From 34114f7aa7097a4e2da2b36d7e93a9b3a0576aec Mon Sep 17 00:00:00 2001
From: Julien Couvreur <julien.couvreur@gmail.com>
Date: Thu, 14 Jul 2016 14:13:49 -0700
Subject: [PATCH 1/4] Adding ITuple implementation

---
 .../src/System/ValueTuple/ValueTuple.cs       | 307 ++++++++++++++++--
 .../tests/ValueTuple/UnitTests.cs             |  84 +++++
 2 files changed, 362 insertions(+), 29 deletions(-)

diff --git a/src/System.ValueTuple/src/System/ValueTuple/ValueTuple.cs b/src/System.ValueTuple/src/System/ValueTuple/ValueTuple.cs
index e8fd6dd28cbe..c265f623d58a 100644
--- a/src/System.ValueTuple/src/System/ValueTuple/ValueTuple.cs
+++ b/src/System.ValueTuple/src/System/ValueTuple/ValueTuple.cs
@@ -8,13 +8,28 @@
 
 namespace System
 {
+    /// <summary>
+    /// This interface is required for types that want to be indexed into by dynamic patterns.
+    /// </summary>
+    public interface ITuple
+    {
+        /// <summary>
+        /// The number of positions in this data structure.
+        /// </summary>
+        int Size { get; }
+
+        /// <summary>
+        /// Get the element at position <param name="index"/>.
+        /// </summary>
+        object this[int index] { get; }
+    }
+
     /// <summary>
     /// Helper so we can call some tuple methods recursively without knowing the underlying types.
     /// </summary>
-    internal interface ITupleInternal
+    internal interface ITupleInternal : ITuple
     {
         int GetHashCode(IEqualityComparer comparer);
-        int Size { get; }
         string ToStringEnd();
     }
 
@@ -27,7 +42,7 @@ internal interface ITupleInternal
     /// - their members (such as Item1, Item2, etc) are fields rather than properties.
     /// </summary>
     public struct ValueTuple
-        : IEquatable<ValueTuple>, IStructuralEquatable, IStructuralComparable, IComparable, IComparable<ValueTuple>, ITupleInternal
+        : IEquatable<ValueTuple>, IStructuralEquatable, IStructuralComparable, IComparable, IComparable<ValueTuple>, ITupleInternal, ITuple
     {
         /// <summary>
         /// Returns a value that indicates whether the current <see cref="ValueTuple"/> instance is equal to a specified object.
@@ -69,7 +84,7 @@ int IComparable.CompareTo(object other)
         /// <returns>
         /// A signed number indicating the relative values of this instance and <paramref name="other"/>.
         /// Returns less than zero if this instance is less than <paramref name="other"/>, zero if this
-        /// instance is equal to <paramref name="other"/>, and greater than zero if this instance is greater 
+        /// instance is equal to <paramref name="other"/>, and greater than zero if this instance is greater
         /// than <paramref name="other"/>.
         /// </returns>
         public int CompareTo(ValueTuple other)
@@ -123,7 +138,21 @@ string ITupleInternal.ToStringEnd()
             return ")";
         }
 
-        int ITupleInternal.Size => 0;
+        /// <summary>
+        /// The number of positions in this data structure.
+        /// </summary>
+        public int Size => 0;
+
+        /// <summary>
+        /// Get the element at position <param name="index"/>.
+        /// </summary>
+        public object this[int index]
+        {
+            get
+            {
+                throw new IndexOutOfRangeException();
+            }
+        }
 
         /// <summary>Creates a new struct 0-tuple.</summary>
         /// <returns>A 0-tuple.</returns>
@@ -282,7 +311,7 @@ internal static int CombineHashCodes(int h1, int h2, int h3, int h4, int h5, int
     /// <summary>Represents a 1-tuple, or singleton, as a value type.</summary>
     /// <typeparam name="T1">The type of the tuple's only component.</typeparam>
     public struct ValueTuple<T1>
-        : IEquatable<ValueTuple<T1>>, IStructuralEquatable, IStructuralComparable, IComparable, IComparable<ValueTuple<T1>>, ITupleInternal
+        : IEquatable<ValueTuple<T1>>, IStructuralEquatable, IStructuralComparable, IComparable, IComparable<ValueTuple<T1>>, ITupleInternal, ITuple
     {
         /// <summary>
         /// The current <see cref="ValueTuple{T1}"/> instance's first component.
@@ -359,7 +388,7 @@ int IComparable.CompareTo(object other)
         /// <returns>
         /// A signed number indicating the relative values of this instance and <paramref name="other"/>.
         /// Returns less than zero if this instance is less than <paramref name="other"/>, zero if this
-        /// instance is equal to <paramref name="other"/>, and greater than zero if this instance is greater 
+        /// instance is equal to <paramref name="other"/>, and greater than zero if this instance is greater
         /// than <paramref name="other"/>.
         /// </returns>
         public int CompareTo(ValueTuple<T1> other)
@@ -419,7 +448,25 @@ string ITupleInternal.ToStringEnd()
             return Item1?.ToString() + ")";
         }
 
-        int ITupleInternal.Size => 1;
+        /// <summary>
+        /// The number of positions in this data structure.
+        /// </summary>
+        public int Size => 1;
+
+        /// <summary>
+        /// Get the element at position <param name="index"/>.
+        /// </summary>
+        public object this[int index]
+        {
+            get
+            {
+                if (index != 0)
+                {
+                    throw new IndexOutOfRangeException();
+                }
+                return Item1;
+            }
+        }
     }
 
