pub fn lam_app_trivial<A: Prop, B: Prop, X: Prop>( ty_b: Ty<B, X>) -> Eq<App<Lam<Ty<A, X>, B>, B>, B>
(b : x) => ((\(a : x) = b)(b) == b.
(b : x) => ((\(a : x) = b)(b) == b