Preserve reflected multiplication for sequence subclasses by 1ndahous3 · Pull Request #9228 · RustPython/RustPython

1ndahous3 · 2026-10-19T18:20:54Z

Summary

Keep inherited sequence repetition out of numeric slots unless an override requires numeric dispatch. Subclasses now honor the right operand's __rmul__, including *=, without prematurely mutating the original container.
Preserve numeric dispatch inherited from mixins and when multiplication and in-place overrides are replaced or removed.

Follow-up to #8865 and #9049.

Performance

Release builds; median of five timing samples.

Windows 11 x64

Operation	Main, ns/op	Patched, ns/op	Speedup
`list` subclass × 2	350	194	1.81×
`str` subclass × 2	320	182	1.75×

Debian 12 amd64

Operation	Main, ns/op	Patched, ns/op	Speedup
`list` subclass × 2	309	163	1.89×
`str` subclass × 2	299	146	2.05×

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Written with Codex (GPT-6), reviewed by a human before submission.

Summary by CodeRabbit

Bug Fixes
- Improved arithmetic operator behavior for inherited sequences. List multiplication and in-place addition or multiplication now handle reflected numeric operators and overrides more consistently, including when temporary overrides are removed.
- Corrected inherited multiplication behavior so both left- and right-hand multiplication operations are preserved.

Assisted-by: Codex:GPT-6

chatgpt-codex-connector · 2026-10-19T18:21:07Z

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-20T06:02:36.617471Z	`1073561`	New commits

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coderabbitai · 2026-10-19T18:32:14Z

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📒 Files selected for processing: 3

crates/vm/src/types/slot.rs
crates/vm/src/types/slot_defs.rs
extra_tests/snippets/operator_arithmetic.py

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📝 Walkthrough

The changes update numeric slot handling for multiplication and in-place addition when inherited native sequence operations and reflected numeric methods are involved. New arithmetic tests cover these dispatch cases.

Changes: Operator Dispatch

Layer / File(s)	Summary
Native sequence and numeric slot dispatch `crates/vm/src/types/slot.rs`, `crates/vm/src/types/slot_defs.rs`	Numeric slot updates detect native sequence wrappers and use dedicated dispatch wrappers. `NbMultiply` now also copies an inherited `right_multiply` slot when the target slot is empty.
Reflected and in-place operator tests `extra_tests/snippets/operator_arithmetic.py`	Tests cover reflected multiplication and addition with inherited list operations, including behavior after temporary `__imul__` and `__iadd__` overrides are deleted.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix

Suggested reviewers: youknowone, youknowdot

Merge Risk: ⚪ Minimal · up to 1c2f0

No actionable merge-blocking issue was identified; the change is mergeable after normal checks.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 20.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 10 functions across 3 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes the main change: preserving reflected multiplication for sequence subclasses.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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codspeed · 2026-10-19T20:59:03Z

Merging this PR will not alter performance

✅ 62 untouched benchmarks
⏩ 4 skipped benchmarks¹

_{Comparing 1ndahous3:sequence_slot_inheritance (1073561) with main (398dd70)}

4 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

Assisted-by: Codex:GPT-6

Preserve reflected multiplication for sequence subclasses

1c2f024

Assisted-by: Codex:GPT-6

Merge main into sequence_slot_inheritance

1073561

Assisted-by: Codex:GPT-6

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Preserve reflected multiplication for sequence subclasses - #9228

Preserve reflected multiplication for sequence subclasses#9228
1ndahous3 wants to merge 2 commits into
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1ndahous3:sequence_slot_inheritance

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Summary

Performance

Windows 11 x64

Debian 12 amd64

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1ndahous3 commented Oct 19, 2026 •

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