     /// <summary>
@@ -428,7 +475,7 @@ string ITupleInternal.ToStringEnd()
     /// <typeparam name="T1">The type of the tuple's first component.</typeparam>
     /// <typeparam name="T2">The type of the tuple's second component.</typeparam>
     public struct ValueTuple<T1, T2>
-        : IEquatable<ValueTuple<T1, T2>>, IStructuralEquatable, IStructuralComparable, IComparable, IComparable<ValueTuple<T1, T2>>, ITupleInternal
+        : IEquatable<ValueTuple<T1, T2>>, IStructuralEquatable, IStructuralComparable, IComparable, IComparable<ValueTuple<T1, T2>>, ITupleInternal, ITuple
     {
         /// <summary>
         /// The current <see cref="ValueTuple{T1, T2}"/> instance's first component.
@@ -530,7 +577,7 @@ int IComparable.CompareTo(object other)
         /// <returns>
         /// A signed number indicating the relative values of this instance and <paramref name="other"/>.
         /// Returns less than zero if this instance is less than <paramref name="other"/>, zero if this
-        /// instance is equal to <paramref name="other"/>, and greater than zero if this instance is greater 
+        /// instance is equal to <paramref name="other"/>, and greater than zero if this instance is greater
         /// than <paramref name="other"/>.
         /// </returns>
         public int CompareTo(ValueTuple<T1, T2> other)
@@ -604,7 +651,29 @@ string ITupleInternal.ToStringEnd()
             return Item1?.ToString() + ", " + Item2?.ToString() + ")";
         }
 
-        int ITupleInternal.Size => 2;
+        /// <summary>
+        /// The number of positions in this data structure.
+        /// </summary>
+        public int Size => 2;
+
+        /// <summary>
+        /// Get the element at position <param name="index"/>.
+        /// </summary>
+        public object this[int index]
+        {
+            get
+            {
+                switch (index)
+                {
+                    case 0:
+                        return Item1;
+                    case 1:
+                        return Item2;
+                    default:
+                        throw new IndexOutOfRangeException();
+                }
+            }
+        }
     }
 
     /// <summary>
@@ -614,7 +683,7 @@ string ITupleInternal.ToStringEnd()
     /// <typeparam name="T2">The type of the tuple's second component.</typeparam>
     /// <typeparam name="T3">The type of the tuple's third component.</typeparam>
     public struct ValueTuple<T1, T2, T3>
-        : IEquatable<ValueTuple<T1, T2, T3>>, IStructuralEquatable, IStructuralComparable, IComparable, IComparable<ValueTuple<T1, T2, T3>>, ITupleInternal
+        : IEquatable<ValueTuple<T1, T2, T3>>, IStructuralEquatable, IStructuralComparable, IComparable, IComparable<ValueTuple<T1, T2, T3>>, ITupleInternal, ITuple
     {
         /// <summary>
         /// The current <see cref="ValueTuple{T1, T2, T3}"/> instance's first component.
@@ -705,7 +774,7 @@ int IComparable.CompareTo(object other)
         /// <returns>
         /// A signed number indicating the relative values of this instance and <paramref name="other"/>.
         /// Returns less than zero if this instance is less than <paramref name="other"/>, zero if this
-        /// instance is equal to <paramref name="other"/>, and greater than zero if this instance is greater 
+        /// instance is equal to <paramref name="other"/>, and greater than zero if this instance is greater
         /// than <paramref name="other"/>.
         /// </returns>
         public int CompareTo(ValueTuple<T1, T2, T3> other)
@@ -785,7 +854,31 @@ string ITupleInternal.ToStringEnd()
             return Item1?.ToString() + ", " + Item2?.ToString() + ", " + Item3?.ToString() + ")";
         }
 
-        int ITupleInternal.Size => 3;
+        /// <summary>
+        /// The number of positions in this data structure.
+        /// </summary>
+        public int Size => 3;
+
+        /// <summary>
+        /// Get the element at position <param name="index"/>.
+        /// </summary>
+        public object this[int index]
+        {
+            get
+            {
+                switch (index)
+                {
+                    case 0:
+                        return Item1;
+                    case 1:
+                        return Item2;
+                    case 2:
+                        return Item3;
+                    default:
+                        throw new IndexOutOfRangeException();
+                }
+            }
+        }
     }
 
     /// <summary>
@@ -796,7 +889,7 @@ string ITupleInternal.ToStringEnd()
     /// <typeparam name="T3">The type of the tuple's third component.</typeparam>
     /// <typeparam name="T4">The type of the tuple's fourth component.</typeparam>
     public struct ValueTuple<T1, T2, T3, T4>
-        : IEquatable<ValueTuple<T1, T2, T3, T4>>, IStructuralEquatable, IStructuralComparable, IComparable, IComparable<ValueTuple<T1, T2, T3, T4>>, ITupleInternal
+        : IEquatable<ValueTuple<T1, T2, T3, T4>>, IStructuralEquatable, IStructuralComparable, IComparable, IComparable<ValueTuple<T1, T2, T3, T4>>, ITupleInternal, ITuple
     {
         /// <summary>
         /// The current <see cref="ValueTuple{T1, T2, T3, T4}"/> instance's first component.
@@ -895,7 +988,7 @@ int IComparable.CompareTo(object other)
         /// <returns>
         /// A signed number indicating the relative values of this instance and <paramref name="other"/>.
         /// Returns less than zero if this instance is less than <paramref name="other"/>, zero if this
-        /// instance is equal to <paramref name="other"/>, and greater than zero if this instance is greater 
+        /// instance is equal to <paramref name="other"/>, and greater than zero if this instance is greater
         /// than <paramref name="other"/>.
         /// </returns>
         public int CompareTo(ValueTuple<T1, T2, T3, T4> other)
@@ -983,7 +1076,33 @@ string ITupleInternal.ToStringEnd()
             return Item1?.ToString() + ", " + Item2?.ToString() + ", " + Item3?.ToString() + ", " + Item4?.ToString() + ")";
         }
 
-        int ITupleInternal.Size => 4;
+        /// <summary>
+        /// The number of positions in this data structure.
+        /// </summary>
+        public int Size => 4;
+
+        /// <summary>
+        /// Get the element at position <param name="index"/>.
+        /// </summary>
+        public object this[int index]
+        {
+            get
+            {
+                switch (index)
+                {
+                    case 0:
+                        return Item1;
+                    case 1:
+                        return Item2;
+                    case 2:
+                        return Item3;
+                    case 3:
+                        return Item4;
+                    default:
+                        throw new IndexOutOfRangeException();
+                }
+            }
+        }
     }
 
