src/tools/clippy/tests/ui/match_as_ref.fixed

#![allow(unused)]
#![warn(clippy::match_as_ref)]

fn match_as_ref() {
    let owned: Option<()> = None;
    let borrowed: Option<&()> = owned.as_ref();

    let mut mut_owned: Option<()> = None;
    let borrow_mut: Option<&mut ()> = mut_owned.as_mut();
}

mod issue4437 {
    use std::error::Error;
    use std::fmt;
    use std::num::ParseIntError;

    #[derive(Debug)]
    struct E {
        source: Option<ParseIntError>,
    }

    impl Error for E {
        fn source(&self) -> Option<&(dyn Error + 'static)> {
            self.source.as_ref().map(|x| x as _)
        }
    }

    impl fmt::Display for E {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            unimplemented!()
        }
    }
}

fn main() {
    // Don't lint
    let _ = match Some(0) {
        #[cfg(feature = "foo")]
        Some(ref x) if *x > 50 => None,
        Some(ref x) => Some(x),
        None => None,
    };
}

mod issue15691 {
    use std::ops::{Deref, DerefMut};

    struct A(B);
    struct B;

    impl Deref for A {
        type Target = B;
        fn deref(&self) -> &Self::Target {
            &self.0
        }
    }

    impl DerefMut for A {
        fn deref_mut(&mut self) -> &mut Self::Target {
            &mut self.0
        }
    }

    fn func() {
        let mut a = Some(A(B));
        let mut b = Some(B);
        // Do not lint, we don't have `None => None`
        let _ = match b {
            Some(ref mut x) => Some(x),
            None => a.as_deref_mut(),
        };
    }
}

fn recv_requiring_parens() {
    struct S;

    impl std::ops::Not for S {
        type Output = Option<u64>;
        fn not(self) -> Self::Output {
            None
        }
    }

    let _ = (!S).as_ref();
}

fn issue15932() {
    let _: Option<&u32> = Some(0).as_ref();

    let _: Option<&dyn std::fmt::Debug> = Some(0).as_ref().map(|x| x as _);
}