error: The function/method `takes_an_immutable_reference` doesn't need a mutable reference --> $DIR/mut_reference.rs:22:34 | 22 | takes_an_immutable_reference(&mut 42); | ^^^^^^^ | = note: `-D unnecessary-mut-passed` implied by `-D warnings` error: The function/method `as_ptr` doesn't need a mutable reference --> $DIR/mut_reference.rs:24:12 | 24 | as_ptr(&mut 42); | ^^^^^^^ error: The function/method `takes_an_immutable_reference` doesn't need a mutable reference --> $DIR/mut_reference.rs:28:44 | 28 | my_struct.takes_an_immutable_reference(&mut 42); | ^^^^^^^