     /// <summary>
@@ -995,7 +1114,7 @@ string ITupleInternal.ToStringEnd()
     /// <typeparam name="T4">The type of the tuple's fourth component.</typeparam>
     /// <typeparam name="T5">The type of the tuple's fifth component.</typeparam>
     public struct ValueTuple<T1, T2, T3, T4, T5>
-        : IEquatable<ValueTuple<T1, T2, T3, T4, T5>>, IStructuralEquatable, IStructuralComparable, IComparable, IComparable<ValueTuple<T1, T2, T3, T4, T5>>, ITupleInternal
+        : IEquatable<ValueTuple<T1, T2, T3, T4, T5>>, IStructuralEquatable, IStructuralComparable, IComparable, IComparable<ValueTuple<T1, T2, T3, T4, T5>>, ITupleInternal, ITuple
     {
         /// <summary>
         /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5}"/> instance's first component.
@@ -1102,7 +1221,7 @@ int IComparable.CompareTo(object other)
         /// <returns>
         /// A signed number indicating the relative values of this instance and <paramref name="other"/>.
         /// Returns less than zero if this instance is less than <paramref name="other"/>, zero if this
-        /// instance is equal to <paramref name="other"/>, and greater than zero if this instance is greater 
+        /// instance is equal to <paramref name="other"/>, and greater than zero if this instance is greater
         /// than <paramref name="other"/>.
         /// </returns>
         public int CompareTo(ValueTuple<T1, T2, T3, T4, T5> other)
@@ -1198,7 +1317,35 @@ string ITupleInternal.ToStringEnd()
             return Item1?.ToString() + ", " + Item2?.ToString() + ", " + Item3?.ToString() + ", " + Item4?.ToString() + ", " + Item5?.ToString() + ")";
         }
 
-        int ITupleInternal.Size => 5;
+        /// <summary>
+        /// The number of positions in this data structure.
+        /// </summary>
+        public int Size => 5;
+
+        /// <summary>
+        /// Get the element at position <param name="index"/>.
+        /// </summary>
+        public object this[int index]
+        {
+            get
+            {
+                switch (index)
+                {
+                    case 0:
+                        return Item1;
+                    case 1:
+                        return Item2;
+                    case 2:
+                        return Item3;
+                    case 3:
+                        return Item4;
+                    case 4:
+                        return Item5;
+                    default:
+                        throw new IndexOutOfRangeException();
+                }
+            }
+        }
     }
 
     /// <summary>
@@ -1211,7 +1358,7 @@ string ITupleInternal.ToStringEnd()
     /// <typeparam name="T5">The type of the tuple's fifth component.</typeparam>
     /// <typeparam name="T6">The type of the tuple's sixth component.</typeparam>
     public struct ValueTuple<T1, T2, T3, T4, T5, T6>
-        : IEquatable<ValueTuple<T1, T2, T3, T4, T5, T6>>, IStructuralEquatable, IStructuralComparable, IComparable, IComparable<ValueTuple<T1, T2, T3, T4, T5, T6>>, ITupleInternal
+        : IEquatable<ValueTuple<T1, T2, T3, T4, T5, T6>>, IStructuralEquatable, IStructuralComparable, IComparable, IComparable<ValueTuple<T1, T2, T3, T4, T5, T6>>, ITupleInternal, ITuple
     {
         /// <summary>
         /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6}"/> instance's first component.
@@ -1326,7 +1473,7 @@ int IComparable.CompareTo(object other)
         /// <returns>
         /// A signed number indicating the relative values of this instance and <paramref name="other"/>.
         /// Returns less than zero if this instance is less than <paramref name="other"/>, zero if this
-        /// instance is equal to <paramref name="other"/>, and greater than zero if this instance is greater 
+        /// instance is equal to <paramref name="other"/>, and greater than zero if this instance is greater
         /// than <paramref name="other"/>.
         /// </returns>
         public int CompareTo(ValueTuple<T1, T2, T3, T4, T5, T6> other)
@@ -1430,7 +1577,37 @@ string ITupleInternal.ToStringEnd()
             return Item1?.ToString() + ", " + Item2?.ToString() + ", " + Item3?.ToString() + ", " + Item4?.ToString() + ", " + Item5?.ToString() + ", " + Item6?.ToString() + ")";
         }
 
-        int ITupleInternal.Size => 6;
+        /// <summary>
+        /// The number of positions in this data structure.
+        /// </summary>
+        public int Size => 6;
+
+        /// <summary>
+        /// Get the element at position <param name="index"/>.
+        /// </summary>
+        public object this[int index]
+        {
+            get
+            {
+                switch (index)
+                {
+                    case 0:
+                        return Item1;
+                    case 1:
+                        return Item2;
+                    case 2:
+                        return Item3;
+                    case 3:
+                        return Item4;
+                    case 4:
+                        return Item5;
+                    case 5:
+                        return Item6;
+                    default:
+                        throw new IndexOutOfRangeException();
+                }
+            }
+        }
     }
 
     /// <summary>
@@ -1444,7 +1621,7 @@ string ITupleInternal.ToStringEnd()
     /// <typeparam name="T6">The type of the tuple's sixth component.</typeparam>
     /// <typeparam name="T7">The type of the tuple's seventh component.</typeparam>
     public struct ValueTuple<T1, T2, T3, T4, T5, T6, T7>
-        : IEquatable<ValueTuple<T1, T2, T3, T4, T5, T6, T7>>, IStructuralEquatable, IStructuralComparable, IComparable, IComparable<ValueTuple<T1, T2, T3, T4, T5, T6, T7>>, ITupleInternal
+        : IEquatable<ValueTuple<T1, T2, T3, T4, T5, T6, T7>>, IStructuralEquatable, IStructuralComparable, IComparable, IComparable<ValueTuple<T1, T2, T3, T4, T5, T6, T7>>, ITupleInternal, ITuple
     {
         /// <summary>
         /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7}"/> instance's first component.
@@ -1567,7 +1744,7 @@ int IComparable.CompareTo(object other)
         /// <returns>
         /// A signed number indicating the relative values of this instance and <paramref name="other"/>.
         /// Returns less than zero if this instance is less than <paramref name="other"/>, zero if this
-        /// instance is equal to <paramref name="other"/>, and greater than zero if this instance is greater 
+        /// instance is equal to <paramref name="other"/>, and greater than zero if this instance is greater
         /// than <paramref name="other"/>.
         /// </returns>
         public int CompareTo(ValueTuple<T1, T2, T3, T4, T5, T6, T7> other)
@@ -1679,7 +1856,39 @@ string ITupleInternal.ToStringEnd()
             return Item1?.ToString() + ", " + Item2?.ToString() + ", " + Item3?.ToString() + ", " + Item4?.ToString() + ", " + Item5?.ToString() + ", " + Item6?.ToString() + ", " + Item7?.ToString() + ")";
         }
 
