if allString(x.typ) != allString(y.typ) {
			return false
		}
		// Untyped nil can only convert to a type that has a nil.
		if x.isNil() {
			return hasNil(y.typ)
		}
		if y.isNil() {
			return hasNil(x.typ)
		}
		// An untyped operand cannot convert to a pointer.
		// TODO(gri) generalize to type parameters
		if isPointer(x.typ) || isPointer(y.typ) {
			return false
		}

		if allString(x.typ) != allString(y.typ) {
			return false
		}
		// Untyped nil can only convert to a type that has a nil.
		if x.isNil() {
			return hasNil(y.typ)
		}
		if y.isNil() {
			return hasNil(x.typ)
		}
		// An untyped operand cannot convert to a pointer.
		// TODO(gri) generalize to type parameters
		if isPointer(x.typ) || isPointer(y.typ) {
			return false
		}

func (t *Type) IsPtrShaped() bool {
	return t.kind == TPTR || t.kind == TUNSAFEPTR ||
		t.kind == TMAP || t.kind == TCHAN || t.kind == TFUNC
}

// HasNil reports whether the set of values determined by t includes nil.
func (t *Type) HasNil() bool {
	switch t.kind {
	case TCHAN, TFUNC, TINTER, TMAP, TNIL, TPTR, TSLICE, TUNSAFEPTR:
		return true
	}
	return false
}