pub fn fun_ext_ty<F: Prop, G: Prop, X: Prop, Y: Prop, A: Prop>() -> Ty<FunExt<F, G>, Pow<FunExtTy<F, G, X, Y, A>, Tauto<Eq<F, G>>>>
fun_ext(f, g) : (f == g)^true -> fun_ext_ty(f, g).
fun_ext(f, g) : (f == g)^true -> fun_ext_ty(f, g)
Type of function extensionality.