From e70e71b16c665e98cb48f464fdc3ab37c614f916 Mon Sep 17 00:00:00 2001
From: Stefan Nikolei <stefan@nikolei.eu>
Date: Wed, 25 Jan 2023 10:57:29 +0100
Subject: [PATCH 1/8] Remove nullable disable from Memory.Allocators

#2231
---
 .../Memory/Allocators/Internals/Gen2GcCallback.cs  | 11 +++++------
 .../Allocators/Internals/ManagedBufferBase.cs      |  2 +-
 .../Internals/RefCountedMemoryLifetimeGuard.cs     |  3 +--
 .../Internals/SharedArrayPoolBuffer{T}.cs          |  6 ++----
 .../Internals/UniformUnmanagedMemoryPool.cs        |  7 +++----
 .../Allocators/Internals/UnmanagedMemoryHandle.cs  | 11 +++++------
 .../UniformUnmanagedMemoryPoolMemoryAllocator.cs   |  2 +-
 src/ImageSharp/Memory/Buffer2DExtensions.cs        |  2 +-
 src/ImageSharp/Memory/Buffer2D{T}.cs               |  4 ++--
 .../DiscontiguousBuffers/MemoryGroupExtensions.cs  |  2 +-
 .../DiscontiguousBuffers/MemoryGroupSpanCache.cs   |  2 +-
 .../DiscontiguousBuffers/MemoryGroupView{T}.cs     |  6 ++++--
 .../MemoryGroup{T}.Consumed.cs                     |  2 +-
 .../DiscontiguousBuffers/MemoryGroup{T}.Owned.cs   | 14 ++++++++------
 .../Memory/DiscontiguousBuffers/MemoryGroup{T}.cs  |  8 ++++----
 15 files changed, 40 insertions(+), 42 deletions(-)

diff --git a/src/ImageSharp/Memory/Allocators/Internals/Gen2GcCallback.cs b/src/ImageSharp/Memory/Allocators/Internals/Gen2GcCallback.cs
index 547f67d6a..c0737a114 100644
--- a/src/ImageSharp/Memory/Allocators/Internals/Gen2GcCallback.cs
+++ b/src/ImageSharp/Memory/Allocators/Internals/Gen2GcCallback.cs
@@ -1,6 +1,5 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
-#nullable disable
 
 // Port of BCL internal utility:
 // https://github.com/dotnet/runtime/blob/57bfe474518ab5b7cfe6bf7424a79ce3af9d6657/src/libraries/System.Private.CoreLib/src/System/Gen2GcCallback.cs
@@ -15,8 +14,8 @@ namespace SixLabors.ImageSharp.Memory.Internals;
 /// </summary>
 internal sealed class Gen2GcCallback : CriticalFinalizerObject
 {
-    private readonly Func<bool> callback0;
-    private readonly Func<object, bool> callback1;
+    private readonly Func<bool>? callback0;
+    private readonly Func<object, bool>? callback1;
     private GCHandle weakTargetObj;
 
     private Gen2GcCallback(Func<bool> callback) => this.callback0 = callback;
@@ -32,7 +31,7 @@ internal sealed class Gen2GcCallback : CriticalFinalizerObject
         if (this.weakTargetObj.IsAllocated)
         {
             // Check to see if the target object is still alive.
-            object targetObj = this.weakTargetObj.Target;
+            object? targetObj = this.weakTargetObj.Target;
             if (targetObj == null)
             {
                 // The target object is dead, so this callback object is no longer needed.
@@ -43,7 +42,7 @@ internal sealed class Gen2GcCallback : CriticalFinalizerObject
             // Execute the callback method.
             try
             {
-                if (!this.callback1(targetObj))
+                if (this.callback1 is not null && !this.callback1(targetObj))
                 {
                     // If the callback returns false, this callback object is no longer needed.
                     this.weakTargetObj.Free();
@@ -64,7 +63,7 @@ internal sealed class Gen2GcCallback : CriticalFinalizerObject
             // Execute the callback method.
             try
             {
-                if (!this.callback0())
+                if (this.callback0 is not null && !this.callback0())
                 {
                     // If the callback returns false, this callback object is no longer needed.
                     return;
diff --git a/src/ImageSharp/Memory/Allocators/Internals/ManagedBufferBase.cs b/src/ImageSharp/Memory/Allocators/Internals/ManagedBufferBase.cs
index a18bd3447..be4cb8c8e 100644
--- a/src/ImageSharp/Memory/Allocators/Internals/ManagedBufferBase.cs
+++ b/src/ImageSharp/Memory/Allocators/Internals/ManagedBufferBase.cs
@@ -43,5 +43,5 @@ internal abstract class ManagedBufferBase<T> : MemoryManager<T>
     /// Gets the object that should be pinned.
     /// </summary>
     /// <returns>The pinnable <see cref="object"/>.</returns>
-    protected abstract object GetPinnableObject();
+    protected abstract object? GetPinnableObject();
 }
diff --git a/src/ImageSharp/Memory/Allocators/Internals/RefCountedMemoryLifetimeGuard.cs b/src/ImageSharp/Memory/Allocators/Internals/RefCountedMemoryLifetimeGuard.cs
index aed5d03e4..4a202a96c 100644
--- a/src/ImageSharp/Memory/Allocators/Internals/RefCountedMemoryLifetimeGuard.cs
+++ b/src/ImageSharp/Memory/Allocators/Internals/RefCountedMemoryLifetimeGuard.cs
@@ -1,6 +1,5 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
-#nullable disable
 
