error[E0412]: cannot find type `XXX` in this scope
  --> $DIR/trait-fn-generic-mismatch.rs:5:11
   |
LL | impl Core<XXX> {
   |           ^^^ not found in this scope
   |
help: you might be missing a type parameter
   |
LL | impl<XXX> Core<XXX> {
   |     +++++

error[E0061]: this method takes 0 arguments but 1 argument was supplied
  --> $DIR/trait-fn-generic-mismatch.rs:11:10
   |
LL |     core.spawn(retry());
   |          ^^^^^ ------- unexpected argument of type `impl Sized`
   |
note: method defined here
  --> $DIR/trait-fn-generic-mismatch.rs:6:12
   |
LL |     pub fn spawn(self) {}
   |            ^^^^^
help: remove the extra argument
   |
LL -     core.spawn(retry());
LL +     core.spawn();
   |

error: aborting due to 2 previous errors

Some errors have detailed explanations: E0061, E0412.
For more information about an error, try `rustc --explain E0061`.