[Bug c++/114901] New: GCC internal_error on CTAD alias

[Bug c++/114901] New: GCC internal_error on CTAD alias

[hokein.wu at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114901

            Bug ID: 114901
           Summary: GCC internal_error on CTAD alias
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hokein.wu at gmail dot com
  Target Milestone: ---

GCC (trunk) crashes on the following code:

https://godbolt.org/z/43Tqf4qs9


```
template <class D>
constexpr bool C = sizeof(D);


template <typename U>
struct T {

  template<typename V, typename N>
  struct Foo {
    Foo(V, N);
  };

  template<typename X, typename N>
  requires (C<N>) // removes the require-clause will make the crash disappear
  Foo(X, N) -> Foo<X, N>;

  template <typename Y, typename Y2, int N = sizeof(Y2)>
  using AFoo = Foo<decltype(N), Y2>;
};

T<double>::AFoo s{1, 2};

```

[Bug c++/114901] GCC internal_error on CTAD alias

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114901

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mpolacek at gcc dot gnu.org
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2024-04-30
     Ever confirmed|0                           |1

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

$ ./cc1plus -quiet 114901.C -std=c++20
114901.C: In static member function ‘static T<double>::Foo(int, Y2)-> Foo<int,
Y2> requires  __is_deducible (T<double>::AFoo, T<double>::Foo<int, Y2>)’:
114901.C:21:23: internal compiler error: in keep_template_parm, at
cp/pt.cc:10933
   21 | T<double>::AFoo s{1, 2};
      |                       ^
0x10dffa0 keep_template_parm
        /home/mpolacek/src/gcc/gcc/cp/pt.cc:10933
0x10df925 for_each_template_parm_r
        /home/mpolacek/src/gcc/gcc/cp/pt.cc:10740
0x1ec3aef walk_tree_1(tree_node**, tree_node* (*)(tree_node**, int*, void*),
void*, hash_set<tree_node*, false, default_hash_traits<tree_node*> >*,
tree_node* (*)(tree_node**, int*, tree_node* (*)(tree_node**, int*, void*),
void*, hash_set<tree_node*, false, default_hash_traits<tree_node*> >*))
        /home/mpolacek/src/gcc/gcc/tree.cc:11429
0x10dfc15 for_each_template_parm
        /home/mpolacek/src/gcc/gcc/cp/pt.cc:10843
0x10e0362 any_template_parm_r
        /home/mpolacek/src/gcc/gcc/cp/pt.cc:10975
0x10dec7e for_each_template_parm_r
        /home/mpolacek/src/gcc/gcc/cp/pt.cc:10632
0x1ec3aef walk_tree_1(tree_node**, tree_node* (*)(tree_node**, int*, void*),
void*, hash_set<tree_node*, false, default_hash_traits<tree_node*> >*,
tree_node* (*)(tree_node**, int*, tree_node* (*)(tree_node**, int*, void*),
void*, hash_set<tree_node*, false, default_hash_traits<tree_node*> >*))
        /home/mpolacek/src/gcc/gcc/tree.cc:11429
0x10dfc15 for_each_template_parm
        /home/mpolacek/src/gcc/gcc/cp/pt.cc:10843
0x10e07aa find_template_parameter_info::find_in(tree_node*)
        /home/mpolacek/src/gcc/gcc/cp/pt.cc:11023
0x10e0a22 find_template_parameters(tree_node*, tree_node*)
        /home/mpolacek/src/gcc/gcc/cp/pt.cc:11075
0xe2a236 build_parameter_mapping
        /home/mpolacek/src/gcc/gcc/cp/constraint.cc:594
0xe2aa02 normalize_atom
        /home/mpolacek/src/gcc/gcc/cp/constraint.cc:819
0xe2ad29 normalize_expression
        /home/mpolacek/src/gcc/gcc/cp/constraint.cc:886
0xe2a4c9 normalize_logical_operation
        /home/mpolacek/src/gcc/gcc/cp/constraint.cc:692
0xe2acb2 normalize_expression
        /home/mpolacek/src/gcc/gcc/cp/constraint.cc:882
0xe2ad82 get_normalized_constraints
        /home/mpolacek/src/gcc/gcc/cp/constraint.cc:898
0xe2ae40 get_normalized_constraints_from_info
        /home/mpolacek/src/gcc/gcc/cp/constraint.cc:914
0xe2b0df get_normalized_constraints_from_decl
        /home/mpolacek/src/gcc/gcc/cp/constraint.cc:990
0xe33953 satisfy_declaration_constraints
        /home/mpolacek/src/gcc/gcc/cp/constraint.cc:3378
0xe33a70 constraint_satisfaction_value
        /home/mpolacek/src/gcc/gcc/cp/constraint.cc:3406

