pkg os, type FileInfo interface, Size() int64
pkg os, type FileInfo interface, Sys() interface{}
pkg os, type FileMode uint32
pkg os, type PathError struct
pkg os, type PathError struct, Err error
pkg os, type PathError struct, Op string
pkg os, type PathError struct, Path string
pkg syscall (darwin-amd64), const ImplementsGetwd = false
pkg syscall (darwin-amd64), func Fchflags(string, int) error

// leading / or ../ elements.
func (r *Reader) Open(name string) (fs.File, error) {
	r.initFileList()

	if !fs.ValidPath(name) {
		return nil, &fs.PathError{Op: "open", Path: name, Err: fs.ErrInvalid}
	}
	e := r.openLookup(name)
	if e == nil {
		return nil, &fs.PathError{Op: "open", Path: name, Err: fs.ErrNotExist}
	}
	if e.isDir {
		return &openDir{e, r.openReadDir(name), 0}, nil
	}
	rc, err := e.file.Open()

// If there are many of these, we could do a more general solution,
// but for now the replacer is fine.
var aliasReplacer = strings.NewReplacer(
	"os.FileInfo", "fs.FileInfo",
	"os.FileMode", "fs.FileMode",
	"os.PathError", "fs.PathError",
)

func fileFeatures(filename string, needApproval bool) []string {
	bs, err := os.ReadFile(filename)
	if err != nil {
		log.Fatal(err)
	}
	s := string(bs)