[libc++] `std::locale(named, unnamed, std::locale::none)` should obtain its name from `named`

[cpplearner]

Reduced from libcxx/test/std/localization/locales/locale/locale.cons/name_construction.pass.cpp:

#include <iostream>
#include <locale>

constexpr auto LOCALE_en_US_UTF_8 = "en_US.UTF-8";
int main(int, char**) {
    std::locale en(LOCALE_en_US_UTF_8);
    std::locale unnamed(std::locale(), new std::ctype<char>);

    {
        std::locale loc(en, unnamed, std::locale::none);
        std::cout << loc.name() << '\n';
    }
  return 0;
}

Both libstdc++ and MSVC's STL print "en_US.UTF-8" for loc.name(), but libc++ prints "*".

I think this can be fixed by swapping the two conditions in build_name.

llvm-project/libcxx/src/locale.cpp

Lines 101 to 110 in 351303c

	string build_name(const string& other, const string& one, locale::category c) {
	if (other == "*" || one == "*")
	return "*";
	if (c == locale::none || other == one)
	return other;
	// FIXME: Handle the more complicated cases, such as when the locale has
	// different names for different categories.
	return "*";
	}

[frederick-vs-ja]

Looks like duplicate #105063.

[cpplearner]

So it turns out that this is actually LWG 3676, which happens to be resolved by the proposed resolution of LWG 2295, and #105063 tracks the latter.