Conversion from unsafe.Pointer to *V violates unsafe package rules about exp

[smallnest]

Yes, theoretically it seems (*V)(expunged) violates unsafe package rules as you mentioned，but here it is trick that we use the expunged as immutable and we don't change its bytes. It only acts as a special value to indicate values in map are deleted, so I personally think it is not a problem.

Why not use unsafe.Pointer? I hope this code can keep up to changes in go official repository.
There is another generic sync.Map to use unsafe.Pointer https://github.com/go-typ/typ/blob/main/sync2/map.go#L78

[DmitriyMV]

It only acts as a special value to indicate values in map are deleted, so I personally think it is not a problem.

It doesn't matter that you are not reading or writing it - the compiler make no promises about not inspecting the value after the conversion. And since V can be bigger than any it can go very bad very fast and will be very hard to catch.

I hope this code can keep up to changes in go official repository.

You can always ask them about safety of certain operations.