Add Application::Executor associated type

futures/src/executor.rs

@@ -0,0 +1,36 @@
+//! Choose your preferred executor to power a runtime.
+mod null;
+
+#[cfg(feature = "thread-pool")]
+mod thread_pool;
+
+#[cfg(feature = "thread-pool")]
+pub use thread_pool::ThreadPool;
+
+#[cfg(feature = "tokio")]
+mod tokio;
+
+#[cfg(feature = "async-std")]
+mod async_std;
+
+pub use null::Null;
+
+#[cfg(feature = "tokio")]
+pub use self::tokio::Tokio;
+
+#[cfg(feature = "async-std")]
+pub use self::async_std::AsyncStd;
+
+use futures::Future;
+
+pub trait Executor: Sized {
+    fn new() -> Result<Self, futures::io::Error>
+    where
+        Self: Sized;
+
+    fn spawn(&self, future: impl Future<Output = ()> + Send + 'static);
+
+    fn enter<R>(&self, f: impl FnOnce() -> R) -> R {
+        f()
+    }
+}