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 sswitch_sound: forall a sl s, sswitch a sl = OK s -> wt_expr ce e a -> wt_lblstmts ce e rt sl -> wt_stmt ce e rt s.