func (f *File) walk(x interface{}, context astContext, visit func(*File, interface{}, astContext)) {
	visit(f, x, context)
	switch n := x.(type) {
	case *ast.Expr:
		f.walk(*n, context, visit)

	// everything else just recurs
	default:
		f.walkUnexpected(x, context, visit)

	case nil:

	// These are ordered and grouped to match ../../go/ast/ast.go
	case *ast.Field:
		if len(n.Names) == 0 && context == ctxField {

			case *ast.TypeSpec:
				if isDeprecated(n.Doc) {
					mark(n.Name)
				}
				return true // recurse into struct or interface type
			case *ast.StructType:
				return true // recurse into fields
			case *ast.InterfaceType:
				return true // recurse into methods
			case *ast.FieldList:
				return true // recurse into fields
			case *ast.ValueSpec:
				if isDeprecated(n.Doc) {
					for _, id := range n.Names {

func (b *Reader) Reset(r io.Reader) {
	// If a Reader r is passed to NewReader, NewReader will return r.
	// Different layers of code may do that, and then later pass r
	// to Reset. Avoid infinite recursion in that case.
	if b == r {
		return
	}
	if b.buf == nil {
		b.buf = make([]byte, defaultBufSize)
	}
	b.reset(b.buf, r)
}

func (b *Reader) reset(buf []byte, r io.Reader) {
	*b = Reader{

	if tok != '\n' {
		in.Error("syntax error in #undef for macro:", name)
	}
	delete(in.macros, name)
}

func (in *Input) Push(r TokenReader) {
	if len(in.tr) > 100 {
		in.Error("input recursion")
	}
	in.Stack.Push(r)
}

func (in *Input) Close() {