Nullable: System.Buffers (#23619)

* Nullable: System.Buffers

* Address PR feedback

66 files changed, 104 insertions, 31 deletions

diff --git a/src/System.Private.CoreLib/shared/System/Buffers/ArrayPool.cs b/src/System.Private.CoreLib/shared/System/Buffers/ArrayPool.cs
index 5e01399a33..8e67e22599 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/ArrayPool.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/ArrayPool.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
 namespace System.Buffers
 {
     /// <summary>
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/ArrayPoolEventSource.cs b/src/System.Private.CoreLib/shared/System/Buffers/ArrayPoolEventSource.cs
index d0563c4977..9ae0e3d913 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/ArrayPoolEventSource.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/ArrayPoolEventSource.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.Diagnostics.Tracing;
 
 namespace System.Buffers
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Binary/Reader.cs b/src/System.Private.CoreLib/shared/System/Buffers/Binary/Reader.cs
index 49d0a2db42..f4a8142731 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Binary/Reader.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Binary/Reader.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.Numerics;
 using System.Runtime.CompilerServices;
 
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Binary/ReaderBigEndian.cs b/src/System.Private.CoreLib/shared/System/Buffers/Binary/ReaderBigEndian.cs
index b45dd8913d..31745dd3cc 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Binary/ReaderBigEndian.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Binary/ReaderBigEndian.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.InteropServices;
 
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Binary/ReaderLittleEndian.cs b/src/System.Private.CoreLib/shared/System/Buffers/Binary/ReaderLittleEndian.cs
index bd832f8995..e4a03c013a 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Binary/ReaderLittleEndian.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Binary/ReaderLittleEndian.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.InteropServices;
 
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Binary/WriterBigEndian.cs b/src/System.Private.CoreLib/shared/System/Buffers/Binary/WriterBigEndian.cs
index 78be9b5a03..ea56c78a4b 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Binary/WriterBigEndian.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Binary/WriterBigEndian.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.InteropServices;
 
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Binary/WriterLittleEndian.cs b/src/System.Private.CoreLib/shared/System/Buffers/Binary/WriterLittleEndian.cs
index 5d63ee5f0b..201ead0e9f 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Binary/WriterLittleEndian.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Binary/WriterLittleEndian.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.InteropServices;
 
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/ConfigurableArrayPool.cs b/src/System.Private.CoreLib/shared/System/Buffers/ConfigurableArrayPool.cs
index f7b6034d20..dd49d8a250 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/ConfigurableArrayPool.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/ConfigurableArrayPool.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.Diagnostics;
 using System.Threading;
 
@@ -74,7 +75,7 @@ namespace System.Buffers
             }
 
             var log = ArrayPoolEventSource.Log;
-            T[] buffer = null;
+            T[]? buffer = null;
 
             int index = Utilities.SelectBucketIndex(minimumLength);
             if (index < _buckets.Length)
@@ -163,7 +164,7 @@ namespace System.Buffers
         private sealed class Bucket
         {
             internal readonly int _bufferLength;
-            private readonly T[][] _buffers;
+            private readonly T[]?[] _buffers;
             private readonly int _poolId;
 
             private SpinLock _lock; // do not make this readonly; it's a mutable struct
@@ -184,10 +185,10 @@ namespace System.Buffers
             internal int Id => GetHashCode();
 
             /// <summary>Takes an array from the bucket.  If the bucket is empty, returns null.</summary>
-            internal T[] Rent()
+            internal T[]? Rent()
             {
-                T[][] buffers = _buffers;
-                T[] buffer = null;
+                T[]?[] buffers = _buffers;
+                T[]? buffer = null;
 
