[ptr] Add TransparentWrapper #958
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joshlf
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TransparentWrapper is implemented for wrapper types which transparently wrap other types (with the same layout and `UnsafeCell` ranges). This allows us to express a number of conversions more generically, and write less location-specific `unsafe` code.
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joshlf
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Feb 27, 2024
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| // SAFETY: `Wrapping<T>` has only one field, which is `pub` [2]. We are also | ||
| // guaranteed per [1] (from the comment above) that `Wrapping<T>` has the | ||
| // same layout as `T`. The only way for both of these to be true | ||
| // simultaneously is for `Wrapping<T>` to have the same bit validity as `T`. | ||
| // In particular, in order to change the bit validity, one of the following | ||
| // would need to happen: | ||
| // - `Wrapping` could change its `repr`, but this would violate the layout | ||
| // guarantee. | ||
| // - `Wrapping` could add or change its fields, but this would be a | ||
| // stability-breaking change. | ||
| // | ||
| // [2] https://doc.rust-lang.org/core/num/struct.Wrapping.html |
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@jswrenn Following up from our conversation offline - you had more suggestions for this comment?
jswrenn
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| // SAFETY: `Wrapping<T>` has only one field, which is `pub` [2]. We are also | ||
| // guaranteed per [1] (from the comment above) that `Wrapping<T>` has the | ||
| // same layout as `T`. The only way for both of these to be true | ||
| // simultaneously is for `Wrapping<T>` to have the same bit validity as `T`. | ||
| // In particular, in order to change the bit validity, one of the following | ||
| // would need to happen: | ||
| // - `Wrapping` could change its `repr`, but this would violate the layout | ||
| // guarantee. | ||
| // - `Wrapping` could add or change its fields, but this would be a | ||
| // stability-breaking change. | ||
| // | ||
| // [2] https://doc.rust-lang.org/core/num/struct.Wrapping.html |
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