From e083b2a4ab3045450005645dab8c009574a75d58 Mon Sep 17 00:00:00 2001
From: Stephen Toub <stoub@microsoft.com>
Date: Wed, 12 Jun 2019 15:09:49 -0400
Subject: [PATCH] Replace 'where T : object` with `where T : notnull`

---
 .../Collections/ObjectModel/ReadOnlyDictionary.cs    |  2 +-
 .../Runtime/InteropServices/Marshal.CoreCLR.cs       |  2 +-
 .../WindowsRuntime/ConstantSplittableMap.cs          |  2 +-
 .../WindowsRuntime/DictionaryKeyCollection.cs        |  4 ++--
 .../WindowsRuntime/DictionaryToMapAdapter.cs         | 14 +++++++-------
 .../WindowsRuntime/DictionaryValueCollection.cs      |  4 ++--
 .../Runtime/InteropServices/WindowsRuntime/IMap.cs   |  2 +-
 .../IMapViewToIReadOnlyDictionaryAdapter.cs          | 16 ++++++++--------
 .../IReadOnlyDictionaryToIMapViewAdapter.cs          |  8 ++++----
 .../WindowsRuntime/MapToCollectionAdapter.cs         | 14 +++++++-------
 .../WindowsRuntime/MapToDictionaryAdapter.cs         | 20 ++++++++++----------
 11 files changed, 44 insertions(+), 44 deletions(-)

diff --git a/src/System.Private.CoreLib/src/System/Collections/ObjectModel/ReadOnlyDictionary.cs b/src/System.Private.CoreLib/src/System/Collections/ObjectModel/ReadOnlyDictionary.cs
index 2a455a4..c1de2ae 100644
--- a/src/System.Private.CoreLib/src/System/Collections/ObjectModel/ReadOnlyDictionary.cs
+++ b/src/System.Private.CoreLib/src/System/Collections/ObjectModel/ReadOnlyDictionary.cs
@@ -20,7 +20,7 @@ namespace System.Collections.ObjectModel
 {
     [DebuggerTypeProxy(typeof(IDictionaryDebugView<,>))]
     [DebuggerDisplay("Count = {Count}")]
-    internal class ReadOnlyDictionary<TKey, TValue> : IDictionary<TKey, TValue>, IDictionary, IReadOnlyDictionary<TKey, TValue> where TKey : object
+    internal class ReadOnlyDictionary<TKey, TValue> : IDictionary<TKey, TValue>, IDictionary, IReadOnlyDictionary<TKey, TValue> where TKey : notnull
     {
         private readonly IDictionary<TKey, TValue> m_dictionary;
         private object? m_syncRoot;
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/Marshal.CoreCLR.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/Marshal.CoreCLR.cs
index 6df19ae..a57d287 100644
--- a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/Marshal.CoreCLR.cs
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/Marshal.CoreCLR.cs
@@ -388,7 +388,7 @@ namespace System.Runtime.InteropServices
         [MethodImpl(MethodImplOptions.InternalCall)]
         public static extern IntPtr CreateAggregatedObject(IntPtr pOuter, object o);
 
-        public static IntPtr CreateAggregatedObject<T>(IntPtr pOuter, T o) where T : object
+        public static IntPtr CreateAggregatedObject<T>(IntPtr pOuter, T o) where T : notnull
         {
             return CreateAggregatedObject(pOuter, (object)o);
         }
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/ConstantSplittableMap.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/ConstantSplittableMap.cs
index 9f5f99b..3d228ab 100644
--- a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/ConstantSplittableMap.cs
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/ConstantSplittableMap.cs
@@ -19,7 +19,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
     /// <typeparam name="TKey">Type of objects that act as keys.</typeparam>    
     /// <typeparam name="TValue">Type of objects that act as entries / values.</typeparam>
     [DebuggerDisplay("Count = {Count}")]
-    internal sealed class ConstantSplittableMap<TKey, TValue> : IMapView<TKey, TValue> where TKey : object
+    internal sealed class ConstantSplittableMap<TKey, TValue> : IMapView<TKey, TValue> where TKey : notnull
     {
         private class KeyValuePairComparator : IComparer<KeyValuePair<TKey, TValue>>
         {
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/DictionaryKeyCollection.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/DictionaryKeyCollection.cs
index 11f3ab2..f78bf0d 100644
--- a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/DictionaryKeyCollection.cs
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/DictionaryKeyCollection.cs
@@ -9,7 +9,7 @@ using System.Diagnostics;
 namespace System.Runtime.InteropServices.WindowsRuntime
 {
     [DebuggerDisplay("Count = {Count}")]
-    internal sealed class DictionaryKeyCollection<TKey, TValue> : ICollection<TKey> where TKey : object
+    internal sealed class DictionaryKeyCollection<TKey, TValue> : ICollection<TKey> where TKey : notnull
     {
         private readonly IDictionary<TKey, TValue> dictionary;
 
