rust-clippy/tests/ui/mut_reference.rs

#![allow(unused_variables, clippy::trivially_copy_pass_by_ref)]

fn takes_an_immutable_reference(a: &i32) {}
fn takes_a_mutable_reference(a: &mut i32) {}

struct MyStruct;

impl MyStruct {
    fn takes_an_immutable_reference(&self, a: &i32) {}

    fn takes_a_mutable_reference(&self, a: &mut i32) {}
}

#[warn(clippy::unnecessary_mut_passed)]
fn main() {
    // Functions
    takes_an_immutable_reference(&mut 42);
    let as_ptr: fn(&i32) = takes_an_immutable_reference;
    as_ptr(&mut 42);

    // Methods
    let my_struct = MyStruct;
    my_struct.takes_an_immutable_reference(&mut 42);

    // No error

    // Functions
    takes_an_immutable_reference(&42);
    let as_ptr: fn(&i32) = takes_an_immutable_reference;
    as_ptr(&42);

    takes_a_mutable_reference(&mut 42);
    let as_ptr: fn(&mut i32) = takes_a_mutable_reference;
    as_ptr(&mut 42);

    let a = &mut 42;
    takes_an_immutable_reference(a);

    // Methods
    my_struct.takes_an_immutable_reference(&42);
    my_struct.takes_a_mutable_reference(&mut 42);
    my_struct.takes_an_immutable_reference(a);
}