Cannot return Self type

It seems there are five return types supported currently. This code prints error message.
How can I return the Self type?
Thanks for the great project!

```
expected one of: parentheses, `&`, `dyn`, identifier
```

```
reflect::library! {
extern crate aa {
mod provider {
type ProviderContext;
type AA;

trait Provider {
fn build(&mut ProviderContext) -> Self;
}
}
}
}
```