[Bug c++/96199] New: internal compiler error: in tsubst_copy with CTAD for alias templates

[Bug c++/96199] New: internal compiler error: in tsubst_copy with CTAD for alias templates

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96199

            Bug ID: 96199
           Summary: internal compiler error: in tsubst_copy with CTAD for
                    alias templates
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mpolacek at gcc dot gnu.org
  Target Milestone: ---

template<int> class A;
template<typename> struct W { };
template<typename, int> class B {
  enum { X };
  B(A<X>) { }
  template <typename T> using U = B<T, 1>;
  W<U()> u;
};

$ ./cc1plus -quiet q.C
q.C:5:3: internal compiler error: in tsubst_copy, at cp/pt.c:16379
    5 |   B(A<X>) { }
      |   ^
0xbf58f3 tsubst_copy
        /home/mpolacek/src/gcc/gcc/cp/pt.c:16379
0xc0d363 tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool,
bool)
        /home/mpolacek/src/gcc/gcc/cp/pt.c:20496
0xc04ffc tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
        /home/mpolacek/src/gcc/gcc/cp/pt.c:18783
0xbdfd4f tsubst_template_arg(tree_node*, tree_node*, int, tree_node*)
        /home/mpolacek/src/gcc/gcc/cp/pt.c:12116
0xbe3b45 tsubst_template_args(tree_node*, tree_node*, int, tree_node*)
        /home/mpolacek/src/gcc/gcc/cp/pt.c:13169
0xbe48d5 tsubst_aggr_type
        /home/mpolacek/src/gcc/gcc/cp/pt.c:13372
0xbf1239 tsubst(tree_node*, tree_node*, int, tree_node*)
        /home/mpolacek/src/gcc/gcc/cp/pt.c:15267
0xbef7bc tsubst_arg_types
        /home/mpolacek/src/gcc/gcc/cp/pt.c:14802
0xbefdce tsubst_function_type
        /home/mpolacek/src/gcc/gcc/cp/pt.c:14943
0xbf2f58 tsubst(tree_node*, tree_node*, int, tree_node*)
        /home/mpolacek/src/gcc/gcc/cp/pt.c:15720
0xbe7642 tsubst_function_decl
        /home/mpolacek/src/gcc/gcc/cp/pt.c:13757
0xbec51f tsubst_decl
        /home/mpolacek/src/gcc/gcc/cp/pt.c:14199
0xc2fd83 alias_ctad_tweaks
        /home/mpolacek/src/gcc/gcc/cp/pt.c:28562
0xc30867 deduction_guides_for
        /home/mpolacek/src/gcc/gcc/cp/pt.c:28703
0xc31104 do_class_deduction
        /home/mpolacek/src/gcc/gcc/cp/pt.c:28808
0xc31d4c do_auto_deduction(tree_node*, tree_node*, tree_node*, int,
auto_deduction_context, tree_node*, int)
        /home/mpolacek/src/gcc/gcc/cp/pt.c:28937
0xce14ca build_functional_cast_1
        /home/mpolacek/src/gcc/gcc/cp/typeck2.c:2313
0xce1919 build_functional_cast(unsigned int, tree_node*, tree_node*, int)
        /home/mpolacek/src/gcc/gcc/cp/typeck2.c:2413
0xb744e9 cp_parser_functional_cast
        /home/mpolacek/src/gcc/gcc/cp/parser.c:29671
0xb46a8e cp_parser_postfix_expression
        /home/mpolacek/src/gcc/gcc/cp/parser.c:7212

[Bug c++/96199] [10/11 Regression] internal compiler error: in tsubst_copy with CTAD for alias templates

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96199

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|internal compiler error: in |[10/11 Regression] internal
                   |tsubst_copy with CTAD for   |compiler error: in
                   |alias templates             |tsubst_copy with CTAD for
                   |                            |alias templates
   Target Milestone|---                         |10.2

--- Comment #1 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Started with r278786.

[Bug c++/96199] [10/11 Regression] internal compiler error: in tsubst_copy with CTAD for alias templates

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96199

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
We're reaching tsubst_copy/CONST_DECL:

          /* We didn't find the name.  That should never happen; if
             name-lookup found it during preliminary parsing, we
             should find it again here during instantiation.  */
        gcc_unreachable ();

[Bug c++/96199] [10/11 Regression] internal compiler error: in tsubst_copy with CTAD for alias templates

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96199

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|                            |10.1.0
            Version|unknown                     |10.1.0
           Priority|P3                          |P2

[Bug c++/96199] [10/11 Regression] internal compiler error: in tsubst_copy with CTAD for alias templates

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96199

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|10.2                        |10.3

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 10.2 is released, adjusting target milestone.

