I think you misunderstand that the offset is encoded in the type of the object, so only your 1st concern is valid. For concern 2, it's as easy as finding the t

I think you misunderstand that the offset is encoded in the type of the object, so only your 1st concern is valid. For concern 2, it's as easy as finding the type. And without knowing the types you wouldn't know what the code did anyway. For concern 3, a type error. And for 4, because it's a type there is zero runtime overhead. A view of the array with the offset the code expects is constructed, often automatically based on the types involved. This view is often a zero cost abstraction at runtime because of how Julia specialization works. So at worst you pay some (extremely minor) compile-time/load-time costs.