 using SixLabors.ImageSharp.Diagnostics;
 
@@ -15,7 +14,7 @@ internal abstract class RefCountedMemoryLifetimeGuard : IDisposable
     private int refCount = 1;
     private int disposed;
     private int released;
-    private string allocationStackTrace;
+    private string? allocationStackTrace;
 
     protected RefCountedMemoryLifetimeGuard()
     {
diff --git a/src/ImageSharp/Memory/Allocators/Internals/SharedArrayPoolBuffer{T}.cs b/src/ImageSharp/Memory/Allocators/Internals/SharedArrayPoolBuffer{T}.cs
index 166992266..1d73b2ddf 100644
--- a/src/ImageSharp/Memory/Allocators/Internals/SharedArrayPoolBuffer{T}.cs
+++ b/src/ImageSharp/Memory/Allocators/Internals/SharedArrayPoolBuffer{T}.cs
@@ -1,6 +1,5 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
-#nullable disable
 
 using System.Buffers;
 using System.Diagnostics;
@@ -22,7 +21,7 @@ internal class SharedArrayPoolBuffer<T> : ManagedBufferBase<T>, IRefCounted
         this.lifetimeGuard = new LifetimeGuard(this.Array);
     }
 
-    public byte[] Array { get; private set; }
+    public byte[]? Array { get; private set; }
 
     protected override void Dispose(bool disposing)
     {
@@ -41,7 +40,7 @@ internal class SharedArrayPoolBuffer<T> : ManagedBufferBase<T>, IRefCounted
         return MemoryMarshal.Cast<byte, T>(this.Array.AsSpan(0, this.lengthInBytes));
     }
 
-    protected override object GetPinnableObject() => this.Array;
+    protected override object? GetPinnableObject() => this.Array;
 
     public void AddRef()
     {
@@ -74,7 +73,6 @@ internal class SharedArrayPoolBuffer<T> : ManagedBufferBase<T>, IRefCounted
             // meaning likely a different bucket than it was rented from,
             // but this is PROBABLY better than not returning the arrays at all.
             ArrayPool<byte>.Shared.Return(this.array);
-            this.array = null;
         }
     }
 }
diff --git a/src/ImageSharp/Memory/Allocators/Internals/UniformUnmanagedMemoryPool.cs b/src/ImageSharp/Memory/Allocators/Internals/UniformUnmanagedMemoryPool.cs
index 464bc2165..aa8bcd385 100644
--- a/src/ImageSharp/Memory/Allocators/Internals/UniformUnmanagedMemoryPool.cs
+++ b/src/ImageSharp/Memory/Allocators/Internals/UniformUnmanagedMemoryPool.cs
@@ -1,6 +1,5 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
-#nullable disable
 
 using System.Diagnostics;
 
@@ -13,7 +12,7 @@ internal partial class UniformUnmanagedMemoryPool : System.Runtime.ConstrainedEx
 {
     private static int minTrimPeriodMilliseconds = int.MaxValue;
     private static readonly List<WeakReference<UniformUnmanagedMemoryPool>> AllPools = new();
-    private static Timer trimTimer;
+    private static Timer? trimTimer;
 
     private static readonly Stopwatch Stopwatch = Stopwatch.StartNew();
 
@@ -97,7 +96,7 @@ internal partial class UniformUnmanagedMemoryPool : System.Runtime.ConstrainedEx
     /// <summary>
     /// Rent <paramref name="bufferCount"/> buffers or return 'null' if the pool is full.
     /// </summary>
-    public UnmanagedMemoryHandle[] Rent(int bufferCount)
+    public UnmanagedMemoryHandle[]? Rent(int bufferCount)
     {
         UnmanagedMemoryHandle[] buffersLocal = this.buffers;
 
