1 files changed, 31 insertions, 0 deletions
diff --git a/src/mscorlib/src/System/ByReference.cs b/src/mscorlib/src/System/ByReference.cs
new file mode 100644
index 0000000000..6f8bb2281e
--- /dev/null
+++ b/src/mscorlib/src/System/ByReference.cs
@@ -0,0 +1,31 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.CompilerServices;
+
+namespace System
+{
+    // ByReference<T> is meant to be used to represent "ref T" fields. It is working
+    // around lack of first class support for byref fields in C# and IL. The JIT and 
+    // type loader has special handling for it that turns it into a thin wrapper around ref T.
+    internal struct ByReference<T>
+    {
+        private IntPtr _value;
+
+        public ByReference(ref T value)
+        {
+            // TODO-SPAN: This has GC hole. It needs to be JIT intrinsic instead
+            unsafe { _value = (IntPtr)Unsafe.AsPointer(ref value); }
+        }
+
+        public ref T Value
+        {
+            get
+            {
+                // TODO-SPAN: This has GC hole. It needs to be JIT intrinsic instead
+                unsafe { return ref Unsafe.As<IntPtr, T>(ref *(IntPtr*)_value); }
+            }
+        }
+    }
+}