Make `tokio::run` panic if called from inside `tokio::run` (#646)

This is implemented by creating an `Enter` instance from within `run`.

This patch also introduces `Enter::block_on`.

Fixes #504

1 files changed, 4 insertions, 1 deletions

diff --git a/src/runtime/mod.rs b/src/runtime/mod.rs
index c23d8dd1..9ff0cc4c 100644
--- a/src/runtime/mod.rs
+++ b/src/runtime/mod.rs
@@ -125,6 +125,7 @@ use reactor::{Background, Handle};
 
 use std::io;
 
+use tokio_executor::enter;
 use tokio_threadpool as threadpool;
 
 use futures;
@@ -210,7 +211,9 @@ where F: Future<Item = (), Error = ()> + Send + 'static,
 {
     let mut runtime = Runtime::new().unwrap();
     runtime.spawn(future);
-    runtime.shutdown_on_idle().wait().unwrap();
+    enter().expect("nested tokio::run")
+        .block_on(runtime.shutdown_on_idle())
+        .unwrap();
 }
 
 impl Runtime {