Strange .cloned() error message mentioning iterators

[enterprisey]

I'm unsure why the error message for this code mentions iterators; there aren't any, I thought.

fn main() {
    Some(1).cloned();
}

(Playground)

Errors:

   Compiling playground v0.0.1 (/playground)
error[E0599]: no method named `cloned` found for enum `std::option::Option<{integer}>` in the current scope
   --> src/main.rs:2:13
    |
2   |   Some(1).cloned();
    |           ^^^^^^ method not found in `std::option::Option<{integer}>`
    |
    = note: the method `cloned` exists but the following trait bounds were not satisfied:
            `std::option::Option<{integer}>: std::iter::Iterator`
            which is required by `&mut std::option::Option<{integer}>: std::iter::Iterator`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0599`.
error: could not compile `playground`.

To learn more, run the command again with --verbose.

[estebank]

A method fn cloned(&self) exists in Iterator. The note is telling you that method that does exist is not callable on Option<_> because Option<_> doesn't implement Iterator. We can probably reword this to make that clearer.

[arora-aman]

Option also has a cloned method. Based on the current usecase (not using an iterator) maybe something along the lines "cloned() defined for &i32 and not i32" along with the iterator lint might be better diagnostically.

[jazeved0]

The solution for the Option case is to use something like:

fn main(){
  Some(1).as_ref().cloned();
}

I encountered the same error, and while I understand the compiler error/message, it sticks out in a toolchain that normally has very helpful compiler error messages. I agree that the help note could be clearer for the case with Option (where the intention likely isn't to use Iterator at all)

[ghubertpalo]

I have got the same error using this test case:

struct Pika {
    a: Option<u32>,
}

impl Pika {
    pub fn get_a(&self) -> Option<u32> {
        self.a.cloned()
    }
}

fn main() {
    let my_pika = Pika { a: Some(12) };
    println!("{:?}", my_pika.get_a());
}

link to playground

This grants the following error message:

Compiling playground v0.0.1 (/playground)
error[[E0599]](https://doc.rust-lang.org/stable/error-index.html#E0599): `Option<u32>` is not an iterator
   --> src/main.rs:7:16
    |
7   |           self.a.cloned()
    |                  ^^^^^^ `Option<u32>` is not an iterator
    |
    = note: the following trait bounds were not satisfied:
            `Option<u32>: Iterator`
            which is required by `&mut Option<u32>: Iterator`

For more information about this error, try `rustc --explain E0599`.
error: could not compile `playground` due to previous error

In a more general way, this error message raises as soon as the cloned() method is called on a borrow of an Option:

let a = Some(12);
let b = &a;
let c = b.cloned(); // Iterator error