Reason for Sync + Send + 'static

[mersinvald]

Hello!

Can you please explain reasoning behind Sync + Send + 'static bound on the NewService here

hyper/src/server/mod.rs

Lines 88 to 92 in 77bfcd9

	pub fn bind<S, Bd>(&self, addr: &SocketAddr, new_service: S) -> ::Result<Server<S, Bd>>
	where S: NewService<Request = Request, Response = Response<Bd>, Error = ::Error> +
	Send + Sync + 'static,
	Bd: Stream<Item=B, Error=::Error>,
	{

and here

hyper/src/server/mod.rs

Lines 339 to 342 in 77bfcd9

	impl<S, B> Server<S, B>
	where S: NewService<Request = Request, Response = Response<B>, Error = ::Error>
	+ Send + Sync + 'static,
	B: Stream<Error=::Error> + 'static,

I've been writing my custom NewService and ran into problems with this bounds.

Are they necessary since hyper moved to async single-thread mode with Tokio?
Removing them will allow to write simpler and way more effective single-thread async code.

[seanmonstar]

This has been addressed in master, and the linked PRs have reasoning around it.