[Bug c++/101733] New: simple-requirement prefixed with typename interpreted as type-requirement

[Bug c++/101733] New: simple-requirement prefixed with typename interpreted as type-requirement

[johelegp at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101733

            Bug ID: 101733
           Summary: simple-requirement prefixed with typename interpreted
                    as type-requirement
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Keywords: rejects-valid
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: johelegp at gmail dot com
                CC: johelegp at gmail dot com
  Target Milestone: ---

See https://godbolt.org/z/q67Mserar.
```C++
template<class T>
concept C = requires {
  typename T::x();
  typename T::x() + 1;
  1 + typename T::x();
};
```
```
<source>:3:16: error: expected ';' before '(' token
    3 |   typename T::x();
      |                ^
      |                ;
<source>:4:16: error: expected ';' before '(' token
    4 |   typename T::x() + 1;
      |                ^
      |                ;
Compiler returned: 1
```

[Bug c++/101733] simple-requirement prefixed with typename interpreted as type-requirement

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101733

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2021-08-02

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.

[Bug c++/101733] simple-requirement prefixed with typename interpreted as type-requirement

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101733

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2021-08-02 00:00:00         |2022-10-18

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
template<class T>
requires requires {
    typename T::type;
    (typename T::type()); // (1)
    T::type();            // (2)
    typename T::type();   // (3)
}
void f(T) { }

All compilers accept (1) and (2) but only Clang accepts (3)

[Bug c++/101733] simple-requirement prefixed with typename interpreted as type-requirement

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101733

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jason at gcc dot gnu.org
   Last reconfirmed|2022-10-18 00:00:00         |2021-08-02 0:00
           Assignee|unassigned at gcc dot gnu.org      |jason at gcc dot gnu.org
             Status|NEW                         |ASSIGNED

[Bug c++/101733] simple-requirement prefixed with typename interpreted as type-requirement

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101733

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jason Merrill <jason@gcc.gnu.org>:

https://gcc.gnu.org/g:2b0ae7fb91f64fb005abf7d7903fd4c0764bb45c

commit r13-4380-g2b0ae7fb91f64fb005abf7d7903fd4c0764bb45c
Author: Jason Merrill <jason@redhat.com>
Date:   Sat Nov 26 11:13:55 2022 -0500

    c++: simple-requirement starting with 'typename' [PR101733]

    Usually a requirement starting with 'typename' is a type-requirement, but
it
    might be a simple-requirement such as a functional cast to a typename-type.

            PR c++/101733

    gcc/cp/ChangeLog:

            * parser.cc (cp_parser_requirement): Parse tentatively for the
            'typename' case.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp2a/concepts-requires32.C: New test.