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option_if_let_else generates wrong suggestion for Results #10335

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EliasHolzmann opened this issue Feb 12, 2023 · 2 comments · Fixed by #10337 · May be fixed by #14429
Open

option_if_let_else generates wrong suggestion for Results #10335

EliasHolzmann opened this issue Feb 12, 2023 · 2 comments · Fixed by #10337 · May be fixed by #14429
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@dgulotta
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C-bug Category: Clippy is not doing the correct thing I-suggestion-causes-error Issue: The suggestions provided by this Lint cause an ICE/error when applied

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@EliasHolzmann
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EliasHolzmann commented Feb 12, 2023 •
edited by rustbot
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Summary

The suggestions generated by the option_if_let_else lint for a Result with an impure expression in the else branch does not compile.

Reproducer

I tried this code:

#![deny(clippy::option_if_let_else)]
fn main() {
    let variable: Result<u32, &str> = Ok(42);
    if let Ok(binding) = variable {
        println!("Ok {binding}");
    } else {
        println!("Err");
    }
}

Playground

I expected Clippy to suggest the following fix:

variable.map_or_else(|_| {
    println!("Err");
}, |binding| {
    println!("Ok {binding}");
})

Instead, Clippy outputs this (notice the missing _ in the arguments to the first closure):

[...]
help: try
  |
4 ~     variable.map_or_else(|| {
5 +         println!("Err");
6 +     }, |binding| {
7 +         println!("Ok {binding}");
8 +     })
  |

Version

rustc 1.67.1 (d5a82bbd2 2023-02-07)
binary: rustc
commit-hash: d5a82bbd26e1ad8b7401f6a718a9c57c96905483
commit-date: 2023-02-07
host: x86_64-unknown-linux-gnu
release: 1.67.1
LLVM version: 15.0.6

Additional Labels

@rustbot label +I-suggestion-causes-error
@EliasHolzmann EliasHolzmann added the C-bug Category: Clippy is not doing the correct thing label Feb 12, 2023
@rustbot rustbot added the I-suggestion-causes-error Issue: The suggestions provided by this Lint cause an ICE/error when applied label Feb 12, 2023
@EliasHolzmann
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@rustbot claim

@EliasHolzmann EliasHolzmann mentioned this issue Feb 12, 2023
Merged
@bors bors closed this as completed in 407c352 May 18, 2023
@dgulotta
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It looks like this is broken again. The code in the original report no longer triggers a warning, but here is a new example that triggers the issue.

#![warn(clippy::option_if_let_else)]
pub fn test(r: Result<&[u8],&[u8]>) -> Vec<u8>  {
    match r {
        Ok(s) => s.to_owned(),
        Err(_) => Vec::new(),
    }
}

pub fn test2(r: Result<&[u8],&[u8]>) -> Vec<u8>  {
    if let Ok(s) = r { s.to_owned() }
    else { Vec::new() }
}

These both result in the suggestion:

try: `r.map_or_else(Vec::new, |s| s.to_owned())`

Playground link

@samueltardieu samueltardieu reopened this Mar 18, 2025
@samueltardieu samueltardieu linked a pull request Mar 18, 2025 that will close this issue
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@dgulotta dgulotta

Labels
C-bug Category: Clippy is not doing the correct thing I-suggestion-causes-error Issue: The suggestions provided by this Lint cause an ICE/error when applied
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@samueltardieu @dgulotta @EliasHolzmann @rustbot