[Bug c++/97034] New: ICE on C++20 code: gcc_assert failure in return type deduction (gcc/cp/pt.c:26984 in type_dependent_expression_p(tree_node*))

[Bug c++/97034] New: ICE on C++20 code: gcc_assert failure in return type deduction (gcc/cp/pt.c:26984 in type_dependent_expression_p(tree_node*))

[dimitri.gorokhovik at free dot fr]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97034

            Bug ID: 97034
           Summary: ICE on C++20 code: gcc_assert failure in return type
                    deduction (gcc/cp/pt.c:26984 in
                    type_dependent_expression_p(tree_node*))
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dimitri.gorokhovik at free dot fr
  Target Milestone: ---

The code:

#include <tuple>

template <unsigned N>
struct s
{
        template <typename R>
        struct ss
        {
                R _1;
                unsigned _2;
        };

        constexpr auto f ()
        {
                return ss { std::pair <char, int> { 'a', 1 }, 1 };
        };
};


when compiled as:
g++  -std=c++20 -o bug-3.o -c bug-3.cpp

produces:

bug-3.cpp: In member function ‘constexpr auto s<N>::f()’:
bug-3.cpp:15:65: internal compiler error: in type_dependent_expression_p, at
cp/pt.c:26984
   15 |                 return ss { std::pair <char, int> { 'a', 1 }, 1 };
      |                                                                 ^
0x680638 type_dependent_expression_p(tree_node*)
        ../../src/gcc/cp/pt.c:26984
0xa22cf9 maybe_instantiate_noexcept(tree_node*, int)
        ../../src/gcc/cp/pt.c:25290
0x9598c2 mark_used(tree_node*, int)
        ../../src/gcc/cp/decl2.c:5552
0xaa8d36 cp_build_addr_expr_1
        ../../src/gcc/cp/typeck.c:6384
0x8ab692 build_over_call
        ../../src/gcc/cp/call.c:8522
0x8ae85a build_new_function_call(tree_node*, vec<tree_node*, va_gc,
vl_embed>**, int)
        ../../src/gcc/cp/call.c:4641
0xa1a4ed do_class_deduction
        ../../src/gcc/cp/pt.c:29027
0xa1a4ed do_auto_deduction(tree_node*, tree_node*, tree_node*, int,
auto_deduction_context, tree_node*, int)
        ../../src/gcc/cp/pt.c:29085
0xa6def9 finish_compound_literal(tree_node*, tree_node*, int, fcl_t)
        ../../src/gcc/cp/semantics.c:2934
0x9ca12a cp_parser_functional_cast
        ../../src/gcc/cp/parser.c:29690
0x9e26d7 cp_parser_postfix_expression
        ../../src/gcc/cp/parser.c:7251
0x9c443a cp_parser_binary_expression
        ../../src/gcc/cp/parser.c:9648
0x9c61ce cp_parser_assignment_expression
        ../../src/gcc/cp/parser.c:9953
0x9c64e2 cp_parser_expression
        ../../src/gcc/cp/parser.c:10121
0x9d5527 cp_parser_jump_statement
        ../../src/gcc/cp/parser.c:13192
0x9d5527 cp_parser_statement
        ../../src/gcc/cp/parser.c:11455
0x9d6a8d cp_parser_statement_seq_opt
        ../../src/gcc/cp/parser.c:11928
0x9d6b68 cp_parser_compound_statement
        ../../src/gcc/cp/parser.c:11878
0x9eecb5 cp_parser_function_body
        ../../src/gcc/cp/parser.c:23177
0x9eecb5 cp_parser_ctor_initializer_opt_and_function_body
        ../../src/gcc/cp/parser.c:23228
Please submit a full bug report,


GCC version:
g++ (GCC) 11.0.0 20200910 (experimental)

[Bug c++/97034] [11 Regression] ICE on C++20 code: gcc_assert failure in return type deduction (gcc/cp/pt.c:26984 in type_dependent_expression_p(tree_node*))

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97034

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
     Ever confirmed|0                           |1
           Assignee|unassigned at gcc dot gnu.org      |mpolacek at gcc dot gnu.org
           Keywords|                            |ice-on-valid-code
            Summary|ICE on C++20 code:          |[11 Regression] ICE on
                   |gcc_assert failure in       |C++20 code: gcc_assert
                   |return type deduction       |failure in return type
                   |(gcc/cp/pt.c:26984 in       |deduction
                   |type_dependent_expression_p |(gcc/cp/pt.c:26984 in
                   |(tree_node*))               |type_dependent_expression_p
                   |                            |(tree_node*))
   Last reconfirmed|                            |2020-09-13
   Target Milestone|---                         |11.0
                 CC|                            |mpolacek at gcc dot gnu.org

--- Comment #1 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Started with r11-1713.

