[Bug c++/123668] [14/15/16 Regression] ICE in convert_nontype_argument when passing a lambda as an explicit template argument to a member function template since r14-9938

[ppalka at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123668

--- Comment #3 from Patrick Palka <ppalka at gcc dot gnu.org> ---
AFAICT before r14-9938 we always rejected this testcase, so this is hardly a
regression IMHO.

Here's a simpler testcase that we always ICEd on (since r9-4045 which
implemented unevaluated lambdas):

struct bad {
  template <auto L = [] {}> static void g();
};

int main() {
  bad::g();

  [] {};
  bad::g<[] {}>();
}