error[E0308]: mismatched types
  --> $DIR/issue-107775.rs:35:16
   |
LL |         map.insert(1, Struct::do_something);
   |         ---           -------------------- this argument has type `fn(u8) -> Pin<Box<dyn Future<Output = ()> + Send>> {<Struct as Trait>::do_something::<'_>}`...
   |         |
   |         ... which causes `map` to have type `HashMap<{integer}, fn(u8) -> Pin<Box<dyn Future<Output = ()> + Send>> {<Struct as Trait>::do_something::<'_>}>`
LL |         Self { map }
   |                ^^^ expected `HashMap<u16, fn(u8) -> Pin<Box<...>>>`, found `HashMap<{integer}, ...>`
   |
   = note: expected struct `HashMap<u16, fn(_) -> Pin<Box<(dyn Future<Output = ()> + Send + 'static)>>>`
              found struct `HashMap<{integer}, fn(_) -> Pin<Box<dyn Future<Output = ()> + Send>> {<Struct as Trait>::do_something::<'_>}>`
   = note: fn items are distinct from fn pointers
   = help: consider casting the fn item to a fn pointer: `<Struct as Trait>::do_something::<'_> as fn(u8) -> Pin<Box<(dyn Future<Output = ()> + Send + 'static)>>`

error: aborting due to 1 previous error

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