error: the function `takes_an_immutable_reference` doesn't need a mutable reference
  --> tests/ui/mut_reference.rs:30:34
   |
LL |     takes_an_immutable_reference(&mut 42);
   |                                  ^^^^^^^
   |
   = note: `-D clippy::unnecessary-mut-passed` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::unnecessary_mut_passed)]`

error: the function `as_ptr` doesn't need a mutable reference
  --> tests/ui/mut_reference.rs:34:12
   |
LL |     as_ptr(&mut 42);
   |            ^^^^^^^

error: the method `takes_an_immutable_reference` doesn't need a mutable reference
  --> tests/ui/mut_reference.rs:39:44
   |
LL |     my_struct.takes_an_immutable_reference(&mut 42);
   |                                            ^^^^^^^

error: aborting due to 3 previous errors