// ==++==
// 
//   Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// ==--==
/*============================================================
**
** Interface:  IEnumerable
** 
** <OWNER>kimhamil</OWNER>
**
**
** Purpose: Interface for providing generic IEnumerators
**
** 
===========================================================*/
namespace System.Collections.Generic {
    using System;
    using System.Collections;
    using System.Runtime.InteropServices;
    using System.Runtime.CompilerServices;
    using System.Diagnostics.Contracts;
 
    // Implement this interface if you need to support foreach semantics.
 
    // Note that T[] : IList<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 hack internally though - see VM\compile.cpp.
    // The same attribute is on IList<T> and ICollection<T>.
    [TypeDependencyAttribute("System.SZArrayHelper")]
#if CONTRACTS_FULL
    [ContractClass(typeof(IEnumerableContract<>))]
#endif // CONTRACTS_FULL
    public interface IEnumerable<out T> : IEnumerable
    {
        // Returns an IEnumerator for this enumerable Object.  The enumerator provides
        // a simple way to access all the contents of a collection.
        /// <include file='doc\IEnumerable.uex' path='docs/doc[@for="IEnumerable.GetEnumerator"]/*' />
        new IEnumerator<T> GetEnumerator();
    }
 
#if CONTRACTS_FULL
    [ContractClassFor(typeof(IEnumerable<>))]
    internal abstract class IEnumerableContract<T> : IEnumerable<T>
    {
        [Pure]
        IEnumerator<T> IEnumerable<T>.GetEnumerator()
        {
            Contract.Ensures(Contract.Result<IEnumerator<T>>() != null);
            return default(IEnumerator<T>);
        }
 
        IEnumerator IEnumerable.GetEnumerator()
        {
            return default(IEnumerator);
        }
    }
#endif // CONTRACTS_FULL
}