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 retype_stmt_sound: forall s s', retype_stmt ce e rt s = OK s' -> wt_stmt ce e rt s' with retype_lblstmts_sound: forall sl sl', retype_lblstmts ce e rt sl = OK sl' -> wt_lblstmts ce e rt sl'.