[Bug c++/61663] New: [DR 976] Deduction for const T& conversion functions

[Bug c++/61663] New: [DR 976] Deduction for const T& conversion functions

[david.d.kretzmer at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61663

            Bug ID: 61663
           Summary: [DR 976] Deduction for const T& conversion functions
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: david.d.kretzmer at gmail dot com

GCC 4.9.0 rejects the following code:

struct F 
{
  template<class T>
  operator const T&() { static T t; return t; }
};

int main() 
{
  F f;
  int i = f;   // error: cannot convert 'F' to 'int' in initialization
}

As explained in the defects report
(http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#976) this used to
be invalid but after the corrections in 14.8.2.3 [temp.deduct.conv] paragraphs
1-3 the above code should compile.

[Bug c++/61663] [DR 976] Deduction for const T& conversion functions

[ville.voutilainen at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61663

Ville Voutilainen <ville.voutilainen at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |rejects-valid
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-12-14
                 CC|                            |ville.voutilainen at gmail dot com
     Ever confirmed|0                           |1
      Known to fail|                            |4.8.2, 4.9.1, 5.0

--- Comment #1 from Ville Voutilainen <ville.voutilainen at gmail dot com> ---
Clang also rejects the code.

[Bug c++/61663] [DR 976] Deduction for const T& conversion functions

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61663

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rs2740 at gmail dot com

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
*** Bug 63217 has been marked as a duplicate of this bug. ***

[Bug c++/61663] [DR 976] Deduction for const T& conversion functions

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61663

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |alvinhochun at gmail dot com

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
*** Bug 107771 has been marked as a duplicate of this bug. ***

[Bug c++/61663] [DR 976] Deduction for const T& conversion functions

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61663

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The trunk branch has been updated by Nathan Sidwell <nathan@gcc.gnu.org>:

https://gcc.gnu.org/g:80f075b410125bddb31459428760645baba1a69f

commit r14-1689-g80f075b410125bddb31459428760645baba1a69f
Author: Nathan Sidwell <nathan@acm.org>
Date:   Sat Jun 10 12:42:17 2023 -0400

    c++: Adjust conversion deduction [PR61663][DR976]

    Drop the return type's reference before doing cvqual and related decays.

            gcc/cp/
            PR c++/61663
            * pt.cc (maybe_adjust_types_for_deduction): Implement DR976.
            gcc/testsuite/
            * g++.dg/template/pr61663.C: New.