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.")
    49  	verbose    = flag.Bool("v", false, "verbose debugging")
    50  	forceCtx   = flag.String("contexts", "", "optional comma-separated list of <goos>-<goarch>[-cgo] to override default contexts.")
    51  )
    52  
    53  // contexts are the default contexts which are scanned, unless
    54  // overridden by the -contexts flag.
    55  var contexts = []*build.Context{
    56  	{GOOS: "linux", GOARCH: "386", CgoEnabled: true},
    57  	{GOOS: "linux", GOARCH: "386"},
    58  	{GOOS: "linux", GOARCH: "amd64", CgoEnabled: true},
    59  	{GOOS: "linux", GOARCH: "amd64"},
    60  	{GOOS: "linux", GOARCH: "arm", CgoEnabled: true},
    61  	{GOOS: "linux", GOARCH: "arm"},
    62  	{GOOS: "darwin", GOARCH: "amd64", CgoEnabled: true},
    63  	{GOOS: "darwin", GOARCH: "amd64"},
    64  	{GOOS: "windows", GOARCH: "amd64"},
    65  	{GOOS: "windows", GOARCH: "386"},
    66  	{GOOS: "freebsd", GOARCH: "386", CgoEnabled: true},
    67  	{GOOS: "freebsd", GOARCH: "386"},
    68  	{GOOS: "freebsd", GOARCH: "amd64", CgoEnabled: true},
    69  	{GOOS: "freebsd", GOARCH: "amd64"},
    70  	{GOOS: "freebsd", GOARCH: "arm", CgoEnabled: true},
    71  	{GOOS: "freebsd", GOARCH: "arm"},
    72  	{GOOS: "netbsd", GOARCH: "386", CgoEnabled: true},
    73  	{GOOS: "netbsd", GOARCH: "386"},
    74  	{GOOS: "netbsd", GOARCH: "amd64", CgoEnabled: true},
    75  	{GOOS: "netbsd", GOARCH: "amd64"},
    76  	{GOOS: "netbsd", GOARCH: "arm", CgoEnabled: true},
    77  	{GOOS: "netbsd", GOARCH: "arm"},
    78  	{GOOS: "netbsd", GOARCH: "arm64", CgoEnabled: true},
    79  	{GOOS: "netbsd", GOARCH: "arm64"},
    80  	{GOOS: "openbsd", GOARCH: "386", CgoEnabled: true},
    81  	{GOOS: "openbsd", GOARCH: "386"},
    82  	{GOOS: "openbsd", GOARCH: "amd64", CgoEnabled: true},
    83  	{GOOS: "openbsd", GOARCH: "amd64"},
    84  }
    85  
    86  func contextName(c *build.Context) string {
    87  	s := c.GOOS + "-" + c.GOARCH
    88  	if c.CgoEnabled {
    89  		s += "-cgo"
    90  	}
    91  	if c.Dir != "" {
    92  		s += fmt.Sprintf(" [%s]", c.Dir)
    93  	}
    94  	return s
    95  }
    96  
    97  func parseContext(c string) *build.Context {
    98  	parts := strings.Split(c, "-")
    99  	if len(parts) < 2 {
   100  		log.Fatalf("bad context: %q", c)
   101  	}
   102  	bc := &build.Context{
   103  		GOOS:   parts[0],
   104  		GOARCH: parts[1],
   105  	}
   106  	if len(parts) == 3 {
   107  		if parts[2] == "cgo" {
   108  			bc.CgoEnabled = true
   109  		} else {
   110  			log.Fatalf("bad context: %q", c)
   111  		}
   112  	}
   113  	return bc
   114  }
   115  
   116  func setContexts() {
   117  	contexts = []*build.Context{}
   118  	for _, c := range strings.Split(*forceCtx, ",") {
   119  		contexts = append(contexts, parseContext(c))
   120  	}
   121  }
   122  
   123  var internalPkg = regexp.MustCompile(`(^|/)internal($|/)`)
   124  
   125  func main() {
   126  	flag.Parse()
   127  
   128  	if !strings.Contains(runtime.Version(), "weekly") && !strings.Contains(runtime.Version(), "devel") {
   129  		if *nextFile != "" {
   130  			fmt.Printf("Go version is %q, ignoring -next %s\n", runtime.Version(), *nextFile)
   131  			*nextFile = ""
   132  		}
   133  	}
   134  
   135  	if *forceCtx != "" {
   136  		setContexts()
   137  	}
   138  	for _, c := range contexts {
   139  		c.Compiler = build.Default.Compiler
   140  	}
   141  
   142  	walkers := make([]*Walker, len(contexts))
   143  	var wg sync.WaitGroup
   144  	for i, context := range contexts {
   145  		i, context := i, context
   146  		wg.Add(1)
   147  		go func() {
   148  			defer wg.Done()
   149  			walkers[i] = NewWalker(context, filepath.Join(build.Default.GOROOT, "src"))
   150  		}()
   151  	}
   152  	wg.Wait()
   153  
   154  	var featureCtx = make(map[string]map[string]bool) // feature -> context name -> true
   155  	for _, w := range walkers {
   156  		pkgNames := w.stdPackages
   157  		if flag.NArg() > 0 {
   158  			pkgNames = flag.Args()
