rust/tests/ui/single_match.rs

#![warn(clippy::single_match)]

fn dummy() {}

fn single_match() {
    let x = Some(1u8);

    match x {
        Some(y) => {
            println!("{:?}", y);
        },
        _ => (),
    };

    let x = Some(1u8);
    match x {
        // Note the missing block braces.
        // We suggest `if let Some(y) = x { .. }` because the macro
        // is expanded before we can do anything.
        Some(y) => println!("{:?}", y),
        _ => (),
    }

    let z = (1u8, 1u8);
    match z {
        (2..=3, 7..=9) => dummy(),
        _ => {},
    };

    // Not linted (pattern guards used)
    match x {
        Some(y) if y == 0 => println!("{:?}", y),
        _ => (),
    }

    // Not linted (no block with statements in the single arm)
    match z {
        (2..=3, 7..=9) => println!("{:?}", z),
        _ => println!("nope"),
    }
}

enum Foo {
    Bar,
    Baz(u8),
}
use std::borrow::Cow;
use Foo::*;

fn single_match_know_enum() {
    let x = Some(1u8);
    let y: Result<_, i8> = Ok(1i8);

    match x {
        Some(y) => dummy(),
        None => (),
    };

    match y {
        Ok(y) => dummy(),
        Err(..) => (),
    };

    let c = Cow::Borrowed("");

    match c {
        Cow::Borrowed(..) => dummy(),
        Cow::Owned(..) => (),
    };

    let z = Foo::Bar;
    // no warning
    match z {
        Bar => println!("42"),
        Baz(_) => (),
    }

    match z {
        Baz(_) => println!("42"),
        Bar => (),
    }
}

macro_rules! single_match {
    ($num:literal) => {
        match $num {
            15 => println!("15"),
            _ => (),
        }
    };
}

fn main() {
    single_match!(5);
}