[cast] Add Project::pointer_inner #2894
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Summary of ChangesHello @joshlf, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed! This pull request refactors the pointer projection mechanism by clearly separating the operations that yield raw pointers from those that produce safe Highlights
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Code Review
This pull request is a nice refactoring that renames Project::project to project_raw and introduces a new Project::project_inner method. This centralizes the logic for creating a PtrInner from a raw projected pointer, improving maintainability and safety. The changes are consistent and well-executed across the codebase. I have one minor suggestion to update a safety comment to reflect the method rename.
| // does not wrap around the address space [1], and so none of the | ||
| // addresses contained in it or one-past-the-end of it are null. | ||
| // | ||
| // By invariant on `Self: Project`, `Self::project` is a |
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The safety comment refers to Self::project, but this method has been renamed to Self::project_raw. Please update the comment to reflect the new name for accuracy.
| // By invariant on `Self: Project`, `Self::project` is a | |
| // By invariant on `Self: Project`, `Self::project_raw` is a |
| /// Projects a [`PtrInner`] from `Src` to `Dst`. | ||
| /// | ||
| /// # Safety | ||
| /// | ||
| /// The caller may assume that the resulting `PtrInner` addresses a | ||
| /// subset of the bytes of `src`'s referent. | ||
| #[must_use] | ||
| #[inline(always)] | ||
| fn project_inner(src: PtrInner<'_, Src>) -> PtrInner<'_, Dst> { | ||
| let projected_raw = Self::project_raw(src); | ||
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| // SAFETY: `src`'s referent lives at a `NonNull` address, and is | ||
| // either zero-sized or lives in an allocation. In either case, it | ||
| // does not wrap around the address space [1], and so none of the | ||
| // addresses contained in it or one-past-the-end of it are null. | ||
| // | ||
| // By invariant on `Self: Project`, `Self::project` is a | ||
| // provenance-preserving projection which preserves or shrinks the | ||
| // set of referent bytes, so `projected_raw` references a subset of | ||
| // `src`'s referent, and so it cannot be null. | ||
| // | ||
| // [1] https://doc.rust-lang.org/1.92.0/std/ptr/index.html#allocation | ||
| let projected_non_null = unsafe { core::ptr::NonNull::new_unchecked(projected_raw) }; | ||
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| // SAFETY: As described in the preceding safety comment, `projected_raw`, | ||
| // and thus `projected_non_null`, addresses a subset of `src`'s | ||
| // referent. Thus, `projected_non_null` either: | ||
| // - Addresses zero bytes or, | ||
| // - Addresses a subset of the referent of `src`. In this case, `src` | ||
| // has provenance for its referent, which lives in an allocation. | ||
| // Since `projected_non_null` was constructed using a sequence of | ||
| // provenance-preserving operations, it also has provenance for its | ||
| // referent and that referent lives in an allocation. By invariant on | ||
| // `src`, that allocation lives for `'a`. | ||
| unsafe { PtrInner::new(projected_non_null) } | ||
| } |
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If there's no case where an implementation of Project would override this default impl, I'd suggest putting it in PtrInner where it cannot be overridden and can be called as a method on a PtrInner.
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## G2eb58496ed1e3c61421020abbbb694d970d43c1c #2894 +/- ##
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+ Coverage 91.82% 91.90% +0.08%
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Files 20 20
Lines 5883 5882 -1
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+ Hits 5402 5406 +4
+ Misses 481 476 -5 ☔ View full report in Codecov by Sentry. 🚀 New features to boost your workflow:
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Rename `Project::project` to `project_raw`, and add a new `project_inner` which returns a `PtrInner` instead of a raw pointer. Remove `HasField::project_inner` since we can use `Project::project_inner` instead. gherrit-pr-id: G82a7bac1fdbde51b23d1760bfc7881a3bf862452
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Rename
Project::projecttoproject_raw, and add a newproject_innerwhich returns aPtrInnerinstead of a raw pointer.Remove
HasField::project_innersince we can useProject::project_innerinstead.Latest Update: v2 — Compare vs v1
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