# Error code E0698

When using generators (or async) all type variables must be bound so a generator can be constructed.

Erroneous code example:

    #![allow(unused)]
    fn main() {
    async fn bar<T>() -> () {}

    async fn foo() {
        bar().await; // error: cannot infer type for `T`
    }
    }

In the above example `T` is unknowable by the compiler. To fix this you must bind `T` to a concrete type such as `String` so that a generator can then be constructed:

    #![allow(unused)]
    fn main() {
    async fn bar<T>() -> () {}

    async fn foo() {
        bar::<String>().await;
        //   ^^^^^^^^ specify type explicitly
    }
    }