[Bug c++/113748] New: GCC rejects valid program involving befriending class with name same as typedef

[Bug c++/113748] New: GCC rejects valid program involving befriending class with name same as typedef

[jlame646 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113748

            Bug ID: 113748
           Summary: GCC rejects valid program involving befriending class
                    with name same as typedef
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jlame646 at gmail dot com
  Target Milestone: ---

The following program is rejected by gcc and clang.
https://godbolt.org/z/3K31ev4YT

```
#include <iostream>
#include <type_traits>

class A {    
};

class B {
    using C = A;


    friend class C;  //gcc and clang rejects this but msvc accepts    
};
```
GCC says:
```
<source>:11:18: error: using typedef-name 'using B::C = class A' after 'class'
   11 |     friend class C;  //gcc and clang rejects this but msvc accepts
      |                  ^
<source>:8:11: note: 'using B::C = class A' has a previous declaration here
    8 |     using C = A;
      |           ^
<source>:11:5: error: friend declaration does not name a class or function
   11 |     friend class C;  //gcc and clang rejects this but msvc accepts
      |     ^~~~~~
Compiler returned: 1
```

This should be valid because `friend class C;` befriend a global class named
`C`.

[Bug c++/113748] GCC rejects valid program involving befriending class with name same as typedef

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113748

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=21498

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
>This should be valid because `friend class C;` befriend a global class named `C`.


Hmm, see PR 21498 ...

[Bug c++/113748] GCC rejects valid program involving befriending class with name same as typedef

[jlame646 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113748

--- Comment #2 from Jason Liam <jlame646 at gmail dot com> ---
(In reply to Andrew Pinski from comment #1)
> >This should be valid because `friend class C;` befriend a global class named `C`.
> 
> 
> Hmm, see PR 21498 ...

This is ill-formed as explained
here:https://stackoverflow.com/questions/77932976/why-is-a-type-alias-not-allowed-to-be-a-friend-class-name-in-c/77932987#77932987

So gcc is correct here.