error[E0061]: this function takes 2 arguments but 1 argument was supplied
  --> $DIR/issue-18819.rs:16:5
   |
LL |     print_x(X);
   |     ^^^^^^^---
   |            ||
   |            |expected reference, found struct `X`
   |            an argument of type `&str` is missing
   |
   = note: expected reference `&dyn Foo<Item = bool>`
                 found struct `X`
note: function defined here
  --> $DIR/issue-18819.rs:11:4
   |
LL | fn print_x(_: &dyn Foo<Item=bool>, extra: &str) {
   |    ^^^^^^^ ----------------------  -----------
help: consider borrowing here
   |
LL |     print_x(&X);
   |             ~~
help: provide the argument
   |
LL |     print_x(/* &dyn Foo<Item = bool> */, /* &str */);
   |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

error: aborting due to previous error

For more information about this error, try `rustc --explain E0061`.