Corollary check_rval_wt:
  forall a x, wt_expr ce e a -> check_rval a = OK x -> wt_rvalue ce e a.Corollary check_lval_wt:
  forall a x, wt_expr ce e a -> check_lval a = OK x -> wt_lvalue ce e a.

Lemma type_sub_int32s: forall ty1 ty2, type_binop Osub ty1 type_int32s = OK ty2 -> ty2 = incrdecr_type ty1.