| t1 == t2 && td == TyApp "Bool" [] = True
sane_ty Monadic (TyF t1 td)
| t1 == td = True
-sane_ty Dyadic (TyF t1 (TyF t2 _))
- | t1 == t2 && t2 == t2 = True
+sane_ty Dyadic (TyF t1 (TyF t2 td))
+ | t1 == td && t2 == td = True
sane_ty GenPrimOp _
= True
sane_ty _ _