Stop applying dereferenceable(n) to return types
#149948
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| // potentially self-referential types (see | ||
| // <https://github.com/rust-lang/unsafe-code-guidelines/issues/381>). If LLVM had a way | ||
| // to say "dereferenceable on entry" we could use it here. | ||
| attrs.pointee_size = match kind { |
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drive-by: I really dislike how we track dereferenceable as pointee_size: Size, this should imo really be dereferenceable: Option<NonZeroU64>, or something.
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Yeah this entire code could benefit from a large-scale refactor.^^
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I might or might not do something about it ^^"
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Could probably make NonZero<Size> work, now?
Size is kinda nice when it's coming from layout as Size anyway, and avoids the "type_ix is bits but this is bytes" problems.
(Also, IIRC we don't put dereferencable(0) on &Zst anyway, so using zero instead of None isn't horrible here.)
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LLVM doesn't allow dereferencable(0).
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Could probably make
NonZero<Size>work, now?
NonZero has a ZeroablePrimitive bound and that trait is sealed, so you can't really make NonZero<Size>, only make your own NonZeroSize...
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It looks like the semantics of
dereferenceable(n)on return types is "dereferenceable until the end of the program", which is not sound for how we were using it. See dereferenceable on return type zulip thread.cc @rust-lang/opsem @nikic