[Bug libstdc++/94520] New: [10 Regression] <charconv> no longer compiles in C++14

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94520

            Bug ID: 94520
           Summary: [10 Regression] <charconv> no longer compiles in C++14
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Keywords: rejects-valid
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org
  Target Milestone: ---

This is supposed to be supported in C++14 as an extension:

#include <charconv>
int main() { }

But since r272695 it no longer works:

/home/jwakely/gcc/10/include/c++/10.0.1/charconv:71:21: error: '__or_v' was not
declared in this scope; did you mean '__or_'?
   71 |       = enable_if_t<__or_v<__is_signed_integer<_Tp>,
      |                     ^~~~~~
      |                     __or_