[Bug c++/67249] New: [concepts] ICE parsing f(pair<auto, concept>)

["cubbi at cubbi dot org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67249

            Bug ID: 67249
           Summary: [concepts] ICE parsing f(pair<auto, concept>)
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: cubbi at cubbi dot org
  Target Milestone: ---

ICE using gcc HEAD 6.0.0 20150816 to compile the following

template<class T> concept bool C1 = true;
template<class A, class B> struct Pair {};
void f(Pair<auto, C1>);
int main() {}

output:

prog.cc:3:19: internal compiler error: Segmentation fault
 void f(Pair<auto, C1>);
                   ^
0xa65abf crash_signal
        /home/heads/gcc/gcc-source/gcc/toplev.c:352
0x629184 get_concept_from_constraint
        /home/heads/gcc/gcc-source/gcc/cp/parser.c:34610
0x629184 synthesize_implicit_template_parm
        /home/heads/gcc/gcc-source/gcc/cp/parser.c:34648
0x6297a2 cp_parser_maybe_constrained_type_specifier
        /home/heads/gcc/gcc-source/gcc/cp/parser.c:15707
0x62e004 cp_parser_maybe_concept_name
        /home/heads/gcc/gcc-source/gcc/cp/parser.c:15732
0x62e004 cp_parser_nonclass_name
        /home/heads/gcc/gcc-source/gcc/cp/parser.c:15785
0x644681 cp_parser_type_name
        /home/heads/gcc/gcc-source/gcc/cp/parser.c:15571
0x644681 cp_parser_simple_type_specifier
        /home/heads/gcc/gcc-source/gcc/cp/parser.c:15485
0x634c55 cp_parser_type_specifier
        /home/heads/gcc/gcc-source/gcc/cp/parser.c:15154
0x637273 cp_parser_type_specifier_seq
        /home/heads/gcc/gcc-source/gcc/cp/parser.c:19139
0x640262 cp_parser_type_id_1
        /home/heads/gcc/gcc-source/gcc/cp/parser.c:19005
0x64035e cp_parser_template_type_arg
        /home/heads/gcc/gcc-source/gcc/cp/parser.c:19060
0x64268b cp_parser_template_argument
        /home/heads/gcc/gcc-source/gcc/cp/parser.c:14578
0x64268b cp_parser_template_argument_list
        /home/heads/gcc/gcc-source/gcc/cp/parser.c:14488
0x64268b cp_parser_enclosed_template_argument_list
        /home/heads/gcc/gcc-source/gcc/cp/parser.c:25096
0x643493 cp_parser_template_id
        /home/heads/gcc/gcc-source/gcc/cp/parser.c:14162
0x643c21 cp_parser_class_name
        /home/heads/gcc/gcc-source/gcc/cp/parser.c:20289
0x63e07e cp_parser_qualifying_entity
        /home/heads/gcc/gcc-source/gcc/cp/parser.c:5776
0x63e07e cp_parser_nested_name_specifier_opt
        /home/heads/gcc/gcc-source/gcc/cp/parser.c:5462
0x64428f cp_parser_simple_type_specifier
        /home/heads/gcc/gcc-source/gcc/cp/parser.c:15457
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