1 files changed, 34 insertions, 0 deletions
diff --git a/src/mscorlib/src/System/Collections/Generic/IReadOnlyList.cs b/src/mscorlib/src/System/Collections/Generic/IReadOnlyList.cs
new file mode 100644
index 0000000000..77366f0b2f
--- /dev/null
+++ b/src/mscorlib/src/System/Collections/Generic/IReadOnlyList.cs
@@ -0,0 +1,34 @@
+// 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.
+
+/*============================================================
+**
+** Interface:  IReadOnlyList<T>
+** 
+** 
+**
+** Purpose: Base interface for read-only generic lists.
+** 
+===========================================================*/
+using System;
+using System.Diagnostics.Contracts;
+using System.Runtime.CompilerServices;
+
+namespace System.Collections.Generic
+{
+
+    // Provides a read-only, covariant view of a generic list.
+
+    // Note that T[] : IReadOnlyList<T>, and we want to ensure that if you use
+    // IList<YourValueType>, we ensure a YourValueType[] can be used 
+    // without jitting.  Hence the TypeDependencyAttribute on SZArrayHelper.
+    // This is a special workaround internally though - see VM\compile.cpp.
+    // The same attribute is on IList<T>, IEnumerable<T>, ICollection<T> and IReadOnlyCollection<T>.
+    [TypeDependencyAttribute("System.SZArrayHelper")]
+    // If we ever implement more interfaces on IReadOnlyList, we should also update RuntimeTypeCache.PopulateInterfaces() in rttype.cs
+    public interface IReadOnlyList<out T> : IReadOnlyCollection<T>
+    {
+        T this[int index] { get; }
+    }
+}