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 wt_subexpr: forall from to C, context from to C -> wt_expr_kind cenv tenv to (C a) -> wt_expr_kind cenv tenv from a with wt_subexprlist: forall from C, contextlist from C -> wt_exprlist cenv tenv (C a) -> wt_expr_kind cenv tenv from a.