                 // While holding the lock, grab whatever is at the next available index and
                 // update the index.  We do as little work as possible while holding the spin
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/IMemoryOwner.cs b/src/System.Private.CoreLib/shared/System/Buffers/IMemoryOwner.cs
index 44f16c5827..19d01166c6 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/IMemoryOwner.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/IMemoryOwner.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
 namespace System.Buffers
 {
     /// <summary>
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/IPinnable.cs b/src/System.Private.CoreLib/shared/System/Buffers/IPinnable.cs
index 623e716a05..b8b49d4cd1 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/IPinnable.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/IPinnable.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
 namespace System.Buffers
 {
     /// <summary>
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/MemoryHandle.cs b/src/System.Private.CoreLib/shared/System/Buffers/MemoryHandle.cs
index b218534c52..23325d5d6e 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/MemoryHandle.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/MemoryHandle.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.InteropServices;
 
 namespace System.Buffers
@@ -13,7 +14,7 @@ namespace System.Buffers
     {
         private void* _pointer;
         private GCHandle _handle;
-        private IPinnable _pinnable;
+        private IPinnable? _pinnable;
 
         /// <summary>
         /// Creates a new memory handle for the memory.
@@ -22,7 +23,7 @@ namespace System.Buffers
         /// <param name="pinnable">reference to manually managed object, or default if there is no memory manager</param>
         /// <param name="handle">handle used to pin array buffers</param>
         [CLSCompliant(false)]
-        public MemoryHandle(void* pointer, GCHandle handle = default, IPinnable pinnable = default)
+        public MemoryHandle(void* pointer, GCHandle handle = default, IPinnable? pinnable = default)
         {
             _pointer = pointer;
             _handle = handle;
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/MemoryManager.cs b/src/System.Private.CoreLib/shared/System/Buffers/MemoryManager.cs
index 1b235b538e..5c4061e9b4 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/MemoryManager.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/MemoryManager.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;
 
 namespace System.Buffers
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/OperationStatus.cs b/src/System.Private.CoreLib/shared/System/Buffers/OperationStatus.cs
index e9ddcab571..c8235f7cc4 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/OperationStatus.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/OperationStatus.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
 namespace System.Buffers
 {
     /// <summary>
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/StandardFormat.cs b/src/System.Private.CoreLib/shared/System/Buffers/StandardFormat.cs
index 83014d06b0..5675f4ced3 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/StandardFormat.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/StandardFormat.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.Diagnostics;
 
 namespace System.Buffers
@@ -79,7 +80,7 @@ namespace System.Buffers
         /// <summary>
         /// Converts a classic .NET format string into a StandardFormat
         /// </summary>
-        public static StandardFormat Parse(string format) => format == null ? default : Parse(format.AsSpan());
+        public static StandardFormat Parse(string? format) => format == null ? default : Parse(format.AsSpan());
 
         /// <summary>
         /// Tries to convert a <see cref="ReadOnlySpan{Char}"/> into a StandardFormat. A return value indicates whether the conversion succeeded or failed.
@@ -129,7 +130,7 @@ namespace System.Buffers
         /// <summary>
         /// Returns true if both the Symbol and Precision are equal.
         /// </summary>
-        public override bool Equals(object obj) => obj is StandardFormat other && Equals(other);
+        public override bool Equals(object? obj) => obj is StandardFormat other && Equals(other);
 
         /// <summary>
         /// Compute a hash code.
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/FormattingHelpers.CountDigits.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/FormattingHelpers.CountDigits.cs
index ac45347a5e..a7a1fc24a8 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/FormattingHelpers.CountDigits.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/FormattingHelpers.CountDigits.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.Diagnostics;
 using System.Numerics;
 using System.Runtime.CompilerServices;
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Constants.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Constants.cs
index e2f70f0b10..25880fcf95 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Constants.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Constants.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
 namespace System.Buffers.Text
 {
     internal static partial class Utf8Constants
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/FormattingHelpers.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/FormattingHelpers.cs
index 1b30d5f013..a9f185aae9 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/FormattingHelpers.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/FormattingHelpers.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.Diagnostics;
 using System.Runtime.CompilerServices;
 