[Bug c++/96199] [10/11 Regression] internal compiler error: in tsubst_copy with CTAD for alias templates

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96199

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jason at gcc dot gnu.org
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2020-08-05
           Assignee|unassigned at gcc dot gnu.org      |jason at gcc dot gnu.org
     Ever confirmed|0                           |1

[Bug c++/96199] [10/11 Regression] internal compiler error: in tsubst_copy with CTAD for alias templates

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96199

--- 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:9125cf8c33b710c378bfb3c7e67ec2f9f1c523c9

commit r11-2747-g9125cf8c33b710c378bfb3c7e67ec2f9f1c523c9
Author: Jason Merrill <jason@redhat.com>
Date:   Thu Aug 6 02:40:10 2020 -0400

    c++: Handle enumerator in C++20 alias CTAD. [PR96199]

    To form a deduction guide for an alias template, we substitute the template
    arguments from the pattern into the deduction guide for the underlying
    class.  In the case of B(A1<X>), that produces B(A1<B<T,1>::X>) -> B<T,1>.
    But since an enumerator doesn't have its own template info, and B<T,1> is a
    dependent scope, trying to look up B<T,1>::X fails and we crash.  So we
need
    to produce a SCOPE_REF instead.

    And trying to use the members of the template class is wrong for other
    members, as well, as it gives a nonsensical result if the class is
    specialized.

    gcc/cp/ChangeLog:

            PR c++/96199
            * pt.c (maybe_dependent_member_ref): New.
            (tsubst_copy) [CONST_DECL]: Use it.
            [VAR_DECL]: Likewise.
            (tsubst_aggr_type): Handle nested type.

    gcc/testsuite/ChangeLog:

            PR c++/96199
            * g++.dg/cpp2a/class-deduction-alias4.C: New test.

[Bug c++/96199] [10/11 Regression] internal compiler error: in tsubst_copy with CTAD for alias templates

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96199

--- Comment #5 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:b871301f09be7061904dc87880919d30e6afef8f

commit r11-2748-gb871301f09be7061904dc87880919d30e6afef8f
Author: Jason Merrill <jason@redhat.com>
Date:   Fri Aug 14 18:01:27 2020 -0400

    c++: Rewrite members for all deduction guides. [PR96199]

    After the last patch, it occurred to me that we could run into the
    specialization issue with non-alias deduction guides as well, so this patch
    extends the rewriting to C++17 mode.

    Doing this revealed that we weren't properly pushing into class scope for
    normalization.

    gcc/cp/ChangeLog:

            PR c++/96199
            * pt.c (tsubst_aggr_type): Rewrite in C++17, too.
            (maybe_dependent_member_ref): Likewise.
            (build_deduction_guide): Re-substitute template parms.
            * cp-tree.h (struct push_nested_class_guard): New.
            * constraint.cc (get_normalized_constraints_from_decl): Use it.

    gcc/testsuite/ChangeLog:

            PR c++/96199
            * g++.dg/cpp1z/class-deduction-spec1.C: New test.

[Bug c++/96199] [10/11 Regression] internal compiler error: in tsubst_copy with CTAD for alias templates

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96199

--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Jason Merrill
<jason@gcc.gnu.org>:

https://gcc.gnu.org/g:7fc49a5777943aab11e227136d00a836f28f12b2

commit r10-8639-g7fc49a5777943aab11e227136d00a836f28f12b2
Author: Jason Merrill <jason@redhat.com>
Date:   Thu Aug 6 02:40:10 2020 -0400

    c++: Handle enumerator in C++20 alias CTAD. [PR96199]

    To form a deduction guide for an alias template, we substitute the template
    arguments from the pattern into the deduction guide for the underlying
    class.  In the case of B(A1<X>), that produces B(A1<B<T,1>::X>) -> B<T,1>.
    But since an enumerator doesn't have its own template info, and B<T,1> is a
    dependent scope, trying to look up B<T,1>::X fails and we crash.  So we
need
    to produce a SCOPE_REF instead.

    And trying to use the members of the template class is wrong for other
    members, as well, as it gives a nonsensical result if the class is
    specialized.

    gcc/cp/ChangeLog:

            PR c++/96199
            * pt.c (maybe_dependent_member_ref): New.
            (tsubst_copy) [CONST_DECL]: Use it.
            [VAR_DECL]: Likewise.
            (tsubst_aggr_type): Handle nested type.

    gcc/testsuite/ChangeLog:

            PR c++/96199
            * g++.dg/cpp2a/class-deduction-alias4.C: New test.

