From 662ae239c7c8746f14713e23e546a7572cbec0fe Mon Sep 17 00:00:00 2001
From: Mikail Bagishov <bagishov.mikail@yandex.ru>
Date: Thu, 30 Jul 2020 23:03:25 +0300
Subject: [PATCH 1/4] Improve Debug impl for Mutex

---
 tokio/src/sync/mutex.rs | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/tokio/src/sync/mutex.rs b/tokio/src/sync/mutex.rs
index 642058be626..757dc9e27be 100644
--- a/tokio/src/sync/mutex.rs
+++ b/tokio/src/sync/mutex.rs
@@ -115,7 +115,6 @@ use std::sync::Arc;
 /// [`std::sync::Mutex`]: struct@std::sync::Mutex
 /// [`Send`]: trait@std::marker::Send
 /// [`lock`]: method@Mutex::lock
-#[derive(Debug)]
 pub struct Mutex<T: ?Sized> {
     s: semaphore::Semaphore,
     c: UnsafeCell<T>,
@@ -373,6 +372,18 @@ where
     }
 }
 
+impl<T> std::fmt::Debug for Mutex<T>
+where
+    T: std::fmt::Debug,
+{
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self.try_lock() {
+            Ok(inner) => f.debug_struct("Mutex").field("inner", &*inner).finish(),
+            Err(_) => f.debug_struct("Mutex").field("inner", &"<locked>").finish(),
+        }
+    }
+}
+
 // === impl MutexGuard ===
 
 impl<T: ?Sized> Drop for MutexGuard<'_, T> {

From c8fb370560bad8dc4460a1d6e432f9d5db29333a Mon Sep 17 00:00:00 2001
From: Mikail Bagishov <bagishov.mikail@yandex.ru>
Date: Fri, 31 Jul 2020 14:37:08 +0300
Subject: [PATCH 2/4] improve code

---
 tokio/src/sync/mutex.rs | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/tokio/src/sync/mutex.rs b/tokio/src/sync/mutex.rs
index 757dc9e27be..df348457fec 100644
--- a/tokio/src/sync/mutex.rs
+++ b/tokio/src/sync/mutex.rs
@@ -377,10 +377,12 @@ where
     T: std::fmt::Debug,
 {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let mut d = f.debug_struct("Mutex");
         match self.try_lock() {
-            Ok(inner) => f.debug_struct("Mutex").field("inner", &*inner).finish(),
-            Err(_) => f.debug_struct("Mutex").field("inner", &"<locked>").finish(),
-        }
+            Ok(inner) => d.field("data", &*inner),
+            Err(_) => d.field("data", &format_args!("<locked>")),
+        };
+        d.finish()
     }
 }
 

From f6f2006d582ea136f2c462e9fa09f9ef541870ca Mon Sep 17 00:00:00 2001
From: Mikail Bagishov <bagishov.mikail@yandex.ru>
Date: Fri, 31 Jul 2020 14:42:48 +0300
Subject: [PATCH 3/4] add test

---
 tokio/tests/sync_mutex.rs | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/tokio/tests/sync_mutex.rs b/tokio/tests/sync_mutex.rs
index 444ebd6a22d..ca1a5cff60e 100644
--- a/tokio/tests/sync_mutex.rs
+++ b/tokio/tests/sync_mutex.rs
@@ -152,3 +152,12 @@ async fn debug_format() {
     let m = Mutex::new(s.to_string());
     assert_eq!(format!("{:?}", s), format!("{:?}", m.lock().await));
 }
+
+#[tokio::test]
+async fn mutex_debug() {
+    let s = "data";
+    let m = Mutex::new(s.to_string());
+    assert_eq!(format!("{:?}", m), r#"Mutex { data: "data" }"#);
+    let _guard = m.lock().await;
+    assert_eq!(format!("{:?}", m), r#"Mutex { data: <locked> }"#)
+}
\ No newline at end of file

From 7d339bde2b299ca861f51f33d539a358ab1b55db Mon Sep 17 00:00:00 2001
From: Mikail Bagishov <bagishov.mikail@yandex.ru>
Date: Fri, 31 Jul 2020 15:44:23 +0300
Subject: [PATCH 4/4] fmt

---
 tokio/tests/sync_mutex.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tokio/tests/sync_mutex.rs b/tokio/tests/sync_mutex.rs
index ca1a5cff60e..96194b31d9d 100644
--- a/tokio/tests/sync_mutex.rs
+++ b/tokio/tests/sync_mutex.rs
@@ -160,4 +160,4 @@ async fn mutex_debug() {
     assert_eq!(format!("{:?}", m), r#"Mutex { data: "data" }"#);
     let _guard = m.lock().await;
     assert_eq!(format!("{:?}", m), r#"Mutex { data: <locked> }"#)
-}
\ No newline at end of file
+}