[Bug c++/113332] [12/13/14 regression] checking ICE when building fcitx-5.1.6

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113332

--- Comment #4 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Another reduced valid testcase:

struct tuple {
  template<class _Tp>
  static constexpr bool __is_implicitly_default_constructible() { return true;
}

  template<class _Tp = void,
           bool = __is_implicitly_default_constructible<_Tp>()>
  tuple();
};

struct DBusStruct {
  DBusStruct() = default;
  tuple data_;
};

struct IBusService {
  int m = [] { DBusStruct{}; return 42; }();
};