[Bug c++/102123] New: Internal Compiler Error occurs during template deduction in use with templates as template parameters

[Bug c++/102123] New: Internal Compiler Error occurs during template deduction in use with templates as template parameters

[friedkeenan at protonmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102123

            Bug ID: 102123
           Summary: Internal Compiler Error occurs during template
                    deduction in use with templates as template parameters
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: friedkeenan at protonmail dot com
  Target Milestone: ---

Minimal example: https://godbolt.org/z/P86MY1ccz

Compiles fine with clang. Compiles with gcc if you specify `Test<int>`, though
the deduction guide should make them equivalent. Possibly related to Bug 93425

[Bug c++/102123] Internal Compiler Error occurs during template deduction in use with templates as template parameters

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102123

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
template<template<typename...> typename Template, typename... Args>
struct _dummy_forwarder {
    using type = Template<Args...>;
};

template<template<typename...> typename Template, typename... Args>
using dummy_forwarder = typename _dummy_forwarder<Template, Args...>::type;

template<typename T>
struct Test {
    template<typename U> using _dummy = U; 

    using Element = dummy_forwarder<_dummy, T>;

    Element _elem;

    constexpr Test(const Element elem) : _elem(elem) { }
};

template<typename T>
Test(T) -> Test<T>;

consteval void test() {
    const auto t = Test(1);
}

[Bug c++/102123] Internal Compiler Error occurs during template deduction in use with templates as template parameters

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102123

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2021-08-30
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1

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

[Bug c++/102123] [11/12 Regression] Internal Compiler Error occurs during template deduction in use with templates as template parameters

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102123

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |11.3
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=103968
      Known to fail|                            |11.2.0, 12.0
                 CC|                            |jason at gcc dot gnu.org,
                   |                            |ppalka at gcc dot gnu.org
      Known to work|                            |10.3.0
            Summary|Internal Compiler Error     |[11/12 Regression] Internal
                   |occurs during template      |Compiler Error occurs
                   |deduction in use with       |during template deduction
                   |templates as template       |in use with templates as
                   |parameters                  |template parameters

--- Comment #3 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Started with r11-2748.

[Bug c++/102123] [11/12 Regression] Internal Compiler Error occurs during template deduction in use with templates as template parameters

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102123

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2

[Bug c++/102123] [11/12 Regression] Internal Compiler Error occurs during template deduction in use with templates as template parameters

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102123

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |jason at gcc dot gnu.org

[Bug c++/102123] [11/12 Regression] Internal Compiler Error occurs during template deduction in use with templates as template parameters

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102123

--- Comment #4 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:b854ce130ebbfdf2f882ef08538746030513b44b

commit r12-7853-gb854ce130ebbfdf2f882ef08538746030513b44b
Author: Jason Merrill <jason@redhat.com>
Date:   Sat Mar 26 23:54:22 2022 -0400

    c++: CTAD and member alias template [PR102123]

    When building a deduction guide from the Test constructor, we need to
    rewrite the use of _dummy into a dependent reference, i.e.
Test<T>::template
    _dummy.  We were using SCOPE_REF for both type and non-type templates; we
    need to use UNBOUND_CLASS_TEMPLATE for type templates.

            PR c++/102123

    gcc/cp/ChangeLog:

            * pt.cc (tsubst_copy): Use make_unbound_class_template for
rewriting
            a type template reference.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp1z/class-deduction110.C: New test.

[Bug c++/102123] [11 Regression] Internal Compiler Error occurs during template deduction in use with templates as template parameters

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102123

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Jason Merrill
<jason@gcc.gnu.org>:

https://gcc.gnu.org/g:e952290874d6b99946dc02e125c0fb0e9b13a1e3

commit r11-9703-ge952290874d6b99946dc02e125c0fb0e9b13a1e3
Author: Jason Merrill <jason@redhat.com>
Date:   Sat Mar 26 23:54:22 2022 -0400

    c++: CTAD and member alias template [PR102123]

    When building a deduction guide from the Test constructor, we need to
    rewrite the use of _dummy into a dependent reference, i.e.
Test<T>::template
    _dummy.  We were using SCOPE_REF for both type and non-type templates; we
    need to use UNBOUND_CLASS_TEMPLATE for type templates.

            PR c++/102123

    gcc/cp/ChangeLog:

            * pt.c (tsubst_copy): Use make_unbound_class_template for rewriting
            a type template reference.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp1z/class-deduction110.C: New test.

[Bug c++/102123] [11 Regression] Internal Compiler Error occurs during template deduction in use with templates as template parameters

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102123

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

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

--- Comment #6 from Jason Merrill <jason at gcc dot gnu.org> ---
Fixed.