Add missing user specified trait bounds in [rpc] macro (#569)

* Add missing user specified trait bounds in [rpc]

Fix #567

* Nit

* Add a test file that should pass the compilation

Author: liuchengxu

derive/src/to_delegate.rs

@@ -458,6 +458,8 @@ pub fn generate_where_clause_serialization_predicates(
 	let mut visitor = FindTyParams::default();
 	visitor.visit_item_trait(item_trait);
 
+	let additional_where_clause = item_trait.generics.where_clause.clone();
+
 	item_trait
 		.generics
 		.type_params()
@@ -483,6 +485,20 @@ pub fn generate_where_clause_serialization_predicates(
 					bounds.push(parse_quote!(_jsonrpc_core::serde::de::DeserializeOwned))
 				}
 			}
+
+			// add the trait bounds specified by the user in where clause.
+			if let Some(ref where_clause) = additional_where_clause {
+				for predicate in where_clause.predicates.iter() {
+					if let syn::WherePredicate::Type(where_ty) = predicate {
+						if let syn::Type::Path(ref predicate) = where_ty.bounded_ty {
+							if *predicate == ty_path {
+								bounds.extend(where_ty.bounds.clone().into_iter());
+							}
+						}
+					}
+				}
+			}
+
 			syn::WherePredicate::Type(syn::PredicateType {
 				lifetimes: None,
 				bounded_ty: syn::Type::Path(ty_path),

derive/tests/run-pass/client_with_generic_trait_bounds.rs

@@ -0,0 +1,39 @@
+use jsonrpc_core::futures::future::{self, FutureResult};
+use jsonrpc_core::{Error, IoHandler, Result};
+use jsonrpc_derive::rpc;
+use std::collections::BTreeMap;
+
+#[rpc]
+pub trait Rpc<One, Two>
+where
+	One: Ord,
+	Two: Ord + Eq,
+{
+	/// Adds two numbers and returns a result
+	#[rpc(name = "setTwo")]
+	fn set_two(&self, a: Two) -> Result<BTreeMap<One, ()>>;
+
+	/// Performs asynchronous operation
+	#[rpc(name = "beFancy")]
+	fn call(&self, a: One) -> FutureResult<(One, Two), Error>;
+}
+
+struct RpcImpl;
+
+impl Rpc<u64, String> for RpcImpl {
+	fn set_two(&self, x: String) -> Result<BTreeMap<u64, ()>> {
+		println!("{}", x);
+		Ok(Default::default())
+	}
+
+	fn call(&self, num: u64) -> FutureResult<(u64, String), Error> {
+		crate::future::finished((num + 999, "hello".into()))
+	}
+}
+
+fn main() {
+	let mut io = IoHandler::new();
+	let rpc = RpcImpl;
+
+	io.extend_with(rpc.to_delegate())
+}