Bit negating const zero flags would give an incorrect result. #1213

releasenotes.md

@@ -23,6 +23,7 @@
 - Bit negate does implicit integer promotion.
 - Bitstructs, unions and flexible arrays now correctly emitted in headers.
 - Fix distinct inline conversions.
+- Bit negating const zero flags would give an incorrect result.
 
 ### Stdlib changes
 - Added `remove_first_item` `remove_last_item` and `remove_item` as aliases for the `match` functions.

src/compiler/sema_initializers.c

@@ -568,6 +568,7 @@ void sema_invert_bitstruct_const_initializer(ConstInitializer *initializer)
 			if (init->kind == CONST_INIT_ZERO)
 			{
 				init->init_value = expr_new_const_bool(INVALID_SPAN, init->type, true);
+				init->kind = CONST_INIT_VALUE;
 				continue;
 			}
 			init->init_value->const_expr.b = !init->init_value->const_expr.b;
@@ -922,11 +923,11 @@ static inline void sema_update_const_initializer_with_designator_array(ConstInit
 	ConstInitializer **array_elements = const_init->init_array.elements;
 
 	unsigned array_count = vec_size(array_elements);
-
 	MemberIndex insert_index = 0;
 
 	for (MemberIndex index = low_index; index <= high_index; index++)
 	{
+		assert(insert_index >= array_count || array_elements);
 		// Walk to the insert point or until we reached the end of the array.
 		while (insert_index < array_count && array_elements[insert_index]->init_array_value.index < index)
 		{

test/unit/regression/bitstruct_ops3.c3

@@ -69,4 +69,22 @@ fn void test_inc_array()
 	assert(x.a++ == 10);
 	assert(x.a == 11, "Value was %d", x.a);
 	assert(--x.a == 10);
+}
+
+bitstruct Flags : int
+{
+	bool flag1;
+	bool flag2;
+}
+
+fn void negate()
+{
+	Flags flags;
+	flags = ~flags;
+	assert(~0 == (int)flags);
+	flags = ~Flags {};
+	assert(3 == (int)flags);
+	const Flags FLAGS = {.flag1 };
+	flags = ~FLAGS;
+	assert(2 == (int)flags);
 }