[Bug c++/97034] [11 Regression] ICE on C++20 code: gcc_assert failure in return type deduction (gcc/cp/pt.c:26984 in type_dependent_expression_p(tree_node*))

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97034

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
// PR c++/97034

namespace N {
template <typename, typename> struct S {
  template <typename T, typename U> S(T, U);
};
} // namespace N
template <int> struct E {
  template <typename T> struct G { T t; };
  void fn() { G{N::S<char, int>{'a', 1}}; }
};

[Bug c++/97034] [11 Regression] ICE on C++20 code: gcc_assert failure in return type deduction (gcc/cp/pt.c:26984 in type_dependent_expression_p(tree_node*))

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97034

--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
The same ICE can be triggered with

template <int>
struct E {
  template <typename T>
  struct G {
    T t;
    G(T) { }
  };

  void fn() { G{1}; }
};

which started with r269093.

[Bug c++/97034] [11 Regression] ICE on C++20 code: gcc_assert failure in return type deduction (gcc/cp/pt.c:26984 in type_dependent_expression_p(tree_node*))

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97034

--- Comment #4 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Another, valid, where C++20 aggregate CTAD should work:

template<typename>
struct E {
  template <typename T>
  struct G {
    T t;
  };

  void fn() { G{1}; }
};

void
g () {
  E<int> e;
  e.fn ();
}

[Bug c++/97034] [11 Regression] ICE on C++20 code: gcc_assert failure in return type deduction (gcc/cp/pt.c:26984 in type_dependent_expression_p(tree_node*))

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97034

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P1

[Bug c++/97034] [11 Regression] ICE on C++20 code: gcc_assert failure in return type deduction (gcc/cp/pt.c:26984 in type_dependent_expression_p(tree_node*))

[arthur.j.odwyer at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97034

Arthur O'Dwyer <arthur.j.odwyer at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |arthur.j.odwyer at gmail dot com

--- Comment #5 from Arthur O'Dwyer <arthur.j.odwyer at gmail dot com> ---
Is mine the same bug? Mine is also a regression (trunk crashes where GCC 10.2
had succeeded).

// https://godbolt.org/z/Ysh6as
struct C { void f(auto) noexcept; };
void C::f(auto) noexcept(C::x) {}

Compile with -std=c++20:


<source>:3:29: error: 'x' is not a member of 'C'
    3 | void C::f(auto) noexcept(C::x) {}
      |                             ^
<source>:3:6: error: declaration of 'void C::f(auto:2)' has a different
exception specifier
    3 | void C::f(auto) noexcept(C::x) {}
      |      ^
<source>:2:17: note: from previous declaration 'void C::f(auto:1) noexcept'
    2 | struct C { void f(auto) noexcept; };
      |                 ^
<source>:3:30: internal compiler error: in type_dependent_expression_p, at
cp/pt.c:27166
    3 | void C::f(auto) noexcept(C::x) {}
      |                              ^
0x1cc31d9 internal_error(char const*, ...)
        ???:0
0x6b25f7 fancy_abort(char const*, int, char const*)
        ???:0
0x8ee70a type_dependent_expression_p(tree_node*)
        ???:0
0x137d4f3 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*> >*))
        ???:0
0x1381b55 walk_tree_without_duplicates_1(tree_node**, tree_node*
(*)(tree_node**, int*, void*), void*, tree_node* (*)(tree_node**, int*,
tree_node* (*)(tree_node**, int*, void*), void*, hash_set<tree_node*, false,
default_hash_traits<tree_node*> >*))
        ???:0
0x8ea937 instantiation_dependent_uneval_expression_p(tree_node*)
        ???:0
0x8f2198 instantiation_dependent_expression_p(tree_node*)
        ???:0
0x8f2216 uses_template_parms(tree_node*)
        ???:0
0x78ffe8 duplicate_decls(tree_node*, tree_node*, bool, bool)
        ???:0
0x79a2b6 grokdeclarator(cp_declarator const*, cp_decl_specifier_seq*,
decl_context, int, tree_node**)
        ???:0
0x79dda6 start_function(cp_decl_specifier_seq*, cp_declarator const*,
tree_node*)
        ???:0
0x8d803d c_parse_file()
        ???:0
0xa54072 c_common_parse_file()
        ???:0

