rust-lang / rust-lang/rust-clippy

`while_let_loop` should not be reported for empty match statements

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#10,037 3 comments 0 reactions 0 assignees View on GitHub

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I-false-positive
Dominant language
Rust
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Description

Description

In case the loop only contains a single match statement, with either an empty block or a break, while_let_loop should IMO not be reported, since the code communicates a slightly different intention.

A loop with a single, empty match communicates, that driving the iterator/stream/generator/... to completion is the main focus, while a while loop communicates, that the iterator/stream/generator/... is just a source of data and not the main focus.

loop {
    match state.process_next() {
        ControlFlow::Continue(_) => {},
        ControlFlow::Break(_) => break,
    }
}
while let ControlFlow::Continue(_) = state.process_next() {}

Small example: playground

Version
rustc 1.67.0-nightly (a00f8ba7f 2022-11-15)
binary: rustc
commit-hash: a00f8ba7fcac1b27341679c51bf5a3271fa82df3
commit-date: 2022-11-15
host: x86_64-unknown-linux-gnu
release: 1.67.0-nightly
LLVM version: 15.0.4

(also on stable)
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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

Start by locating the while_let_loop lint and reproducing the provided Rust playground example. The work is done when loops containing a single empty match or a match ending in break are not reported, while the existing lint behavior remains covered by tests.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
tooling
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
45/100

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