[Bug c++/97358] New: [8/9/10/11 Regression] ICE while building firefox since r8-2720

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97358

            Bug ID: 97358
           Summary: [8/9/10/11 Regression] ICE while building firefox
                    since r8-2720
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jakub at gcc dot gnu.org
  Target Milestone: ---

The following testcase reduced from firefox ICEs with -std=c++17 starting with
r8-2720-gf44a8dd56f5bfbd0596c39693e268ef880c06221 (before it has been
rejected).
clang++ accepts it, though unsure if the reduction didn't make it invalid (or
whether the original 13MB+ :( testcase is valid).

struct A;
struct B { A foo (); };
enum C { E };
struct A { template <typename... T> void bar (T... x) { auto v {[x...] { x;
}...}; } };
template <typename, C> using F = B;
struct G { F<int, E> baz (); };
enum H { J };
struct D { using K = G; };
template <H> struct I : D { void qux (); };
template <H h> void I<h>::qux () { K a; a.baz ().foo ().bar (); }
template class I<J>;