-        int ITupleInternal.Size => 7;
+        /// <summary>
+        ///
+        /// </summary>
+        public int Size => 7;
+
+        /// <summary>
+        ///
+        /// </summary>
+        public object this[int index]
+        {
+            get
+            {
+                switch (index)
+                {
+                    case 0:
+                        return Item1;
+                    case 1:
+                        return Item2;
+                    case 2:
+                        return Item3;
+                    case 3:
+                        return Item4;
+                    case 4:
+                        return Item5;
+                    case 5:
+                        return Item6;
+                    case 6:
+                        return Item7;
+                    default:
+                        throw new IndexOutOfRangeException();
+                }
+            }
+        }
     }
 
     /// <summary>
@@ -1694,7 +1903,7 @@ string ITupleInternal.ToStringEnd()
     /// <typeparam name="T7">The type of the tuple's seventh component.</typeparam>
     /// <typeparam name="TRest">The type of the tuple's eigth component.</typeparam>
     public struct ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest>
-        : IEquatable<ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest>>, IStructuralEquatable, IStructuralComparable, IComparable, IComparable<ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest>>, ITupleInternal
+        : IEquatable<ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest>>, IStructuralEquatable, IStructuralComparable, IComparable, IComparable<ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest>>, ITupleInternal, ITuple
         where TRest : struct
     {
         /// <summary>
@@ -1831,7 +2040,7 @@ int IComparable.CompareTo(object other)
         /// <returns>
         /// A signed number indicating the relative values of this instance and <paramref name="other"/>.
         /// Returns less than zero if this instance is less than <paramref name="other"/>, zero if this
-        /// instance is equal to <paramref name="other"/>, and greater than zero if this instance is greater 
+        /// instance is equal to <paramref name="other"/>, and greater than zero if this instance is greater
         /// than <paramref name="other"/>.
         /// </returns>
         public int CompareTo(ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest> other)
@@ -2060,7 +2269,10 @@ string ITupleInternal.ToStringEnd()
             }
         }
 
-        int ITupleInternal.Size
+        /// <summary>
+        /// The number of positions in this data structure.
+        /// </summary>
+        public int Size
         {
             get
             {
@@ -2068,5 +2280,42 @@ int ITupleInternal.Size
                 return rest == null ? 8 : 7 + rest.Size;
             }
         }
+
+        /// <summary>
+        /// Get the element at position <param name="index"/>.
+        /// </summary>
+        public object this[int index]
+        {
+            get
+            {
+                switch (index)
+                {
+                    case 0:
+                        return Item1;
+                    case 1:
+                        return Item2;
+                    case 2:
+                        return Item3;
+                    case 3:
+                        return Item4;
+                    case 4:
+                        return Item5;
+                    case 5:
+                        return Item6;
+                    case 6:
+                        return Item7;
+                }
+
+                ITupleInternal rest = Rest as ITupleInternal;
+                if (index > 0 && index < Size && rest != null)
+                {
+                    return rest[index - 7];
+                }
+                else
+                {
+                    throw new IndexOutOfRangeException();
+                }
+            }
+        }
     }
 }
\ No newline at end of file
diff --git a/src/System.ValueTuple/tests/ValueTuple/UnitTests.cs b/src/System.ValueTuple/tests/ValueTuple/UnitTests.cs
index 3ebe247158a7..a2bbafd8251e 100644
--- a/src/System.ValueTuple/tests/ValueTuple/UnitTests.cs
+++ b/src/System.ValueTuple/tests/ValueTuple/UnitTests.cs
@@ -724,6 +724,11 @@ public static void ZeroTuples()
         Assert.Throws<ArgumentException>(() => ((IStructuralComparable)a).CompareTo("string", DummyTestComparer.Instance));
 
         Assert.Equal("(1, 2, 3, 4, 5, 6, 7, )", CreateLong(1, 2, 3, 4, 5, 6, 7, new ValueTuple()).ToString());
+
+        ITuple it = ValueTuple.Create();
+        Assert.Throws<IndexOutOfRangeException>(() => it[-1]);
+        Assert.Throws<IndexOutOfRangeException>(() => it[0]);
+        Assert.Throws<IndexOutOfRangeException>(() => it[1]);
     }
 
     [Fact]
@@ -748,6 +753,11 @@ public static void OneTuples()
         var tupleWithNull = new Tuple<string>(null);
         Assert.Equal("()", vtWithNull.ToString());
         Assert.Equal(tupleWithNull.ToString(), vtWithNull.ToString());
+
+        ITuple it = ValueTuple.Create(1);
+        Assert.Throws<IndexOutOfRangeException>(() => it[-1]);
+        Assert.Equal(1, it[0]);
+        Assert.Throws<IndexOutOfRangeException>(() => it[1]);
     }
 
     [Fact]
@@ -773,6 +783,12 @@ public static void TwoTuples()
         var tupleWithNull = new Tuple<string, string>(null, null);
         Assert.Equal("(, )", vtWithNull.ToString());
         Assert.Equal(tupleWithNull.ToString(), vtWithNull.ToString());
+
+        ITuple it = ValueTuple.Create(1, 2);
+        Assert.Throws<IndexOutOfRangeException>(() => it[-1]);
+        Assert.Equal(1, it[0]);
+        Assert.Equal(2, it[1]);
+        Assert.Throws<IndexOutOfRangeException>(() => it[2]);
     }
 
