Nullable: Comparers, Dictionary and Friends (dotnet/coreclr#23971)

* Nullable: Comparers, Dictionary and Friends

* Add object constraint to Dictionary

* Fix warning from new compiler and annotating dictionary

* PR Feedback

Signed-off-by: dotnet-bot <dotnet-bot@microsoft.com>

Author: safern

netcore/System.Private.CoreLib/shared/System/Array.cs

@@ -384,7 +384,7 @@ int IStructuralEquatable.GetHashCode(IEqualityComparer comparer)
 
             for (int i = (this.Length >= 8 ? this.Length - 8 : 0); i < this.Length; i++)
             {
-                ret = CombineHashCodes(ret, comparer!.GetHashCode(GetValue(i))); // TODO-NULLABLE: https://github.com/dotnet/csharplang/issues/538
+                ret = CombineHashCodes(ret, comparer!.GetHashCode(GetValue(i)!)); // TODO-NULLABLE: https://github.com/dotnet/csharplang/issues/538
             }
 
             return ret;
@@ -1592,7 +1592,7 @@ public static void Sort<T>(T[] array, Comparison<T> comparison)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.comparison);
             }
 
-            ArraySortHelper<T>.Sort(array!, 0, array!.Length, comparison); // TODO-NULLABLE: https://github.com/dotnet/csharplang/issues/538
+            ArraySortHelper<T>.Sort(array!, 0, array!.Length, comparison!); // TODO-NULLABLE: https://github.com/dotnet/csharplang/issues/538
         }
 
         public static bool TrueForAll<T>(T[] array, Predicate<T> match)

netcore/System.Private.CoreLib/shared/System/Collections/DictionaryEntry.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
 using System.ComponentModel;
 
 namespace System.Collections
@@ -13,11 +14,11 @@ namespace System.Collections
     public struct DictionaryEntry
     {
         private object _key; // Do not rename (binary serialization)
-        private object _value; // Do not rename (binary serialization)
+        private object? _value; // Do not rename (binary serialization)
 
         // Constructs a new DictionaryEnumerator by setting the Key
         // and Value fields appropriately.
-        public DictionaryEntry(object key, object value)
+        public DictionaryEntry(object key, object? value)
         {
             _key = key;
             _value = value;
@@ -36,7 +37,7 @@ public object Key
             }
         }
 
-        public object Value
+        public object? Value
         {
             get
             {
@@ -50,7 +51,7 @@ public object Value
         }
 
         [EditorBrowsable(EditorBrowsableState.Never)]
-        public void Deconstruct(out object key, out object value)
+        public void Deconstruct(out object key, out object? value)
         {
             key = Key;
             value = Value;

netcore/System.Private.CoreLib/shared/System/Collections/Generic/ArraySortHelper.cs

@@ -13,6 +13,7 @@
 ** 
 ===========================================================*/
 
+#nullable enable
 using System.Diagnostics;
 using System.Runtime.CompilerServices;
 
@@ -38,7 +39,7 @@ internal static int FloorLog2PlusOne(int n)
             return result;
         }
 
-        internal static void ThrowOrIgnoreBadComparer(object comparer)
+        internal static void ThrowOrIgnoreBadComparer(object? comparer)
         {
             throw new ArgumentException(SR.Format(SR.Arg_BogusIComparer, comparer));
         }
@@ -48,7 +49,7 @@ internal partial class ArraySortHelper<T>
     {
         #region IArraySortHelper<T> Members
 
-        public void Sort(T[] keys, int index, int length, IComparer<T> comparer)
+        public void Sort(T[] keys, int index, int length, IComparer<T>? comparer)
         {
             Debug.Assert(keys != null, "Check the arguments in the caller!");
             Debug.Assert(index >= 0 && length >= 0 && (keys.Length - index >= length), "Check the arguments in the caller!");
@@ -74,7 +75,7 @@ public void Sort(T[] keys, int index, int length, IComparer<T> comparer)
             }
         }
 
-        public int BinarySearch(T[] array, int index, int length, T value, IComparer<T> comparer)
+        public int BinarySearch(T[] array, int index, int length, T value, IComparer<T>? comparer)
         {
             try
             {
@@ -335,7 +336,7 @@ internal partial class GenericArraySortHelper<T>
 
         #region IArraySortHelper<T> Members
 
-        public void Sort(T[] keys, int index, int length, IComparer<T> comparer)
+        public void Sort(T[] keys, int index, int length, IComparer<T>? comparer)
         {
             Debug.Assert(keys != null, "Check the arguments in the caller!");
             Debug.Assert(index >= 0 && length >= 0 && (keys.Length - index >= length), "Check the arguments in the caller!");
@@ -361,7 +362,7 @@ public void Sort(T[] keys, int index, int length, IComparer<T> comparer)
             }
         }
 
