rust-clippy/tests/ui/needless_borrow.rs

// run-rustfix

#[warn(clippy::all, clippy::needless_borrow)]
#[allow(unused_variables)]
fn main() {
    let a = 5;
    let _ = x(&a); // no warning
    let _ = x(&&a); // warn

    let mut b = 5;
    mut_ref(&mut b); // no warning
    mut_ref(&mut &mut b); // warn

    let s = &String::from("hi");
    let s_ident = f(&s); // should not error, because `&String` implements Copy, but `String` does not
    let g_val = g(&Vec::new()); // should not error, because `&Vec<T>` derefs to `&[T]`
    let vec = Vec::new();
    let vec_val = g(&vec); // should not error, because `&Vec<T>` derefs to `&[T]`
    h(&"foo"); // should not error, because the `&&str` is required, due to `&Trait`
    let garbl = match 42 {
        44 => &a,
        45 => {
            println!("foo");
            &&a // FIXME: this should lint, too
        },
        46 => &&a,
        _ => panic!(),
    };
}

#[allow(clippy::needless_borrowed_reference)]
fn x(y: &i32) -> i32 {
    *y
}

fn mut_ref(y: &mut i32) {
    *y = 5;
}

fn f<T: Copy>(y: &T) -> T {
    *y
}

fn g(y: &[u8]) -> u8 {
    y[0]
}

trait Trait {}

impl<'a> Trait for &'a str {}

fn h(_: &dyn Trait) {}