From 72185771e8dfd87d5a45732aec1566d8f3147c6e Mon Sep 17 00:00:00 2001
From: Marek Safar <marek.safar@gmail.com>
Date: Mon, 23 Nov 2020 13:58:33 +0100
Subject: [PATCH] Create cancellation token registration wrapper only when it's
 needed (#45075)

Co-authored-by: Stephen Toub <stoub@microsoft.com>
---
 .../src/System/Threading/CancellationToken.cs     | 15 ++-------------
 1 file changed, 2 insertions(+), 13 deletions(-)

diff --git a/src/libraries/System.Private.CoreLib/src/System/Threading/CancellationToken.cs b/src/libraries/System.Private.CoreLib/src/System/Threading/CancellationToken.cs
index 18d7194fbd770..196956c57331a 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Threading/CancellationToken.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Threading/CancellationToken.cs
@@ -35,12 +35,6 @@ public readonly struct CancellationToken
         private readonly CancellationTokenSource? _source;
         // !! warning. If more fields are added, the assumptions in CreateLinkedToken may no longer be valid
 
-        private static readonly Action<object?> s_actionToActionObjShunt = obj =>
-        {
-            Debug.Assert(obj is Action, $"Expected {typeof(Action)}, got {obj}");
-            ((Action)obj)();
-        };
-
         /// <summary>
         /// Returns an empty CancellationToken value.
         /// </summary>
@@ -136,12 +130,7 @@ public CancellationToken(bool canceled) : this(canceled ? CancellationTokenSourc
         /// <returns>The <see cref="System.Threading.CancellationTokenRegistration"/> instance that can
         /// be used to unregister the callback.</returns>
         /// <exception cref="System.ArgumentNullException"><paramref name="callback"/> is null.</exception>
-        public CancellationTokenRegistration Register(Action callback) =>
-            Register(
-                s_actionToActionObjShunt,
-                callback ?? throw new ArgumentNullException(nameof(callback)),
-                useSynchronizationContext: false,
-                useExecutionContext: true);
+        public CancellationTokenRegistration Register(Action callback) => Register(callback, useSynchronizationContext: false);
 
         /// <summary>
         /// Registers a delegate that will be called when this
@@ -167,7 +156,7 @@ public CancellationTokenRegistration Register(Action callback) =>
         /// <exception cref="System.ArgumentNullException"><paramref name="callback"/> is null.</exception>
         public CancellationTokenRegistration Register(Action callback, bool useSynchronizationContext) =>
             Register(
-                s_actionToActionObjShunt,
+                (Action<object?>)(static obj => ((Action)obj!)()),
                 callback ?? throw new ArgumentNullException(nameof(callback)),
                 useSynchronizationContext,
                 useExecutionContext: true);