I'm not sure these are intended to be the same.

@RalfJung Is the definition of place projection intended to be the same for these two scenarios (closure capture and UB pointer arithmetic)?

Yeah this changes the opsem page to suddenly include pointer deref's and that doesn't make sense in that context (since it is talking about pointer arithmetic, and a deref isn't pointer arithmetic).

since this is about pointer arithmetic, should field expression be removed from the more narrow definiton of place expression

We should probably reword the UB page to use a different term, since it only refers to a few specific place projections.

would this work

A tuple index expression or an array/slice index expression that violates the (safety) requirements of in-bounds pointer arithmetic.