[Bug c++/114901] GCC internal_error on CTAD alias

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114901

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jason at gcc dot gnu.org

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Started with r13-6555:

commit 9e6170098d5e7756e85e880f8f4cb18e885a64fd
Author: Jason Merrill <jason@redhat.com>
Date:   Wed Feb 8 22:06:22 2023 -0800

    c++: fix alias CTAD [PR105841]

[Bug c++/114901] GCC internal_error on CTAD alias

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114901

--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Before, it was rejected:

114901.C:21:23: error: class template argument deduction failed:
   21 | T<double>::AFoo s{1, 2};
      |                       ^
114901.C:21:23: error: no matching function for call to ‘Foo(int, int)’

[Bug c++/114901] GCC internal_error on CTAD alias

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114901

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |ice-on-valid-code
            Version|unknown                     |13.2.1

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
I suppose it's valid code?

[Bug c++/114901] GCC internal_error on CTAD alias

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114901

--- Comment #5 from GCC 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:6d31a370e26eeb950c326332633b3e8e84b6630b

commit r15-434-g6d31a370e26eeb950c326332633b3e8e84b6630b
Author: Patrick Palka <ppalka@redhat.com>
Date:   Mon May 13 09:53:40 2024 -0400

    c++: nested aggregate/alias CTAD fixes [PR114974, PR114901, PR114903]

    During maybe_aggr_guide with a nested class template and paren init,
    like with list init we need to consider the generic template type rather
    than the partially instantiated type since partial instantiations don't
    have (partially instantiated) TYPE_FIELDS.  In turn we need to partially
    substitute PARMs in the paren init case as well.  As a drive-by improvement
    it seems better to use outer_template_args instead of DECL_TI_ARGS during
    this partial substitution so that we lower instead of substitute the
    innermost template parameters, which is generally more robust.

    And during alias_ctad_tweaks with a nested class template, even though
    the guides may be already partially instantiated we still need to
    substitute the outermost arguments into its constraints.

            PR c++/114974
            PR c++/114901
            PR c++/114903

    gcc/cp/ChangeLog:

            * pt.cc (maybe_aggr_guide): Fix obtaining TYPE_FIELDS in
            the paren init case.  Hoist out partial substitution logic
            to apply to the paren init case as well.
            (alias_ctad_tweaks): Substitute outer template arguments into
            a guide's constraints.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp2a/class-deduction-aggr14.C: New test.
            * g++.dg/cpp2a/class-deduction-alias20.C: New test.
            * g++.dg/cpp2a/class-deduction-alias21.C: New test.

    Reviewed-by: Jason Merrill <jason@redhat.com>

[Bug c++/114901] GCC internal_error on CTAD alias

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114901

--- Comment #6 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-14 branch has been updated by Patrick Palka
<ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:57cd8665fea4c339369a43be017583621aa82fed

commit r14-10201-g57cd8665fea4c339369a43be017583621aa82fed
Author: Patrick Palka <ppalka@redhat.com>
Date:   Mon May 13 09:53:40 2024 -0400

    c++: nested aggregate/alias CTAD fixes [PR114974, PR114901, PR114903]

    During maybe_aggr_guide with a nested class template and paren init,
    like with list init we need to consider the generic template type rather
    than the partially instantiated type since partial instantiations don't
    have (partially instantiated) TYPE_FIELDS.  In turn we need to partially
    substitute PARMs in the paren init case as well.  As a drive-by improvement
    it seems better to use outer_template_args instead of DECL_TI_ARGS during
    this partial substitution so that we lower instead of substitute the
    innermost template parameters, which is generally more robust.

    And during alias_ctad_tweaks with a nested class template, even though
    the guides may be already partially instantiated we still need to
    substitute the outermost arguments into its constraints.

            PR c++/114974
            PR c++/114901
            PR c++/114903

    gcc/cp/ChangeLog:

            * pt.cc (maybe_aggr_guide): Fix obtaining TYPE_FIELDS in
            the paren init case.  Hoist out partial substitution logic
            to apply to the paren init case as well.
            (alias_ctad_tweaks): Substitute outer template arguments into
            a guide's constraints.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp2a/class-deduction-aggr14.C: New test.
            * g++.dg/cpp2a/class-deduction-alias20.C: New test.
            * g++.dg/cpp2a/class-deduction-alias21.C: New test.

    Reviewed-by: Jason Merrill <jason@redhat.com>
    (cherry picked from commit 6d31a370e26eeb950c326332633b3e8e84b6630b)

[Bug c++/114901] GCC internal_error on CTAD alias

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114901

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |14.2
                 CC|                            |ppalka at gcc dot gnu.org
           Assignee|unassigned at gcc dot gnu.org      |ppalka at gcc dot gnu.org
         Resolution|---                         |FIXED
             Status|NEW                         |RESOLVED

--- Comment #7 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Fixed for GCC 14.2