@@ -248,7 +247,7 @@ internal partial class UniformUnmanagedMemoryPool : System.Runtime.ConstrainedEx
 
             foreach (WeakReference<UniformUnmanagedMemoryPool> weakPoolRef in AllPools)
             {
-                if (weakPoolRef.TryGetTarget(out UniformUnmanagedMemoryPool pool))
+                if (weakPoolRef.TryGetTarget(out UniformUnmanagedMemoryPool? pool))
                 {
                     pool.Trim();
                 }
diff --git a/src/ImageSharp/Memory/Allocators/Internals/UnmanagedMemoryHandle.cs b/src/ImageSharp/Memory/Allocators/Internals/UnmanagedMemoryHandle.cs
index a6da445b6..c13fa754e 100644
--- a/src/ImageSharp/Memory/Allocators/Internals/UnmanagedMemoryHandle.cs
+++ b/src/ImageSharp/Memory/Allocators/Internals/UnmanagedMemoryHandle.cs
@@ -1,6 +1,5 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
-#nullable disable
 
 using System.Runtime.InteropServices;
 
@@ -20,7 +19,7 @@ internal struct UnmanagedMemoryHandle : IEquatable<UnmanagedMemoryHandle>
     private static long totalOomRetries;
 
     // A Monitor to wait/signal when we are low on memory.
-    private static object lowMemoryMonitor;
+    private static object? lowMemoryMonitor;
 
     public static readonly UnmanagedMemoryHandle NullHandle;
 
@@ -114,9 +113,9 @@ internal struct UnmanagedMemoryHandle : IEquatable<UnmanagedMemoryHandle>
         if (Volatile.Read(ref lowMemoryMonitor) != null)
         {
             // We are low on memory. Signal all threads waiting in AllocateHandle().
-            Monitor.Enter(lowMemoryMonitor);
-            Monitor.PulseAll(lowMemoryMonitor);
-            Monitor.Exit(lowMemoryMonitor);
+            Monitor.Enter(lowMemoryMonitor!);
+            Monitor.PulseAll(lowMemoryMonitor!);
+            Monitor.Exit(lowMemoryMonitor!);
         }
 
         this.lengthInBytes = 0;
@@ -124,7 +123,7 @@ internal struct UnmanagedMemoryHandle : IEquatable<UnmanagedMemoryHandle>
 
     public bool Equals(UnmanagedMemoryHandle other) => this.handle.Equals(other.handle);
 
-    public override bool Equals(object obj) => obj is UnmanagedMemoryHandle other && this.Equals(other);
+    public override bool Equals(object? obj) => obj is UnmanagedMemoryHandle other && this.Equals(other);
 
     public override int GetHashCode() => this.handle.GetHashCode();
 }
diff --git a/src/ImageSharp/Memory/Allocators/UniformUnmanagedMemoryPoolMemoryAllocator.cs b/src/ImageSharp/Memory/Allocators/UniformUnmanagedMemoryPoolMemoryAllocator.cs
index bf75a716d..2cb4421d5 100644
--- a/src/ImageSharp/Memory/Allocators/UniformUnmanagedMemoryPoolMemoryAllocator.cs
+++ b/src/ImageSharp/Memory/Allocators/UniformUnmanagedMemoryPoolMemoryAllocator.cs
@@ -135,7 +135,7 @@ internal sealed class UniformUnmanagedMemoryPoolMemoryAllocator : MemoryAllocato
         }
 
         // Attempt to rent the whole group from the pool, allocate a group of unmanaged buffers if the attempt fails:
-        if (MemoryGroup<T>.TryAllocate(this.pool, totalLength, bufferAlignment, options, out MemoryGroup<T> poolGroup))
+        if (MemoryGroup<T>.TryAllocate(this.pool, totalLength, bufferAlignment, options, out MemoryGroup<T>? poolGroup))
         {
             return poolGroup;
         }
diff --git a/src/ImageSharp/Memory/Buffer2DExtensions.cs b/src/ImageSharp/Memory/Buffer2DExtensions.cs
index 2eb05ea93..e7ac64eda 100644
--- a/src/ImageSharp/Memory/Buffer2DExtensions.cs
+++ b/src/ImageSharp/Memory/Buffer2DExtensions.cs
@@ -22,7 +22,7 @@ public static class Buffer2DExtensions
         where T : struct
     {
         Guard.NotNull(buffer, nameof(buffer));
-        return buffer.FastMemoryGroup.View;
+        return buffer.FastMemoryGroup.View!;
     }
 
