Enable nullable reference types and annotate codebase

Enabled C# nullable reference types and updated all relevant code to use nullable annotations and null-forgiving operators where appropriate. Constructors, method signatures, and interface implementations now accept nullable parameters as needed. Updated default assignments and enumerator implementations to avoid nullable warnings. Added [DoesNotReturn] to ThrowHelper methods and improved exception handling for nullability. These changes enhance code safety and compatibility with modern C# nullability analysis.

Author: tolzy88

Collections.Pooled/Collections.Pooled.csproj

@@ -37,6 +37,7 @@
 	<IncludeContentInPack>true</IncludeContentInPack>
 	<GenerateDocumentationFile>true</GenerateDocumentationFile>
 	<IncludeSymbols>false</IncludeSymbols>
+	<Nullable>enable</Nullable>
 </PropertyGroup>
 
 </Project>

Collections.Pooled/HashHelpers.SerializationInfoTable.cs

@@ -5,15 +5,15 @@
 // Used by Hashtable and Dictionary's SeralizationInfo .ctor's to store the SeralizationInfo
 // object until OnDeserialization is called.
 
-using System.Threading;
 using System.Runtime.CompilerServices;
 using System.Runtime.Serialization;
+using System.Threading;
 
 namespace Collections.Pooled
 {
     internal static partial class HashHelpers
-    {        
-        private static ConditionalWeakTable<object, SerializationInfo> s_serializationInfoTable;
+    {
+        private static ConditionalWeakTable<object, SerializationInfo>? s_serializationInfoTable;
 
         public static ConditionalWeakTable<object, SerializationInfo> SerializationInfoTable
         {

Collections.Pooled/NonRandomizedStringEqualityComparer.cs

@@ -5,7 +5,6 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
-using System.Runtime.CompilerServices;
 using System.Runtime.Serialization;
 
 namespace Collections.Pooled
@@ -30,7 +29,7 @@ private NonRandomizedStringEqualityComparer(SerializationInfo information, Strea
 
         public sealed override bool Equals(string x, string y) => string.Equals(x, y);
 
-        public sealed override int GetHashCode(string str) 
+        public sealed override int GetHashCode(string str)
             => str is null ? 0 : str.Length == 0 ? s_empyStringHashCode : GetNonRandomizedHashCode(str);
 
         void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context)

