[Bug c++/114795] internal compiler error: in finish_member_declaration after module import in gcc 14.0.1 snapshot

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114795

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2024-04-23
                 CC|                            |ppalka at gcc dot gnu.org

--- Comment #7 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Reduced version of comment #6 testcase:

$ cat 114795_a.H
template<class T>
struct A {
  auto f() { return 0; }
};

template<class T>
inline void g() {
  A<int> a;
  a.f();
}

$ cat 114795_b.C
template<class T>
struct A {
  auto f() { return 0; }
};

A<int> a;

import "114795_a.H";

int main() {
  g<int>();
}

$ g++ -fmodules-ts 114795_*
In module ./114795-2_a.H, imported at 114795_b.C:8:
114795_a.H: In instantiation of ‘void g() [with T = int]’:
114795_b.C:11:9:   required from here
   11 |   g<int>();
      |   ~~~~~~^~
114795_a.H:9:6: error: use of ‘auto A<T>::f() [with T = int]’ before deduction
of ‘auto’
    9 |   a.f();
      |   ~~~^~
114795_a.H:9:6: error: use of ‘auto A<T>::f() [with T = int]’ before deduction
of ‘auto’


I think I have a fix -- we need to propagate an already-deduced return type
during deduplication.