   159  		}
   160  
   161  		for _, name := range pkgNames {
   162  			pkg, err := w.Import(name)
   163  			if _, nogo := err.(*build.NoGoError); nogo {
   164  				continue
   165  			}
   166  			if err != nil {
   167  				log.Fatalf("Import(%q): %v", name, err)
   168  			}
   169  			w.export(pkg)
   170  		}
   171  
   172  		ctxName := contextName(w.context)
   173  		for _, f := range w.Features() {
   174  			if featureCtx[f] == nil {
   175  				featureCtx[f] = make(map[string]bool)
   176  			}
   177  			featureCtx[f][ctxName] = true
   178  		}
   179  	}
   180  
   181  	var features []string
   182  	for f, cmap := range featureCtx {
   183  		if len(cmap) == len(contexts) {
   184  			features = append(features, f)
   185  			continue
   186  		}
   187  		comma := strings.Index(f, ",")
   188  		for cname := range cmap {
   189  			f2 := fmt.Sprintf("%s (%s)%s", f[:comma], cname, f[comma:])
   190  			features = append(features, f2)
   191  		}
   192  	}
   193  
   194  	fail := false
   195  	defer func() {
   196  		if fail {
   197  			os.Exit(1)
   198  		}
   199  	}()
   200  
   201  	bw := bufio.NewWriter(os.Stdout)
   202  	defer bw.Flush()
   203  
   204  	if *checkFile == "" {
   205  		sort.Strings(features)
   206  		for _, f := range features {
   207  			fmt.Fprintln(bw, f)
   208  		}
   209  		return
   210  	}
   211  
   212  	var required []string
   213  	for _, file := range strings.Split(*checkFile, ",") {
   214  		required = append(required, fileFeatures(file)...)
   215  	}
   216  	optional := fileFeatures(*nextFile)
   217  	exception := fileFeatures(*exceptFile)
   218  	fail = !compareAPI(bw, features, required, optional, exception,
   219  		*allowNew && strings.Contains(runtime.Version(), "devel"))
   220  }
   221  
   222  // export emits the exported package features.
   223  func (w *Walker) export(pkg *types.Package) {
   224  	if *verbose {
   225  		log.Println(pkg)
   226  	}
   227  	pop := w.pushScope("pkg " + pkg.Path())
   228  	w.current = pkg
   229  	scope := pkg.Scope()
   230  	for _, name := range scope.Names() {
   231  		if token.IsExported(name) {
   232  			w.emitObj(scope.Lookup(name))
   233  		}
   234  	}
   235  	pop()
   236  }
   237  
   238  func set(items []string) map[string]bool {
   239  	s := make(map[string]bool)
   240  	for _, v := range items {
   241  		s[v] = true
   242  	}
   243  	return s
   244  }
   245  
   246  var spaceParensRx = regexp.MustCompile(` \(\S+?\)`)
   247  
   248  func featureWithoutContext(f string) string {
   249  	if !strings.Contains(f, "(") {
   250  		return f
   251  	}
   252  	return spaceParensRx.ReplaceAllString(f, "")
   253  }
   254  
   255  // portRemoved reports whether the given port-specific API feature is
   256  // okay to no longer exist because its port was removed.
   257  func portRemoved(feature string) bool {
   258  	return strings.Contains(feature, "(darwin-386)") ||
   259  		strings.Contains(feature, "(darwin-386-cgo)")
   260  }
   261  
   262  func compareAPI(w io.Writer, features, required, optional, exception []string, allowAdd bool) (ok bool) {
   263  	ok = true
   264  
   265  	optionalSet := set(optional)
   266  	exceptionSet := set(exception)
   267  	featureSet := set(features)
   268  
   269  	sort.Strings(features)
   270  	sort.Strings(required)
   271  
   272  	take := func(sl *[]string) string {
   273  		s := (*sl)[0]
   274  		*sl = (*sl)[1:]
   275  		return s
   276  	}
   277  
   278  	for len(required) > 0 || len(features) > 0 {
   279  		switch {
   280  		case len(features) == 0 || (len(required) > 0 && required[0] < features[0]):
   281  			feature := take(&required)
   282  			if exceptionSet[feature] {
   283  				// An "unfortunate" case: the feature was once
   284  				// included in the API (e.g. go1.txt), but was
   285  				// subsequently removed. These are already
   286  				// acknowledged by being in the file
   287  				// "api/except.txt". No need to print them out
   288  				// here.
