[Bug c++/109859] New: ICE on concept mis-typed as template type parameter

["saifi.khan at nishan dot io" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109859

            Bug ID: 109859
           Summary: ICE on concept mis-typed as template type parameter
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: saifi.khan at nishan dot io
  Target Milestone: ---

while exploring ranges, i mis-typed the code as follows.

should have written

template <std::ranges::random_access_range R>

--

#include <ranges>

template <typename R = std::ranges::random_access_range>

int  fn (R);

int main () {;}

--

using gcc version 14.0.0 20230514 (experimental) (GCC)

g++ -std=c++23 file.cc

--

output is

file.cc:3:37: internal compiler error: in cp_parser_placeholder_type_specifier,
at cp/parser.cc:20242
    3 | template <typename R = std::ranges::random_access_range>
      |                                     ^~~~~~~~~~~~~~~~~~~
0x75a5de cp_parser_placeholder_type_specifier
        /opt/gcc/src/gcc/cp/parser.cc:20242
0xbb9e11 cp_parser_simple_type_specifier
        /opt/gcc/src/gcc/cp/parser.cc:20079
0xb8ec55 cp_parser_type_specifier
        /opt/gcc/src/gcc/cp/parser.cc:19614
0xba3e42 cp_parser_type_specifier_seq
        /opt/gcc/src/gcc/cp/parser.cc:24615
0xba1a3d cp_parser_type_id_1
        /opt/gcc/src/gcc/cp/parser.cc:24412
0xba1d50 cp_parser_type_id
        /opt/gcc/src/gcc/cp/parser.cc:24511
0xba1d50 cp_parser_default_type_template_argument
        /opt/gcc/src/gcc/cp/parser.cc:17963
0xbb5617 cp_parser_type_parameter
        /opt/gcc/src/gcc/cp/parser.cc:18199
0xbb46d4 cp_parser_template_parameter
        /opt/gcc/src/gcc/cp/parser.cc:18080
0xbb46d4 cp_parser_template_parameter_list
        /opt/gcc/src/gcc/cp/parser.cc:17679
0xbc6ce7 cp_parser_explicit_template_declaration
        /opt/gcc/src/gcc/cp/parser.cc:32382
0xbc9a95 cp_parser_declaration
        /opt/gcc/src/gcc/cp/parser.cc:15050
0xbca553 cp_parser_toplevel_declaration
        /opt/gcc/src/gcc/cp/parser.cc:15142
0xbca553 cp_parser_translation_unit
        /opt/gcc/src/gcc/cp/parser.cc:5131
0xbca553 c_parse_file()
        /opt/gcc/src/gcc/cp/parser.cc:49635
0xd17685 c_common_parse_file()
        /opt/gcc/src/gcc/c-family/c-opts.cc:1248

---

Thanks for your time !