error: variable does not need to be mutable
  --> $DIR/lint-unused-mut-self.rs:18:12
   |
LL |     fn foo(mut self) {} //~ ERROR: variable does not need to be mutable
   |            ----^^^^
   |            |
   |            help: remove this `mut`
   |
note: lint level defined here
  --> $DIR/lint-unused-mut-self.rs:14:9
   |
LL | #![deny(unused_mut)]
   |         ^^^^^^^^^^

error: variable does not need to be mutable
  --> $DIR/lint-unused-mut-self.rs:19:12
   |
LL |     fn bar(mut self: Box<Foo>) {} //~ ERROR: variable does not need to be mutable
   |            ----^^^^
   |            |
   |            help: remove this `mut`

error: aborting due to 2 previous errors