   289  			} else if portRemoved(feature) {
   290  				// okay.
   291  			} else if featureSet[featureWithoutContext(feature)] {
   292  				// okay.
   293  			} else {
   294  				fmt.Fprintf(w, "-%s\n", feature)
   295  				ok = false // broke compatibility
   296  			}
   297  		case len(required) == 0 || (len(features) > 0 && required[0] > features[0]):
   298  			newFeature := take(&features)
   299  			if optionalSet[newFeature] {
   300  				// Known added feature to the upcoming release.
   301  				// Delete it from the map so we can detect any upcoming features
   302  				// which were never seen.  (so we can clean up the nextFile)
   303  				delete(optionalSet, newFeature)
   304  			} else {
   305  				fmt.Fprintf(w, "+%s\n", newFeature)
   306  				if !allowAdd {
   307  					ok = false // we're in lock-down mode for next release
   308  				}
   309  			}
   310  		default:
   311  			take(&required)
   312  			take(&features)
   313  		}
   314  	}
   315  
   316  	// In next file, but not in API.
   317  	var missing []string
   318  	for feature := range optionalSet {
   319  		missing = append(missing, feature)
   320  	}
   321  	sort.Strings(missing)
   322  	for _, feature := range missing {
   323  		fmt.Fprintf(w, "±%s\n", feature)
   324  	}
   325  	return
   326  }
   327  
   328  // aliasReplacer applies type aliases to earlier API files,
   329  // to avoid misleading negative results.
   330  // This makes all the references to os.FileInfo in go1.txt
   331  // be read as if they said fs.FileInfo, since os.FileInfo is now an alias.
   332  // If there are many of these, we could do a more general solution,
   333  // but for now the replacer is fine.
   334  var aliasReplacer = strings.NewReplacer(
   335  	"os.FileInfo", "fs.FileInfo",
   336  	"os.FileMode", "fs.FileMode",
   337  	"os.PathError", "fs.PathError",
   338  )
   339  
   340  func fileFeatures(filename string) []string {
   341  	if filename == "" {
   342  		return nil
   343  	}
   344  	bs, err := os.ReadFile(filename)
   345  	if err != nil {
   346  		log.Fatalf("Error reading file %s: %v", filename, err)
   347  	}
   348  	s := string(bs)
   349  	s = aliasReplacer.Replace(s)
   350  	lines := strings.Split(s, "\n")
   351  	var nonblank []string
   352  	for _, line := range lines {
   353  		line = strings.TrimSpace(line)
   354  		if line != "" && !strings.HasPrefix(line, "#") {
   355  			nonblank = append(nonblank, line)
   356  		}
   357  	}
   358  	return nonblank
   359  }
   360  
   361  var fset = token.NewFileSet()
   362  
   363  type Walker struct {
   364  	context     *build.Context
   365  	root        string
   366  	scope       []string
   367  	current     *types.Package
   368  	features    map[string]bool              // set
   369  	imported    map[string]*types.Package    // packages already imported
   370  	stdPackages []string                     // names, omitting "unsafe", internal, and vendored packages
   371  	importMap   map[string]map[string]string // importer dir -> import path -> canonical path
   372  	importDir   map[string]string            // canonical import path -> dir
   373  
   374  }
   375  
   376  func NewWalker(context *build.Context, root string) *Walker {
   377  	w := &Walker{
   378  		context:  context,
   379  		root:     root,
   380  		features: map[string]bool{},
   381  		imported: map[string]*types.Package{"unsafe": types.Unsafe},
   382  	}
   383  	w.loadImports()
   384  	return w
   385  }
   386  
   387  func (w *Walker) Features() (fs []string) {
   388  	for f := range w.features {
   389  		fs = append(fs, f)
   390  	}
   391  	sort.Strings(fs)
   392  	return
   393  }
   394  
   395  var parsedFileCache = make(map[string]*ast.File)
   396  
   397  func (w *Walker) parseFile(dir, file string) (*ast.File, error) {
   398  	filename := filepath.Join(dir, file)
   399  	if f := parsedFileCache[filename]; f != nil {
   400  		return f, nil
   401  	}
   402  
   403  	f, err := parser.ParseFile(fset, filename, nil, 0)
   404  	if err != nil {
   405  		return nil, err
   406  	}
   407  	parsedFileCache[filename] = f
   408  
   409  	return f, nil
   410  }
   411  
   412  // Disable before debugging non-obvious errors from the type-checker.
