Section SOUNDNESS_CONSTRUCTORS.
Variable ce: composite_env.
Variable e: typenv.
Variable rt: type.
Hint Resolve check_rval_wt check_lval_wt: ty.
Hint Extern 1 (wt_expr _ _ _) => (unfold wt_expr; simpl): ty.

Lemma ebuiltin_sound:
forall ef tyargs args tyres a,
ebuiltin ef tyargs args tyres = OK a -> wt_exprlist ce e args -> wt_expr ce e a.