Potentially it plays out in a lot of ways.
1) You could go to the buffet.
2) You could pack your long pants in your carry on.
3) You could not close your suitcase until you get back to your room, put your long pants in it, and then set it outside.
4) You could wear your long pants the next morning.
5) You could hope the Maitre’D doesn’t kick you out of the MDR and switch to option 1) if he does.
6) You could eat dinner, go back to your room change clothes, put your suitcase out, and go to the show.
I typically do either 3 or 6, although I have done 4 as well.