y vs la

Question

Can I say, "Vas-tu a ta chambre? Cache-t'y!" as y refers to a ta chambre? All grammar books seem to indicate that y replaces a + noun (except persons).

Accepted Answer

To be perfectly correct, it would need to be cache-toi y (y replaces à ta chambre), you wouldn't say Cache-t'y! in spoken French. It's more common to use Cache-toi là. When referring to a specific and well understood place, là is more frequently used than y. It is also less formal.

Answer

I finally found the answer from the best grammar book, "Le Bon Usage" by Maurice Grevisse. "Cache-toi-z'y" in spoken French. See https://www.eurekoi.org/langue-doit-on-dire-tiens-ty-tiens-y-toi-tiens-toi-zy-ou-autre-chose/