IReadOnlyList.cs

// 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; }
    }
}