[Bug c++/96199] [10/11 Regression] internal compiler error: in tsubst_copy with CTAD for alias templates

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96199

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

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

--- Comment #7 from Jason Merrill <jason at gcc dot gnu.org> ---
Fixed for 10.3/11.

[Bug c++/96199] [10/11 Regression] internal compiler error: in tsubst_copy with CTAD for alias templates

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96199

--- Comment #8 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:1c56c143b2011080d8a4516f37f78f647b0ee258

commit r11-3738-g1c56c143b2011080d8a4516f37f78f647b0ee258
Author: Jason Merrill <jason@redhat.com>
Date:   Thu Oct 8 15:43:26 2020 -0400

    c++: Fix member alias template in C++17 and up. [PR96805]

    Here we're trying to push into a<T>::c<N> in order to instantiate t<N>, but
    were building a TYPENAME_TYPE for it because a<T> isn't open yet.  Don't
    do that when we know we're trying to enter the scope.

    gcc/cp/ChangeLog:

            PR c++/96805
            PR c++/96199
            * pt.c (tsubst_aggr_type): Don't build a TYPENAME_TYPE when
            entering_scope.
            (tsubst_template_decl): Use tsubst_aggr_type.

    gcc/testsuite/ChangeLog:

            PR c++/96805
            * g++.dg/cpp0x/alias-decl-pr96805.C: New test.

[Bug c++/96199] [10/11 Regression] internal compiler error: in tsubst_copy with CTAD for alias templates

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96199

--- Comment #9 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Jason Merrill
<jason@gcc.gnu.org>:

https://gcc.gnu.org/g:e89ebd3e896f27d4afc400044d5a2b69cb524bcb

commit r10-9069-ge89ebd3e896f27d4afc400044d5a2b69cb524bcb
Author: Jason Merrill <jason@redhat.com>
Date:   Thu Oct 8 15:43:26 2020 -0400

    c++: Fix member alias template in C++17 and up. [PR96805]

    Here we're trying to push into a<T>::c<N> in order to instantiate t<N>, but
    were building a TYPENAME_TYPE for it because a<T> isn't open yet.  Don't
    do that when we know we're trying to enter the scope.

    gcc/cp/ChangeLog:

            PR c++/96805
            PR c++/96199
            * pt.c (tsubst_aggr_type): Don't build a TYPENAME_TYPE when
            entering_scope.
            (tsubst_template_decl): Use tsubst_aggr_type.

    gcc/testsuite/ChangeLog:

            PR c++/96805
            * g++.dg/cpp0x/alias-decl-pr96805.C: New test.

[Bug c++/96199] [10/11 Regression] internal compiler error: in tsubst_copy with CTAD for alias templates

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96199

--- Comment #10 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:709718d4d89e5976257f53e67dcb8ba704574c56

commit r11-7044-g709718d4d89e5976257f53e67dcb8ba704574c56
Author: Jason Merrill <jason@redhat.com>
Date:   Tue Feb 2 10:08:48 2021 -0500

    c++: Member fns and deduction guide rewriting [PR98929]

    My patch for 96199 had us re-substitute the parameter types of a
constructor
    in order to rewrite mentions of members into dependent references.  We need
    to do that for member functions, too.

    gcc/cp/ChangeLog:

            PR c++/98929
            PR c++/96199
            * error.c (dump_expr): Ignore dummy object.
            * pt.c (tsubst_baselink): Handle dependent scope.

    gcc/testsuite/ChangeLog:

            PR c++/98929
            * g++.dg/cpp1z/class-deduction-decltype1.C: New test.

[Bug c++/96199] [10/11 Regression] internal compiler error: in tsubst_copy with CTAD for alias templates

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96199

--- Comment #11 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Jason Merrill
<jason@gcc.gnu.org>:

https://gcc.gnu.org/g:a588c87ba309492b351c1a55b08d907b65913e2c

commit r10-9415-ga588c87ba309492b351c1a55b08d907b65913e2c
Author: Jason Merrill <jason@redhat.com>
Date:   Wed Mar 3 17:38:55 2021 -0500

    c++: Normalization and deduction guide rewriting [PR96199]

    This is a subset of r11-2748; we don't want to rewrite all deduction guides
    in GCC 10, but we do need the push_nested_class in normalization to avoid
    breaking cmcstl2.

    gcc/cp/ChangeLog:

            PR c++/96199
            * cp-tree.h (struct push_nested_class_guard): New.
            * constraint.cc (get_normalized_constraints_from_decl): Use it.