error[E0308]: mismatched types
  --> $DIR/issue-74282.rs:8:15
   |
LL |   type Closure = impl Fn() -> u64;
   |                  ---------------- the expected opaque type
...
LL |       Anonymous(|| {
   |  _____---------_^
   | |     |
   | |     arguments to this struct are incorrect
LL | |
LL | |         3
LL | |     })
   | |_____^ expected opaque type, found closure
   |
   = note: expected opaque type `Closure`
                  found closure `{closure@$DIR/issue-74282.rs:8:15: 8:17}`
   = note: no two closures, even if identical, have the same type
   = help: consider boxing your closure and/or using it as a trait object
note: tuple struct defined here
  --> $DIR/issue-74282.rs:4:8
   |
LL | struct Anonymous(Closure);
   |        ^^^^^^^^^

error[E0308]: mismatched types
  --> $DIR/issue-74282.rs:8:5
   |
LL | /     Anonymous(|| {
LL | |
LL | |         3
LL | |     })
   | |______^ expected `()`, found `Anonymous`
   |
help: consider using a semicolon here
   |
LL |     });
   |       +
help: try adding a return type
   |
LL | fn bop(_: Closure) -> Anonymous {
   |                    ++++++++++++

error: aborting due to 2 previous errors

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