if err != nil {
		return ""
	}
	defer f.Close()

	var src [4 << 10]byte // read at most 4KB
	n, _ := f.Read(src[:])

	var first string
	var s scanner.Scanner
	s.Init(fset.AddFile("", fset.Base(), n), src[:n], nil /* ignore errors */, scanner.ScanComments)
	for {
		_, tok, lit := s.Scan()
		switch tok {
		case token.COMMENT:
			// remove trailing */ of multi-line comment
			if lit[1] == '*' {

// only as long as required to hold the tag with the largest index i. Consequently,
// if no field has a tag, tags may be nil.
func NewStruct(fields []*Var, tags []string) *Struct {
	var fset objset
	for _, f := range fields {
		if f.name != "_" && fset.insert(f) != nil {
			panic("multiple fields with the same name")
		}
	}
	if len(tags) > len(fields) {
		panic("more tags than fields")
	}
	s := &Struct{fields: fields, tags: tags}

.*have M5[(]struct{b[.]S; b[.]t}[)]
.*want M5[(]struct{b[.]S; t}[)]`},
	}

	fset := token.NewFileSet()
	test := func(main, b, want string) {
		re := regexp.MustCompile(want)
		bpkg := mustTypecheck(b, nil, nil)
		mast := mustParse(fset, main)
		conf := Config{Importer: importHelper{pkg: bpkg}}
		_, err := conf.Check(mast.Name.Name, fset, []*ast.File{mast}, nil)
		if err == nil {
			t.Error("Expected failure, but it did not")

// parse may be called concurrently.
func parse(filename string, src any) (*ast.File, error) {
	if *verbose {
		fmt.Println(filename)
	}
	file, err := parser.ParseFile(fset, filename, src, parserMode) // ok to access fset concurrently
	if *printAST {
		ast.Print(fset, file)
	}
	return file, err
}

func parseStdin() (*ast.File, error) {
	src, err := io.ReadAll(os.Stdin)
	if err != nil {
		return nil, err
	}

// only as long as required to hold the tag with the largest index i. Consequently,
// if no field has a tag, tags may be nil.
func NewStruct(fields []*Var, tags []string) *Struct {
	var fset objset
	for _, f := range fields {
		if f.name != "_" && fset.insert(f) != nil {
			panic("multiple fields with the same name")
		}
	}
	if len(tags) > len(fields) {
		panic("more tags than fields")
	}
	s := &Struct{fields: fields, tags: tags}

	if err != nil {
		t.Fatal(err)
	}

	for _, fi := range fis {
		t.Run(fi.Name(), func(t *testing.T) {
			fset := token.NewFileSet()
			path := filepath.Join(dir, fi.Name())
			src := readFile(path) // panics on failure
			var mode Mode
			file, err := ParseFile(fset, path, src, mode)
			if err != nil {
				t.Fatal(err)
			}

			// Compare the positions of objects resolved during parsing (fromParser)

	"golang.org/x/tools/internal/aliases"
	"golang.org/x/tools/internal/analysisinternal"
)

// Format returns a string representation of the expression.
func Format(fset *token.FileSet, x ast.Expr) string {
	var b bytes.Buffer
	printer.Fprint(&b, fset, x)
	return b.String()
}

// HasSideEffects reports whether evaluation of e has side effects.
func HasSideEffects(info *types.Info, e ast.Expr) bool {
	safe := true

	src, err := os.ReadFile("doc.go")
	if err != nil {
		t.Fatal(err)
	}
	fset := token.NewFileSet()
	f, err := parser.ParseFile(fset, "doc.go", src, parser.ParseComments)
	if err != nil {
		t.Fatal(err)
	}
	fdoc := f.Doc
	if fdoc == nil {
		t.Fatal("no doc comment in doc.go")
	}
	pkg, err := doc.NewFromFiles(fset, []*ast.File{f}, "runtime/metrics")
	if err != nil {
		t.Fatal(err)
	}

func (*Tree[R]) N(r R) R { return r }

type Node[T any] struct {
	*Tree[T]
}

func (Node[Q]) M(Q) {}

type Inst = *Tree[int]
`

	fset := token.NewFileSet()
	f := mustParse(fset, src)
	pkg := NewPackage("p", f.Name.Name)
	if err := NewChecker(nil, fset, pkg, nil).Files([]*ast.File{f}); err != nil {
		t.Fatal(err)
	}

	firstFieldType := func(n *Named) *Named {

				continue // expressions may not be equal
			}
			if reflect.TypeOf(lhs) != reflect.TypeOf(rhs) {
				continue // short-circuit the heavy-weight gofmt check
			}
			le := analysisutil.Format(pass.Fset, lhs)
			re := analysisutil.Format(pass.Fset, rhs)
			if le == re {
				pass.Report(analysis.Diagnostic{
					Pos: stmt.Pos(), Message: fmt.Sprintf("self-assignment of %s to %s", re, le),
					SuggestedFixes: []analysis.SuggestedFix{