Nullable: System.Object (dotnet#23466)

Author: safern

src/System.Private.CoreLib/shared/System/Object.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 using System.Runtime.Versioning;
@@ -44,12 +45,12 @@ public virtual string ToString()
         // Equal to this.  Equality is defined as object equality for reference
         // types and bitwise equality for value types using a loader trick to
         // replace Equals with EqualsValue for value types).
-        public virtual bool Equals(object obj)
+        public virtual bool Equals(object? obj)
         {
             return RuntimeHelpers.Equals(this, obj);
         }
 
-        public static bool Equals(object objA, object objB)
+        public static bool Equals(object? objA, object? objB)
         {
             if (objA == objB)
             {
@@ -63,7 +64,7 @@ public static bool Equals(object objA, object objB)
         }
 
         [NonVersionable]
-        public static bool ReferenceEquals(object objA, object objB)
+        public static bool ReferenceEquals(object? objA, object? objB)
         {
             return objA == objB;
         }

src/System.Private.CoreLib/src/System/Object.CoreCLR.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
 using System.Runtime.CompilerServices;
 
 namespace System