}

func (s *ImportStack) Top() string {
	if len(*s) == 0 {
		return ""
	}
	return (*s)[len(*s)-1]
}

// shorterThan reports whether sp is shorter than t.
// We use this to record the shortest import sequence
// that leads to a particular package.
func (sp *ImportStack) shorterThan(t []string) bool {
	s := *sp
	if len(s) != len(t) {
		return len(s) < len(t)
	}