[rustc.git] / src / librustc_error_codes / error_codes / E0698.md

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

Erroneous code example:

```edition2018,compile_fail,E0698
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:

```edition2018
async fn bar<T>() -> () {}

async fn foo() {
    bar::<String>().await;
    //   ^^^^^^^^ specify type explicitly
}
```
Commit	Line	Data
60c5eb7d XL	1	When using generators (or async) all type variables must be bound so a
	2	generator can be constructed.
	3
	4	Erroneous code example:
	5
f9f354fc	6	```edition2018,compile_fail,E0698
60c5eb7d XL	7	async fn bar<T>() -> () {}
	8
	9	async fn foo() {
	10	bar().await; // error: cannot infer type for `T`
	11	}
	12	```
	13
	14	In the above example `T` is unknowable by the compiler.
	15	To fix this you must bind `T` to a concrete type such as `String`
	16	so that a generator can then be constructed:
	17
	18	```edition2018
	19	async fn bar<T>() -> () {}
	20
	21	async fn foo() {
	22	bar::<String>().await;
	23	// ^^^^^^^^ specify type explicitly
	24	}
	25	```