async-recursion 0.1.1

Recursion for async functions
Documentation 
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<h5>Procedural macro for recursive async functions</h5>

Consider the following recursive implementation of the fibonacci numbers:

```rust
async fn fib(n : u32) -> u64 {
   match n {
       0     => panic!("zero is not a valid argument to fib()!"),
       1 | 2 => 1,
       3     => 2,
       _ => fib(n-1).await + fib(n-2).await
   }
}
```

The compiler helpfully tells us that:

```console
error[E0733]: recursion in an `async fn` requires boxing

--> src/main.rs:1:26
 |
1 | async fn fib(n : u32) -> u64 {
 |                          ^^^ recursive `async fn`
 |
 = note: a recursive `async fn` must be rewritten to return a boxed `dyn Future`.
```

This crate provides an attribute macro to automatically convert an async recursive function
to one returning a boxed Future.

# Example


```rust
use async_recursion::async_recursion;

#[async_recursion]

async fn fib(n : u32) -> u64 {
   match n {
       0     => panic!("zero is not a valid argument to fib()!"),
       1 | 2 => 1,
       3     => 2,
       _ => fib(n-1).await + fib(n-2).await
   }
}
```

# Limitations

Currently the macro doesn't consider lifetimes at all; this is something I plan to work
on in the future.

### License

Licensed under either of
 * Apache License, Version 2.0
   ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
 * MIT license
   ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
at your option.