[Bug c++/97034] [11 Regression] ICE on C++20 code: gcc_assert failure in return type deduction (gcc/cp/pt.c:26984 in type_dependent_expression_p(tree_node*))

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97034

--- Comment #6 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
(In reply to Arthur O'Dwyer from comment #5)
> Is mine the same bug? Mine is also a regression (trunk crashes where GCC
> 10.2 had succeeded).
> 
> // https://godbolt.org/z/Ysh6as
> struct C { void f(auto) noexcept; };
> void C::f(auto) noexcept(C::x) {}
> 
> Compile with -std=c++20:
> 
> 
> <source>:3:29: error: 'x' is not a member of 'C'
>     3 | void C::f(auto) noexcept(C::x) {}
>       |                             ^
> <source>:3:6: error: declaration of 'void C::f(auto:2)' has a different
> exception specifier
>     3 | void C::f(auto) noexcept(C::x) {}
>       |      ^
> <source>:2:17: note: from previous declaration 'void C::f(auto:1) noexcept'
>     2 | struct C { void f(auto) noexcept; };
>       |                 ^
> <source>:3:30: internal compiler error: in type_dependent_expression_p, at
> cp/pt.c:27166
>     3 | void C::f(auto) noexcept(C::x) {}
>       |                              ^
> 0x1cc31d9 internal_error(char const*, ...)
> 	???:0
> 0x6b25f7 fancy_abort(char const*, int, char const*)
> 	???:0
> 0x8ee70a type_dependent_expression_p(tree_node*)
> 	???:0
> 0x137d4f3 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*> >*))
> 	???:0
> 0x1381b55 walk_tree_without_duplicates_1(tree_node**, tree_node*
> (*)(tree_node**, int*, void*), void*, tree_node* (*)(tree_node**, int*,
> tree_node* (*)(tree_node**, int*, void*), void*, hash_set<tree_node*, false,
> default_hash_traits<tree_node*> >*))
> 	???:0
> 0x8ea937 instantiation_dependent_uneval_expression_p(tree_node*)
> 	???:0
> 0x8f2198 instantiation_dependent_expression_p(tree_node*)
> 	???:0
> 0x8f2216 uses_template_parms(tree_node*)
> 	???:0
> 0x78ffe8 duplicate_decls(tree_node*, tree_node*, bool, bool)
> 	???:0
> 0x79a2b6 grokdeclarator(cp_declarator const*, cp_decl_specifier_seq*,
> decl_context, int, tree_node**)
> 	???:0
> 0x79dda6 start_function(cp_decl_specifier_seq*, cp_declarator const*,
> tree_node*)
> 	???:0
> 0x8d803d c_parse_file()
> 	???:0
> 0xa54072 c_common_parse_file()
> 	???:0

I think that is a different problem (the original problem here was with
deduction guides).

[Bug c++/97034] [11 Regression] ICE on C++20 code: gcc_assert failure in return type deduction (gcc/cp/pt.c:26984 in type_dependent_expression_p(tree_node*))

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97034

--- Comment #7 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Candidate patch:

--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -27279,7 +27279,10 @@ type_dependent_expression_p (tree expression)
       && DECL_UNIQUE_FRIEND_P (expression)
       && (!DECL_FRIEND_CONTEXT (expression)
           || dependent_type_p (DECL_FRIEND_CONTEXT (expression))))
-      && !DECL_LOCAL_DECL_P (expression))
+      && !DECL_LOCAL_DECL_P (expression)
+      /* We build deduction guides without any DECL_CONTEXT, but they can
+    be type-dependent.  */
+      && !deduction_guide_p (expression))
     {
       gcc_assert (!dependent_type_p (TREE_TYPE (expression))
          || undeduced_auto_decl (expression));

