rust-lang / rust-lang/rust-clippy

new lint: let_underscore_var

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A-lint
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Rust
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Description

What it does

Unlike let _ = <expr> (it's a drop), let _ = <variable> is a no-op. I believe it's useless.

Also the discription of let_underscore_drop maybe inprecise becasue it ignored this case.

Lint Name

let_underscore_var

Category

correctness, suspicious

Advantage

No response

Drawbacks

No response

Example
let _ = x;

should warn: this is a no-op. Use let _x = x; to move x but extend it's lifetime until the end of the block, or use mem::drop(x) to drop x;

Contributor guide

Open the contributing guide

First steps

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  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the existing let_underscore_drop lint and its linked documentation, then inspect how Rust Clippy defines and tests lints. Completion should add the proposed let_underscore_var lint for the shown let _ = x; case and clarify the let_underscore_drop description.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
tooling
Issue type
Feature
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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