     [Fact]
@@ -800,6 +816,13 @@ public static void ThreeTuples()
         var tupleWithNull = new Tuple<string, string, string>(null, null, null);
         Assert.Equal("(, , )", vtWithNull.ToString());
         Assert.Equal(tupleWithNull.ToString(), vtWithNull.ToString());
+
+        ITuple it = ValueTuple.Create(1, 2, 3);
+        Assert.Throws<IndexOutOfRangeException>(() => it[-1]);
+        Assert.Equal(1, it[0]);
+        Assert.Equal(2, it[1]);
+        Assert.Equal(3, it[2]);
+        Assert.Throws<IndexOutOfRangeException>(() => it[3]);
     }
 
     [Fact]
@@ -830,6 +853,14 @@ public static void FourTuples()
         var tupleWithNull = new Tuple<string, string, string, string>(null, null, null, null);
         Assert.Equal("(, , , )", vtWithNull.ToString());
         Assert.Equal(tupleWithNull.ToString(), vtWithNull.ToString());
+
+        ITuple it = ValueTuple.Create(1, 2, 3, 4);
+        Assert.Throws<IndexOutOfRangeException>(() => it[-1]);
+        Assert.Equal(1, it[0]);
+        Assert.Equal(2, it[1]);
+        Assert.Equal(3, it[2]);
+        Assert.Equal(4, it[3]);
+        Assert.Throws<IndexOutOfRangeException>(() => it[4]);
     }
 
     [Fact]
@@ -862,6 +893,15 @@ public static void FiveTuples()
         var tupleWithNull = new Tuple<string, string, string, string, string>(null, null, null, null, null);
         Assert.Equal("(, , , , )", vtWithNull.ToString());
         Assert.Equal(tupleWithNull.ToString(), vtWithNull.ToString());
+
+        ITuple it = ValueTuple.Create(1, 2, 3, 4, 5);
+        Assert.Throws<IndexOutOfRangeException>(() => it[-1]);
+        Assert.Equal(1, it[0]);
+        Assert.Equal(2, it[1]);
+        Assert.Equal(3, it[2]);
+        Assert.Equal(4, it[3]);
+        Assert.Equal(5, it[4]);
+        Assert.Throws<IndexOutOfRangeException>(() => it[5]);
     }
 
     [Fact]
@@ -896,6 +936,16 @@ public static void SixTuples()
         var tupleWithNull = new Tuple<string, string, string, string, string, string>(null, null, null, null, null, null);
         Assert.Equal("(, , , , , )", vtWithNull.ToString());
         Assert.Equal(tupleWithNull.ToString(), vtWithNull.ToString());
+
+        ITuple it = ValueTuple.Create(1, 2, 3, 4, 5, 6);
+        Assert.Throws<IndexOutOfRangeException>(() => it[-1]);
+        Assert.Equal(1, it[0]);
+        Assert.Equal(2, it[1]);
+        Assert.Equal(3, it[2]);
+        Assert.Equal(4, it[3]);
+        Assert.Equal(5, it[4]);
+        Assert.Equal(6, it[5]);
+        Assert.Throws<IndexOutOfRangeException>(() => it[6]);
     }
 
     [Fact]
@@ -932,6 +982,17 @@ public static void SevenTuples()
         var tupleWithNull = new Tuple<string, string, string, string, string, string, string>(null, null, null, null, null, null, null);
         Assert.Equal("(, , , , , , )", vtWithNull.ToString());
         Assert.Equal(tupleWithNull.ToString(), vtWithNull.ToString());
+
+        ITuple it = ValueTuple.Create(1, 2, 3, 4, 5, 6, 7);
+        Assert.Throws<IndexOutOfRangeException>(() => it[-1]);
+        Assert.Equal(1, it[0]);
+        Assert.Equal(2, it[1]);
+        Assert.Equal(3, it[2]);
+        Assert.Equal(4, it[3]);
+        Assert.Equal(5, it[4]);
+        Assert.Equal(6, it[5]);
+        Assert.Equal(7, it[6]);
+        Assert.Throws<IndexOutOfRangeException>(() => it[7]);
     }
 
     public static ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest> CreateLong<T1, T2, T3, T4, T5, T6, T7, TRest>(T1 item1, T2 item2, T3 item3, T4 item4, T5 item5, T6 item6, T7 item7, TRest rest) where TRest : struct =>
@@ -1009,6 +1070,18 @@ public static void EightTuples()
         var tupleWithNull = new Tuple<string, string, string, string, string, string, string, Tuple<string>>(null, null, null, null, null, null, null, new Tuple<string>(null));
         Assert.Equal("(, , , , , , , )", vtWithNull.ToString());
         Assert.Equal(tupleWithNull.ToString(), vtWithNull.ToString());
+
+        ITuple it = CreateLong(1, 2, 3, 4, 5, 6, 7, ValueTuple.Create(8));
+        Assert.Throws<IndexOutOfRangeException>(() => it[-1]);
+        Assert.Equal(1, it[0]);
+        Assert.Equal(2, it[1]);
+        Assert.Equal(3, it[2]);
+        Assert.Equal(4, it[3]);
+        Assert.Equal(5, it[4]);
+        Assert.Equal(6, it[5]);
+        Assert.Equal(7, it[6]);
+        Assert.Equal(8, it[7]);
+        Assert.Throws<IndexOutOfRangeException>(() => it[8]);
     }
 
     [Fact]
@@ -1088,6 +1161,17 @@ public static void EightTuplesWithBadRest()
         Assert.Equal(((IStructuralEquatable)ValueTuple.Create(1, 0, 0, 0, 0, 0, 0)).GetHashCode(TestEqualityComparer.Instance), ((IStructuralEquatable)d).GetHashCode(TestEqualityComparer.Instance));
 
