Type error creating traits for hashmaps

[pocketsize-pi]

Hi, I'm having some trouble creating traits for some Hashmaps.
This is my code:

type InstrumentOptions = HashMap<InstrumentName,Instrument>;

trait ComponentOptions<K,V> where K: fmt::Display + Clone {

    fn keys(&self) -> Keys<K,V>;

    fn get_options (&self) -> Vec<K>  {
        let mut choices : Vec<K> = vec![];
        for (i, key) in self.keys().enumerate() {
            println!("{}. {}", i+1, key);
            choices[0] = key.clone();
        }
        choices
    }
}

impl <InstrumentName: fmt::Display + Clone, Instrument> ComponentOptions<InstrumentName, Instrument> for InstrumentOptions {
    fn keys(&self) -> Keys<InstrumentName, Instrument> {
        self.keys()
    }
}

where InstrumentName is an enumeration, and Instrument is a structure. There will be similar hashmaps of enumeration and structures.

when I try to compile, what I get is...

error[E0308]: mismatched types
  --> src\mission.rs:58:9
   |
56 | impl <InstrumentName: fmt::Display + Clone, Instrument> ComponentOptions<InstrumentName, Instrument> for InstrumentOptions {
   |       -------------- this type parameter
57 |     fn keys(&self) -> Keys<InstrumentName, Instrument> {
   |                       -------------------------------- expected `std::collections::hash_map::Keys<'_, InstrumentName, Instrument>` because of return type
58 |         self.keys()
   |         ^^^^^^^^^^^ expected type parameter `InstrumentName`, found `InstrumentName`
   |
   = note: expected struct `std::collections::hash_map::Keys<'_, InstrumentName, Instrument>`
              found struct `std::collections::hash_map::Keys<'_, InstrumentName, item::Instrument>`

Instrument is technically in another file, item, so item::Instrument is technically correct, but InstrumentName is in another file too, and it has no problem wit that.

It is possible that traits are not the right things, but I have some operations that are the same across some similar HashMaps (as you can see in get options), and it feels like it should be the right thing.
Thanks a lot!

[H2CO3]

You have a concrete type named InstrumentName but you are also using InstrumentName as a type variable. Don't do that.

Did you mean this?

impl ComponentOptions<InstrumentName, Instrument> for InstrumentOptions {
    fn keys(&self) -> Keys<InstrumentName, Instrument> {
        self.keys()
    }
}

[pocketsize-pi]

Thank you, yes, that's it!

I feel quite silly now...