   413  const usePkgCache = true
   414  
   415  var (
   416  	pkgCache = map[string]*types.Package{} // map tagKey to package
   417  	pkgTags  = map[string][]string{}       // map import dir to list of relevant tags
   418  )
   419  
   420  // tagKey returns the tag-based key to use in the pkgCache.
   421  // It is a comma-separated string; the first part is dir, the rest tags.
   422  // The satisfied tags are derived from context but only those that
   423  // matter (the ones listed in the tags argument plus GOOS and GOARCH) are used.
   424  // The tags list, which came from go/build's Package.AllTags,
   425  // is known to be sorted.
   426  func tagKey(dir string, context *build.Context, tags []string) string {
   427  	ctags := map[string]bool{
   428  		context.GOOS:   true,
   429  		context.GOARCH: true,
   430  	}
   431  	if context.CgoEnabled {
   432  		ctags["cgo"] = true
   433  	}
   434  	for _, tag := range context.BuildTags {
   435  		ctags[tag] = true
   436  	}
   437  	// TODO: ReleaseTags (need to load default)
   438  	key := dir
   439  
   440  	// explicit on GOOS and GOARCH as global cache will use "all" cached packages for
   441  	// an indirect imported package. See https://github.com/golang/go/issues/21181
   442  	// for more detail.
   443  	tags = append(tags, context.GOOS, context.GOARCH)
   444  	sort.Strings(tags)
   445  
   446  	for _, tag := range tags {
   447  		if ctags[tag] {
   448  			key += "," + tag
   449  			ctags[tag] = false
   450  		}
   451  	}
   452  	return key
   453  }
   454  
   455  type listImports struct {
   456  	stdPackages []string                     // names, omitting "unsafe", internal, and vendored packages
   457  	importDir   map[string]string            // canonical import path → directory
   458  	importMap   map[string]map[string]string // import path → canonical import path
   459  }
   460  
   461  var listCache sync.Map // map[string]listImports, keyed by contextName
   462  
   463  // listSem is a semaphore restricting concurrent invocations of 'go list'.
   464  var listSem = make(chan semToken, runtime.GOMAXPROCS(0))
   465  
   466  type semToken struct{}
   467  
   468  // loadImports populates w with information about the packages in the standard
   469  // library and the packages they themselves import in w's build context.
   470  //
   471  // The source import path and expanded import path are identical except for vendored packages.
   472  // For example, on return:
   473  //
   474  //	w.importMap["math"] = "math"
   475  //	w.importDir["math"] = "<goroot>/src/math"
   476  //
   477  //	w.importMap["golang.org/x/net/route"] = "vendor/golang.org/x/net/route"
   478  //	w.importDir["vendor/golang.org/x/net/route"] = "<goroot>/src/vendor/golang.org/x/net/route"
   479  //
   480  // Since the set of packages that exist depends on context, the result of
   481  // loadImports also depends on context. However, to improve test running time
   482  // the configuration for each environment is cached across runs.
   483  func (w *Walker) loadImports() {
   484  	if w.context == nil {
   485  		return // test-only Walker; does not use the import map
   486  	}
   487  
   488  	name := contextName(w.context)
   489  
   490  	imports, ok := listCache.Load(name)
   491  	if !ok {
   492  		listSem <- semToken{}
   493  		defer func() { <-listSem }()
   494  
   495  		cmd := exec.Command(goCmd(), "list", "-e", "-deps", "-json", "std")
   496  		cmd.Env = listEnv(w.context)
   497  		if w.context.Dir != "" {
   498  			cmd.Dir = w.context.Dir
   499  		}
   500  		out, err := cmd.CombinedOutput()
   501  		if err != nil {
   502  			log.Fatalf("loading imports: %v\n%s", err, out)
   503  		}
   504  
   505  		var stdPackages []string
   506  		importMap := make(map[string]map[string]string)
   507  		importDir := make(map[string]string)
   508  		dec := json.NewDecoder(bytes.NewReader(out))
   509  		for {
   510  			var pkg struct {
   511  				ImportPath, Dir string
   512  				ImportMap       map[string]string
   513  				Standard        bool
   514  			}
   515  			err := dec.Decode(&pkg)
   516  			if err == io.EOF {
   517  				break
   518  			}
   519  			if err != nil {
   520  				log.Fatalf("go list: invalid output: %v", err)
   521  			}
   522  
   523  			// - Package "unsafe" contains special signatures requiring
   524  			//   extra care when printing them - ignore since it is not
   525  			//   going to change w/o a language change.