         Assert.Equal("(1, 2, 3, 4, 5, 6, 7, 1, 0, 0, 0, 0, 0, 0, 42)", CreateLong(1, 2, 3, 4, 5, 6, 7, d).ToString());
+
+        ITuple it = d;
+        Assert.Throws<IndexOutOfRangeException>(() => it[-1]);
+        Assert.Equal(1, it[0]);
+        Assert.Equal(0, it[1]);
+        Assert.Equal(0, it[2]);
+        Assert.Equal(0, it[3]);
+        Assert.Equal(0, it[4]);
+        Assert.Equal(0, it[5]);
+        Assert.Equal(0, it[6]);
+        Assert.Throws<IndexOutOfRangeException>(() => it[7]);
     }
 
     private class TestClass : IComparable

From 176a739d7170369d089535df032a87374265b376 Mon Sep 17 00:00:00 2001
From: Julien Couvreur <julien.couvreur@gmail.com>
Date: Thu, 14 Jul 2016 14:26:31 -0700
Subject: [PATCH 2/4] Renaming from Size to Length

---
 .../src/System/ValueTuple/ValueTuple.cs       | 32 +++++++++----------
 1 file changed, 16 insertions(+), 16 deletions(-)

diff --git a/src/System.ValueTuple/src/System/ValueTuple/ValueTuple.cs b/src/System.ValueTuple/src/System/ValueTuple/ValueTuple.cs
index c265f623d58a..2558d1b32f86 100644
--- a/src/System.ValueTuple/src/System/ValueTuple/ValueTuple.cs
+++ b/src/System.ValueTuple/src/System/ValueTuple/ValueTuple.cs
@@ -16,7 +16,7 @@ public interface ITuple
         /// <summary>
         /// The number of positions in this data structure.
         /// </summary>
-        int Size { get; }
+        int Length { get; }
 
         /// <summary>
         /// Get the element at position <param name="index"/>.
@@ -141,7 +141,7 @@ string ITupleInternal.ToStringEnd()
         /// <summary>
         /// The number of positions in this data structure.
         /// </summary>
-        public int Size => 0;
+        public int Length => 0;
 
         /// <summary>
         /// Get the element at position <param name="index"/>.
@@ -451,7 +451,7 @@ string ITupleInternal.ToStringEnd()
         /// <summary>
         /// The number of positions in this data structure.
         /// </summary>
-        public int Size => 1;
+        public int Length => 1;
 
         /// <summary>
         /// Get the element at position <param name="index"/>.
@@ -654,7 +654,7 @@ string ITupleInternal.ToStringEnd()
         /// <summary>
         /// The number of positions in this data structure.
         /// </summary>
-        public int Size => 2;
+        public int Length => 2;
 
         /// <summary>
         /// Get the element at position <param name="index"/>.
@@ -857,7 +857,7 @@ string ITupleInternal.ToStringEnd()
         /// <summary>
         /// The number of positions in this data structure.
         /// </summary>
-        public int Size => 3;
+        public int Length => 3;
 
         /// <summary>
         /// Get the element at position <param name="index"/>.
@@ -1079,7 +1079,7 @@ string ITupleInternal.ToStringEnd()
         /// <summary>
         /// The number of positions in this data structure.
         /// </summary>
-        public int Size => 4;
+        public int Length => 4;
 
         /// <summary>
         /// Get the element at position <param name="index"/>.
@@ -1320,7 +1320,7 @@ string ITupleInternal.ToStringEnd()
         /// <summary>
         /// The number of positions in this data structure.
         /// </summary>
-        public int Size => 5;
+        public int Length => 5;
 
         /// <summary>
         /// Get the element at position <param name="index"/>.
@@ -1580,7 +1580,7 @@ string ITupleInternal.ToStringEnd()
         /// <summary>
         /// The number of positions in this data structure.
         /// </summary>
-        public int Size => 6;
+        public int Length => 6;
 
         /// <summary>
         /// Get the element at position <param name="index"/>.
@@ -1857,12 +1857,12 @@ string ITupleInternal.ToStringEnd()
         }
 
         /// <summary>
-        ///
+        /// The number of positions in this data structure.
         /// </summary>
-        public int Size => 7;
+        public int Length => 7;
 
         /// <summary>
-        ///
+        /// Get the element at position <param name="index"/>.
         /// </summary>
         public object this[int index]
         {
@@ -2123,7 +2123,7 @@ public override int GetHashCode()
                                                    EqualityComparer<T7>.Default.GetHashCode(Item7));
             }
 
-            int size = rest.Size;
+            int size = rest.Length;
             if (size >= 8) { return rest.GetHashCode(); }
 
             // In this case, the rest member has less than 8 elements so we need to combine some our elements with the elements in rest
@@ -2195,7 +2195,7 @@ private int GetHashCodeCore(IEqualityComparer comparer)
                                                    comparer.GetHashCode(Item7));
             }
 
-            int size = rest.Size;
+            int size = rest.Length;
             if (size >= 8) { return rest.GetHashCode(comparer); }
 
             // In this case, the rest member has less than 8 elements so we need to combine some our elements with the elements in rest
@@ -2272,12 +2272,12 @@ string ITupleInternal.ToStringEnd()
         /// <summary>
         /// The number of positions in this data structure.
         /// </summary>
-        public int Size
+        public int Length
         {
             get
             {
                 ITupleInternal rest = Rest as ITupleInternal;
-                return rest == null ? 8 : 7 + rest.Size;
+                return rest == null ? 8 : 7 + rest.Length;
             }
         }
 
@@ -2307,7 +2307,7 @@ public object this[int index]
                 }
 
                 ITupleInternal rest = Rest as ITupleInternal;
-                if (index > 0 && index < Size && rest != null)
+                if (index > 0 && index < Length && rest != null)
                 {
                     return rest[index - 7];
                 }

From 7589bb6910f191d37935e60d2ebe58f94fbaa2f5 Mon Sep 17 00:00:00 2001
From: Julien Couvreur <julien.couvreur@gmail.com>
Date: Thu, 14 Jul 2016 15:07:06 -0700
Subject: [PATCH 3/4] Using ITuple as constraint on TRest

