Hint Resolve check_rval_wt check_lval_wt: ty.
Hint Extern 1 (wt_expr _ _ _) => (unfold wt_expr; simpl): ty.

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'.