[Bug libstdc++/110853] [c++-concepts] Bad interaction between deduction guide with decay and constraints (CTAD, std::pair and function lvalue)

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110853

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
This should fix it:

--- a/libstdc++-v3/include/bits/stl_pair.h
+++ b/libstdc++-v3/include/bits/stl_pair.h
@@ -445,7 +445,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION

       /// Constructor accepting lvalues of `first_type` and `second_type`
       constexpr explicit(!_S_convertible<const _T1&, const _T2&>())
-      pair(const _T1& __x, const _T2& __y)
+      pair(const type_identity_t<_T1>& __x, const _T2& __y)
       noexcept(_S_nothrow_constructible<const _T1&, const _T2&>())
       requires (_S_constructible<const _T1&, const _T2&>())
       : first(__x), second(__y)