---
 .../src/System/ValueTuple/TupleExtensions.cs  |  2 +-
 .../src/System/ValueTuple/ValueTuple.cs       | 51 ++++++++-----------
 .../tests/ValueTuple/UnitTests.cs             | 41 ++++++++++++---
 3 files changed, 57 insertions(+), 37 deletions(-)

diff --git a/src/System.ValueTuple/src/System/ValueTuple/TupleExtensions.cs b/src/System.ValueTuple/src/System/ValueTuple/TupleExtensions.cs
index 096df957124a..9cd91201fc2d 100644
--- a/src/System.ValueTuple/src/System/ValueTuple/TupleExtensions.cs
+++ b/src/System.ValueTuple/src/System/ValueTuple/TupleExtensions.cs
@@ -920,7 +920,7 @@ public static Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12, T13
         }
         #endregion
 
-        private static ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest> CreateLong<T1, T2, T3, T4, T5, T6, T7, TRest>(T1 item1, T2 item2, T3 item3, T4 item4, T5 item5, T6 item6, T7 item7, TRest rest) where TRest : struct =>
+        private static ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest> CreateLong<T1, T2, T3, T4, T5, T6, T7, TRest>(T1 item1, T2 item2, T3 item3, T4 item4, T5 item5, T6 item6, T7 item7, TRest rest) where TRest : struct, ITuple =>
             new ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest>(item1, item2, item3, item4, item5, item6, item7, rest);
 
         private static Tuple<T1, T2, T3, T4, T5, T6, T7, TRest> CreateLongRef<T1, T2, T3, T4, T5, T6, T7, TRest>(T1 item1, T2 item2, T3 item3, T4 item4, T5 item5, T6 item6, T7 item7, TRest rest) =>
diff --git a/src/System.ValueTuple/src/System/ValueTuple/ValueTuple.cs b/src/System.ValueTuple/src/System/ValueTuple/ValueTuple.cs
index 2558d1b32f86..7fd60e42321c 100644
--- a/src/System.ValueTuple/src/System/ValueTuple/ValueTuple.cs
+++ b/src/System.ValueTuple/src/System/ValueTuple/ValueTuple.cs
@@ -141,12 +141,12 @@ string ITupleInternal.ToStringEnd()
         /// <summary>
         /// The number of positions in this data structure.
         /// </summary>
-        public int Length => 0;
+        int ITuple.Length => 0;
 
         /// <summary>
         /// Get the element at position <param name="index"/>.
         /// </summary>
-        public object this[int index]
+        object ITuple.this[int index]
         {
             get
             {
@@ -451,12 +451,12 @@ string ITupleInternal.ToStringEnd()
         /// <summary>
         /// The number of positions in this data structure.
         /// </summary>
-        public int Length => 1;
+        int ITuple.Length => 1;
 
         /// <summary>
         /// Get the element at position <param name="index"/>.
         /// </summary>
-        public object this[int index]
+        object ITuple.this[int index]
         {
             get
             {
@@ -654,12 +654,12 @@ string ITupleInternal.ToStringEnd()
         /// <summary>
         /// The number of positions in this data structure.
         /// </summary>
-        public int Length => 2;
+        int ITuple.Length => 2;
 
         /// <summary>
         /// Get the element at position <param name="index"/>.
         /// </summary>
-        public object this[int index]
+        object ITuple.this[int index]
         {
             get
             {
@@ -857,12 +857,12 @@ string ITupleInternal.ToStringEnd()
         /// <summary>
         /// The number of positions in this data structure.
         /// </summary>
-        public int Length => 3;
+        int ITuple.Length => 3;
 
         /// <summary>
         /// Get the element at position <param name="index"/>.
         /// </summary>
-        public object this[int index]
+        object ITuple.this[int index]
         {
             get
             {
@@ -1079,12 +1079,12 @@ string ITupleInternal.ToStringEnd()
         /// <summary>
         /// The number of positions in this data structure.
         /// </summary>
-        public int Length => 4;
+        int ITuple.Length => 4;
 
         /// <summary>
         /// Get the element at position <param name="index"/>.
         /// </summary>
-        public object this[int index]
+        object ITuple.this[int index]
         {
             get
             {
@@ -1320,12 +1320,12 @@ string ITupleInternal.ToStringEnd()
         /// <summary>
         /// The number of positions in this data structure.
         /// </summary>
-        public int Length => 5;
+        int ITuple.Length => 5;
 
         /// <summary>
         /// Get the element at position <param name="index"/>.
         /// </summary>
-        public object this[int index]
+        object ITuple.this[int index]
         {
             get
             {
@@ -1580,12 +1580,12 @@ string ITupleInternal.ToStringEnd()
         /// <summary>
         /// The number of positions in this data structure.
         /// </summary>
-        public int Length => 6;
+        int ITuple.Length => 6;
 
         /// <summary>
         /// Get the element at position <param name="index"/>.
         /// </summary>
-        public object this[int index]
+        object ITuple.this[int index]
         {
             get
             {
@@ -1859,12 +1859,12 @@ string ITupleInternal.ToStringEnd()
         /// <summary>
         /// The number of positions in this data structure.
         /// </summary>
-        public int Length => 7;
+        int ITuple.Length => 7;
 
         /// <summary>
         /// Get the element at position <param name="index"/>.
         /// </summary>
-        public object this[int index]
+        object ITuple.this[int index]
         {
             get
             {
@@ -1904,7 +1904,7 @@ public object this[int index]
     /// <typeparam name="TRest">The type of the tuple's eigth component.</typeparam>
     public struct ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest>
         : IEquatable<ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest>>, IStructuralEquatable, IStructuralComparable, IComparable, IComparable<ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest>>, ITupleInternal, ITuple
-        where TRest : struct
+        where TRest : struct, ITuple
     {
         /// <summary>
         /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7, TRest}"/> instance's first component.
@@ -2272,19 +2272,18 @@ string ITupleInternal.ToStringEnd()
         /// <summary>
         /// The number of positions in this data structure.
         /// </summary>
-        public int Length
+        int ITuple.Length
         {
             get
             {
-                ITupleInternal rest = Rest as ITupleInternal;
-                return rest == null ? 8 : 7 + rest.Length;
+                return 7 + ((ITuple)Rest).Length;
             }
         }
 
         /// <summary>
         /// Get the element at position <param name="index"/>.
         /// </summary>
-        public object this[int index]
+        object ITuple.this[int index]
         {
             get
             {
@@ -2306,15 +2305,7 @@ public object this[int index]
                         return Item7;
                 }
 
