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When it returns a copy of `A`, it absolutely must preserve the same type. As such, this function is designed to be specialized on `A`, typically like:\r\n\r\n    Base.unalias(dest, A::T) = mightalias(dest, A) ? typeof(A)(unalias(dest, A.a), unalias(dest, A.b), ...) : A\r\n\r\n`mightalias(A, B)` is a quick and rough check to see if two arrays alias eachother.  Instead of requiring every array to know about every other array type, it simply asks both arrays for their `dataids` and then looks for an empty intersection between every pair.\r\n\r\nFinally, `dataids(A)` returns a tuple of ranges that describe something about the region of memory the array occupies. It could be simply `(objectid(A):objectid(A),)` or for an array with multiple fields, `(dataids(A.a)..., dataids(A.b)..., ...)`.\r\n\r\nFixes #21693, fixes #15209, and a pre-req to get tests passing for #24368 (since we had spot checks for `Array` aliasing, but moving to broadcast means we need a slightly more generic solution).  I haven't exported any of these functions since I'd like us to use them a bit more before we officially document and support them for all custom 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