[Bug c++/99659] New: internal compiler error: tree check: expected tree that contains 'decl common' structure, have 'error_mark' in synthesize_implicit_template_parm, at cp/parser.c:45415

[hewillk at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99659

            Bug ID: 99659
           Summary: internal compiler error: tree check: expected tree
                    that contains 'decl common' structure, have
                    'error_mark' in synthesize_implicit_template_parm, at
                    cp/parser.c:45415
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hewillk at gmail dot com
  Target Milestone: ---

https://godbolt.org/z/qePTPh

====
template <...args> bar(auto);
====

<source>:1:11: error: expected identifier before '...' token
    1 | template <...args> bar(auto);
      |           ^~~
<source>:1:24: internal compiler error: tree check: expected tree that contains
'decl common' structure, have 'error_mark' in
synthesize_implicit_template_parm, at cp/parser.c:45415
    1 | template <...args> bar(auto);
      |                        ^~~~
0x1cfa259 internal_error(char const*, ...)
        ???:0
0x67bb5d tree_contains_struct_check_failed(tree_node const*,
tree_node_structure_enum, char const*, int, char const*)
        ???:0
0x8e136d c_parse_file()
        ???:0
0xa5f962 c_common_parse_file()
        ???:0
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