error[E0053]: method `bar` has an incompatible type for trait
  --> $DIR/issue-13033.rs:8:30
   |
LL |     fn bar(&mut self, other: &mut dyn Foo);
   |                              ------------ type in trait
...
LL |     fn bar(&mut self, other: &dyn Foo) {}
   |                              ^^^^^^^^ types differ in mutability
   |
   = note: expected fn pointer `fn(&mut Baz, &mut dyn Foo)`
              found fn pointer `fn(&mut Baz, &dyn Foo)`
help: consider change the type to match the mutability in trait
   |
LL |     fn bar(&mut self, other: &mut dyn Foo) {}
   |                              ^^^^^^^^^^^^

error: aborting due to previous error

For more information about this error, try `rustc --explain E0053`.