[Bug c++/97034] [11 Regression] ICE on C++20 code: gcc_assert failure in return type deduction (gcc/cp/pt.c:26984 in type_dependent_expression_p(tree_node*))

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97034

--- Comment #8 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Alternative patch that I'm more happy about:

--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -28761,6 +28761,7 @@ build_deduction_guide (tree type, tree ctor, tree
outer_args, tsubst_flags_t com
   tree ded_fn = build_lang_decl_loc (loc,
                     FUNCTION_DECL,
                     dguide_name (type), fntype);
+  DECL_CONTEXT (ded_fn) = type;
   DECL_ARGUMENTS (ded_fn) = fargs;
   DECL_ARTIFICIAL (ded_fn) = true;
   DECL_NONCONVERTING_P (ded_fn) = explicit_p;

[Bug c++/97034] [11 Regression] ICE on C++20 code: gcc_assert failure in return type deduction (gcc/cp/pt.c:26984 in type_dependent_expression_p(tree_node*))

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97034

--- Comment #9 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Marek Polacek <mpolacek@gcc.gnu.org>:

https://gcc.gnu.org/g:1dabbfb0f4a9fbdc77e1ea4db7302586f00895e1

commit r11-7483-g1dabbfb0f4a9fbdc77e1ea4db7302586f00895e1
Author: Marek Polacek <polacek@redhat.com>
Date:   Fri Feb 12 12:21:15 2021 -0500

    c++: ICE with deduction guide in checking type-dep [PR99009, PR97034]

    We represent deduction guides with FUNCTION_DECLs, but they are built
    without DECL_CONTEXT, leading to an ICE in type_dependent_expression_p
    on the assert that the type of a function template with no dependent
    (innermost!) template arguments must be non-dependent.  Consider the
    attached class-deduction79.C: we create a deduction guide:

      template<class T> G(T)-> E<Z>::G<T>

    we deduce T and create a partial instantiation:

      G(T) -> E<Z>::G<T> [with T = int]

    And then do_class_deduction wants to create a CALL_EXPR from the above
    using build_new_function_call -> build_over_call which calls mark_used
    -> maybe_instantiate_noexcept -> type_dependent_expression_p.

    There, the innermost template arguments are non-dependent (<int>), but
    the fntype is dependent -- the return type is a TYPENAME_TYPE, and
    since we have no DECL_CONTEXT, this check holds:

      /* Otherwise, if the function decl isn't from a dependent scope, it can't
be
         type-dependent.  Checking this is important for functions with auto
return
         type, which looks like a dependent type.  */
      if (TREE_CODE (expression) == FUNCTION_DECL
          && !(DECL_CLASS_SCOPE_P (expression)
               && dependent_type_p (DECL_CONTEXT (expression)))

    whereupon we ICE.

    This patch fixes it by deferring the class deduction until the
    enclosing scope is non-dependent.  build_deduction_guide and
maybe_aggr_guide
    needed a little tweaking to make the deduction work in a member
    template.

    Co-Authored-By: Jason Merrill <jason@redhat.com>

    gcc/cp/ChangeLog:

            PR c++/97034
            PR c++/99009
            * pt.c (build_deduction_guide): Use INNERMOST_TEMPLATE_ARGS.
            (maybe_aggr_guide): Use the original template type where needed. 
In
            a class member template, partially instantiate the result of
            collect_ctor_idx_types.
            (do_class_deduction): Defer the deduction until the enclosing
            scope is non-dependent.

    gcc/testsuite/ChangeLog:

            PR c++/97034
            PR c++/99009
            * g++.dg/cpp1z/class-deduction81.C: New test.
            * g++.dg/cpp1z/class-deduction82.C: New test.
            * g++.dg/cpp2a/class-deduction-aggr8.C: New test.
            * g++.dg/cpp2a/class-deduction-aggr9.C: New test.
            * g++.dg/cpp2a/class-deduction-aggr10.C: New test.

[Bug c++/97034] [11 Regression] ICE on C++20 code: gcc_assert failure in return type deduction (gcc/cp/pt.c:26984 in type_dependent_expression_p(tree_node*))

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97034

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

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

--- Comment #10 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Fixed.