Definition cast_no_val_change (from: type)(to:type) : bool :=
match from, to with
| Tint _ _ _, Tint I32 _ _ => true
| Tpointer _ _, Tpointer _ _ => 
    eqb_type from to || 
    negb (eqb_type from int_or_ptr_type) && 
    negb (eqb_type to int_or_ptr_type)
| Tfloat F64 _ , Tfloat F64 _ => true
| Tfloat F32 _ , Tfloat F32 _ => true
| _, _ => false
end.

Lemma neutral_cast_tc_val : forall {CS: compspecs} e t rho phi Delta, true = is_neutral_cast (implicit_deref (typeof e)) t -> denote_tc_assert (isCastResultType (implicit_deref (typeof e)) t e) rho phi -> denote_tc_assert (typecheck_expr Delta e) rho phi -> typecheck_environ Delta rho -> tc_val t (eval_expr e rho).