     /// <summary>
diff --git a/src/ImageSharp/Memory/Buffer2D{T}.cs b/src/ImageSharp/Memory/Buffer2D{T}.cs
index 8d6465389..a7957a987 100644
--- a/src/ImageSharp/Memory/Buffer2D{T}.cs
+++ b/src/ImageSharp/Memory/Buffer2D{T}.cs
@@ -43,7 +43,7 @@ public sealed class Buffer2D<T> : IDisposable
     /// Gets the backing <see cref="IMemoryGroup{T}"/>.
     /// </summary>
     /// <returns>The MemoryGroup.</returns>
-    public IMemoryGroup<T> MemoryGroup => this.FastMemoryGroup.View;
+    public IMemoryGroup<T>? MemoryGroup => this.FastMemoryGroup.View;
 
     /// <summary>
     /// Gets the backing <see cref="MemoryGroup{T}"/> without the view abstraction.
@@ -138,7 +138,7 @@ public sealed class Buffer2D<T> : IDisposable
     {
         DebugGuard.MustBeGreaterThanOrEqualTo(y, 0, nameof(y));
         DebugGuard.MustBeLessThan(y, this.Height, nameof(y));
-        return this.FastMemoryGroup.View.GetBoundedMemorySlice(y * (long)this.Width, this.Width);
+        return this.FastMemoryGroup.View!.GetBoundedMemorySlice(y * (long)this.Width, this.Width);
     }
 
     /// <summary>
diff --git a/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroupExtensions.cs b/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroupExtensions.cs
index 4656e6ef9..b4b1ffc6f 100644
--- a/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroupExtensions.cs
+++ b/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroupExtensions.cs
@@ -106,7 +106,7 @@ internal static class MemoryGroupExtensions
         }
     }
 
-    internal static void CopyTo<T>(this IMemoryGroup<T> source, IMemoryGroup<T> target)
+    internal static void CopyTo<T>(this IMemoryGroup<T>? source, IMemoryGroup<T>? target)
         where T : struct
     {
         Guard.NotNull(source, nameof(source));
diff --git a/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroupSpanCache.cs b/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroupSpanCache.cs
index 36abfba88..dd3e67c37 100644
--- a/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroupSpanCache.cs
+++ b/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroupSpanCache.cs
@@ -13,7 +13,7 @@ namespace SixLabors.ImageSharp.Memory;
 internal unsafe struct MemoryGroupSpanCache
 {
     public SpanCacheMode Mode;
-    public byte[] SingleArray;
+    public byte[]? SingleArray;
     public void* SinglePointer;
     public void*[] MultiPointer;
 
diff --git a/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroupView{T}.cs b/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroupView{T}.cs
index 54e347e46..76371e674 100644
--- a/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroupView{T}.cs
+++ b/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroupView{T}.cs
@@ -1,9 +1,9 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
-#nullable disable
 
 using System.Buffers;
 using System.Collections;
+using System.Diagnostics.CodeAnalysis;
 using System.Runtime.CompilerServices;
 
 namespace SixLabors.ImageSharp.Memory;
@@ -21,7 +21,7 @@ namespace SixLabors.ImageSharp.Memory;
 internal class MemoryGroupView<T> : IMemoryGroup<T>
     where T : struct
 {
-    private MemoryGroup<T> owner;
+    private MemoryGroup<T>? owner;
     private readonly MemoryOwnerWrapper[] memoryWrappers;
 
     public MemoryGroupView(MemoryGroup<T> owner)
@@ -63,6 +63,7 @@ internal class MemoryGroupView<T> : IMemoryGroup<T>
         }
     }
 
+    [MemberNotNullWhen(true, nameof(owner))]
     public bool IsValid => this.owner != null;
 
     public Memory<T> this[int index]
@@ -99,6 +100,7 @@ internal class MemoryGroupView<T> : IMemoryGroup<T>
         this.owner = null;
     }
 
+    [MemberNotNull(nameof(owner))]
     private void EnsureIsValid()
     {
         if (!this.IsValid)
diff --git a/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.Consumed.cs b/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.Consumed.cs
index 950e2a019..03a2fb78f 100644
--- a/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.Consumed.cs
+++ b/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.Consumed.cs
@@ -48,6 +48,6 @@ internal abstract partial class MemoryGroup<T>
             return ((IList<Memory<T>>)this.source).GetEnumerator();
         }
 