@@ -81,7 +81,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
     }  // public class DictionaryKeyCollection<TKey, TValue>
 
 
-    internal sealed class DictionaryKeyEnumerator<TKey, TValue> : IEnumerator<TKey> where TKey : object
+    internal sealed class DictionaryKeyEnumerator<TKey, TValue> : IEnumerator<TKey> where TKey : notnull
     {
         private readonly IDictionary<TKey, TValue> dictionary;
         private IEnumerator<KeyValuePair<TKey, TValue>> enumeration;
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/DictionaryToMapAdapter.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/DictionaryToMapAdapter.cs
index 57482f9..0feb7a1 100644
--- a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/DictionaryToMapAdapter.cs
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/DictionaryToMapAdapter.cs
@@ -25,7 +25,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
         }
 
         // V Lookup(K key)
-        internal V Lookup<K, V>(K key) where K : object
+        internal V Lookup<K, V>(K key) where K : notnull
         {
             IDictionary<K, V> _this = Unsafe.As<IDictionary<K, V>>(this);
             V value;
@@ -43,21 +43,21 @@ namespace System.Runtime.InteropServices.WindowsRuntime
         }
 
         // uint Size { get }
-        internal uint Size<K, V>() where K : object
+        internal uint Size<K, V>() where K : notnull
         {
             IDictionary<K, V> _this = Unsafe.As<IDictionary<K, V>>(this);
             return (uint)_this.Count;
         }
 
         // bool HasKey(K key)
-        internal bool HasKey<K, V>(K key) where K : object
+        internal bool HasKey<K, V>(K key) where K : notnull
         {
             IDictionary<K, V> _this = Unsafe.As<IDictionary<K, V>>(this);
             return _this.ContainsKey(key);
         }
 
         // IMapView<K, V> GetView()
-        internal IReadOnlyDictionary<K, V> GetView<K, V>() where K : object
+        internal IReadOnlyDictionary<K, V> GetView<K, V>() where K : notnull
         {
             IDictionary<K, V> _this = Unsafe.As<IDictionary<K, V>>(this);
             Debug.Assert(_this != null);
@@ -72,7 +72,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
         }
 
         // bool Insert(K key, V value)
-        internal bool Insert<K, V>(K key, V value) where K : object
+        internal bool Insert<K, V>(K key, V value) where K : notnull
         {
             IDictionary<K, V> _this = Unsafe.As<IDictionary<K, V>>(this);
             bool replacing = _this.ContainsKey(key);
@@ -81,7 +81,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
         }
 
         // void Remove(K key)
-        internal void Remove<K, V>(K key) where K : object
+        internal void Remove<K, V>(K key) where K : notnull
         {
             IDictionary<K, V> _this = Unsafe.As<IDictionary<K, V>>(this);
             bool removed = _this.Remove(key);
@@ -96,7 +96,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
         }
 
         // void Clear()
-        internal void Clear<K, V>() where K : object
+        internal void Clear<K, V>() where K : notnull
         {
             IDictionary<K, V> _this = Unsafe.As<IDictionary<K, V>>(this);
             _this.Clear();
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/DictionaryValueCollection.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/DictionaryValueCollection.cs
index 9860efc..dd111ff 100644
--- a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/DictionaryValueCollection.cs
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/DictionaryValueCollection.cs
@@ -9,7 +9,7 @@ using System.Diagnostics;
 namespace System.Runtime.InteropServices.WindowsRuntime
 {
     [DebuggerDisplay("Count = {Count}")]
-    internal sealed class DictionaryValueCollection<TKey, TValue> : ICollection<TValue> where TKey : object
+    internal sealed class DictionaryValueCollection<TKey, TValue> : ICollection<TValue> where TKey : notnull
     {
         private readonly IDictionary<TKey, TValue> dictionary;
 