-        public int BinarySearch(T[] array, int index, int length, T value, IComparer<T> comparer)
+        public int BinarySearch(T[] array, int index, int length, T value, IComparer<T>? comparer)
         {
             Debug.Assert(array != null, "Check the arguments in the caller!");
             Debug.Assert(index >= 0 && length >= 0 && (array.Length - index >= length), "Check the arguments in the caller!");
@@ -624,7 +625,7 @@ private static void InsertionSort(T[] keys, int lo, int hi)
 
     internal partial class ArraySortHelper<TKey, TValue>
     {
-        public void Sort(TKey[] keys, TValue[] values, int index, int length, IComparer<TKey> comparer)
+        public void Sort(TKey[] keys, TValue[] values, int index, int length, IComparer<TKey>? comparer)
         {
             Debug.Assert(keys != null, "Check the arguments in the caller!");  // Precondition on interface method
             Debug.Assert(values != null, "Check the arguments in the caller!");
@@ -871,7 +872,7 @@ private static void InsertionSort(TKey[] keys, TValue[] values, int lo, int hi,
     internal partial class GenericArraySortHelper<TKey, TValue>
         where TKey : IComparable<TKey>
     {
-        public void Sort(TKey[] keys, TValue[] values, int index, int length, IComparer<TKey> comparer)
+        public void Sort(TKey[] keys, TValue[] values, int index, int length, IComparer<TKey>? comparer)
         {
             Debug.Assert(keys != null, "Check the arguments in the caller!");
             Debug.Assert(index >= 0 && length >= 0 && (keys.Length - index >= length), "Check the arguments in the caller!");

netcore/System.Private.CoreLib/shared/System/Collections/Generic/Comparer.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
 using System.Runtime.CompilerServices;
 using System.Runtime.Serialization;
 
@@ -21,9 +22,9 @@ public static Comparer<T> Create(Comparison<T> comparison)
             return new ComparisonComparer<T>(comparison);
         }
 
-        public abstract int Compare(T x, T y);
+        public abstract int Compare(T x, T y); // TODO-NULLABLE-GENERIC: x and y must be marked as nullable
 
-        int IComparer.Compare(object x, object y)
+        int IComparer.Compare(object? x, object? y)
         {
             if (x == null) return y == null ? 0 : -1;
             if (y == null) return 1;
@@ -58,7 +59,7 @@ public override int Compare(T x, T y)
     // Needs to be public to support binary serialization compatibility
     public sealed partial class GenericComparer<T> : Comparer<T> where T : IComparable<T>
     {
-        public override int Compare(T x, T y)
+        public override int Compare(T x, T y) // TODO-NULLABLE-GENERIC: x and y must be marked as nullable
         {
             if (x != null)
             {
@@ -70,7 +71,7 @@ public override int Compare(T x, T y)
         }
 
         // Equals method for the comparer itself. 
-        public override bool Equals(object obj) =>
+        public override bool Equals(object? obj) =>
             obj != null && GetType() == obj.GetType();
 
         public override int GetHashCode() =>
@@ -94,7 +95,7 @@ public override int Compare(T? x, T? y)
         }
 
         // Equals method for the comparer itself. 
-        public override bool Equals(object obj) =>
+        public override bool Equals(object? obj) =>
             obj != null && GetType() == obj.GetType();
 
         public override int GetHashCode() =>
@@ -106,13 +107,13 @@ public override int GetHashCode() =>
     // Needs to be public to support binary serialization compatibility
     public sealed partial class ObjectComparer<T> : Comparer<T>
     {
-        public override int Compare(T x, T y)
+        public override int Compare(T x, T y) // TODO-NULLABLE-GENERIC: x and y must be marked as nullable
         {
             return System.Collections.Comparer.Default.Compare(x, y);
         }
 
         // Equals method for the comparer itself. 
-        public override bool Equals(object obj) =>
+        public override bool Equals(object? obj) =>
             obj != null && GetType() == obj.GetType();
 
         public override int GetHashCode() =>
@@ -130,7 +131,7 @@ private EnumComparer(SerializationInfo info, StreamingContext context) { }
         // public override int Compare(T x, T y) is runtime-specific
 
         // Equals method for the comparer itself. 
-        public override bool Equals(object obj) =>
+        public override bool Equals(object? obj) =>
             obj != null && GetType() == obj.GetType();
 
         public override int GetHashCode() =>