-                ITupleInternal rest = Rest as ITupleInternal;
-                if (index > 0 && index < Length && rest != null)
-                {
-                    return rest[index - 7];
-                }
-                else
-                {
-                    throw new IndexOutOfRangeException();
-                }
+                return ((ITuple)Rest)[index - 7];
             }
         }
     }
diff --git a/src/System.ValueTuple/tests/ValueTuple/UnitTests.cs b/src/System.ValueTuple/tests/ValueTuple/UnitTests.cs
index a2bbafd8251e..3d4bfc708616 100644
--- a/src/System.ValueTuple/tests/ValueTuple/UnitTests.cs
+++ b/src/System.ValueTuple/tests/ValueTuple/UnitTests.cs
@@ -995,7 +995,7 @@ public static void SevenTuples()
         Assert.Throws<IndexOutOfRangeException>(() => it[7]);
     }
 
-    public static ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest> CreateLong<T1, T2, T3, T4, T5, T6, T7, TRest>(T1 item1, T2 item2, T3 item3, T4 item4, T5 item5, T6 item6, T7 item7, TRest rest) where TRest : struct =>
+    public static ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest> CreateLong<T1, T2, T3, T4, T5, T6, T7, TRest>(T1 item1, T2 item2, T3 item3, T4 item4, T5 item5, T6 item6, T7 item7, TRest rest) where TRest : struct, ITuple =>
         new ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest>(item1, item2, item3, item4, item5, item6, item7, rest);
 
     public static Tuple<T1, T2, T3, T4, T5, T6, T7, TRest> CreateLongRef<T1, T2, T3, T4, T5, T6, T7, TRest>(T1 item1, T2 item2, T3 item3, T4 item4, T5 item5, T6 item6, T7 item7, TRest rest) =>
@@ -1147,12 +1147,11 @@ public static void LongTuplesWithNull()
     [Fact]
     public static void EightTuplesWithBadRest()
     {
-        var d = default(ValueTuple<int, int, int, int, int, int, int, int>);
+        var d = default(ValueTuple<int, int, int, int, int, int, int, BadTuple>);
         d.Item1 = 1;
-        d.Rest = 42;
         Assert.Equal(35937, d.GetHashCode());
         Assert.Equal(35937, ((IStructuralEquatable)d).GetHashCode());
-        Assert.Equal("(1, 0, 0, 0, 0, 0, 0, 42)", d.ToString());
+        Assert.Equal("(1, 0, 0, 0, 0, 0, 0, BadTuple)", d.ToString());
 
         Assert.Equal(35937, CreateLong(1, 2, 3, 4, 5, 6, 7, d).GetHashCode());
 
@@ -1160,7 +1159,9 @@ public static void EightTuplesWithBadRest()
         Assert.Equal(ValueTuple.Create(1, 0, 0, 0, 0, 0, 0).GetHashCode(), d.GetHashCode());
         Assert.Equal(((IStructuralEquatable)ValueTuple.Create(1, 0, 0, 0, 0, 0, 0)).GetHashCode(TestEqualityComparer.Instance), ((IStructuralEquatable)d).GetHashCode(TestEqualityComparer.Instance));
 
-        Assert.Equal("(1, 2, 3, 4, 5, 6, 7, 1, 0, 0, 0, 0, 0, 0, 42)", CreateLong(1, 2, 3, 4, 5, 6, 7, d).ToString());
+        Assert.Equal("(1, 2, 3, 4, 5, 6, 7, 1, 0, 0, 0, 0, 0, 0, BadTuple)", CreateLong(1, 2, 3, 4, 5, 6, 7, d).ToString());
+
+        Assert.Throws<ArgumentException>(() => CreateLong(1, 2, 3, 4, 5, 6, 7, new BadTuple()));
 
         ITuple it = d;
         Assert.Throws<IndexOutOfRangeException>(() => it[-1]);
@@ -1171,7 +1172,35 @@ public static void EightTuplesWithBadRest()
         Assert.Equal(0, it[4]);
         Assert.Equal(0, it[5]);
         Assert.Equal(0, it[6]);
-        Assert.Throws<IndexOutOfRangeException>(() => it[7]);
+        Assert.Equal(42, it[7]);
+        Assert.Throws<IndexOutOfRangeException>(() => it[8]);
+    }
+
+    private struct BadTuple : ITuple
+    {
+        // doesn't implement ITupleInternal
+
+        int ITuple.Length => 1;
+
+        object ITuple.this[int index]
+        {
+            get
+            {
+                if (index == 0)
+                {
+                    return 42;
+                }
+                else
+                {
+                    throw new IndexOutOfRangeException();
+                }
+            }
+        }
+
+        public override string ToString()
+        {
+            return "BadTuple";
+        }
     }
 
     private class TestClass : IComparable

From c02d8372e2b68dd7359db76401ebe3de2d8dcbc0 Mon Sep 17 00:00:00 2001
From: Julien Couvreur <julien.couvreur@gmail.com>
Date: Fri, 15 Jul 2016 13:21:16 -0700
Subject: [PATCH 4/4] Removing boxing cast to ITuple

---
 src/System.ValueTuple/src/System/ValueTuple/ValueTuple.cs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/System.ValueTuple/src/System/ValueTuple/ValueTuple.cs b/src/System.ValueTuple/src/System/ValueTuple/ValueTuple.cs
index 7fd60e42321c..4f68b9a17e16 100644
--- a/src/System.ValueTuple/src/System/ValueTuple/ValueTuple.cs
+++ b/src/System.ValueTuple/src/System/ValueTuple/ValueTuple.cs
@@ -2276,7 +2276,7 @@ int ITuple.Length
         {
             get
             {
-                return 7 + ((ITuple)Rest).Length;
+                return 7 + Rest.Length;
             }
         }
 
@@ -2305,7 +2305,7 @@ object ITuple.this[int index]
                         return Item7;
                 }
 
-                return ((ITuple)Rest)[index - 7];
+                return Rest[index - 7];
             }
         }
     }