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Shared code in if and else #5234

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Luro02 opened this issue Feb 27, 2020 · 1 comment · Fixed by #6463
Closed

Shared code in if and else #5234

Luro02 opened this issue Feb 27, 2020 · 1 comment · Fixed by #6463
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@xFrednet
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A-lint Area: New lints E-medium Call for participation: Medium difficulty level problem and requires some initial experience. L-complexity Lint: Belongs in the complexity lint group

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@Luro02
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Luro02 commented Feb 27, 2020 •
edited by rustbot
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The lint would trigger if the if, else if and else clasues have the same code in all branches.

let mut result = "";
let is_something = 20;

if is_something == 20 {
    result = "hello";

    println!("yes");
} else {
    result = "hello";

    println!("nope!");
}

println!("{}", result);

could be optimized to

let mut result = "";
let is_something = 20;

result = "hello";

if is_something == 20 {
    println!("yes");
} else {
    println!("nope!");
}

println!("{}", result);

playground
@flip1995 flip1995 added L-complexity Lint: Belongs in the complexity lint group E-hard Call for participation: This a hard problem and requires more experience or effort to work on A-lint Area: New lints E-medium Call for participation: Medium difficulty level problem and requires some initial experience. and removed E-hard Call for participation: This a hard problem and requires more experience or effort to work on labels Mar 2, 2020
@xFrednet
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I would like to work on this 🙃.

@rustbot claim

@xFrednet xFrednet mentioned this issue Dec 17, 2020
Merged
bors added a commit that referenced this issue Apr 5, 2021
@bors
Auto merge of #6463 - xFrednet:5234-shared-code-in-if-blocks, r=phansch
ead70c3 
New Lint: `branches_sharing_code`

This lint checks if all `if`-blocks contain some statements that are the same and can be moved out of the blocks to prevent code duplication. Here is an example:

```rust
let _ = if ... {
    println!("Start"); // <-- Lint for code duplication
    let _a = 99;
    println!("End"); // <-- Lint for code duplication
    false
} else {
    println!("Start");
    let _b = 17;
    println!("End");
    false
};
```

This could be written as:

```rust
println!("Start");

let _ = if ... {
    let _a = 99;
    false
} else {
    let _b = 17;
    false
};

println!("End");
```

---

This lint will get masked by the `IF_SAME_THEN_ELSE` lint. I think it makes more sense to only emit one lint per if block. This means that the folloing example:

```rust
if ... {
    let _a = 17;
} else {
    let _a = 17;
}
```

Will only trigger the `IF_SAME_THEN_ELSE` lint and not the `SHARED_CODE_IN_IF_BLOCKS` lint.

---

closes: #5234

changelog: Added a new lint: `branches_sharing_code`

And hello to the one that is writing the changelog for this release :D
bors added a commit that referenced this issue Apr 5, 2021
@bors
Auto merge of #6463 - xFrednet:5234-shared-code-in-if-blocks, r=phansch
d34cb85 
New Lint: `branches_sharing_code`

This lint checks if all `if`-blocks contain some statements that are the same and can be moved out of the blocks to prevent code duplication. Here is an example:

```rust
let _ = if ... {
    println!("Start"); // <-- Lint for code duplication
    let _a = 99;
    println!("End"); // <-- Lint for code duplication
    false
} else {
    println!("Start");
    let _b = 17;
    println!("End");
    false
};
```

This could be written as:

```rust
println!("Start");

let _ = if ... {
    let _a = 99;
    false
} else {
    let _b = 17;
    false
};

println!("End");
```

---

This lint will get masked by the `IF_SAME_THEN_ELSE` lint. I think it makes more sense to only emit one lint per if block. This means that the folloing example:

```rust
if ... {
    let _a = 17;
} else {
    let _a = 17;
}
```

Will only trigger the `IF_SAME_THEN_ELSE` lint and not the `SHARED_CODE_IN_IF_BLOCKS` lint.

---

closes: #5234

changelog: Added a new lint: `branches_sharing_code`

And hello to the one that is writing the changelog for this release :D
@bors bors closed this as completed in d91da40 Apr 5, 2021
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A-lint Area: New lints E-medium Call for participation: Medium difficulty level problem and requires some initial experience. L-complexity Lint: Belongs in the complexity lint group
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New Lint: branches_sharing_code xFrednet/rust-clippy
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@flip1995 @xFrednet @Luro02