[derive] Factor out core_reexport path generation

[joshlf]

While we're here, remove a number of use statements from generated
code. These statements are dangerous beacause they risk bringing items
into scope whose names shadow the identifiers which we have parsed from
the derive input and will emit into the scope. This will cause those
references to erroneously refer to the use'd items instead of their
intended referents.

---

• 　 [WIP][derive] Factor out unsafe impl block building #2893
• 👉 [derive] Factor out core_reexport path generation #2899

Latest Update: v2 — Compare vs v1

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[gemini-code-assist]

Summary of Changes

Hello @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 zerocopy-derive crate by introducing a centralized mechanism for generating paths to core library items. By consolidating the core_reexport path generation into a dedicated ctx.core_path() method, the change significantly improves code consistency and maintainability across the derive macros. This abstraction simplifies future updates and ensures a uniform approach to referencing standard library components.

Highlights

• Centralized Core Path Generation: The pull request introduces a new core_path() method within the Ctx struct. This method centralizes the generation of the core_reexport path, which is used to refer to items from Rust's core library.
• Refactored Path Usage: All instances where core_reexport::... paths were directly used have been updated to call ctx.core_path() instead. This includes usages for PhantomData, MaybeUninit, ManuallyDrop, NonZeroUsize, NonNull, primitive::bool, marker::Sized, compile_error!, hash::Hash, hash::Hasher, cmp::PartialEq, and cmp::Eq.
• Simplified Trait Path Resolution: The Trait::crate_path method and the ImplBlockBuilder::bound_tt function now accept the Ctx object directly, allowing them to utilize the new core_path() method for resolving core library paths.
• Reduced Redundancy: Explicit use statements for core_reexport items have been removed from various functions, as the core_path() method now handles their resolution.

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[gemini-code-assist]

Code Review

The pull request successfully refactors the generation of the core_reexport path into a dedicated method ctx.core_path(). This change significantly improves code maintainability by centralizing the logic for constructing this path, reducing duplication, and making future modifications easier. The changes are consistently applied across all affected files, and the logic remains sound.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.90%. Comparing base (e0607e0) to head (c97f53b).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2899   +/-   ##
=======================================
  Coverage   91.90%   91.90%           
=======================================
  Files          20       20           
  Lines        5877     5877           
=======================================
  Hits         5401     5401           
  Misses        476      476           

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