Remark type_expect_incr:
  forall e ty1 ty2 e' te, type_expect e ty1 ty2 = OK e' -> S.satisf te e' -> S.satisf te e.

Lemma wt_init_regs: forall env rl args, Val.has_type_list args (List.map env rl) -> wt_regset env (init_regs args rl).