rust-lang / rust-lang/rust-clippy

`.clone().takes_self_ref()` isn't caught by clippy::redundant_clone

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C-bug I-false-negative L-nursery
Dominant language
Rust
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Description

Summary

Code of the form .clone().method(), where method takes &self, has a redundant clone. Clippy should catch this

Lint Name

redundant_clone

Reproducer

I tried this code:

#[derive(Clone)]
struct Foo;
impl Foo {
    fn method(&self) {}
}

fn example(foo: &Foo) {
    foo.clone().method();
}

I expected to see this happen: a warning that the .clone() call is redundant

Instead, this happened: no such warning

Version
rustc 1.63.0 (4b91a6ea7 2022-08-08)
binary: rustc
commit-hash: 4b91a6ea7258a947e59c6522cd5898e7c0a6a88f
commit-date: 2022-08-08
host: x86_64-unknown-linux-gnu
release: 1.63.0
LLVM version: 14.0.5

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 by locating the redundant_clone lint implementation and its tests, then reproduce the reported Foo example where clone() is followed by a method taking &self. Add coverage for this pattern and make the lint emit a redundant-clone warning, confirming the expected behavior with the Clippy test suite.

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
Active
Clarity
Clearly specified
Newbie friendliness
68/100

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