-        public override void Dispose() => this.View.Invalidate();
+        public override void Dispose() => this.View?.Invalidate();
     }
 }
diff --git a/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.Owned.cs b/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.Owned.cs
index e5bc91c98..664c137c1 100644
--- a/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.Owned.cs
+++ b/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.Owned.cs
@@ -1,8 +1,8 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
-#nullable disable
 
 using System.Buffers;
+using System.Diagnostics.CodeAnalysis;
 using System.Runtime.CompilerServices;
 using SixLabors.ImageSharp.Memory.Internals;
 
@@ -15,8 +15,8 @@ internal abstract partial class MemoryGroup<T>
     /// </summary>
     public sealed class Owned : MemoryGroup<T>, IEnumerable<Memory<T>>
     {
-        private IMemoryOwner<T>[] memoryOwners;
-        private RefCountedMemoryLifetimeGuard groupLifetimeGuard;
+        private IMemoryOwner<T>[]? memoryOwners;
+        private RefCountedMemoryLifetimeGuard? groupLifetimeGuard;
 
         public Owned(IMemoryOwner<T>[] memoryOwners, int bufferLength, long totalLength, bool swappable)
             : base(bufferLength, totalLength)
@@ -123,7 +123,7 @@ internal abstract partial class MemoryGroup<T>
 
         public override void RecreateViewAfterSwap()
         {
-            this.View.Invalidate();
+            this.View?.Invalidate();
             this.View = new MemoryGroupView<T>(this);
         }
 
@@ -141,7 +141,7 @@ internal abstract partial class MemoryGroup<T>
                 return;
             }
 
-            this.View.Invalidate();
+            this.View?.Invalidate();
 
             if (this.groupLifetimeGuard != null)
             {
@@ -149,7 +149,7 @@ internal abstract partial class MemoryGroup<T>
             }
             else
             {
-                foreach (IMemoryOwner<T> memoryOwner in this.memoryOwners)
+                foreach (IMemoryOwner<T> memoryOwner in this.memoryOwners!)
                 {
                     memoryOwner.Dispose();
                 }
@@ -161,6 +161,7 @@ internal abstract partial class MemoryGroup<T>
         }
 
         [MethodImpl(InliningOptions.ShortMethod)]
+        [MemberNotNull(nameof(memoryOwners))]
         private void EnsureNotDisposed()
         {
             if (this.memoryOwners is null)
@@ -170,6 +171,7 @@ internal abstract partial class MemoryGroup<T>
         }
 
         [MethodImpl(MethodImplOptions.NoInlining)]
+        [DoesNotReturn]
         private static void ThrowObjectDisposedException() => throw new ObjectDisposedException(nameof(MemoryGroup<T>));
 
         // When the MemoryGroup points to multiple buffers via `groupLifetimeGuard`,
diff --git a/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.cs b/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.cs
index 1ef30e354..237cbad7a 100644
--- a/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.cs
+++ b/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.cs
@@ -1,9 +1,9 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
-#nullable disable
 
 using System.Buffers;
 using System.Collections;
+using System.Diagnostics.CodeAnalysis;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 using SixLabors.ImageSharp.Memory.Internals;
@@ -41,7 +41,7 @@ internal abstract partial class MemoryGroup<T> : IMemoryGroup<T>, IDisposable
     /// <inheritdoc />
     public bool IsValid { get; private set; } = true;
 
-    public MemoryGroupView<T> View { get; private set; }
+    public MemoryGroupView<T>? View { get; private set; }
 
     /// <inheritdoc />
     public abstract Memory<T> this[int index] { get; }
@@ -150,7 +150,7 @@ internal abstract partial class MemoryGroup<T> : IMemoryGroup<T>, IDisposable
         long totalLengthInElements,
         int bufferAlignmentInElements,
         AllocationOptions options,
-        out MemoryGroup<T> memoryGroup)
+        [NotNullWhen(true)] out MemoryGroup<T>? memoryGroup)
     {
         Guard.NotNull(pool, nameof(pool));
         Guard.MustBeGreaterThanOrEqualTo(totalLengthInElements, 0, nameof(totalLengthInElements));
@@ -188,7 +188,7 @@ internal abstract partial class MemoryGroup<T> : IMemoryGroup<T>, IDisposable
             bufferCount++;
         }
 
