### What it does
Checks for async blocks that yield values of types
that can themselves be awaited.

### Why is this bad?
An await is likely missing.

### Example
```
async fn foo() {}

fn bar() {
  let x = async {
    foo()
  };
}
```

Use instead:
```
async fn foo() {}

fn bar() {
  let x = async {
    foo().await
  };
}
```