// TODO(mdempsky): Consider using some non-nil pointer to indicate
	// the universe scope, so we don't need to keep re-reading it.
	if pkg := pr.pkgs[idx]; pkg != nil {
		return pkg
	}

	pkg := pr.newReader(pkgbits.RelocPkg, idx, pkgbits.SyncPkgDef).doPkg()
	pr.pkgs[idx] = pkg
	return pkg
}

func (r *reader) doPkg() *types.Package {
	path := r.String()
	switch path {
	case "":
		path = r.p.PkgPath()

// type-checks.
func (c *stdlibChecker) getDirPackage(dir string) (*Package, error) {
	c.mu.Lock()
	fut, ok := c.pkgs[dir]
	if !ok {
		// First request for this package dir; type check.
		fut = &futurePackage{
			done: make(chan struct{}),
		}
		c.pkgs[dir] = fut
		files, ok := c.dirFiles[dir]
		c.mu.Unlock()
		if !ok {
			fut.err = fmt.Errorf("no files for %s", dir)
		} else {

// both retain the same versions of all packages in pkgs and satisfy the
// graph-pruning invariants (if applicable).
func tidyRoots(ctx context.Context, rs *Requirements, pkgs []*loadPkg) (*Requirements, error) {
	mainModule := MainModules.mustGetSingleMainModule()
	if rs.pruning == unpruned {
		return tidyUnprunedRoots(ctx, mainModule, rs, pkgs)
	}
	return tidyPrunedRoots(ctx, mainModule, rs, pkgs)
}

		name := filepath.ToSlash(path[len(src):])
		if name == "builtin" || name == "cmd" {
			return filepath.SkipDir
		}

		pkgs = append(pkgs, strings.TrimPrefix(name, "vendor/"))
		return nil
	}
	if err := filepath.WalkDir(src, walkFn); err != nil {
		return nil, err
	}
	return pkgs, nil
}

func TestDependencies(t *testing.T) {
	if !testenv.HasSrc() {
		// Tests run in a limited file system and we do not

	cmd.Stderr = &stderr
	out, err := cmd.Output()
	if err != nil {
		t.Fatalf("failed to run go list to determine stdlib packages: %v\nstderr:\n%v", err, stderr.String())
	}
	pkgs := strings.Fields(string(out))

	var nimports int
	for _, pkg := range pkgs {
		t.Run(pkg, func(t *testing.T) {
			if testPath(t, pkg, filepath.Join(testenv.GOROOT(t), "src", path.Dir(pkg))) != nil {
				nimports++
			}
		})
	}

	return r.matchInModuleCache.Do(matchInModuleKey{pattern, m}, func() ([]string, error) {
		match := modload.MatchInModule(ctx, pattern, m, imports.AnyTags())
		if len(match.Errs) > 0 {
			return match.Pkgs, match.Errs[0]
		}
		return match.Pkgs, nil
	})
}

// queryNone adds a candidate set to q for each module matching q.pattern.
// Each candidate set has only one possible module version: the matched
// module at version "none".

		}
	}
	stk.Pop()

	parallelizablePart := func() {
		if cover != nil && cover.Pkgs != nil && !cfg.Experiment.CoverageRedesign {
			// Add imports, but avoid duplicates.
			seen := map[*Package]bool{p: true, ptest: true}
			for _, p1 := range pmain.Internal.Imports {
				seen[p1] = true
			}
			for _, p1 := range cover.Pkgs {
				if seen[p1] {
					// Don't add duplicate imports.
					continue
				}

		var pcflags []string
		var pkgs []string
		for _, pcarg := range pcargs {
			if pcarg == "--" {
				// We're going to add our own "--" argument.
			} else if strings.HasPrefix(pcarg, "--") {
				pcflags = append(pcflags, pcarg)
			} else {
				pkgs = append(pkgs, pcarg)
			}
		}
		for _, pkg := range pkgs {
			if !load.SafeArg(pkg) {

	// Copy the runtime packages into a temporary GOROOT
	// so that we can change files.
	var dirs []string
	tg.run("list", "-deps", "runtime")
	pkgs := strings.Split(strings.TrimSpace(tg.getStdout()), "\n")
	for _, pkg := range pkgs {
		dirs = append(dirs, filepath.Join("src", pkg))
	}
	dirs = append(dirs,
		filepath.Join("pkg/tool", goHostOS+"_"+goHostArch),
		"pkg/include",
	)

	if l.flags&FlagCheckLinkname == 0 {
		return
	}

	error := func() {
		log.Fatalf("%s: invalid reference to %s", pkg, name)
	}
	pkgs, ok := blockedLinknames[name]
	if ok {
		for _, p := range pkgs {
			if pkg == p {
				return // pkg is allowed
			}
		}
		error()
	}
	r, li := l.toLocal(s)
	if r == l.extReader { // referencing external symbol is okay