func (d *openDir) Read([]byte) (int, error) {
	return 0, &fs.PathError{Op: "read", Path: d.e.name, Err: errors.New("is a directory")}
}

func (d *openDir) ReadDir(count int) ([]fs.DirEntry, error) {
	n := len(d.files) - d.offset
	if count > 0 && n > count {
		n = count
	}
	if n == 0 {
		if count <= 0 {
			return nil, nil
		}
		return nil, io.EOF
	}

pkg os, func OpenFile(string, int, FileMode) (*File, error)
pkg os, func SameFile(FileInfo, FileInfo) bool
pkg os, func Stat(string) (FileInfo, error)
pkg os, method (*File) Chmod(FileMode) error
pkg os, method (*File) Readdir(int) ([]FileInfo, error)
pkg os, method (*File) Stat() (FileInfo, error)
pkg os, method (*PathError) Error() string
pkg os, method (*PathError) Timeout() bool
pkg os, method (*PathError) Unwrap() error

		// slow, not worth repeating in -check
		t.Skip("skipping with -check set")
	}

	testenv.MustHaveGoBuild(t)

	td, err := os.Open("testdata/src/pkg")
	if err != nil {
		t.Fatal(err)
	}
	fis, err := td.Readdir(0)
	if err != nil {
		t.Fatal(err)
	}
	for _, fi := range fis {
		if !fi.IsDir() {
			continue
		}

		// TODO(gri) remove extra pkg directory eventually

		t.Errorf("Opening %q with fs.FS API succeeded", "")
	}
	if _, err := r.Open("test.txt"); err != nil {
		t.Errorf("Error opening %q with fs.FS API: %v", "test.txt", err)
	}
	dirEntries, err := fs.ReadDir(r, ".")
	if err != nil {
		t.Fatalf("Error reading the root directory: %v", err)
	}
	if len(dirEntries) != 1 || dirEntries[0].Name() != "test.txt" {
		t.Errorf("Unexpected directory entries")