[Bug c++/102784] New: ICE: tree check: expected tree that contains 'decl common' structure, have 'error_mark' in synthesize_implicit_template_parm, at cp/parser.c:47991

[hewillk at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102784

            Bug ID: 102784
           Summary: ICE: tree check: expected tree that contains 'decl
                    common' structure, have 'error_mark' in
                    synthesize_implicit_template_parm, at
                    cp/parser.c:47991
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hewillk at gmail dot com
  Target Milestone: ---

12 Regression:

template<class>
concept C = true;

template<C T, class T>
  requires
auto operator<<(auto) = delete;

https://godbolt.org/z/TPh9GETx5