Is extract::State really necessary?

[AlphaKeks]

State passed to Router::with_state() must implement Clone, correct? Because of this, wouldn't it be possible to have a blanket implementation for FromRequestParts<S> for S, and get rid of the State extractor altogether?

#[async_trait]
impl<S> FromRequestParts<S> for S
where
    S: Clone,
{
    type Rejection = Infallible;

    async fn from_request_parts(_parts: &mut http::request::Parts, state: &S) -> Result<Self, Self::Rejection> {
        Ok(state.clone())
    }
}

I would think State does the same thing anyway, although I can't find an actual implementation for FromRequestParts, except for this blanket impl.

In my own application I can implement FromRequestParts<MyState> for MyState successfully, but I don't know if another blanket impl would conflict with the existing one.

[jplatte]

This impl would conflict with all of the existing impls for extractors that implement Clone, so no, we can't do that.