Add a new requirements trait LocalRpcMessage

The idea is to use this instead of manual bounds so it is easier to configure
required bounds based on feature flags.

Author: rklaehn

src/lib.rs

@@ -87,19 +87,27 @@ pub mod util;
 #[cfg(not(feature = "rpc"))]
 mod util;
 
+/// Requirements for a local RPC message.
+///
+/// Local RPC messages must be Send and Sync so they can be sent between
+/// threads, but they don't have to be serializable. They can not be serializable
+/// since they contain channels.
+///
+/// In addition we require Debug for convenience.
+pub trait LocalRpcMessage: Debug + Send + Sync + Unpin + 'static {}
+
+impl<T> LocalRpcMessage for T where T: Debug + Send + Sync + Unpin + 'static {}
+
 /// Requirements for a RPC message
 ///
 /// Even when just using the mem transport, we require messages to be Serializable and Deserializable.
 /// Likewise, even when using the quinn transport, we require messages to be Send.
 ///
 /// This does not seem like a big restriction. If you want a pure memory channel without the possibility
 /// to also use the quinn transport, you might want to use a mpsc channel directly.
-pub trait RpcMessage: Debug + Serialize + DeserializeOwned + Send + Sync + Unpin + 'static {}
+pub trait RpcMessage: LocalRpcMessage + Serialize + DeserializeOwned {}
 
-impl<T> RpcMessage for T where
-    T: Debug + Serialize + DeserializeOwned + Send + Sync + Unpin + 'static
-{
-}
+impl<T> RpcMessage for T where T: LocalRpcMessage + Serialize + DeserializeOwned {}
 
 /// Marker trait for a service
 ///