error[E0053]: method `jumbo` has an incompatible type for trait
  --> $DIR/impl-method-mismatch.rs:7:5
   |
LL |     unsafe fn jumbo(&self, x: &usize) { *self + *x; }
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected safe fn, found unsafe fn
   |
note: type in trait
  --> $DIR/impl-method-mismatch.rs:2:5
   |
LL |     fn jumbo(&self, x: &usize) -> usize;
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   = note: expected signature `fn(&_, &_) -> usize`
              found signature `unsafe fn(&_, &_) -> ()`

error: aborting due to 1 previous error

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