[Bug c++/109070] New: ICE in class template member function overloads distinguished by non-functionally-equivalent constraints and return type

["ed at catmur dot uk" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109070

            Bug ID: 109070
           Summary: ICE in class template member function overloads
                    distinguished by non-functionally-equivalent
                    constraints and return type
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ed at catmur dot uk
  Target Milestone: ---

template<int I> concept C = true;
template<typename T> struct A {
    int f() requires C<42> { return 1; }  // #1
    unsigned f() requires true { return 2u; }  // #2
};
int main() {
    int (A<int>::*p)() = &A<int>::f;
    unsigned (A<int>::*q)() = &A<int>::f;
    return (A<int>().*p)() + (A<int>().*q)();
}

<source>:10:1: error: Two symbols with same comdat_group are not linked by the
same_comdat_group list.
   10 | }
      | ^
_ZN1AIiE1fEv/2 (unsigned int A<T>::f() requires  true [with T = int])
  Type: function definition analyzed
  Visibility: semantic_interposition public weak comdat
comdat_group:_ZN1AIiE1fEv one_only
  previous sharing asm name: 1
  Address is taken.
  References: 
  Referring: main/0 (addr) 
  Function flags: body
  Called by: 
  Calls: 
_ZN1AIiE1fEv/1 (int A<T>::f() requires  C<42> [with T = int])
  Type: function definition analyzed
  Visibility: semantic_interposition public weak comdat
comdat_group:_ZN1AIiE1fEv one_only
  next sharing asm name: 2
  Address is taken.
  References: 
  Referring: main/0 (addr) 
  Function flags: body
  Called by: 
  Calls: 
<source>:10:1: internal compiler error: symtab_node::verify failed
0x247b73e internal_error(char const*, ...)
        ???:0
0xed5c22 symtab_node::verify_symtab_nodes()
        ???:0
0xef042b symbol_table::finalize_compilation_unit()
        ???:0

This is valid per [temp.over.link]/5, but that seems impossible to implement -
I've filed https://github.com/cplusplus/CWG/issues/256.