From 9eca96aa214cb8e2fd695cbed179f93826b3ef46 Mon Sep 17 00:00:00 2001
From: Avery Harnish <EverlastingBugstopper@users.noreply.github.com>
Date: Fri, 24 Jan 2020 17:10:12 -0600
Subject: [PATCH] rt: improve "no runtime" panic messages (#2145)

---
 tokio/src/io/driver/mod.rs      |  3 ++-
 tokio/src/time/driver/handle.rs |  3 ++-
 tokio/src/time/error.rs         |  2 +-
 tokio/tests/no_rt.rs            | 27 +++++++++++++++++++++++++++
 4 files changed, 32 insertions(+), 3 deletions(-)
 create mode 100644 tokio/tests/no_rt.rs

diff --git a/tokio/src/io/driver/mod.rs b/tokio/src/io/driver/mod.rs
index fb3104f157a..8385448c186 100644
--- a/tokio/src/io/driver/mod.rs
+++ b/tokio/src/io/driver/mod.rs
@@ -198,7 +198,8 @@ impl Handle {
     ///
     /// This function panics if there is no current reactor set.
     pub(super) fn current() -> Self {
-        context::io_handle().expect("no current reactor")
+        context::io_handle()
+            .expect("there is no reactor running, must be called from the context of Tokio runtime")
     }
 
     /// Forces a reactor blocked in a call to `turn` to wakeup, or otherwise
diff --git a/tokio/src/time/driver/handle.rs b/tokio/src/time/driver/handle.rs
index 3a424800b85..38b1761c8e4 100644
--- a/tokio/src/time/driver/handle.rs
+++ b/tokio/src/time/driver/handle.rs
@@ -21,7 +21,8 @@ impl Handle {
     ///
     /// This function panics if there is no current timer set.
     pub(crate) fn current() -> Self {
-        context::time_handle().expect("no current timer")
+        context::time_handle()
+            .expect("there is no timer running, must be called from the context of Tokio runtime")
     }
 
     /// Tries to return a strong ref to the inner
diff --git a/tokio/src/time/error.rs b/tokio/src/time/error.rs
index 82a17275f50..0667b97ac1e 100644
--- a/tokio/src/time/error.rs
+++ b/tokio/src/time/error.rs
@@ -64,7 +64,7 @@ impl fmt::Display for Error {
     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
         use self::Kind::*;
         let descr = match self.0 {
-            Shutdown => "timer is shutdown",
+            Shutdown => "the timer is shutdown, must be called from the context of Tokio runtime",
             AtCapacity => "timer is at capacity and cannot create a new entry",
         };
         write!(fmt, "{}", descr)
diff --git a/tokio/tests/no_rt.rs b/tokio/tests/no_rt.rs
new file mode 100644
index 00000000000..962eed7952d
--- /dev/null
+++ b/tokio/tests/no_rt.rs
@@ -0,0 +1,27 @@
+use tokio::net::TcpStream;
+use tokio::sync::oneshot;
+use tokio::time::{timeout, Duration};
+
+use futures::executor::block_on;
+
+use std::net::TcpListener;
+
+#[test]
+#[should_panic(expected = "no timer running")]
+fn panics_when_no_timer() {
+    block_on(timeout_value());
+}
+
+#[test]
+#[should_panic(expected = "no reactor running")]
+fn panics_when_no_reactor() {
+    let srv = TcpListener::bind("127.0.0.1:0").unwrap();
+    let addr = srv.local_addr().unwrap();
+    block_on(TcpStream::connect(&addr)).unwrap();
+}
+
+async fn timeout_value() {
+    let (_tx, rx) = oneshot::channel::<()>();
+    let dur = Duration::from_millis(20);
+    let _ = timeout(dur, rx).await;
+}