The question was, what I WOULD do, after x/3♦ 3♠ from partner. The only solution is IMHO, to play X at the 3-level as asking for stopper (wasnt that an idea from larry cohen?)
I try to find sth else than 3♣ in this situation. So with this ok-stop in ♦ and the correct range of points I see no real choice but an opportunity to bid NT
Well I have thiy in my mind for several years...
My Opinion: My own behaviour is not an UI. So is my knowledge, that my partner is obyeing the rules. So:
No UI, no infraction of law using this "information"