-        UnmanagedMemoryHandle[] arrays = pool.Rent(bufferCount);
+        UnmanagedMemoryHandle[]? arrays = pool.Rent(bufferCount);
 
         if (arrays == null)
         {

From dfde8d8bf521681b8638980253f0c4ae5b88bb4f Mon Sep 17 00:00:00 2001
From: Stefan Nikolei <stefan@nikolei.eu>
Date: Wed, 25 Jan 2023 17:11:25 +0100
Subject: [PATCH 2/8] Resolve PR comments

---
 .../Memory/Allocators/Internals/Gen2GcCallback.cs           | 4 ++--
 .../Memory/Allocators/Internals/ManagedBufferBase.cs        | 2 +-
 .../Memory/Allocators/Internals/SharedArrayPoolBuffer{T}.cs | 6 +++++-
 src/ImageSharp/Memory/Buffer2D{T}.cs                        | 2 +-
 .../Memory/DiscontiguousBuffers/MemoryGroup{T}.cs           | 2 +-
 5 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/src/ImageSharp/Memory/Allocators/Internals/Gen2GcCallback.cs b/src/ImageSharp/Memory/Allocators/Internals/Gen2GcCallback.cs
index c0737a114..6f48c5669 100644
--- a/src/ImageSharp/Memory/Allocators/Internals/Gen2GcCallback.cs
+++ b/src/ImageSharp/Memory/Allocators/Internals/Gen2GcCallback.cs
@@ -42,7 +42,7 @@ internal sealed class Gen2GcCallback : CriticalFinalizerObject
             // Execute the callback method.
             try
             {
-                if (this.callback1 is not null && !this.callback1(targetObj))
+                if (!this.callback1!(targetObj))
                 {
                     // If the callback returns false, this callback object is no longer needed.
                     this.weakTargetObj.Free();
@@ -63,7 +63,7 @@ internal sealed class Gen2GcCallback : CriticalFinalizerObject
             // Execute the callback method.
             try
             {
-                if (this.callback0 is not null && !this.callback0())
+                if (!this.callback0!())
                 {
                     // If the callback returns false, this callback object is no longer needed.
                     return;
diff --git a/src/ImageSharp/Memory/Allocators/Internals/ManagedBufferBase.cs b/src/ImageSharp/Memory/Allocators/Internals/ManagedBufferBase.cs
index be4cb8c8e..a18bd3447 100644
--- a/src/ImageSharp/Memory/Allocators/Internals/ManagedBufferBase.cs
+++ b/src/ImageSharp/Memory/Allocators/Internals/ManagedBufferBase.cs
@@ -43,5 +43,5 @@ internal abstract class ManagedBufferBase<T> : MemoryManager<T>
     /// Gets the object that should be pinned.
     /// </summary>
     /// <returns>The pinnable <see cref="object"/>.</returns>
-    protected abstract object? GetPinnableObject();
+    protected abstract object GetPinnableObject();
 }
diff --git a/src/ImageSharp/Memory/Allocators/Internals/SharedArrayPoolBuffer{T}.cs b/src/ImageSharp/Memory/Allocators/Internals/SharedArrayPoolBuffer{T}.cs
index 1d73b2ddf..4952c6b5e 100644
--- a/src/ImageSharp/Memory/Allocators/Internals/SharedArrayPoolBuffer{T}.cs
+++ b/src/ImageSharp/Memory/Allocators/Internals/SharedArrayPoolBuffer{T}.cs
@@ -40,7 +40,11 @@ internal class SharedArrayPoolBuffer<T> : ManagedBufferBase<T>, IRefCounted
         return MemoryMarshal.Cast<byte, T>(this.Array.AsSpan(0, this.lengthInBytes));
     }
 
-    protected override object? GetPinnableObject() => this.Array;
+    protected override object GetPinnableObject()
+    {
+        Guard.NotNull(this.Array);
+        return this.Array;
+    }
 
     public void AddRef()
     {
diff --git a/src/ImageSharp/Memory/Buffer2D{T}.cs b/src/ImageSharp/Memory/Buffer2D{T}.cs
index a7957a987..8c9093a35 100644
--- a/src/ImageSharp/Memory/Buffer2D{T}.cs
+++ b/src/ImageSharp/Memory/Buffer2D{T}.cs
@@ -43,7 +43,7 @@ public sealed class Buffer2D<T> : IDisposable
     /// Gets the backing <see cref="IMemoryGroup{T}"/>.
     /// </summary>
     /// <returns>The MemoryGroup.</returns>
-    public IMemoryGroup<T>? MemoryGroup => this.FastMemoryGroup.View;
+    public IMemoryGroup<T> MemoryGroup => this.FastMemoryGroup.View;
 
