rust-lang / rust-lang/rust-clippy

Lint suggesting use of TryFrom for checked integer conversion

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A-lint L-complexity L-style
Dominant language
Rust
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Description

Checked integer conversion code has historically looked something like this:

if foo <= i32::max_value() as usize {
    thing_a
} else {
    thing_b
}

But now that TryFrom is stable, it can be done in a more foolproof way like this:

match i32::try_from(foo) {
    Ok(foo) => thing_a,
    Err(_) => thing_b,
}

It'd be cool if there was a lint guiding users to migrate their 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

Start with the checked integer conversion examples in the issue and inspect Clippy's existing lint implementations and tests to find the appropriate entry point. Define the supported conversion patterns and add coverage showing that the lint recommends TryFrom while preserving the Ok and Err behavior.

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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