1 files changed, 26 insertions, 7 deletions

diff --git a/src/runtime/task/error.rs b/src/runtime/task/error.rs
index 1a8129b..f7ead77 100644
--- a/src/runtime/task/error.rs
+++ b/src/runtime/task/error.rs
@@ -2,12 +2,13 @@ use std::any::Any;
 use std::fmt;
 use std::io;
 
+use super::Id;
 use crate::util::SyncWrapper;
-
 cfg_rt! {
     /// Task failed to execute to completion.
     pub struct JoinError {
         repr: Repr,
+        id: Id,
     }
 }
 
@@ -17,15 +18,17 @@ enum Repr {
 }
 
 impl JoinError {
-    pub(crate) fn cancelled() -> JoinError {
+    pub(crate) fn cancelled(id: Id) -> JoinError {
         JoinError {
             repr: Repr::Cancelled,
+            id,
         }
     }
 
-    pub(crate) fn panic(err: Box<dyn Any + Send + 'static>) -> JoinError {
+    pub(crate) fn panic(id: Id, err: Box<dyn Any + Send + 'static>) -> JoinError {
         JoinError {
             repr: Repr::Panic(SyncWrapper::new(err)),
+            id,
         }
     }
 
@@ -79,6 +82,7 @@ impl JoinError {
     ///     }
     /// }
     /// ```
+    #[track_caller]
     pub fn into_panic(self) -> Box<dyn Any + Send + 'static> {
         self.try_into_panic()
             .expect("`JoinError` reason is not a panic.")
@@ -111,13 +115,28 @@ impl JoinError {
             _ => Err(self),
         }
     }
+
+    /// Returns a [task ID] that identifies the task which errored relative to
+    /// other currently spawned tasks.
+    ///
+    /// **Note**: This is an [unstable API][unstable]. The public API of this type
+    /// may break in 1.x releases. See [the documentation on unstable
+    /// features][unstable] for details.
+    ///
+    /// [task ID]: crate::task::Id
+    /// [unstable]: crate#unstable-features
+    #[cfg(tokio_unstable)]
+    #[cfg_attr(docsrs, doc(cfg(tokio_unstable)))]
+    pub fn id(&self) -> Id {
+        self.id
+    }
 }
 
 impl fmt::Display for JoinError {
     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
         match &self.repr {
-            Repr::Cancelled => write!(fmt, "cancelled"),
-            Repr::Panic(_) => write!(fmt, "panic"),
+            Repr::Cancelled => write!(fmt, "task {} was cancelled", self.id),
+            Repr::Panic(_) => write!(fmt, "task {} panicked", self.id),
         }
     }
 }
@@ -125,8 +144,8 @@ impl fmt::Display for JoinError {
 impl fmt::Debug for JoinError {
     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
         match &self.repr {
-            Repr::Cancelled => write!(fmt, "JoinError::Cancelled"),
-            Repr::Panic(_) => write!(fmt, "JoinError::Panic(...)"),
+            Repr::Cancelled => write!(fmt, "JoinError::Cancelled({:?})", self.id),
+            Repr::Panic(_) => write!(fmt, "JoinError::Panic({:?}, ...)", self.id),
         }
     }
 }