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Boolean.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Boolean.cs
index 31bb6cae55..bc6b894be7 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Boolean.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Boolean.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.Buffers.Binary;
 
 namespace System.Buffers.Text
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Date.G.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Date.G.cs
index 7c4a2e342d..2290a10726 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Date.G.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Date.G.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
 namespace System.Buffers.Text
 {
     public static partial class Utf8Formatter
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Date.L.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Date.L.cs
index 699f91f39c..e817064bf8 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Date.L.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Date.L.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
 namespace System.Buffers.Text
 {
     public static partial class Utf8Formatter
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Date.O.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Date.O.cs
index d9b7b181bc..706c634ddd 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Date.O.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Date.O.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
 namespace System.Buffers.Text
 {
     public static partial class Utf8Formatter
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Date.R.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Date.R.cs
index dd9ec459b7..aed0795b39 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Date.R.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Date.R.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
 namespace System.Buffers.Text
 {
     public static partial class Utf8Formatter
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Date.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Date.cs
index 046885d162..31da577c82 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Date.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Date.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
 namespace System.Buffers.Text
 {
     public static partial class Utf8Formatter
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Decimal.E.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Decimal.E.cs
index 89b54f2fd5..859adea1ca 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Decimal.E.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Decimal.E.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.Diagnostics;
 
 namespace System.Buffers.Text
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Decimal.F.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Decimal.F.cs
index 51bc20b8d2..1efe257f54 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Decimal.F.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Decimal.F.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.Diagnostics;
 
 namespace System.Buffers.Text
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Decimal.G.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Decimal.G.cs
index b867eaec1a..c737749394 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Decimal.G.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Decimal.G.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.Diagnostics;
 
 namespace System.Buffers.Text
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Decimal.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Decimal.cs
index bb93b992ef..72b9fca51b 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Decimal.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Decimal.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.Diagnostics;
 
 namespace System.Buffers.Text
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Float.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Float.cs
index 96e70bada9..c4d70b4da9 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Float.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Float.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.Diagnostics;
 using System.Globalization;
 using System.Text;
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Guid.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Guid.cs
index 479f1dd1cb..61085b8924 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Guid.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Guid.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.InteropServices;
 
 namespace System.Buffers.Text
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Signed.D.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Signed.D.cs
index 7532f0cf15..88f4c16028 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Signed.D.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Signed.D.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;
 
 namespace System.Buffers.Text
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Signed.Default.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Signed.Default.cs
index 046f5baf66..1c213e3879 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Signed.Default.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Signed.Default.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.Diagnostics;
 using System.Runtime.CompilerServices;
 
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Signed.N.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Signed.N.cs
index 1c01b8d60d..542bd1eeb7 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Signed.N.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Signed.N.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;
 
 namespace System.Buffers.Text
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Signed.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Signed.cs
index fcd20b312d..025fc8b45e 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Signed.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Signed.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;
 
 namespace System.Buffers.Text
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Unsigned.D.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Unsigned.D.cs
index 9cb8d64bc0..78542eb4cf 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Unsigned.D.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Unsigned.D.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
 namespace System.Buffers.Text
 {
     /// <summary>
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Unsigned.Default.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Unsigned.Default.cs
index d83591ed98..5d8f1f0118 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Unsigned.Default.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Unsigned.Default.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.Diagnostics;
 using System.Runtime.CompilerServices;
 
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Unsigned.N.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Unsigned.N.cs
index ce21c0d3dd..b6caaa6cf9 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Unsigned.N.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Unsigned.N.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
 namespace System.Buffers.Text
 {
     /// <summary>
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Unsigned.X.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Unsigned.X.cs
index 4cf4d52b5c..1db31dfe59 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Unsigned.X.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Unsigned.X.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
 namespace System.Buffers.Text
 {
     /// <summary>
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Unsigned.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Unsigned.cs
index 0040c5075a..b531ba714d 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Unsigned.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.Unsigned.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;
 
 namespace System.Buffers.Text
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.cs
index 3b83fb7512..2024551ff9 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.Integer.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
 namespace System.Buffers.Text
 {
     /// <summary>
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.TimeSpan.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.TimeSpan.cs
index 38bb35f7df..b41cb75d0e 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.TimeSpan.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Formatter/Utf8Formatter.TimeSpan.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.Diagnostics;
 
 namespace System.Buffers.Text
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/ParserHelpers.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/ParserHelpers.cs
index f440182bf9..7630277464 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/ParserHelpers.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/ParserHelpers.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;
 