@@ -85,7 +85,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
     }  // public class DictionaryValueCollection<TKey, TValue>
 
 
-    internal sealed class DictionaryValueEnumerator<TKey, TValue> : IEnumerator<TValue> where TKey : object
+    internal sealed class DictionaryValueEnumerator<TKey, TValue> : IEnumerator<TValue> where TKey : notnull
     {
         private readonly IDictionary<TKey, TValue> dictionary;
         private IEnumerator<KeyValuePair<TKey, TValue>> enumeration;
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IMap.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IMap.cs
index 4dfdbbb..164350a 100644
--- a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IMap.cs
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IMap.cs
@@ -13,7 +13,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
     [ComImport]
     [Guid("3c2925fe-8519-45c1-aa79-197b6718c1c1")]
     [WindowsRuntimeImport]
-    internal interface IMap<K, V> : IIterable<IKeyValuePair<K, V>> where K : object
+    internal interface IMap<K, V> : IIterable<IKeyValuePair<K, V>> where K : notnull
     {
         V Lookup(K key);
         uint Size { get; }
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IMapViewToIReadOnlyDictionaryAdapter.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IMapViewToIReadOnlyDictionaryAdapter.cs
index 7a8b11b..d0b9aa4 100644
--- a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IMapViewToIReadOnlyDictionaryAdapter.cs
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IMapViewToIReadOnlyDictionaryAdapter.cs
@@ -37,7 +37,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
         }
 
         // IEnumerable<K> Keys { get }
-        internal IEnumerable<K> Keys<K, V>() where K : object
+        internal IEnumerable<K> Keys<K, V>() where K : notnull
         {
             IMapView<K, V> _this = Unsafe.As<IMapView<K, V>>(this);
             IReadOnlyDictionary<K, V> roDictionary = (IReadOnlyDictionary<K, V>)_this;
@@ -45,7 +45,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
         }
 
         // IEnumerable<V> Values { get }
-        internal IEnumerable<V> Values<K, V>() where K : object
+        internal IEnumerable<V> Values<K, V>() where K : notnull
         {
             IMapView<K, V> _this = Unsafe.As<IMapView<K, V>>(this);
             IReadOnlyDictionary<K, V> roDictionary = (IReadOnlyDictionary<K, V>)_this;
@@ -53,7 +53,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
         }
 
         // bool ContainsKey(K key)
-        internal bool ContainsKey<K, V>(K key) where K : object
+        internal bool ContainsKey<K, V>(K key) where K : notnull
         {
             if (key == null)
                 throw new ArgumentNullException(nameof(key));
@@ -63,7 +63,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
         }
 
         // bool TryGetValue(TKey key, out TValue value)
-        internal bool TryGetValue<K, V>(K key, [MaybeNullWhen(false)] out V value) where K : object
+        internal bool TryGetValue<K, V>(K key, [MaybeNullWhen(false)] out V value) where K : notnull
         {
             if (key == null)
                 throw new ArgumentNullException(nameof(key));
@@ -117,7 +117,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
 
     // Note: One day we may make these return IReadOnlyCollection<T>
     [DebuggerDisplay("Count = {Count}")]
-    internal sealed class ReadOnlyDictionaryKeyCollection<TKey, TValue> : IEnumerable<TKey> where TKey : object
+    internal sealed class ReadOnlyDictionaryKeyCollection<TKey, TValue> : IEnumerable<TKey> where TKey : notnull
     {
         private readonly IReadOnlyDictionary<TKey, TValue> dictionary;
 
@@ -170,7 +170,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
     }  // public class ReadOnlyDictionaryKeyCollection<TKey, TValue>
 
 
-    internal sealed class ReadOnlyDictionaryKeyEnumerator<TKey, TValue> : IEnumerator<TKey> where TKey : object
+    internal sealed class ReadOnlyDictionaryKeyEnumerator<TKey, TValue> : IEnumerator<TKey> where TKey : notnull
     {
         private readonly IReadOnlyDictionary<TKey, TValue> dictionary;
         private IEnumerator<KeyValuePair<TKey, TValue>> enumeration;
@@ -212,7 +212,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
 
