error[E0412]: cannot find type `Missing` in this scope
  --> $DIR/issue-110157.rs:6:12
   |
LL |     F: Fn(&Missing) -> Result<I, ()>,
   |            ^^^^^^^ not found in this scope

error[E0412]: cannot find type `Missing` in this scope
  --> $DIR/issue-110157.rs:8:24
   |
LL |     I: Iterator<Item = Missing>,
   |                        ^^^^^^^ not found in this scope

error[E0046]: not all trait items implemented, missing: `Item`, `next`
  --> $DIR/issue-110157.rs:3:1
   |
LL | / impl<'tcx, F, I> Iterator for NeedsDropTypes<'tcx, F>
LL | |
LL | | where
LL | |     F: Fn(&Missing) -> Result<I, ()>,
LL | |
LL | |     I: Iterator<Item = Missing>,
   | |________________________________^ missing `Item`, `next` in implementation
   |
   = help: implement the missing item: `type Item = /* Type */;`
   = help: implement the missing item: `fn next(&mut self) -> Option<<Self as Iterator>::Item> { todo!() }`

error: aborting due to 3 previous errors

Some errors have detailed explanations: E0046, E0412.
For more information about an error, try `rustc --explain E0046`.