Traits other than NoCell permit UnsafeCells#682
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NoCell permit UnsafeCells
NoCell permit UnsafeCellsNoCell permit UnsafeCells
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joshlf
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Dec 7, 2023
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jswrenn
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Dec 8, 2023
Previously, `FromZeros`, `FromBytes`, and `AsBytes` could not be implemented for types containing `UnsafeCell`s. This is a soundness precondition for some types of reference transmutations (notably transmuting either direction between `&[u8]` and `&T`). However, some of our machinery operates only on values (e.g. `transmute!`), and that machinery should in principle be able to support types which contain `UnsafeCell`s. In this commit, we remove the "no `UnsafeCell`" restriction from `FromZeros`, `FromBytes`, and `AsBytes`. We use the recently-added `NoCell` trait as a bound on individual functions and methods where `UnsafeCell`s would be unsound. This permits some APIs to support `UnsafeCell`s which could not previously support them. Closes #251
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jswrenn
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Dec 8, 2023
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joshlf
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Previously, `T: AsBytes` indicated that `&T -> &[u8]` was a valid transformation. As of #682, `T: AsBytes` only indicates that `T -> [u8]` is a valid transformation. This slightly changes the meaning of `AsBytes` and makes `ToBytes` a more appropriate name since it only permits value rather than reference transmutations. This also brings the pair of `FromBytes` and `ToBytes` in line with the standard library `From` and `Into` traits from a naming perspective. Closes #695
joshlf
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Previously, `T: AsBytes` indicated that `&T -> &[u8]` was a valid transformation. As of #682, `T: AsBytes` only indicates that `T -> [u8]` is a valid transformation. This slightly changes the meaning of `AsBytes` and makes `IntoBytes` a more appropriate name since it only permits value rather than reference transmutations. This also brings the pair of `FromBytes` and `IntoBytes` in line with the standard library `From` and `Into` traits from a naming perspective. Closes #695
joshlf
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Dec 11, 2023
Previously, `T: AsBytes` indicated that `&T -> &[u8]` was a valid transformation. As of #682, `T: AsBytes` only indicates that `T -> [u8]` is a valid transformation. This slightly changes the meaning of `AsBytes` and makes `IntoBytes` a more appropriate name since it only permits value rather than reference transmutations. This also brings the pair of `FromBytes` and `IntoBytes` in line with the standard library `From` and `Into` traits from a naming perspective. Closes #695
joshlf
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Dec 11, 2023
Previously, `T: AsBytes` indicated that `&T -> &[u8]` was a valid transformation. As of #682, `T: AsBytes` only indicates that `T -> [u8]` is a valid transformation. This slightly changes the meaning of `AsBytes` and makes `IntoBytes` a more appropriate name since it only permits value rather than reference transmutations. This also brings the pair of `FromBytes` and `IntoBytes` in line with the standard library `From` and `Into` traits from a naming perspective. Closes #695
joshlf
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Dec 11, 2023
Previously, `T: AsBytes` indicated that `&T -> &[u8]` was a valid transformation. As of #682, `T: AsBytes` only indicates that `T -> [u8]` is a valid transformation. This slightly changes the meaning of `AsBytes` and makes `IntoBytes` a more appropriate name since it only permits value rather than reference transmutations. This also brings the pair of `FromBytes` and `IntoBytes` in line with the standard library `From` and `Into` traits from a naming perspective. Closes #695
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Dec 14, 2023
Previously, `T: AsBytes` indicated that `&T -> &[u8]` was a valid transformation. As of #682, `T: AsBytes` only indicates that `T -> [u8]` is a valid transformation. This slightly changes the meaning of `AsBytes` and makes `IntoBytes` a more appropriate name since it only permits value rather than reference transmutations. This also brings the pair of `FromBytes` and `IntoBytes` in line with the standard library `From` and `Into` traits from a naming perspective. Closes #695
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Previously,
FromZeros,FromBytes, andAsBytescould not beimplemented for types containing
UnsafeCells. This is a soundnessprecondition for some types of reference transmutations (notably
transmuting either direction between
&[u8]and&T). However, some ofour machinery operates only on values (e.g.
transmute!), and thatmachinery should in principle be able to support types which contain
UnsafeCells.In this commit, we remove the "no
UnsafeCell" restriction fromFromZeros,FromBytes, andAsBytes. We use the recently-addedNoCelltrait as a bound on individual functions and methods whereUnsafeCells would be unsound. This permits some APIs to supportUnsafeCells which could not previously support them.Closes #251