#![allow(unused_imports)]
use std::sync::{RwLock, RwLockWriteGuard};

struct Struct(());

trait Trait<T> {
    fn add(&mut self, _key: i32, _value: T) {}
    fn remove(&mut self, _key: i32) {}
}

impl Trait<String> for Struct {}
impl Trait<usize> for Struct {}

fn main () {

    {
        let mut value = Struct(());
        value.add(123, String::new());
        Trait::<String>::remove(&mut value, 123);
    }

    {
        let mut value = RwLock::new(Struct(()));
        let value_lock: RwLockWriteGuard<Struct> = value.write().unwrap();
        value_lock.add(123, String::new());
        // type annotations needed
        //value_lock.remove(123);

        // the trait bound `std::sync::RwLockWriteGuard<'_, Struct>: Trait<std::string::String>` is not satisfied
        //Trait::<String>::remove(&mut value_lock, 123);

        // non-primitive cast: `std::sync::RwLockWriteGuard<'_, Struct>` as `std::sync::RwLockWriteGuard<'_, dyn Trait<std::string::String>>`
        //(value_lock as RwLockWriteGuard::<dyn Trait::<String>>).remove(123);
    }

}