[Bug libstdc++/94901] New: [10 Regression] uses BADNAME _T

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94901

            Bug ID: 94901
           Summary: [10 Regression] <type_traits> uses BADNAME _T
           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: ---

GCC 10 adds:

  template <typename _T, size_t = sizeof(_T)>
    constexpr true_type __is_complete_or_unbounded(__type_identity<_T>)
    { return {}; }


But _T is a documented BADNAME and needs to be replaced with _Tp.

This was reported on IRC, I don't have a full reproducer, but it's clearly a
bug.