[Bug c++/114600] [14 Regression] [modules] redefinition errors when using certain std headers in GMF

["ppalka at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114600

Patrick Palka <ppalka at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |nshead at gcc dot gnu.org,
                   |                            |ppalka at gcc dot gnu.org
           Keywords|                            |rejects-valid
   Target Milestone|---                         |14.0
             Blocks|                            |103524
            Summary|[modules] redefinition      |[14 Regression] [modules]
                   |errors when using certain   |redefinition errors when
                   |std headers in GMF          |using certain std headers
                   |                            |in GMF
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2024-04-05
             Status|UNCONFIRMED                 |NEW

--- Comment #2 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Confirmed, started with r14-6978.

Mechanical reduction:

$ cat 114600.h
namespace std {
template <typename> struct integral_constant {
  typedef integral_constant type;
};
template <bool> using __enable_if_t = int;
template <typename> auto __and_fn() -> integral_constant<bool>;
template <typename... _Bn> struct __and_ : decltype(__and_fn<_Bn...>) {};
template <typename... _Cond>
using _Require = __enable_if_t<__and_<_Cond...>::value>;
template <typename _Tp> _Require<_Tp> swap();
namespace __swappable_details {
using std::swap;
}
} // namespace std

$ cat 114600_a.C
module;

#include "114600.h"

export module std;

$ cat 114600_b.C
import std;

#include "114600.h"

int main()
{
}

$ g++ -fmodules-ts 114600_*.C
114600.h:3:29: error: template definition of non-template 'typedef struct
std::integral_constant< <template-parameter-1-1> > std::integral_constant<
<template-parameter-1-1> >::type'


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103524
[Bug 103524] [meta-bug] modules issue