[pointer][transmute] Support generic TransmuteFrom #1910
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This was referenced Oct 15, 2024
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Codecov ReportAttention: Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## I1ac2ae177a235083e33b09fc848423220d3da042 #1910 +/- ##
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Coverage ? 89.76%
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Files ? 17
Lines ? 5806
Branches ? 0
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Hits ? 5212
Misses ? 594
Partials ? 0 ☔ View full report in Codecov by Sentry. |
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This prepares us to rename `TransparentWrapper` to `TransmuteFrom`, which we'll do in a follow-up commit to preserve nice git diffs. Makes progress on #1122 gherrit-pr-id: Ifc49755af0d90eeefe7822d755d508403c266bda
We previously used `AliasingMapping`s and `Inaccessible` to model `UnsafeCell` agreement. This abuses the notion of a mapping since one doesn't ever actually want to change the aliasing of a pointer (and certainly not to `Inaccessible`) - really this was meant to model pointer casts which should never be performed. In addition to being an awkward fit, the presence of `Inaccessible` meant that code could not assume that any `Aliasing` invariant permitted reading, and so we had to add extra machinery to work around this. Future commits will use a different, simpler model for denoting `UnsafeCell` agreement or disagreement. While we're here, make `Read` slightly more permissive, implemented for `A: Aliasing, T: Immutable` rather than just `A: Reference, T: Immutable`. Makes progress on #1122, #1866 gherrit-pr-id: I1ac2ae177a235083e33b09fc848423220d3da042
This commit replaces the `TransparentWrapper` trait with a more generic, bidirectional `TransmuteFrom<T>` trait. `U: TransmuteFrom<T>` indicates that `T` and `U` have the same sizes and that `T` can be transmuted into `U` given certain alignment and validity invariant mappings. Makes progress on #1122 gherrit-pr-id: I7af68cdaa5ea47ab245a942d1cbd8bc5e6407223
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February 5, 2025 19:55
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This commit replaces the
TransparentWrappertrait with a more generic,bidirectional
TransmuteFrom<T>trait.U: TransmuteFrom<T>indicatesthat
TandUhave the same sizes and thatTcan be transmuted intoUgiven certain alignment and validity invariant mappings.Makes progress on #1122
This PR is on branch ptr-overhaul.