[derive] Split repr(C) logic from derive_known_layout_inner

[joshlf]

---

• 　 [WIP][derive] Factor out unsafe impl block building #2893
• 　 [derive] Introduce Ctx type #2890
• 　 [derive] Move find_zero_variant to enum module #2889
• 👉 [derive] Split repr(C) logic from derive_known_layout_inner #2888

Latest Update: v5 — Compare vs v4

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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 focuses on improving the internal structure of the zerocopy-derive crate by refactoring the KnownLayout derive macro. It extracts the specialized logic for repr(C) structs into a new, distinct function, making the overall implementation cleaner and easier to maintain. This separation of concerns helps to clarify the different code paths for various struct representations without altering the external behavior or capabilities of the derive macro.

Highlights

• Code Refactoring: The logic for handling repr(C) structs within the derive_known_layout_inner function has been extracted into a new, dedicated helper function named derive_known_layout_for_repr_c_struct.
• Improved Modularity: This change enhances the modularity and readability of the KnownLayout derive macro implementation by separating concerns related to repr(C) specific layout handling.
• Maintain Existing Functionality: The core functionality for deriving KnownLayout for repr(C) structs, including handling of PointerMetadata, MaybeUninit, LAYOUT constants, and pointer manipulation methods, remains unchanged but is now encapsulated in the new function.

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[gemini-code-assist]

Code Review

This pull request is a good refactoring that splits out the logic for repr(C) structs from derive_known_layout_inner into a new function, derive_known_layout_for_repr_c_struct. This improves the structure and readability of the code. The implementation appears correct and preserves the original logic. I have one suggestion to further improve maintainability by breaking down the new, large function.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.90%. Comparing base (0f16595) to head (24a2fec).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2888   +/-   ##
=======================================
  Coverage   91.90%   91.90%           
=======================================
  Files          20       20           
  Lines        5878     5878           
=======================================
  Hits         5402     5402           
  Misses        476      476           

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