rust-lang/rust-clippy

Rewrite `arithmetic_side_effects` to not use matching on string representation of types

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#16,359 opened on Jan 8, 2026

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Description

Description

arithmetic_side_effects uses the string representation of types to compare them. This will miss aliases (including core/alloc → std), takes longer to compare, etc.

It should use a method similar to what is done in the disallowed_types lint, where maps of DefId or PrimTy are built at lint initialization time and then used throughout the tree walk. Some type lookup code could probably even be shared (including the part where unloaded crates don't cause errors).

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Research direction
Study the implementation of the `disallowed types` lint in clippy to understand how it uses maps of DefId or PrimTy, then apply similar approach to `arithmetic side effects`. Ensure that unloaded crates are handled gracefully.
Tech stack
rust
Domain
tooling
Issue type
Refactor
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
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Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
RustGit
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65