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

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.