likely
unlikely
copy
copy_overlapping
Test was added in PR #84404. The intent here is: The `copy`/`copy_overlapping` intrinsics are going through some flip-flopping now of "are they intrinsics or not". We can achieve the same effect that the test intended by using `likely`/`unlikely`.
Return an error if coercing function items / non-capturing closures to a common function pointer type would require reifying an intrinsic.