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Overzealous clippy::needless_match with multiple chained if let blocks #13574

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scd31 opened this issue Oct 21, 2024 · 3 comments · May be fixed by #13646
Open

Overzealous clippy::needless_match with multiple chained if let blocks #13574

scd31 opened this issue Oct 21, 2024 · 3 comments · May be fixed by #13646
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@blyxyas
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C-bug Category: Clippy is not doing the correct thing I-false-positive Issue: The lint was triggered on code it shouldn't have

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@scd31
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scd31 commented Oct 21, 2024 •
edited by rustbot
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Summary

It seems that needless_match can fire incorrectly with multiple if let blocks chained together.

Lint Name

clippy::needless_match

Reproducer

I tried this code:

pub fn color_text_to_rgb_tuple(text: &str) -> Option<RGBTuple> {
    if let Some(rgb) = full_hex_color_to_rgb_tuple(text) {
        Some(rgb)
    } else if let Some(rgb) = short_hex_color_to_rgb_tuple(text) {
        Some(rgb)
    } else if let Some(rgb) = color_name_to_rgb_tuple(text) {
        Some(rgb)
    } else {
        None
    }
}

I saw this happen:

warning: this if-let expression is unnecessary
  --> src/colors.rs:4:5
   |
4  | /     if let Some(rgb) = full_hex_color_to_rgb_tuple(text) {
5  | |         Some(rgb)
6  | |     } else if let Some(rgb) = short_hex_color_to_rgb_tuple(text) {
7  | |         Some(rgb)
...  |
11 | |         None
12 | |     }
   | |_____^ help: replace it with: `full_hex_color_to_rgb_tuple(text)`
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_match
   = note: `#[warn(clippy::needless_match)]` on by default

I expected to see this happen: No error

Version

rustc 1.82.0 (f6e511eec 2024-10-15)
binary: rustc
commit-hash: f6e511eec7342f59a25f7c0534f1dbea00d01b14
commit-date: 2024-10-15
host: x86_64-unknown-linux-gnu
release: 1.82.0
LLVM version: 19.1.1

Additional Labels

No response
@scd31 scd31 added C-bug Category: Clippy is not doing the correct thing I-false-positive Issue: The lint was triggered on code it shouldn't have labels Oct 21, 2024
@blyxyas
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blyxyas commented Oct 21, 2024

Here's a repro:

pub fn A() -> Option<bool> {
    if let Some(a) = None {
        Some(a)
    } else if let Some(a) = None {
        Some(a)
    } else if let Some(a) = None {
        Some(a)
    } else {
        None
    }
}

@SpriteOvO
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@rustbot claim

@SpriteOvO
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@blyxyas It's okay, you go ahead. I didn't start the work, just claimed it for a look at it tomorrow.

@rustbot release-assignment

@blyxyas blyxyas self-assigned this Oct 21, 2024
@blyxyas blyxyas linked a pull request Nov 2, 2024 that will close this issue
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C-bug Category: Clippy is not doing the correct thing I-false-positive Issue: The lint was triggered on code it shouldn't have
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Fix needless_match FP on if-lets blyxyas/rust-clippy
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@SpriteOvO @scd31 @blyxyas