Collections.Pooled/PooledDictionary.cs

@@ -42,7 +42,7 @@ public static PooledList<T> ToPooledList<T>(this Memory<T> memory)
         public static PooledDictionary<TKey, TValue> ToPooledDictionary<TSource, TKey, TValue>(
             this IEnumerable<TSource> source,
             Func<TSource, TKey> keySelector, Func<TSource, TValue> valueSelector,
-            IEqualityComparer<TKey> comparer = null)
+            IEqualityComparer<TKey>? comparer = null)
         {
             if (source == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.source);
@@ -62,7 +62,7 @@ public static PooledDictionary<TKey, TValue> ToPooledDictionary<TSource, TKey, T
         public static PooledDictionary<TKey, TValue> ToPooledDictionary<TSource, TKey, TValue>(
             this ReadOnlySpan<TSource> source,
             Func<TSource, TKey> keySelector, Func<TSource, TValue> valueSelector,
-            IEqualityComparer<TKey> comparer = null)
+            IEqualityComparer<TKey>? comparer = null)
         {
             var dict = new PooledDictionary<TKey, TValue>(source.Length, comparer);
             foreach (var item in source)
@@ -112,7 +112,7 @@ public static PooledDictionary<TKey, TValue> ToPooledDictionary<TSource, TKey, T
         /// </summary>
         public static PooledDictionary<TKey, TSource> ToPooledDictionary<TSource, TKey>(
             this IEnumerable<TSource> source,
-            Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer = null)
+            Func<TSource, TKey> keySelector, IEqualityComparer<TKey>? comparer = null)
         {
             if (source == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.source);
@@ -131,7 +131,7 @@ public static PooledDictionary<TKey, TSource> ToPooledDictionary<TSource, TKey>(
         /// </summary>
         public static PooledDictionary<TKey, TSource> ToPooledDictionary<TSource, TKey>(
             this ReadOnlySpan<TSource> source,
-            Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer = null)
+            Func<TSource, TKey> keySelector, IEqualityComparer<TKey>? comparer = null)
         {
             var dict = new PooledDictionary<TKey, TSource>(source.Length, comparer);
             foreach (var item in source)
@@ -147,7 +147,7 @@ public static PooledDictionary<TKey, TSource> ToPooledDictionary<TSource, TKey>(
         /// key selector and comparer.
         /// </summary>
         public static PooledDictionary<TKey, TSource> ToPooledDictionary<TSource, TKey>(this Span<TSource> source,
-            Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer = null)
+            Func<TSource, TKey> keySelector, IEqualityComparer<TKey>? comparer = null)
         {
             return ToPooledDictionary((ReadOnlySpan<TSource>)source, keySelector, comparer);
         }
@@ -158,7 +158,7 @@ public static PooledDictionary<TKey, TSource> ToPooledDictionary<TSource, TKey>(
         /// </summary>
         public static PooledDictionary<TKey, TSource> ToPooledDictionary<TSource, TKey>(
             this ReadOnlyMemory<TSource> source,
-            Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer = null)
+            Func<TSource, TKey> keySelector, IEqualityComparer<TKey>? comparer = null)
         {
             return ToPooledDictionary(source.Span, keySelector, comparer);
         }
@@ -168,7 +168,7 @@ public static PooledDictionary<TKey, TSource> ToPooledDictionary<TSource, TKey>(
         /// key selector and comparer.
         /// </summary>
         public static PooledDictionary<TKey, TSource> ToPooledDictionary<TSource, TKey>(this Memory<TSource> source,
-            Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer = null)
+            Func<TSource, TKey> keySelector, IEqualityComparer<TKey>? comparer = null)
         {
             return ToPooledDictionary(source.Span, keySelector, comparer);
         }
@@ -178,7 +178,7 @@ public static PooledDictionary<TKey, TSource> ToPooledDictionary<TSource, TKey>(
         /// </summary>
         public static PooledDictionary<TKey, TValue> ToPooledDictionary<TKey, TValue>(
             this IEnumerable<(TKey, TValue)> source,
-            IEqualityComparer<TKey> comparer = null)
+            IEqualityComparer<TKey>? comparer = null)
         {
             return new PooledDictionary<TKey, TValue>(source, comparer);
         }
@@ -188,7 +188,7 @@ public static PooledDictionary<TKey, TValue> ToPooledDictionary<TKey, TValue>(
         /// </summary>
         public static PooledDictionary<TKey, TValue> ToPooledDictionary<TKey, TValue>(
             this IEnumerable<KeyValuePair<TKey, TValue>> source,
-            IEqualityComparer<TKey> comparer = null)
+            IEqualityComparer<TKey>? comparer = null)
         {
             return new PooledDictionary<TKey, TValue>(source, comparer);
         }
@@ -198,7 +198,7 @@ public static PooledDictionary<TKey, TValue> ToPooledDictionary<TKey, TValue>(
         /// </summary>
         public static PooledDictionary<TKey, TValue> ToPooledDictionary<TKey, TValue>(
             this IEnumerable<Tuple<TKey, TValue>> source,
-            IEqualityComparer<TKey> comparer = null)
+            IEqualityComparer<TKey>? comparer = null)
         {
             if (source == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.source);
@@ -217,7 +217,7 @@ public static PooledDictionary<TKey, TValue> ToPooledDictionary<TKey, TValue>(
         /// </summary>
         public static PooledDictionary<TKey, TValue> ToPooledDictionary<TKey, TValue>(
             this ReadOnlySpan<(TKey, TValue)> source,
-            IEqualityComparer<TKey> comparer = null)
+            IEqualityComparer<TKey>? comparer = null)
         {
             return new PooledDictionary<TKey, TValue>(source, comparer);
         }
@@ -226,7 +226,7 @@ public static PooledDictionary<TKey, TValue> ToPooledDictionary<TKey, TValue>(
         /// Creates a <see cref="PooledDictionary{TKey,TValue}"/> from a span of key/value tuples.
         /// </summary>
         public static PooledDictionary<TKey, TValue> ToPooledDictionary<TKey, TValue>(this Span<(TKey, TValue)> source,
-            IEqualityComparer<TKey> comparer = null)
+            IEqualityComparer<TKey>? comparer = null)
         {
             return new PooledDictionary<TKey, TValue>(source, comparer);
         }
@@ -235,19 +235,19 @@ public static PooledDictionary<TKey, TValue> ToPooledDictionary<TKey, TValue>(th
 
