Merge pull request #2523 from dotnet-bot/from-tfs

Merge changes from TFS

3 files changed, 42 insertions, 17 deletions

diff --git a/src/System.Private.CoreLib/src/System.Private.CoreLib.csproj b/src/System.Private.CoreLib/src/System.Private.CoreLib.csproj
index 15ea8ef11..baf7c70b5 100644
--- a/src/System.Private.CoreLib/src/System.Private.CoreLib.csproj
+++ b/src/System.Private.CoreLib/src/System.Private.CoreLib.csproj
@@ -222,6 +222,7 @@
     <Compile Include="System\BadImageFormatException.cs" />
     <Compile Include="System\Boolean.cs" />
     <Compile Include="System\Buffer.cs" />
+    <Compile Include="System\ByReference.cs" />
     <Compile Include="System\Byte.cs" />
     <Compile Include="System\Char.cs" />
     <Compile Include="System\CharEnumerator.cs" />
diff --git a/src/System.Private.CoreLib/src/System/ByReference.cs b/src/System.Private.CoreLib/src/System/ByReference.cs
new file mode 100644
index 000000000..d0129c2ee
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/ByReference.cs
@@ -0,0 +1,41 @@
+// 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 have special handling for it that turns it into a thin wrapper around ref T.
+    [StackOnly]
+    internal struct ByReference<T>
+    {
+        // CS0169: The private field '{blah}' is never used
+#pragma warning disable 169
+        private IntPtr _value;
+#pragma warning restore
+
+        [Intrinsic]
+        public ByReference(ref T value)
+        {
+            // Implemented as a JIT intrinsic - This default implementation is for 
+            // completeness and to provide a concrete error if called via reflection
+            // or if intrinsic is missed.
+            throw new System.PlatformNotSupportedException();
+        }
+
+        public ref T Value
+        {
+            [Intrinsic]
+            get
+            {
+                // Implemented as a JIT intrinsic - This default implementation is for 
+                // completeness and to provide a concrete error if called via reflection
+                // or if the intrinsic is missed.
+                throw new System.PlatformNotSupportedException();
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/CompilerServices/InternalCompilerAttributes.cs b/src/System.Private.CoreLib/src/System/Runtime/CompilerServices/InternalCompilerAttributes.cs
index 298b4e466..3ad095e91 100644
--- a/src/System.Private.CoreLib/src/System/Runtime/CompilerServices/InternalCompilerAttributes.cs
+++ b/src/System.Private.CoreLib/src/System/Runtime/CompilerServices/InternalCompilerAttributes.cs
@@ -21,21 +21,4 @@ namespace System.Runtime.CompilerServices
 
     [AttributeUsage(AttributeTargets.Struct)]
     public sealed class StackOnlyAttribute : Attribute { }
-
-#if false // Unused right now. It is likely going to be useful for Span<T> implementation.
-    // This is a dummy class to be replaced by the compiler with a ref T
-    // It has to be a dummy class to avoid complicated type substitution
-    // and other complications in the compiler.
-    public sealed class ByReference<T>
-    {
-        //
-        // Managed pointer creation
-        //
-        [Intrinsic]
-        public static extern ByReference<T> FromRef(ref T source);
-
-        [Intrinsic]
-        public static extern ref T ToRef(ByReference<T> source);
-    }
-#endif
 }