https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101670
Joe Loser <joeloser93 at gmail dot com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |joeloser93 at gmail dot com --- Comment #1 from Joe Loser <joeloser93 at gmail dot com> --- Here's a simple workaround using concepts directly: ``` template <class T> concept Complete = requires(T t) { sizeof(t); }; template <class T> concept Incomplete = !Complete<T>; template <Incomplete> struct S {}; struct A; S<A> s1; struct A {}; S<A> s2; ``` See it live at https://gcc.godbolt.org/z/MjKoM8dP6