         #region PooledSet
 
-        public static PooledSet<T> ToPooledSet<T>(this IEnumerable<T> source, IEqualityComparer<T> comparer = null)
+        public static PooledSet<T> ToPooledSet<T>(this IEnumerable<T> source, IEqualityComparer<T>? comparer = null)
             => new PooledSet<T>(source, comparer);
 
-        public static PooledSet<T> ToPooledSet<T>(this Span<T> source, IEqualityComparer<T> comparer = null)
+        public static PooledSet<T> ToPooledSet<T>(this Span<T> source, IEqualityComparer<T>? comparer = null)
             => new PooledSet<T>(source, comparer);
 
-        public static PooledSet<T> ToPooledSet<T>(this ReadOnlySpan<T> source, IEqualityComparer<T> comparer = null)
+        public static PooledSet<T> ToPooledSet<T>(this ReadOnlySpan<T> source, IEqualityComparer<T>? comparer = null)
             => new PooledSet<T>(source, comparer);
 
-        public static PooledSet<T> ToPooledSet<T>(this Memory<T> source, IEqualityComparer<T> comparer = null)
+        public static PooledSet<T> ToPooledSet<T>(this Memory<T> source, IEqualityComparer<T>? comparer = null)
             => new PooledSet<T>(source.Span, comparer);
 
-        public static PooledSet<T> ToPooledSet<T>(this ReadOnlyMemory<T> source, IEqualityComparer<T> comparer = null)
+        public static PooledSet<T> ToPooledSet<T>(this ReadOnlyMemory<T> source, IEqualityComparer<T>? comparer = null)
             => new PooledSet<T>(source.Span, comparer);
 
         #endregion

Collections.Pooled/PooledExtensions.cs

@@ -37,7 +37,7 @@ public class PooledList<T> : IList<T>, IReadOnlyPooledList<T>, IList, IDisposabl
         private static readonly T[] s_emptyArray = Array.Empty<T>();
 
         [NonSerialized] private ArrayPool<T> _pool;
-        [NonSerialized] private object _syncRoot;
+        [NonSerialized] private object? _syncRoot;
 
         private T[] _items; // Do not rename (binary serialization)
         private int _size; // Do not rename (binary serialization)
@@ -334,59 +334,59 @@ public PooledList(IEnumerable<T> collection, ClearMode clearMode, ArrayPool<T> c
                     break;
 
                 case ICollection<T> c:
-                {
-                    int count = c.Count;
-                    if (count == 0)
-                    {
-                        _items = s_emptyArray;
-                    }
-                    else
                     {
-                        _items = _pool.Rent(count);
-                        c.CopyTo(_items, 0);
-                        _size = count;
-                    }
+                        int count = c.Count;
+                        if (count == 0)
+                        {
+                            _items = s_emptyArray;
+                        }
+                        else
+                        {
+                            _items = _pool.Rent(count);
+                            c.CopyTo(_items, 0);
+                            _size = count;
+                        }
 
-                    break;
-                }
+                        break;
+                    }
 
                 case ICollection c:
-                {
-                    int count = c.Count;
-                    if (count == 0)
                     {
-                        _items = s_emptyArray;
-                    }
-                    else
-                    {
-                        _items = _pool.Rent(count);
-                        c.CopyTo(_items, 0);
-                        _size = count;
-                    }
+                        int count = c.Count;
+                        if (count == 0)
+                        {
+                            _items = s_emptyArray;
+                        }
+                        else
+                        {
+                            _items = _pool.Rent(count);
+                            c.CopyTo(_items, 0);
+                            _size = count;
+                        }
 
