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Improve object traversal for heap types and mro#6976

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youknowone merged 1 commit intoRustPython:mainfrom
youknowone:traverse-improvements
Feb 3, 2026
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Improve object traversal for heap types and mro#6976
youknowone merged 1 commit intoRustPython:mainfrom
youknowone:traverse-improvements

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@youknowone youknowone commented Feb 3, 2026 •
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  • Fix heap type instance traversal to include type reference (enables correct cycle detection for instance ↔ type references)
  • Enable mro traversal in PyType (was previously disabled)

Summary by CodeRabbit

  • Refactor
    • Improved garbage collection traversal for type objects to ensure proper memory management of type hierarchies and heap-allocated types.

@youknowone
Improve object traversal for heap types and mro
f358d86 
- Fix heap type instance traversal to include type reference
  (enables correct cycle detection for instance ↔ type references)
- Enable mro traversal in PyType (was previously disabled)
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coderabbitai bot commented Feb 3, 2026 •
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📝 Walkthrough

Walkthrough

This PR enhances garbage collection tracing in the RustPython VM by re-enabling MRO traversal in PyType and adding explicit heap-type reference tracing in PyInner object traversal. These changes ensure complete marking of type relationships during GC cycles.

Changes

Cohort / File(s) Summary
GC Traversal Enablement
crates/vm/src/builtins/type.rs		 Re-enabled MRO traversal in PyType's traverse implementation by uncommenting self.mro.traverse(tracer_fn), ensuring all MRO entries are visited during GC tracing.
Heap Type Reference Tracing
crates/vm/src/object/traverse_object.rs		 Added explicit tracing of heap-type references in both PyInner and PyInner paths. When a type is a heap type, the type object is now converted to PyObject and traced before dict/slots traversal continues.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~22 minutes

Possibly related PRs

Poem

🐰 Hop, hop, the MRO flows,
No more gaps in traces that the garbage knows,
Heap types shine with reference bright,
GC cycles now collect all in sight! ✨

🚥 Pre-merge checks | ✅ 2 | ❌ 1
❌ Failed checks (1 warning)
Check name Status Explanation Resolution
Docstring Coverage ⚠️ Warning Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%. Write docstrings for the functions missing them to satisfy the coverage threshold.
✅ Passed checks (2 passed)
Check name Status Explanation
Description Check ✅ Passed Check skipped - CodeRabbit’s high-level summary is enabled.
Title check ✅ Passed The title 'Improve object traversal for heap types and mro' directly and accurately summarizes the main changes: enabling MRO traversal in PyType and improving heap type instance traversal to include type references.

✏️ Tip: You can configure your own custom pre-merge checks in the settings.

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@youknowone youknowone marked this pull request as ready for review February 3, 2026 08:10
@youknowone youknowone merged commit d6aab01 into RustPython:main Feb 3, 2026
13 checks passed
@youknowone youknowone deleted the traverse-improvements branch February 3, 2026 08:54
@coderabbitai coderabbitai bot mentioned this pull request Feb 3, 2026
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