 
     [DebuggerDisplay("Count = {Count}")]
-    internal sealed class ReadOnlyDictionaryValueCollection<TKey, TValue> : IEnumerable<TValue> where TKey : object
+    internal sealed class ReadOnlyDictionaryValueCollection<TKey, TValue> : IEnumerable<TValue> where TKey : notnull
     {
         private readonly IReadOnlyDictionary<TKey, TValue> dictionary;
 
@@ -269,7 +269,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
     }  // public class ReadOnlyDictionaryValueCollection<TKey, TValue>
 
 
-    internal sealed class ReadOnlyDictionaryValueEnumerator<TKey, TValue> : IEnumerator<TValue> where TKey : object
+    internal sealed class ReadOnlyDictionaryValueEnumerator<TKey, TValue> : IEnumerator<TValue> where TKey : notnull
     {
         private readonly IReadOnlyDictionary<TKey, TValue> dictionary;
         private IEnumerator<KeyValuePair<TKey, TValue>> enumeration;
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IReadOnlyDictionaryToIMapViewAdapter.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IReadOnlyDictionaryToIMapViewAdapter.cs
index 2327e7c..ae4c80f 100644
--- a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IReadOnlyDictionaryToIMapViewAdapter.cs
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IReadOnlyDictionaryToIMapViewAdapter.cs
@@ -25,7 +25,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
         }
 
         // V Lookup(K key)
-        internal V Lookup<K, V>(K key) where K : object
+        internal V Lookup<K, V>(K key) where K : notnull
         {
             IReadOnlyDictionary<K, V> _this = Unsafe.As<IReadOnlyDictionary<K, V>>(this);
             V value;
@@ -43,21 +43,21 @@ namespace System.Runtime.InteropServices.WindowsRuntime
         }
 
         // uint Size { get }
-        internal uint Size<K, V>() where K : object
+        internal uint Size<K, V>() where K : notnull
         {
             IReadOnlyDictionary<K, V> _this = Unsafe.As<IReadOnlyDictionary<K, V>>(this);
             return (uint)_this.Count;
         }
 
         // bool HasKey(K key)
-        internal bool HasKey<K, V>(K key) where K : object
+        internal bool HasKey<K, V>(K key) where K : notnull
         {
             IReadOnlyDictionary<K, V> _this = Unsafe.As<IReadOnlyDictionary<K, V>>(this);
             return _this.ContainsKey(key);
         }
 
         // void Split(out IMapView<K, V> first, out IMapView<K, V> second)
-        internal void Split<K, V>(out IMapView<K, V>? first, out IMapView<K, V>? second) where K : object
+        internal void Split<K, V>(out IMapView<K, V>? first, out IMapView<K, V>? second) where K : notnull
         {
             IReadOnlyDictionary<K, V> _this = Unsafe.As<IReadOnlyDictionary<K, V>>(this);
 
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/MapToCollectionAdapter.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/MapToCollectionAdapter.cs
index 9dd1abe..7183c46 100644
--- a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/MapToCollectionAdapter.cs
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/MapToCollectionAdapter.cs
@@ -27,7 +27,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
         }
 
         // int Count { get }
-        internal int Count<K, V>() where K : object
+        internal int Count<K, V>() where K : notnull
         {
             object _this = Unsafe.As<object>(this);
 
@@ -57,13 +57,13 @@ namespace System.Runtime.InteropServices.WindowsRuntime
         }
 
         // bool IsReadOnly { get }
-        internal bool IsReadOnly<K, V>() where K : object
+        internal bool IsReadOnly<K, V>() where K : notnull
         {
             return false;
         }
 
         // void Add(T item)
-        internal void Add<K, V>(KeyValuePair<K, V> item) where K : object
+        internal void Add<K, V>(KeyValuePair<K, V> item) where K : notnull
         {
             object _this = Unsafe.As<object>(this);
 
@@ -79,7 +79,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
         }
 
         // void Clear()
-        internal void Clear<K, V>() where K : object
+        internal void Clear<K, V>() where K : notnull
         {
             object _this = Unsafe.As<object>(this);
 
@@ -95,7 +95,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
         }
 
         // bool Contains(T item)
-        internal bool Contains<K, V>(KeyValuePair<K, V> item) where K : object
+        internal bool Contains<K, V>(KeyValuePair<K, V> item) where K : notnull
         {
             object _this = Unsafe.As<object>(this);
 
