[Bug c++/98832] New: CTAD fails for alias template of aggregate with specified undeducible template parameter

[Bug c++/98832] New: CTAD fails for alias template of aggregate with specified undeducible template parameter

[johelegp at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98832

            Bug ID: 98832
           Summary: CTAD fails for alias template of aggregate with
                    specified undeducible template parameter
           Product: gcc
           Version: 11.0
               URL: https://godbolt.org/z/M1eqvq
            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/M1eqvq.
```C++
template<class T,class U>struct X{U u;};
template<class T>using Y=X<int,T>;
Y y{0};
```

[Bug c++/98832] CTAD fails for alias template of aggregate with specified undeducible template parameter

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98832

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ppalka at gcc dot gnu.org
     Ever confirmed|0                           |1
           Assignee|unassigned at gcc dot gnu.org      |ppalka at gcc dot gnu.org
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2021-06-24

--- Comment #1 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Confirmed.  It looks like we're overlooking the aggregate deduction candidate
for the underlying template when building the set of guides for the alias.

[Bug c++/98832] CTAD fails for alias template of aggregate with specified undeducible template parameter

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98832

--- Comment #2 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:c761be53f6b62e22ac5de18c4aaf88648f64f5b7

commit r12-1793-gc761be53f6b62e22ac5de18c4aaf88648f64f5b7
Author: Patrick Palka <ppalka@redhat.com>
Date:   Thu Jun 24 13:11:44 2021 -0400

    c++: alias CTAD and aggregate deduction cand [PR98832]

    During alias CTAD, we're accidentally ignoring the aggregate deduction
    candidate for the underlying template because this guide is added
    separately via maybe_aggr_guide (which doesn't yet handle alias
    templates) instead of via deduction_guides_for (which does).  This patch
    makes maybe_aggr_guide handle alias templates in a manner similar to
    deduction_guides_for.

            PR c++/98832

    gcc/cp/ChangeLog:

            * pt.c (maybe_aggr_guide): Handle alias templates appropriately.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp2a/class-deduction-alias9.C: New test.

[Bug c++/98832] CTAD fails for alias template of aggregate with specified undeducible template parameter

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98832

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Patrick Palka
<ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:660cbbae327fbfa315e26d286b03efffc3c21cb5

commit r11-8730-g660cbbae327fbfa315e26d286b03efffc3c21cb5
Author: Patrick Palka <ppalka@redhat.com>
Date:   Thu Jun 24 13:11:44 2021 -0400

    c++: alias CTAD and aggregate deduction cand [PR98832]

    During alias CTAD, we're accidentally ignoring the aggregate deduction
    candidate for the underlying template because this guide is added
    separately via maybe_aggr_guide (which doesn't yet handle alias
    templates) instead of via deduction_guides_for (which does).  This patch
    makes maybe_aggr_guide handle alias templates in a manner similar to
    deduction_guides_for.

            PR c++/98832

    gcc/cp/ChangeLog:

            * pt.c (maybe_aggr_guide): Handle alias templates appropriately.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp2a/class-deduction-alias9.C: New test.

    (cherry picked from commit c761be53f6b62e22ac5de18c4aaf88648f64f5b7)

[Bug c++/98832] CTAD fails for alias template of aggregate with specified undeducible template parameter

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98832

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED
   Target Milestone|---                         |11.2

--- Comment #4 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Fixed for 11.2/12