     /// <summary>
     /// Gets the backing <see cref="MemoryGroup{T}"/> without the view abstraction.
diff --git a/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.cs b/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.cs
index 237cbad7a..d63fd2076 100644
--- a/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.cs
+++ b/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.cs
@@ -41,7 +41,7 @@ internal abstract partial class MemoryGroup<T> : IMemoryGroup<T>, IDisposable
     /// <inheritdoc />
     public bool IsValid { get; private set; } = true;
 
-    public MemoryGroupView<T>? View { get; private set; }
+    public MemoryGroupView<T> View { get; private set; } = null!;
 
     /// <inheritdoc />
     public abstract Memory<T> this[int index] { get; }

From 12cf563c5c54dd6feca7d3acaa0c72d994ae65d1 Mon Sep 17 00:00:00 2001
From: Stefan Nikolei <stefan@nikolei.eu>
Date: Wed, 25 Jan 2023 17:15:42 +0100
Subject: [PATCH 3/8] Use CheckDisposed

---
 .../Memory/Allocators/Internals/SharedArrayPoolBuffer{T}.cs   | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/ImageSharp/Memory/Allocators/Internals/SharedArrayPoolBuffer{T}.cs b/src/ImageSharp/Memory/Allocators/Internals/SharedArrayPoolBuffer{T}.cs
index 4952c6b5e..609bb34a5 100644
--- a/src/ImageSharp/Memory/Allocators/Internals/SharedArrayPoolBuffer{T}.cs
+++ b/src/ImageSharp/Memory/Allocators/Internals/SharedArrayPoolBuffer{T}.cs
@@ -3,6 +3,7 @@
 
 using System.Buffers;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 
@@ -42,7 +43,7 @@ internal class SharedArrayPoolBuffer<T> : ManagedBufferBase<T>, IRefCounted
 
     protected override object GetPinnableObject()
     {
-        Guard.NotNull(this.Array);
+        this.CheckDisposed();
         return this.Array;
     }
 
@@ -55,6 +56,7 @@ internal class SharedArrayPoolBuffer<T> : ManagedBufferBase<T>, IRefCounted
     public void ReleaseRef() => this.lifetimeGuard.ReleaseRef();
 
     [Conditional("DEBUG")]
+    [MemberNotNull(nameof(Array))]
     private void CheckDisposed()
     {
         if (this.Array == null)

From 4efd49295a227ac57509db045774c07ee4283825 Mon Sep 17 00:00:00 2001
From: Stefan Nikolei <stefan@nikolei.eu>
Date: Wed, 25 Jan 2023 17:56:21 +0100
Subject: [PATCH 4/8] Resolve PR issues

---
 .../Memory/Allocators/Internals/SharedArrayPoolBuffer{T}.cs  | 5 +++--
 .../Memory/DiscontiguousBuffers/MemoryGroup{T}.Consumed.cs   | 2 +-
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/ImageSharp/Memory/Allocators/Internals/SharedArrayPoolBuffer{T}.cs b/src/ImageSharp/Memory/Allocators/Internals/SharedArrayPoolBuffer{T}.cs
index 609bb34a5..f9434ee94 100644
--- a/src/ImageSharp/Memory/Allocators/Internals/SharedArrayPoolBuffer{T}.cs
+++ b/src/ImageSharp/Memory/Allocators/Internals/SharedArrayPoolBuffer{T}.cs
@@ -67,7 +67,7 @@ internal class SharedArrayPoolBuffer<T> : ManagedBufferBase<T>, IRefCounted
 
     private sealed class LifetimeGuard : RefCountedMemoryLifetimeGuard
     {
-        private byte[] array;
+        private byte[]? array;
 
         public LifetimeGuard(byte[] array) => this.array = array;
 
@@ -78,7 +78,8 @@ internal class SharedArrayPoolBuffer<T> : ManagedBufferBase<T>, IRefCounted
             // This is not ideal, but subsequent leaks will end up returning arrays to per-cpu buckets,
             // meaning likely a different bucket than it was rented from,
             // but this is PROBABLY better than not returning the arrays at all.
-            ArrayPool<byte>.Shared.Return(this.array);
+            ArrayPool<byte>.Shared.Return(this.array!);
+            this.array = null;
         }
     }
 }
diff --git a/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.Consumed.cs b/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.Consumed.cs
index 03a2fb78f..950e2a019 100644
--- a/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.Consumed.cs
+++ b/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.Consumed.cs
@@ -48,6 +48,6 @@ internal abstract partial class MemoryGroup<T>
             return ((IList<Memory<T>>)this.source).GetEnumerator();
         }
 
