[libcxx-commits] [libcxx] Adds back special-case for booleans in std::variant gated by _LIBCPP_ENABLE_NARROWING_CONVERSIONS_IN_VARIANT. (PR #73121)

[Jordan Rupprecht via libcxx-commits]

================
@@ -199,19 +204,23 @@ void test_construction_with_repeated_types() {
   static_assert(std::is_constructible<V, Bar>::value, "");
 }
 
+#if !defined(_LIBCPP_ENABLE_NARROWING_CONVERSIONS_IN_VARIANT)
 void test_vector_bool() {
   std::vector<bool> vec = {true};
   std::variant<bool, int> v = vec[0];
   assert(v.index() == 0);
   assert(std::get<0>(v) == true);
 }
+#endif
 
 int main(int, char**) {
   test_T_ctor_basic();
   test_T_ctor_noexcept();
   test_T_ctor_sfinae();
   test_no_narrowing_check_for_class_types();
   test_construction_with_repeated_types();
+#if !defined(_LIBCPP_ENABLE_NARROWING_CONVERSIONS_IN_VARIANT)
----------------
rupprecht wrote:

Instead of having multiple ifdefs, just have `test_vector_bool` always be defined, but possibly empty, i.e.

```cpp
void test_vector_bool() {
#ifndef _LIBCPP_ENABLE_NARROWING_CONVERSIONS_IN_VARIANT
  std::vector<bool> vec = {true};
  std::variant<bool, int> v = vec[0];
  assert(v.index() == 0);
  assert(std::get<0>(v) == true);
#endif  // _LIBCPP_ENABLE_NARROWING_CONVERSIONS_IN_VARIANT
}

int main(int, char**) {
  test_T_ctor_basic();
  test_T_ctor_noexcept();
  test_T_ctor_sfinae();
  test_no_narrowing_check_for_class_types();
  test_construction_with_repeated_types();
  test_vector_bool();
```

https://github.com/llvm/llvm-project/pull/73121