https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97034
--- Comment #4 from Marek Polacek <mpolacek at gcc dot gnu.org> --- Another, valid, where C++20 aggregate CTAD should work: template<typename> struct E { template <typename T> struct G { T t; }; void fn() { G{1}; } }; void g () { E<int> e; e.fn (); }