@@ -119,7 +119,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
         }
 
         // void CopyTo(T[] array, int arrayIndex)
-        internal void CopyTo<K, V>(KeyValuePair<K, V>[] array, int arrayIndex) where K : object
+        internal void CopyTo<K, V>(KeyValuePair<K, V>[] array, int arrayIndex) where K : notnull
         {
             if (array == null)
                 throw new ArgumentNullException(nameof(array));
@@ -142,7 +142,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
         }
 
         // bool Remove(T item)
-        internal bool Remove<K, V>(KeyValuePair<K, V> item) where K : object
+        internal bool Remove<K, V>(KeyValuePair<K, V> item) where K : notnull
         {
             object _this = Unsafe.As<object>(this);
 
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/MapToDictionaryAdapter.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/MapToDictionaryAdapter.cs
index e0ad2d7..7ab9288 100644
--- a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/MapToDictionaryAdapter.cs
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/MapToDictionaryAdapter.cs
@@ -25,7 +25,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
         }
 
         // V this[K key] { get }
-        internal V Indexer_Get<K, V>(K key) where K : object
+        internal V Indexer_Get<K, V>(K key) where K : notnull
         {
             if (key == null)
                 throw new ArgumentNullException(nameof(key));
@@ -36,7 +36,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
         }
 
         // V this[K key] { set }
-        internal void Indexer_Set<K, V>(K key, V value) where K : object
+        internal void Indexer_Set<K, V>(K key, V value) where K : notnull
         {
             if (key == null)
                 throw new ArgumentNullException(nameof(key));
@@ -47,7 +47,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
         }
 
         // ICollection<K> Keys { get }
-        internal ICollection<K> Keys<K, V>() where K : object
+        internal ICollection<K> Keys<K, V>() where K : notnull
         {
             IMap<K, V> _this = Unsafe.As<IMap<K, V>>(this);
             IDictionary<K, V> dictionary = (IDictionary<K, V>)_this;
@@ -55,7 +55,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
         }
 
         // ICollection<V> Values { get }
-        internal ICollection<V> Values<K, V>() where K : object
+        internal ICollection<V> Values<K, V>() where K : notnull
         {
             IMap<K, V> _this = Unsafe.As<IMap<K, V>>(this);
             IDictionary<K, V> dictionary = (IDictionary<K, V>)_this;
@@ -63,7 +63,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
         }
 
         // bool ContainsKey(K key)
-        internal bool ContainsKey<K, V>(K key) where K : object
+        internal bool ContainsKey<K, V>(K key) where K : notnull
         {
             if (key == null)
                 throw new ArgumentNullException(nameof(key));
@@ -73,7 +73,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
         }
 
         // void Add(K key, V value)
-        internal void Add<K, V>(K key, V value) where K : object
+        internal void Add<K, V>(K key, V value) where K : notnull
         {
             if (key == null)
                 throw new ArgumentNullException(nameof(key));
@@ -87,7 +87,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
         }
 
         // bool Remove(TKey key)
-        internal bool Remove<K, V>(K key) where K : object
+        internal bool Remove<K, V>(K key) where K : notnull
         {
             if (key == null)
                 throw new ArgumentNullException(nameof(key));
@@ -111,7 +111,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
         }
 
         // bool TryGetValue(TKey key, out TValue value)
-        internal bool TryGetValue<K, V>(K key, [MaybeNullWhen(false)] out V value) where K : object
+        internal bool TryGetValue<K, V>(K key, [MaybeNullWhen(false)] out V value) where K : notnull
         {
             if (key == null)
                 throw new ArgumentNullException(nameof(key));
@@ -137,7 +137,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
 
         // Helpers:
 
-        private static V Lookup<K, V>(IMap<K, V> _this, K key) where K : object
+        private static V Lookup<K, V>(IMap<K, V> _this, K key) where K : notnull
         {
             Debug.Assert(null != key);
 
@@ -153,7 +153,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
             }
         }
 
-        private static bool Insert<K, V>(IMap<K, V> _this, K key, V value) where K : object
+        private static bool Insert<K, V>(IMap<K, V> _this, K key, V value) where K : notnull
         {
             Debug.Assert(null != key);
 
-- 
2.7.4