rust-lang / rust-lang/rust-clippy

New lint: let statement with no effect

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A-lint L-unnecessary
Dominant language
Rust
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Description

As featured in this Twitter poll.

A statement of the form let _ = <place> has no effect (modulo Deref coersion) as the place is not moved from. This should instead be omited (if all Deref coersion is pure) or otherwise written to be more clear on intent (explicitly calling side-effectful Deref).

50% of people had the wrong intuition of behavior here, so this definitely would help avoid potentially misleading code.

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  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

No file, test, or entry point is named in the issue. Start by locating existing rust-clippy lints for let statements and their tests, then determine how the proposed no-effect behavior should distinguish pure dereference coercions from explicitly side-effectful dereference. Done means the lint behavior and its diagnostic are covered by focused tests.

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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