1 files changed, 66 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..833f3800d4
--- /dev/null
+++ b/src/mscorlib/src/System/Collections/Generic/IReadOnlyList.cs
@@ -0,0 +1,66 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license 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 CONTRACTS_FULL
+    [ContractClass(typeof(IReadOnlyListContract<>))]
+#endif
+    // 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; }
+    }
+
+#if CONTRACTS_FULL
+    [ContractClassFor(typeof(IReadOnlyList<>))]
+    internal abstract class IReadOnlyListContract<T> : IReadOnlyList<T>
+    {
+        T IReadOnlyList<T>.this[int index] {
+            get {
+                //Contract.Requires(index >= 0);
+                //Contract.Requires(index < ((ICollection<T>)this).Count);
+                return default(T);
+            }
+        }
+
+        int IReadOnlyCollection<T>.Count {
+            get {
+                return default(int);
+            }
+        }
+
+        IEnumerator<T> IEnumerable<T>.GetEnumerator()
+        {
+            return default(IEnumerator<T>);
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return default(IEnumerator);
+        }
+    }
+#endif
+}