 namespace System.Buffers.Text
@@ -65,7 +66,7 @@ namespace System.Buffers.Text
         //
         // Enable use of ThrowHelper from TryParse() routines without introducing dozens of non-code-coveraged "value= default; bytesConsumed = 0; return false" boilerplate.
         //
-        public static bool TryParseThrowFormatException<T>(out T value, out int bytesConsumed)
+        public static bool TryParseThrowFormatException<T>(out T value, out int bytesConsumed) where T : struct
         {
             value = default;
             return TryParseThrowFormatException(out bytesConsumed);
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Boolean.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Boolean.cs
index 3b039bae25..56d88e9d46 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Boolean.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Boolean.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.Buffers.Binary;
 
 namespace System.Buffers.Text
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Date.Default.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Date.Default.cs
index 73578ea88c..fdf79985ee 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Date.Default.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Date.Default.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
 namespace System.Buffers.Text
 {
     public static partial class Utf8Parser
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Date.G.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Date.G.cs
index 6e8edbcbdf..d930831b60 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Date.G.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Date.G.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
 namespace System.Buffers.Text
 {
     public static partial class Utf8Parser
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Date.Helpers.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Date.Helpers.cs
index d2fb06829a..0d62d81883 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Date.Helpers.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Date.Helpers.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.Diagnostics;
 
 namespace System.Buffers.Text
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Date.O.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Date.O.cs
index 8d2c681f68..9ea3fa34f1 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Date.O.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Date.O.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.Diagnostics;
 
 namespace System.Buffers.Text
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Date.R.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Date.R.cs
index 316bee01b4..7a16b07e18 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Date.R.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Date.R.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
 namespace System.Buffers.Text
 {
     public static partial class Utf8Parser
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Date.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Date.cs
index 35ad716705..37070ef5cf 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Date.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Date.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.Diagnostics;
 
 namespace System.Buffers.Text
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Decimal.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Decimal.cs
index 5ed385a71b..84bc7797de 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Decimal.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Decimal.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
 namespace System.Buffers.Text
 {
     public static partial class Utf8Parser
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Float.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Float.cs
index f68945cb5a..c2f84dd2b4 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Float.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Float.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.Buffers.Binary;
 
 namespace System.Buffers.Text
@@ -113,7 +114,7 @@ namespace System.Buffers.Text
         //
         // Assuming the text doesn't look like a normal floating point, we attempt to parse it as one the special floating point values.
         //
-        private static bool TryParseAsSpecialFloatingPoint<T>(ReadOnlySpan<byte> source, T positiveInfinity, T negativeInfinity, T nan, out T value, out int bytesConsumed)
+        private static bool TryParseAsSpecialFloatingPoint<T>(ReadOnlySpan<byte> source, T positiveInfinity, T negativeInfinity, T nan, out T value, out int bytesConsumed) where T : struct
         {            
             int srcIndex = 0;
             int remaining = source.Length;
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Guid.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Guid.cs
index f0a99dd522..18aaf64212 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Guid.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Guid.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
 namespace System.Buffers.Text
 {
     public static partial class Utf8Parser
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Integer.Signed.D.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Integer.Signed.D.cs
index bf1871a1c9..fc9eb5ea25 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Integer.Signed.D.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Integer.Signed.D.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
 namespace System.Buffers.Text
 {
     public static partial class Utf8Parser
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Integer.Signed.N.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Integer.Signed.N.cs
index fd8ce572f2..8cf986b18e 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Integer.Signed.N.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Integer.Signed.N.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
 namespace System.Buffers.Text
 {
     public static partial class Utf8Parser
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Integer.Signed.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Integer.Signed.cs
index 2e861b1cfd..0ee5b7e3f9 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Integer.Signed.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Integer.Signed.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 Internal.Runtime.CompilerServices;
 
 namespace System.Buffers.Text
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Integer.Unsigned.D.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Integer.Unsigned.D.cs
index 46753f5c57..675231b26f 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Integer.Unsigned.D.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Integer.Unsigned.D.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
 namespace System.Buffers.Text
 {
     public static partial class Utf8Parser
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Integer.Unsigned.N.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Integer.Unsigned.N.cs
index 2db20c1270..72f2831e62 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Integer.Unsigned.N.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Integer.Unsigned.N.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
 namespace System.Buffers.Text
 {
     //
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Integer.Unsigned.X.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Integer.Unsigned.X.cs
index 7e7867a56f..1042faece2 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Integer.Unsigned.X.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Integer.Unsigned.X.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
 namespace System.Buffers.Text
 {
     public static partial class Utf8Parser
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Integer.Unsigned.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Integer.Unsigned.cs
index 7c4e94e56f..f420bf1818 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Integer.Unsigned.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Integer.Unsigned.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
 namespace System.Buffers.Text
 {
     public static partial class Utf8Parser
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Number.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Number.cs
index 799a3fe6a7..2727747d34 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Number.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.Number.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.Diagnostics;
 
