https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95870
--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> --- Reduced, but invalid: template <typename> class a { public: a(); int b = [] { enum E {}; }; }; class c : a<int> { c(); }; template <typename d> a<d>::a() = default; c::c() {}