error[E0308]: arguments to this function are incorrect
  --> $DIR/coerce-in-may-coerce.rs:17:5
   |
LL |     arg_error((), || ());
   |     ^^^^^^^^^ --  ----- expected `()`, found `{closure@$DIR/coerce-in-may-coerce.rs:17:19: 17:21}`
   |               |
   |               expected `<fn() as Mirror>::Assoc`, found `()`
   |
note: function defined here
  --> $DIR/coerce-in-may-coerce.rs:12:4
   |
LL | fn arg_error(x: <fn() as Mirror>::Assoc, y: ()) { todo!() }
   |    ^^^^^^^^^
help: swap these arguments
   |
LL -     arg_error((), || ());
LL +     arg_error(|| (), ());
   |

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0308`.