rust-lang/rust-clippy

False positive for boxed local with `wasm_bindgen`

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#4351 opened on Aug 7, 2019

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 (14 comments) (0 reactions) (0 assignees)Rust (10,406 stars) (1,391 forks)batch import
C-bugI-false-positivegood first issue

Description

wasm_bindgen is a little bit different than the issue that's been resolved with traits. In particular, wasm_bindgen just generates code around the non-trait implemented function, and the only way to use native JS arrays as parameters is to use Box<[...]>.

In general, I think maybe boxed slices should be considered ok for local parameters, as they're conceptually very similar to vectors.

Contributor guide

Tech stack
rust
Domain
developer experiencetooling
Issue type
bug
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.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
Rustclippy internalswasm bindgen
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30
Research direction
Investigate the clippy lint for boxed local parameters (likely in clippy lints/src/boxed.rs or similar). Understand how wasm bindgen generates code and why boxed slices are treated as local parameters. Check existing tests for boxed lints and add a test case with wasm bindgen to reproduce the false positive. Consider if the lint should allow boxed slices for wasm bindgen functions or if a more general fix is needed.