[Bug c++/95938] New: ICE in synthesize_implicit_template_parm, at cp/parser.c:44077

[haoxintu at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95938

            Bug ID: 95938
           Summary: ICE in synthesize_implicit_template_parm, at
                    cp/parser.c:44077
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Keywords: ice-on-invalid-code
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: haoxintu at gmail dot com
  Target Milestone: ---

This code, bug.cc, reduced by C-Reduce, makes GCC-trunk ICE.

$cat bug.cc
a ( union { auto


$g++ bug.cc
bug.cc:1:11: error: types may not be defined in parameter types
    1 | a ( union { auto
      |           ^
bug.cc:1:13: internal compiler error: in synthesize_implicit_template_parm, at
cp/parser.c:44077
    1 | a ( union { auto
      |             ^~~~
0x642457 synthesize_implicit_template_parm
        ../../gcc/cp/parser.c:44077
0x9bd740 cp_parser_simple_type_specifier
        ../../gcc/cp/parser.c:18029
0x9a1a3d cp_parser_type_specifier
        ../../gcc/cp/parser.c:17838
0x9a2a02 cp_parser_decl_specifier_seq
        ../../gcc/cp/parser.c:14410
0x9cb167 cp_parser_member_declaration
        ../../gcc/cp/parser.c:24995
0x99f921 cp_parser_member_specification_opt
        ../../gcc/cp/parser.c:24850
0x99f921 cp_parser_class_specifier_1
        ../../gcc/cp/parser.c:23947
0x9a1aa3 cp_parser_class_specifier
        ../../gcc/cp/parser.c:24254
0x9a1aa3 cp_parser_type_specifier
        ../../gcc/cp/parser.c:17762
0x9a2a02 cp_parser_decl_specifier_seq
        ../../gcc/cp/parser.c:14410
0x9bf3ef cp_parser_parameter_declaration
        ../../gcc/cp/parser.c:22818
0x9bfdd2 cp_parser_parameter_declaration_list
        ../../gcc/cp/parser.c:22641
0x9c01bc cp_parser_parameter_declaration_clause
        ../../gcc/cp/parser.c:22568
0x9ad617 cp_parser_direct_declarator
        ../../gcc/cp/parser.c:21245
0x9ad617 cp_parser_declarator
        ../../gcc/cp/parser.c:21109
0x9c1ba6 cp_parser_init_declarator
        ../../gcc/cp/parser.c:20609
0x9a36d2 cp_parser_simple_declaration
        ../../gcc/cp/parser.c:13785
0x9cc926 cp_parser_declaration
        ../../gcc/cp/parser.c:13484
0x9cd06a cp_parser_translation_unit
        ../../gcc/cp/parser.c:4761
0x9cd06a c_parse_file()
        ../../gcc/cp/parser.c:44043
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$g++ --version
g++ (GCC) 11.0.0 20200626 (experimental)
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