// into equivalence classes (Types that compare CMPeq) matters.
func (t *Type) Compare(x *Type) Cmp {
	if x == t {
		return CMPeq
	}
	return t.cmp(x)
}

func cmpForNe(x bool) Cmp {
	if x {
		return CMPlt
	}
	return CMPgt
}

func (r *Sym) cmpsym(s *Sym) Cmp {
	if r == s {
		return CMPeq
	}
	if r == nil {
		return CMPlt
	}
	if s == nil {