executor: add TypedExecutor (#993)

Adds a `TypedExecutor` trait that describes how to spawn futures of a specific
type. This is useful for implementing functions that are generic over an executor
and wish to support both `Send` and `!Send` cases.

tokio/Cargo.toml

@@ -71,7 +71,7 @@ tokio-codec = { version = "0.1.0", optional = true }
 tokio-current-thread = { version = "0.1.3", optional = true }
 tokio-fs = { version = "0.1.6", optional = true }
 tokio-io = { version = "0.1.6", optional = true }
-tokio-executor = { version = "0.1.5", optional = true }
+tokio-executor = { version = "0.1.5", optional = true, path = "../tokio-executor" }
 tokio-reactor = { version = "0.1.1", optional = true }
 tokio-sync = { version = "0.1.3", optional = true }
 tokio-threadpool = { version = "0.1.8", optional = true }

tokio/src/executor/mod.rs

@@ -60,7 +60,7 @@ pub mod thread_pool {
     };
 }
 
-pub use tokio_executor::{Executor, DefaultExecutor, SpawnError};
+pub use tokio_executor::{Executor, TypedExecutor, DefaultExecutor, SpawnError};
 
 use futures::{Future, IntoFuture};
 use futures::future::{self, FutureResult};

tokio/src/runtime/current_thread/runtime.rs

@@ -76,6 +76,15 @@ where T: Future<Item = (), Error = ()> + Send + 'static,
     }
 }
 
+impl<T> ::executor::TypedExecutor<T> for Handle
+where
+    T: Future<Item = (), Error = ()> + Send + 'static,
+{
+    fn spawn(&mut self, future: T) -> Result<(), ::executor::SpawnError> {
+        Handle::spawn(self, future)
+    }
+}
+
 /// Error returned by the `run` function.
 #[derive(Debug)]
 pub struct RunError {

tokio/src/runtime/threadpool/task_executor.rs

@@ -73,3 +73,12 @@ impl ::executor::Executor for TaskExecutor {
         self.inner.spawn(future)
     }
 }
+
+impl<T> ::executor::TypedExecutor<T> for TaskExecutor
+where
+    T: Future<Item = (), Error = ()> + Send + 'static,
+{
+    fn spawn(&mut self, future: T) -> Result<(), ::executor::SpawnError> {
+        ::executor::Executor::spawn(self, Box::new(future))
+    }
+}