[Bug c++/103807] New: Unable to make template class instance with default parameter of lambda::function

[Bug c++/103807] New: Unable to make template class instance with default parameter of lambda::function

[fchelnokov at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103807

            Bug ID: 103807
           Summary: Unable to make template class instance with default
                    parameter of lambda::function
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: fchelnokov at gmail dot com
  Target Milestone: ---

Below code:
```
template <auto x = +[]{}>
struct A {};

int main() {
    [[maybe_unused]] A x;
}
```
is accepted by Clang and MSVC.

But GCC prints the error:
```
error: class template argument deduction failed:
    5 |     [[maybe_unused]] A x;
      |                        ^
<source>:5:24: error: no matching function for call to 'A()'
```
Demo: https://gcc.godbolt.org/z/4azGT5fso

[Bug c++/103807] Unable to make template class instance with default parameter of lambda::function

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103807

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Depends on|                            |97700

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Very similar to PR 97700 if not a dup of that bug.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97700
[Bug 97700] Bogus error when a class containing a function pointer is used as a
non-type template parameter

[Bug c++/103807] Unable to make template class instance with default parameter of lambda::function

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103807

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2021-12-22
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.

[Bug c++/103807] Unable to make template class instance with default parameter of lambda::function

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103807

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

https://gcc.gnu.org/g:0d0c467d216bf538faa7ceb75875e4efa73ae23f

commit r14-710-g0d0c467d216bf538faa7ceb75875e4efa73ae23f
Author: Patrick Palka <ppalka@redhat.com>
Date:   Thu May 11 10:38:02 2023 -0400

    c++: Add testcase for already fixed PR [PR103807]

    We accept this testcase since r13-806-g221acd67ca50f8.

            PR c++/103807

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp2a/lambda-targ1.C: New test.

[Bug c++/103807] Unable to make template class instance with default parameter of lambda::function

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103807

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=105652
   Target Milestone|---                         |12.2
                 CC|                            |ppalka at gcc dot gnu.org

--- Comment #4 from Patrick Palka <ppalka at gcc dot gnu.org> ---
This is incidentally fixed for GCC 12.2+ by the fix for PR105652

[Bug c++/103807] Unable to make template class instance with default parameter of lambda::function

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103807

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-13 branch has been updated by Patrick Palka
<ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:2aa1ab10ae0fd244dfea5fbf3705d7a1c0afff5a

commit r13-7325-g2aa1ab10ae0fd244dfea5fbf3705d7a1c0afff5a
Author: Patrick Palka <ppalka@redhat.com>
Date:   Thu May 11 10:38:02 2023 -0400

    c++: Add testcase for already fixed PR [PR103807]

    We accept this testcase since r13-806-g221acd67ca50f8.

            PR c++/103807

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp2a/lambda-targ1.C: New test.

    (cherry picked from commit 0d0c467d216bf538faa7ceb75875e4efa73ae23f)

[Bug c++/103807] Unable to make template class instance with default parameter of lambda::function

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103807
Bug 103807 depends on bug 97700, which changed state.

Bug 97700 Summary: Bogus error when a class containing a function pointer is used as a non-type template parameter
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97700

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

[Bug c++/103807] Unable to make template class instance with default parameter of lambda::function

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103807

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Fixed so closing.