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new lint: using let mut a = a at start of function #5102

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jyn514 opened this issue Jan 27, 2020 · 9 comments
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new lint: using let mut a = a at start of function #5102

jyn514 opened this issue Jan 27, 2020 · 9 comments
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@max-niederman
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A-lint Area: New lints good-first-issue These issues are a good way to get started with Clippy L-complexity Lint: Belongs in the complexity lint group L-suggestion Lint: Improving, adding or fixing lint suggestions

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@jyn514
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jyn514 commented Jan 27, 2020 •
edited by rustbot
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I inherited a codebase from someone new to Rust and there were lots of function definitions that looked like this:

fn f(a: Vec<u8>) {
    let mut a = a;
    // rest of code
}

It would be nice if there were a lint saying this would be better as fn f(mut a: Vec<u8>) instead.
@flip1995 flip1995 added L-complexity Lint: Belongs in the complexity lint group L-suggestion Lint: Improving, adding or fixing lint suggestions good-first-issue These issues are a good way to get started with Clippy A-lint Area: New lints labels Jan 27, 2020
@sonng
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sonng commented Jan 30, 2020

Looks like a good first issue. Could this be assigned to me please?

Thanks

@sonng
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sonng commented Feb 5, 2020

Hey guys,

I'm on the last leg of the work (cargo test) and making sure everything is fine. I noticed that while running that, our new lint gets triggered and causes an error, causing the whole thing to fail.

My question is, how do I turn this from an error to a warning?
or alternatively, I could update the problematic code and make them fn parameters mutable.

Cheers

@flip1995
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flip1995 commented Feb 5, 2020

Can you open a WIP PR, so I can have a look at the code and the dogfood error?

@sonng sonng mentioned this issue Feb 6, 2020
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@sonng
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sonng commented Feb 6, 2020

I'm happy for any feedback on the overall change too.

@brightly-salty
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I'm willing to attempt to implement this and submit a PR if it would be accepted if @sonng isn't working on it. I expect to restart (to avoid merge conflicts) using their PR as a guide/inspiration?

@flip1995
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flip1995 commented Jan 4, 2021

@brightly-salty Thanks! Yes you can use they're PR as inspiration. I think my comments on the PR should also help you with dos and don'ts.

@max-niederman
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@rustbot claim

@rustbot rustbot assigned max-niederman and unassigned sonng Jun 3, 2023
@max-niederman
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I think this should probably be generalized to redefined locals as well.

@max-niederman max-niederman mentioned this issue Jun 4, 2023
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bors added a commit that referenced this issue Jul 22, 2023
@bors
Auto merge of #10885 - max-niederman:redundant_local, r=Centri3
a44dcf8 
new lint: `redundant_locals`

This lint checks for code like the following:

```rs
let x = 1;
let x = x;
```

It checks (afaik) all cases where a binding is shadowed by its own value in the same block, including function parameters. This has no effect and is almost certainly accidental, so it's in the `correctness` category like `self_assignment`.

This also lays the groundwork for a more generalized version of #5102.

changelog: new lint: [`redundant_local`]
@maxcnunes
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Is this issue still relevant? It seems #10885 covered what have been requested here and we could close it.

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A-lint Area: New lints good-first-issue These issues are a good way to get started with Clippy L-complexity Lint: Belongs in the complexity lint group L-suggestion Lint: Improving, adding or fixing lint suggestions
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[WIP] - new lint: using let mut a = a at start of function sonng/rust-clippy
7 participants
@sonng @maxcnunes @ebroto @flip1995 @max-niederman @jyn514 @brightly-salty