error[E0053]: method `foo` has an incompatible type for trait
  --> $DIR/trait-impl-fn-incompatibility.rs:9:15
   |
LL |     fn foo(x: u16);
   |               --- type in trait
...
LL |     fn foo(x: i16) { }
   |               ^^^ expected `u16`, found `i16`
   |
   = note: expected fn pointer `fn(u16)`
              found fn pointer `fn(i16)`

error[E0053]: method `bar` has an incompatible type for trait
  --> $DIR/trait-impl-fn-incompatibility.rs:10:28
   |
LL |     fn bar(&mut self, bar: &mut Bar);
   |                            -------- type in trait
...
LL |     fn bar(&mut self, bar: &Bar) { }
   |                            ^^^^
   |                            |
   |                            types differ in mutability
   |                            help: consider changing the mutability to match the trait: `&mut Bar`
   |
   = note: expected fn pointer `fn(&mut Bar, &mut Bar)`
              found fn pointer `fn(&mut Bar, &Bar)`

error: aborting due to 2 previous errors

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