   526  			// - Internal and vendored packages do not contribute to our
   527  			//   API surface. (If we are running within the "std" module,
   528  			//   vendored dependencies appear as themselves instead of
   529  			//   their "vendor/" standard-library copies.)
   530  			// - 'go list std' does not include commands, which cannot be
   531  			//   imported anyway.
   532  			if ip := pkg.ImportPath; pkg.Standard && ip != "unsafe" && !strings.HasPrefix(ip, "vendor/") && !internalPkg.MatchString(ip) {
   533  				stdPackages = append(stdPackages, ip)
   534  			}
   535  			importDir[pkg.ImportPath] = pkg.Dir
   536  			if len(pkg.ImportMap) > 0 {
   537  				importMap[pkg.Dir] = make(map[string]string, len(pkg.ImportMap))
   538  			}
   539  			for k, v := range pkg.ImportMap {
   540  				importMap[pkg.Dir][k] = v
   541  			}
   542  		}
   543  
   544  		sort.Strings(stdPackages)
   545  		imports = listImports{
   546  			stdPackages: stdPackages,
   547  			importMap:   importMap,
   548  			importDir:   importDir,
   549  		}
   550  		imports, _ = listCache.LoadOrStore(name, imports)
   551  	}
   552  
   553  	li := imports.(listImports)
   554  	w.stdPackages = li.stdPackages
   555  	w.importDir = li.importDir
   556  	w.importMap = li.importMap
   557  }
   558  
   559  // listEnv returns the process environment to use when invoking 'go list' for
   560  // the given context.
   561  func listEnv(c *build.Context) []string {
   562  	if c == nil {
   563  		return os.Environ()
   564  	}
   565  
   566  	environ := append(os.Environ(),
   567  		"GOOS="+c.GOOS,
   568  		"GOARCH="+c.GOARCH)
   569  	if c.CgoEnabled {
   570  		environ = append(environ, "CGO_ENABLED=1")
   571  	} else {
   572  		environ = append(environ, "CGO_ENABLED=0")
   573  	}
   574  	return environ
   575  }
   576  
   577  // Importing is a sentinel taking the place in Walker.imported
   578  // for a package that is in the process of being imported.
   579  var importing types.Package
   580  
   581  func (w *Walker) Import(name string) (*types.Package, error) {
   582  	return w.ImportFrom(name, "", 0)
   583  }
   584  
   585  func (w *Walker) ImportFrom(fromPath, fromDir string, mode types.ImportMode) (*types.Package, error) {
   586  	name := fromPath
   587  	if canonical, ok := w.importMap[fromDir][fromPath]; ok {
   588  		name = canonical
   589  	}
   590  
   591  	pkg := w.imported[name]
   592  	if pkg != nil {
   593  		if pkg == &importing {
   594  			log.Fatalf("cycle importing package %q", name)
   595  		}
   596  		return pkg, nil
   597  	}
   598  	w.imported[name] = &importing
   599  
   600  	// Determine package files.
   601  	dir := w.importDir[name]
   602  	if dir == "" {
   603  		dir = filepath.Join(w.root, filepath.FromSlash(name))
   604  	}
   605  	if fi, err := os.Stat(dir); err != nil || !fi.IsDir() {
   606  		log.Panicf("no source in tree for import %q (from import %s in %s): %v", name, fromPath, fromDir, err)
   607  	}
   608  
   609  	context := w.context
   610  	if context == nil {
   611  		context = &build.Default
   612  	}
   613  
   614  	// Look in cache.
   615  	// If we've already done an import with the same set
   616  	// of relevant tags, reuse the result.
   617  	var key string
   618  	if usePkgCache {
   619  		if tags, ok := pkgTags[dir]; ok {
   620  			key = tagKey(dir, context, tags)
   621  			if pkg := pkgCache[key]; pkg != nil {
   622  				w.imported[name] = pkg
   623  				return pkg, nil
   624  			}
   625  		}
   626  	}
   627  
   628  	info, err := context.ImportDir(dir, 0)
   629  	if err != nil {
   630  		if _, nogo := err.(*build.NoGoError); nogo {
   631  			return nil, err
   632  		}
   633  		log.Fatalf("pkg %q, dir %q: ScanDir: %v", name, dir, err)
   634  	}
   635  
   636  	// Save tags list first time we see a directory.
