Confusing Trait bound

[esemeniuc]

I get this error when running the following code:

use backon::{ExponentialBuilder, Retryable};
async fn get_thing(a: String) -> Result<String, String> {
    Ok(a.clone())
}
fn demo() {
    let retry_strat = ExponentialBuilder::default();
    let magic = get_thing(String::new()).retry(&retry_strat);
}

Error:

error[E0599]: the method `retry` exists for opaque type `impl Future<Output = Result<String, String>>`, but its trait bounds were not satisfied
  --> src/heartbeat.rs:33:42
   |
33 |     let magic = get_thing(String::new()).retry(&retry_strat);
   |                                          ^^^^^ method cannot be called on `impl Future<Output = Result<String, String>>` due to unsatisfied trait bounds
   |
   = note: the following trait bounds were not satisfied:
           `<impl std::future::Future<Output = Result<std::string::String, std::string::String>> as FnOnce<()>>::Output = _`
           which is required by `impl std::future::Future<Output = Result<std::string::String, std::string::String>>: Retryable<_, _, _, _, impl std::future::Future<Output = Result<std::string::String, std::string::String>>>`
           `impl std::future::Future<Output = Result<std::string::String, std::string::String>>: FnMut<()>`
           which is required by `impl std::future::Future<Output = Result<std::string::String, std::string::String>>: Retryable<_, _, _, _, impl std::future::Future<Output = Result<std::string::String, std::string::String>>>`
           `<&impl std::future::Future<Output = Result<std::string::String, std::string::String>> as FnOnce<()>>::Output = _`
           which is required by `&impl std::future::Future<Output = Result<std::string::String, std::string::String>>: Retryable<_, _, _, _, &impl std::future::Future<Output = Result<std::string::String, std::string::String>>>`
           `&impl std::future::Future<Output = Result<std::string::String, std::string::String>>: FnMut<()>`
           which is required by `&impl std::future::Future<Output = Result<std::string::String, std::string::String>>: Retryable<_, _, _, _, &impl std::future::Future<Output = Result<std::string::String, std::string::String>>>`
           `<&mut impl std::future::Future<Output = Result<std::string::String, std::string::String>> as FnOnce<()>>::Output = _`
           which is required by `&mut impl std::future::Future<Output = Result<std::string::String, std::string::String>>: Retryable<_, _, _, _, &mut impl std::future::Future<Output = Result<std::string::String, std::string::String>>>`
           `&mut impl std::future::Future<Output = Result<std::string::String, std::string::String>>: FnMut<()>`
           which is required by `&mut impl std::future::Future<Output = Result<std::string::String, std::string::String>>: Retryable<_, _, _, _, &mut impl std::future::Future<Output = Result<std::string::String, std::string::String>>>`

warning: unused import: `Retryable`
  --> src/heartbeat.rs:11:34
   |
11 | use backon::{ExponentialBuilder, Retryable};
   |                                  ^^^^^^^^^
   |
   = note: `#[warn(unused_imports)]` on by default

[esemeniuc]

Didn't see #50