-                    break;
-                }
+                        break;
+                    }
 
                 case IReadOnlyCollection<T> c:
-                {
-                    int count = c.Count;
-                    if (count == 0)
-                    {
-                        _items = s_emptyArray;
-                    }
-                    else
                     {
-                        _items = _pool.Rent(count);
-                        _size = 0;
-                        using (var en = c.GetEnumerator())
+                        int count = c.Count;
+                        if (count == 0)
                         {
-                            while (en.MoveNext())
-                                Add(en.Current);
+                            _items = s_emptyArray;
+                        }
+                        else
+                        {
+                            _items = _pool.Rent(count);
+                            _size = 0;
+                            using (var en = c.GetEnumerator())
+                            {
+                                while (en.MoveNext())
+                                    Add(en.Current);
+                            }
                         }
-                    }
 
-                    break;
-                }
+                        break;
+                    }
 
                 default:
 
@@ -490,7 +490,7 @@ object ICollection.SyncRoot
             {
                 if (_syncRoot == null)
                 {
-                    Interlocked.CompareExchange<object>(ref _syncRoot, new object(), null);
+                    Interlocked.CompareExchange<object?>(ref _syncRoot, new object(), null);
                 }
 
                 return _syncRoot;
@@ -532,20 +532,20 @@ private static bool IsCompatibleObject(object value)
             return ((value is T) || (value == null && default(T) == null));
         }
 
-        object IList.this[int index]
+        object? IList.this[int index]
         {
             get { return this[index]; }
             set
             {
-                ThrowHelper.IfNullAndNullsAreIllegalThenThrow<T>(value, ExceptionArgument.value);
+                ThrowHelper.IfNullAndNullsAreIllegalThenThrow<T>(value!, ExceptionArgument.value);
 
                 try
                 {
-                    this[index] = (T)value;
+                    this[index] = (T)value!;
                 }
                 catch (InvalidCastException)
                 {
-                    ThrowHelper.ThrowWrongValueTypeArgumentException(value, typeof(T));
+                    ThrowHelper.ThrowWrongValueTypeArgumentException(value!, typeof(T));
                 }
             }
         }
@@ -677,7 +677,7 @@ public int BinarySearch(int index, int count, T item, IComparer<T> comparer)
         /// then that is used for comparison, otherwise <see cref="Comparer{T}.Default"/> is used.
         /// </summary>
         public int BinarySearch(T item)
-            => BinarySearch(0, Count, item, null);
+            => BinarySearch(0, Count, item, null!);
 
         /// <summary>
         /// Searches the list for a given element using a binary search
@@ -821,7 +821,7 @@ public bool TryFind(Func<T, bool> match, out T result)
                 }
             }
 
-            result = default;
+            result = default!;
             return false;
         }
 
@@ -884,7 +884,7 @@ public bool TryFindLast(Func<T, bool> match, out T result)
                 }
             }
 
-            result = default;
+            result = default!;
             return false;
         }
 
@@ -1350,7 +1350,7 @@ public void RemoveAt(int index)
             if (_clearOnFree)
             {
                 // Clear the removed element so that the gc can reclaim the reference.
-                _items[_size] = default;
+                _items[_size] = default!;
             }
         }
 
@@ -1424,7 +1424,7 @@ public void Reverse(int index, int count)
         /// Array.Sort.
         /// </summary>
         public void Sort()
-            => Sort(0, Count, null);
+            => Sort(0, Count, null!);
 
         /// <summary>
         /// Sorts the elements in this list.  Uses Array.Sort with the
@@ -1587,7 +1587,7 @@ internal Enumerator(PooledList<T> list)
                 _list = list;
                 _index = 0;
                 _version = list._version;
-                _current = default;
+                _current = default!;
             }
 
             public void Dispose()
@@ -1616,13 +1616,13 @@ private bool MoveNextRare()
                 }
 
                 _index = _list._size + 1;
-                _current = default;
+                _current = default!;
                 return false;
             }
 
             public T Current => _current;
 
-            object IEnumerator.Current
+            object? IEnumerator.Current
             {
                 get
                 {
@@ -1643,7 +1643,7 @@ void IEnumerator.Reset()
                 }
 
                 _index = 0;
-                _current = default;
+                _current = default!;
             }
         }