Allow comparisons between empty `struct{}` and `union{}`

src/llvm_backend_expr.cpp

@@ -2210,6 +2210,15 @@ gb_internal lbValue lb_compare_records(lbProcedure *p, TokenKind op_kind, lbValu
 	lbValue left_ptr  = lb_address_from_load_or_generate_local(p, left);
 	lbValue right_ptr = lb_address_from_load_or_generate_local(p, right);
 	lbValue res = {};
+	if (type_size_of(type) == 0) {
+		switch (op_kind) {
+		case Token_CmpEq:
+			return lb_const_bool(p->module, t_bool, true);
+		case Token_NotEq:
+			return lb_const_bool(p->module, t_bool, false);
+		}
+		GB_PANIC("invalid operator");
+	}
 	if (is_type_simple_compare(type)) {
 		// TODO(bill): Test to see if this is actually faster!!!!
 		auto args = array_make<lbValue>(permanent_allocator(), 3);

src/types.cpp

@@ -2313,9 +2313,6 @@ gb_internal bool is_type_comparable(Type *t) {
 		return true;
 
 	case Type_Struct:
-		if (type_size_of(t) == 0) {
-			return false;
-		}
 		if (t->Struct.soa_kind != StructSoa_None) {
 			return false;
 		}
@@ -2331,9 +2328,6 @@ gb_internal bool is_type_comparable(Type *t) {
 		return true;
 
 	case Type_Union:
-		if (type_size_of(t) == 0) {
-			return false;
-		}
 		for_array(i, t->Union.variants) {
 			Type *v = t->Union.variants[i];
 			if (!is_type_comparable(v)) {