libstdc++: Check string value_type in std::make_format_args [PR112607]

libstdc++-v3/ChangeLog:

	PR libstdc++/112607
	* include/std/format (basic_format_arg::_S_to_arg_type): Check
	value_type for basic_string_view and basic_string
	specializations.
	* testsuite/std/format/arguments/112607.cc: New test.

1 files changed, 30 insertions, 0 deletions

diff --git a/libstdc++-v3/testsuite/std/format/arguments/112607.cc b/libstdc++-v3/testsuite/std/format/arguments/112607.cc
new file mode 100644
index 0000000..19eec76
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/format/arguments/112607.cc
@@ -0,0 +1,30 @@
+// { dg-do compile { target c++20 } }
+
+// PR libstdc++/112607
+// _Normalize does not consider char_type for the basic_string_view case
+
+#include <format>
+
+template<typename T>
+struct Alloc
+{
+  using value_type = T;
+  Alloc() = default;
+  template<typename U>
+    Alloc(const Alloc<U>&) { }
+  T* allocate(std::size_t);
+  void deallocate(T*, std::size_t);
+  bool operator==(const Alloc&) const;
+};
+
+template<typename C>
+using String = std::basic_string<C, std::char_traits<C>, Alloc<C>>;
+
+template<>
+struct std::formatter<String<wchar_t>> : std::formatter<std::string> {
+  auto format(const String<wchar_t>&, auto& ctx) const {
+    return std::formatter<std::string>::format(" ", ctx);
+  }
+};
+
+std::string str = std::format("{}", String<wchar_t>{});