   637  	if usePkgCache {
   638  		if _, ok := pkgTags[dir]; !ok {
   639  			pkgTags[dir] = info.AllTags
   640  			key = tagKey(dir, context, info.AllTags)
   641  		}
   642  	}
   643  
   644  	filenames := append(append([]string{}, info.GoFiles...), info.CgoFiles...)
   645  
   646  	// Parse package files.
   647  	var files []*ast.File
   648  	for _, file := range filenames {
   649  		f, err := w.parseFile(dir, file)
   650  		if err != nil {
   651  			log.Fatalf("error parsing package %s: %s", name, err)
   652  		}
   653  		files = append(files, f)
   654  	}
   655  
   656  	// Type-check package files.
   657  	conf := types.Config{
   658  		IgnoreFuncBodies: true,
   659  		FakeImportC:      true,
   660  		Importer:         w,
   661  	}
   662  	pkg, err = conf.Check(name, fset, files, nil)
   663  	if err != nil {
   664  		ctxt := "<no context>"
   665  		if w.context != nil {
   666  			ctxt = fmt.Sprintf("%s-%s", w.context.GOOS, w.context.GOARCH)
   667  		}
   668  		log.Fatalf("error typechecking package %s: %s (%s)", name, err, ctxt)
   669  	}
   670  
   671  	if usePkgCache {
   672  		pkgCache[key] = pkg
   673  	}
   674  
   675  	w.imported[name] = pkg
   676  	return pkg, nil
   677  }
   678  
   679  // pushScope enters a new scope (walking a package, type, node, etc)
   680  // and returns a function that will leave the scope (with sanity checking
   681  // for mismatched pushes & pops)
   682  func (w *Walker) pushScope(name string) (popFunc func()) {
   683  	w.scope = append(w.scope, name)
   684  	return func() {
   685  		if len(w.scope) == 0 {
   686  			log.Fatalf("attempt to leave scope %q with empty scope list", name)
   687  		}
   688  		if w.scope[len(w.scope)-1] != name {
   689  			log.Fatalf("attempt to leave scope %q, but scope is currently %#v", name, w.scope)
   690  		}
   691  		w.scope = w.scope[:len(w.scope)-1]
   692  	}
   693  }
   694  
   695  func sortedMethodNames(typ *types.Interface) []string {
   696  	n := typ.NumMethods()
   697  	list := make([]string, n)
   698  	for i := range list {
   699  		list[i] = typ.Method(i).Name()
   700  	}
   701  	sort.Strings(list)
   702  	return list
   703  }
   704  
   705  func (w *Walker) writeType(buf *bytes.Buffer, typ types.Type) {
   706  	switch typ := typ.(type) {
   707  	case *types.Basic:
   708  		s := typ.Name()
   709  		switch typ.Kind() {
   710  		case types.UnsafePointer:
   711  			s = "unsafe.Pointer"
   712  		case types.UntypedBool:
   713  			s = "ideal-bool"
   714  		case types.UntypedInt:
   715  			s = "ideal-int"
   716  		case types.UntypedRune:
   717  			// "ideal-char" for compatibility with old tool
   718  			// TODO(gri) change to "ideal-rune"
   719  			s = "ideal-char"
   720  		case types.UntypedFloat:
   721  			s = "ideal-float"
   722  		case types.UntypedComplex:
   723  			s = "ideal-complex"
   724  		case types.UntypedString:
   725  			s = "ideal-string"
   726  		case types.UntypedNil:
   727  			panic("should never see untyped nil type")
   728  		default:
   729  			switch s {
   730  			case "byte":
   731  				s = "uint8"
   732  			case "rune":
   733  				s = "int32"
   734  			}
   735  		}
   736  		buf.WriteString(s)
   737  
   738  	case *types.Array:
   739  		fmt.Fprintf(buf, "[%d]", typ.Len())
   740  		w.writeType(buf, typ.Elem())
   741  
   742  	case *types.Slice:
   743  		buf.WriteString("[]")
   744  		w.writeType(buf, typ.Elem())
   745  
   746  	case *types.Struct:
   747  		buf.WriteString("struct")
   748  
   749  	case *types.Pointer:
   750  		buf.WriteByte('*')
   751  		w.writeType(buf, typ.Elem())
   752  
   753  	case *types.Tuple:
   754  		panic("should never see a tuple type")
   755  
   756  	case *types.Signature:
   757  		buf.WriteString("func")
   758  		w.writeSignature(buf, typ)
   759  
   760  	case *types.Interface:
   761  		buf.WriteString("interface{")
   762  		if typ.NumMethods() > 0 {
   763  			buf.WriteByte(' ')
   764  			buf.WriteString(strings.Join(sortedMethodNames(typ), ", "))
   765  			buf.WriteByte(' ')
   766  		}
   767  		buf.WriteString("}")
   768  
   769  	case *types.Map:
   770  		buf.WriteString("map[")
   771  		w.writeType(buf, typ.Key())
   772  		buf.WriteByte(']')
   773  		w.writeType(buf, typ.Elem())
   774  
   775  	case *types.Chan:
   776  		var s string
   777  		switch typ.Dir() {
   778  		case types.SendOnly:
   779  			s = "chan<- "
   780  		case types.RecvOnly:
   781  			s = "<-chan "
   782  		case types.SendRecv:
   783  			s = "chan "
   784  		default:
   785  			panic("unreachable")
   786  		}
   787  		buf.WriteString(s)
   788  		w.writeType(buf, typ.Elem())
   789  
   790  	case *types.Named:
   791  		obj := typ.Obj()
   792  		pkg := obj.Pkg()
   793  		if pkg != nil && pkg != w.current {
   794  			buf.WriteString(pkg.Name())
   795  			buf.WriteByte('.')
