[Bug c++/99478] New: ICE when decltype lambda in template list

[hewillk at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99478

            Bug ID: 99478
           Summary: ICE when decltype lambda in template list
           Product: gcc
           Version: 9.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hewillk at gmail dot com
  Target Milestone: ---

The following code will trigger ICE on gcc-9.1 ~ gcc-trunk with "-std=c++2a"
mode:

template <decltype ([] {})> auto f() {}

int main() { f<{}>(); }

(godbolt: https://godbolt.org/z/dEP5PT)