[gcc r12-4404] libstdc++: Fix brainwrong in path::_S_convert(T) [PR102743]

[Jonathan Wakely <redi@gcc.gnu.org>]

https://gcc.gnu.org/g:5e3f88838994b67580594c4679c839fff7cdeba0

commit r12-4404-g5e3f88838994b67580594c4679c839fff7cdeba0
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu Oct 14 13:20:57 2021 +0100

    libstdc++: Fix brainwrong in path::_S_convert(T) [PR102743]
    
    This function was supposed to check whether the parameter's value type
    is the same as path::value_type, and therefore needs no conversion.
    Instead it checks whether the parameter is the same as its own value
    type, which is never true. This means we incorrectly return a string
    view for the case where T is path::string_type, instead of just
    returning the string itself. The only place that happens is
    path::_S_convert_loc for Windows, where we call _S_convert with a
    std::wstring rvalue.
    
    This fixes the condition in _S_convert(T).
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/102743
            * include/bits/fs_path.h (path::_S_convert(T)): Fix condition
            for returning the same string unchanged.

Diff:
---
 libstdc++-v3/include/bits/fs_path.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/bits/fs_path.h b/libstdc++-v3/include/bits/fs_path.h
index c51bfa3095a..a63e4b9ab07 100644
--- a/libstdc++-v3/include/bits/fs_path.h
+++ b/libstdc++-v3/include/bits/fs_path.h
@@ -625,7 +625,7 @@ namespace __detail
       static auto
       _S_convert(_Tp __str)
       {
-	if constexpr (is_same_v<_Tp, typename _Tp::value_type>)
+	if constexpr (is_same_v<typename _Tp::value_type, value_type>)
 	  return __str; // No conversion needed.
 #if !defined _GLIBCXX_FILESYSTEM_IS_WINDOWS && defined _GLIBCXX_USE_CHAR8_T
 	else if constexpr (is_same_v<_Tp, std::u8string>)