   796  		}
   797  		buf.WriteString(typ.Obj().Name())
   798  
   799  	default:
   800  		panic(fmt.Sprintf("unknown type %T", typ))
   801  	}
   802  }
   803  
   804  func (w *Walker) writeSignature(buf *bytes.Buffer, sig *types.Signature) {
   805  	w.writeParams(buf, sig.Params(), sig.Variadic())
   806  	switch res := sig.Results(); res.Len() {
   807  	case 0:
   808  		// nothing to do
   809  	case 1:
   810  		buf.WriteByte(' ')
   811  		w.writeType(buf, res.At(0).Type())
   812  	default:
   813  		buf.WriteByte(' ')
   814  		w.writeParams(buf, res, false)
   815  	}
   816  }
   817  
   818  func (w *Walker) writeParams(buf *bytes.Buffer, t *types.Tuple, variadic bool) {
   819  	buf.WriteByte('(')
   820  	for i, n := 0, t.Len(); i < n; i++ {
   821  		if i > 0 {
   822  			buf.WriteString(", ")
   823  		}
   824  		typ := t.At(i).Type()
   825  		if variadic && i+1 == n {
   826  			buf.WriteString("...")
   827  			typ = typ.(*types.Slice).Elem()
   828  		}
   829  		w.writeType(buf, typ)
   830  	}
   831  	buf.WriteByte(')')
   832  }
   833  
   834  func (w *Walker) typeString(typ types.Type) string {
   835  	var buf bytes.Buffer
   836  	w.writeType(&buf, typ)
   837  	return buf.String()
   838  }
   839  
   840  func (w *Walker) signatureString(sig *types.Signature) string {
   841  	var buf bytes.Buffer
   842  	w.writeSignature(&buf, sig)
   843  	return buf.String()
   844  }
   845  
   846  func (w *Walker) emitObj(obj types.Object) {
   847  	switch obj := obj.(type) {
   848  	case *types.Const:
   849  		w.emitf("const %s %s", obj.Name(), w.typeString(obj.Type()))
   850  		x := obj.Val()
   851  		short := x.String()
   852  		exact := x.ExactString()
   853  		if short == exact {
   854  			w.emitf("const %s = %s", obj.Name(), short)
   855  		} else {
   856  			w.emitf("const %s = %s  // %s", obj.Name(), short, exact)
   857  		}
   858  	case *types.Var:
   859  		w.emitf("var %s %s", obj.Name(), w.typeString(obj.Type()))
   860  	case *types.TypeName:
   861  		w.emitType(obj)
   862  	case *types.Func:
   863  		w.emitFunc(obj)
   864  	default:
   865  		panic("unknown object: " + obj.String())
   866  	}
   867  }
   868  
   869  func (w *Walker) emitType(obj *types.TypeName) {
   870  	name := obj.Name()
   871  	typ := obj.Type()
   872  	if obj.IsAlias() {
   873  		w.emitf("type %s = %s", name, w.typeString(typ))
   874  		return
   875  	}
   876  	switch typ := typ.Underlying().(type) {
   877  	case *types.Struct:
   878  		w.emitStructType(name, typ)
   879  	case *types.Interface:
   880  		w.emitIfaceType(name, typ)
   881  		return // methods are handled by emitIfaceType
   882  	default:
   883  		w.emitf("type %s %s", name, w.typeString(typ.Underlying()))
   884  	}
   885  
   886  	// emit methods with value receiver
   887  	var methodNames map[string]bool
   888  	vset := types.NewMethodSet(typ)
   889  	for i, n := 0, vset.Len(); i < n; i++ {
   890  		m := vset.At(i)
   891  		if m.Obj().Exported() {
   892  			w.emitMethod(m)
   893  			if methodNames == nil {
   894  				methodNames = make(map[string]bool)
   895  			}
   896  			methodNames[m.Obj().Name()] = true
   897  		}
   898  	}
   899  
   900  	// emit methods with pointer receiver; exclude
   901  	// methods that we have emitted already
   902  	// (the method set of *T includes the methods of T)
   903  	pset := types.NewMethodSet(types.NewPointer(typ))
   904  	for i, n := 0, pset.Len(); i < n; i++ {
   905  		m := pset.At(i)
   906  		if m.Obj().Exported() && !methodNames[m.Obj().Name()] {
