add Task::spawner

Signed-off-by: Marc-Antoine Perennou <Marc-Antoine@Perennou.com>

Author: Keruspe

src/lib.rs

@@ -488,6 +488,35 @@ impl<T> Task<T> {
     }
 }
 
+impl Task<()> {
+    /// Get a Spawner for the current multi-threaded executor.
+    ///
+    /// If called from an [`Executor`], get its Spawner.
+    ///
+    /// Otherwise, this method panics.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use async_executor::{Executor, Task};
+    ///
+    /// let ex = Executor::new();
+    ///
+    /// ex.run(async {
+    ///     let spawner = Task::<_>::spawner();
+    ///     let task = spawner.spawn(async { 1 + 2 });
+    ///     assert_eq!(task.await, 3);
+    /// });
+    /// ```
+    pub fn spawner() -> Spawner {
+        if EX.is_set() {
+            EX.with(|ex| ex.spawner())
+        } else {
+            panic!("`Task::spawner()` must be called from an `Executor`")
+        }
+    }
+}
+
 impl<T> Future for Task<T> {
     type Output = T;