rust-lang / rust-lang/rust-clippy

Lint uses of map entries that could be replaced with `or_insert`

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A-lint
Dominant language
Rust
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Description

For example:

let val = match map.entry(key) {
    Occupied(ref e) => e.into_mut(),
    Vacant(ref e) => e.insert(something),
};

could be replaced with:

let val = map.entry(key).or_insert_with(|| something);

Contributor guide

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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

The issue names no implementation file or test; start by examining rust-clippy's existing lint implementations and tests for map.entry patterns. Use the two map.entry examples as the behavioral boundary, and verify that the lint identifies the replaceable match while leaving other cases unchanged.

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
45/100

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