-        public override void Dispose() => this.View?.Invalidate();
+        public override void Dispose() => this.View.Invalidate();
     }
 }

From 12421030c2846ceee2e886f397b9c84d7bc9cb1a Mon Sep 17 00:00:00 2001
From: Stefan Nikolei <stefan@nikolei.eu>
Date: Wed, 25 Jan 2023 19:42:05 +0100
Subject: [PATCH 5/8] Update
 src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.Owned.cs

Co-authored-by: Anton Firszov <antonfir@gmail.com>
---
 .../Memory/DiscontiguousBuffers/MemoryGroup{T}.Owned.cs         | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.Owned.cs b/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.Owned.cs
index 664c137c1..eab90ee5a 100644
--- a/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.Owned.cs
+++ b/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.Owned.cs
@@ -123,7 +123,7 @@ internal abstract partial class MemoryGroup<T>
 
         public override void RecreateViewAfterSwap()
         {
-            this.View?.Invalidate();
+            this.View.Invalidate();
             this.View = new MemoryGroupView<T>(this);
         }
 

From 8f18e3596089a237d7a9bf59cbb9997b4219af5a Mon Sep 17 00:00:00 2001
From: Stefan Nikolei <stefan@nikolei.eu>
Date: Wed, 25 Jan 2023 19:42:13 +0100
Subject: [PATCH 6/8] Update
 src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.Owned.cs

Co-authored-by: Anton Firszov <antonfir@gmail.com>
---
 .../Memory/DiscontiguousBuffers/MemoryGroup{T}.Owned.cs         | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.Owned.cs b/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.Owned.cs
index eab90ee5a..9da0139e6 100644
--- a/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.Owned.cs
+++ b/src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.Owned.cs
@@ -141,7 +141,7 @@ internal abstract partial class MemoryGroup<T>
                 return;
             }
 
-            this.View?.Invalidate();
+            this.View.Invalidate();
 
             if (this.groupLifetimeGuard != null)
             {

From 6e70477cf2e477c1fbc981a1a31e68c6ff9399e2 Mon Sep 17 00:00:00 2001
From: Stefan Nikolei <stefan@nikolei.eu>
Date: Wed, 25 Jan 2023 19:42:21 +0100
Subject: [PATCH 7/8] Update src/ImageSharp/Memory/Buffer2D{T}.cs

Co-authored-by: Anton Firszov <antonfir@gmail.com>
---
 src/ImageSharp/Memory/Buffer2D{T}.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/ImageSharp/Memory/Buffer2D{T}.cs b/src/ImageSharp/Memory/Buffer2D{T}.cs
index 8c9093a35..8d6465389 100644
--- a/src/ImageSharp/Memory/Buffer2D{T}.cs
+++ b/src/ImageSharp/Memory/Buffer2D{T}.cs
@@ -138,7 +138,7 @@ public sealed class Buffer2D<T> : IDisposable
     {
         DebugGuard.MustBeGreaterThanOrEqualTo(y, 0, nameof(y));
         DebugGuard.MustBeLessThan(y, this.Height, nameof(y));
-        return this.FastMemoryGroup.View!.GetBoundedMemorySlice(y * (long)this.Width, this.Width);
+        return this.FastMemoryGroup.View.GetBoundedMemorySlice(y * (long)this.Width, this.Width);
     }
 
     /// <summary>

From 9c3d68f1f55f87d44822f91a98e053847218e674 Mon Sep 17 00:00:00 2001
From: Stefan Nikolei <stefan@nikolei.eu>
Date: Wed, 25 Jan 2023 19:42:28 +0100
Subject: [PATCH 8/8] Update src/ImageSharp/Memory/Buffer2DExtensions.cs

Co-authored-by: Anton Firszov <antonfir@gmail.com>
---
 src/ImageSharp/Memory/Buffer2DExtensions.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/ImageSharp/Memory/Buffer2DExtensions.cs b/src/ImageSharp/Memory/Buffer2DExtensions.cs
index e7ac64eda..2eb05ea93 100644
--- a/src/ImageSharp/Memory/Buffer2DExtensions.cs
+++ b/src/ImageSharp/Memory/Buffer2DExtensions.cs
@@ -22,7 +22,7 @@ public static class Buffer2DExtensions
         where T : struct
     {
         Guard.NotNull(buffer, nameof(buffer));
-        return buffer.FastMemoryGroup.View!;
+        return buffer.FastMemoryGroup.View;
     }
 
     /// <summary>