   907  			w.emitMethod(m)
   908  		}
   909  	}
   910  }
   911  
   912  func (w *Walker) emitStructType(name string, typ *types.Struct) {
   913  	typeStruct := fmt.Sprintf("type %s struct", name)
   914  	w.emitf(typeStruct)
   915  	defer w.pushScope(typeStruct)()
   916  
   917  	for i := 0; i < typ.NumFields(); i++ {
   918  		f := typ.Field(i)
   919  		if !f.Exported() {
   920  			continue
   921  		}
   922  		typ := f.Type()
   923  		if f.Anonymous() {
   924  			w.emitf("embedded %s", w.typeString(typ))
   925  			continue
   926  		}
   927  		w.emitf("%s %s", f.Name(), w.typeString(typ))
   928  	}
   929  }
   930  
   931  func (w *Walker) emitIfaceType(name string, typ *types.Interface) {
   932  	pop := w.pushScope("type " + name + " interface")
   933  
   934  	var methodNames []string
   935  	complete := true
   936  	mset := types.NewMethodSet(typ)
   937  	for i, n := 0, mset.Len(); i < n; i++ {
   938  		m := mset.At(i).Obj().(*types.Func)
   939  		if !m.Exported() {
   940  			complete = false
   941  			continue
   942  		}
   943  		methodNames = append(methodNames, m.Name())
   944  		w.emitf("%s%s", m.Name(), w.signatureString(m.Type().(*types.Signature)))
   945  	}
   946  
   947  	if !complete {
   948  		// The method set has unexported methods, so all the
   949  		// implementations are provided by the same package,
   950  		// so the method set can be extended. Instead of recording
   951  		// the full set of names (below), record only that there were
   952  		// unexported methods. (If the interface shrinks, we will notice
   953  		// because a method signature emitted during the last loop
   954  		// will disappear.)
   955  		w.emitf("unexported methods")
   956  	}
   957  
   958  	pop()
   959  
   960  	if !complete {
   961  		return
   962  	}
   963  
   964  	if len(methodNames) == 0 {
   965  		w.emitf("type %s interface {}", name)
   966  		return
   967  	}
   968  
   969  	sort.Strings(methodNames)
   970  	w.emitf("type %s interface { %s }", name, strings.Join(methodNames, ", "))
   971  }
   972  
   973  func (w *Walker) emitFunc(f *types.Func) {
   974  	sig := f.Type().(*types.Signature)
   975  	if sig.Recv() != nil {
   976  		panic("method considered a regular function: " + f.String())
   977  	}
   978  	w.emitf("func %s%s", f.Name(), w.signatureString(sig))
   979  }
   980  
   981  func (w *Walker) emitMethod(m *types.Selection) {
   982  	sig := m.Type().(*types.Signature)
   983  	recv := sig.Recv().Type()
   984  	// report exported methods with unexported receiver base type
   985  	if true {
   986  		base := recv
   987  		if p, _ := recv.(*types.Pointer); p != nil {
   988  			base = p.Elem()
   989  		}
   990  		if obj := base.(*types.Named).Obj(); !obj.Exported() {
   991  			log.Fatalf("exported method with unexported receiver base type: %s", m)
   992  		}
   993  	}
   994  	w.emitf("method (%s) %s%s", w.typeString(recv), m.Obj().Name(), w.signatureString(sig))
   995  }
   996  
   997  func (w *Walker) emitf(format string, args ...interface{}) {
   998  	f := strings.Join(w.scope, ", ") + ", " + fmt.Sprintf(format, args...)
   999  	if strings.Contains(f, "\n") {
  1000  		panic("feature contains newlines: " + f)
  1001  	}
  1002  
  1003  	if _, dup := w.features[f]; dup {
  1004  		panic("duplicate feature inserted: " + f)
  1005  	}
  1006  	w.features[f] = true
  1007  
  1008  	if *verbose {
  1009  		log.Printf("feature: %s", f)
  1010  	}
  1011  }
  1012  

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