rust-clippy/tests/ui/try_err.rs

#![deny(clippy::try_err)]

// Tests that a simple case works
// Should flag `Err(err)?`
pub fn basic_test() -> Result<i32, i32> {
    let err: i32 = 1;
    Err(err)?;
    Ok(0)
}

// Tests that `.into()` is added when appropriate
pub fn into_test() -> Result<i32, i32> {
    let err: u8 = 1;
    Err(err)?;
    Ok(0)
}

// Tests that tries in general don't trigger the error
pub fn negative_test() -> Result<i32, i32> {
    Ok(nested_error()? + 1)
}


// Tests that `.into()` isn't added when the error type
// matches the surrounding closure's return type, even
// when it doesn't match the surrounding function's.
pub fn closure_matches_test() -> Result<i32, i32> {
    let res: Result<i32, i8> = Some(1).into_iter()
        .map(|i| {
            let err: i8 = 1;
            Err(err)?;
            Ok(i)
        })
        .next()
        .unwrap();

    Ok(res?)
}

// Tests that `.into()` isn't added when the error type
// doesn't match the surrounding closure's return type.
pub fn closure_into_test() -> Result<i32, i32> {
    let res: Result<i32, i16> = Some(1).into_iter()
        .map(|i| {
            let err: i8 = 1;
            Err(err)?;
            Ok(i)
        })
        .next()
        .unwrap();

    Ok(res?)
}

fn nested_error() -> Result<i32, i32> {
    Ok(1)
}

fn main() {
    basic_test().unwrap();
    into_test().unwrap();
    negative_test().unwrap();
    closure_matches_test().unwrap();
    closure_into_test().unwrap();
}