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 wt_select_switch: forall n ce e rt sl, wt_lblstmts ce e rt sl -> wt_lblstmts ce e rt (select_switch n sl).