 namespace System.Buffers.Text
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.TimeSpan.BigG.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.TimeSpan.BigG.cs
index 6bcb4d5277..e05523c45f 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.TimeSpan.BigG.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.TimeSpan.BigG.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
 namespace System.Buffers.Text
 {
     public static partial class Utf8Parser
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.TimeSpan.C.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.TimeSpan.C.cs
index d0a28969be..94d539fa88 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.TimeSpan.C.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.TimeSpan.C.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
 namespace System.Buffers.Text
 {
     public static partial class Utf8Parser
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.TimeSpan.LittleG.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.TimeSpan.LittleG.cs
index 19208b9eac..7172da4e0c 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.TimeSpan.LittleG.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.TimeSpan.LittleG.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
 namespace System.Buffers.Text
 {
     public static partial class Utf8Parser
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.TimeSpan.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.TimeSpan.cs
index b49cccb6a2..641a0b3f03 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.TimeSpan.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.TimeSpan.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.Diagnostics;
 
 namespace System.Buffers.Text
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.TimeSpanSplitter.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.TimeSpanSplitter.cs
index 0c72d1f3a2..4340399ec9 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.TimeSpanSplitter.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/Utf8Parser/Utf8Parser.TimeSpanSplitter.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.Diagnostics;
 
 namespace System.Buffers.Text
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/TlsOverPerCoreLockedStacksArrayPool.cs b/src/System.Private.CoreLib/shared/System/Buffers/TlsOverPerCoreLockedStacksArrayPool.cs
index 1a933a5014..5c5fd994ed 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/TlsOverPerCoreLockedStacksArrayPool.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/TlsOverPerCoreLockedStacksArrayPool.cs
@@ -2,8 +2,10 @@
 // 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;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Runtime.CompilerServices;
 using System.Threading;
 using Internal.Runtime.CompilerServices;
@@ -42,10 +44,10 @@ namespace System.Buffers
         /// An array of per-core array stacks. The slots are lazily initialized to avoid creating
         /// lots of overhead for unused array sizes.
         /// </summary>
-        private readonly PerCoreLockedStacks[] _buckets = new PerCoreLockedStacks[NumBuckets];
+        private readonly PerCoreLockedStacks?[] _buckets = new PerCoreLockedStacks[NumBuckets];
         /// <summary>A per-thread array of arrays, to cache one array per array size per thread.</summary>
         [ThreadStatic]
-        private static T[][] t_tlsBuckets;
+        private static T[]?[]? t_tlsBuckets;
 
         private int _callbackCreated;
 
@@ -54,7 +56,8 @@ namespace System.Buffers
         /// <summary>
         /// Used to keep track of all thread local buckets for trimming if needed
         /// </summary>
-        private static readonly ConditionalWeakTable<T[][], object> s_allTlsBuckets = s_trimBuffers ? new ConditionalWeakTable<T[][], object>() : null;
+        private static readonly ConditionalWeakTable<T[]?[], object?>? s_allTlsBuckets =
+            s_trimBuffers ? new ConditionalWeakTable<T[]?[], object?>() : null;
 
         /// <summary>Initialize the pool.</summary>
         public TlsOverPerCoreLockedStacksArrayPool()
@@ -94,7 +97,7 @@ namespace System.Buffers
             }
 
             ArrayPoolEventSource log = ArrayPoolEventSource.Log;
-            T[] buffer;
+            T[]? buffer;
 
             // Get the bucket number for the array length
             int bucketIndex = Utilities.SelectBucketIndex(minimumLength);
@@ -103,7 +106,7 @@ namespace System.Buffers
             if (bucketIndex < _buckets.Length)
             {
                 // First try to get it from TLS if possible.
-                T[][] tlsBuckets = t_tlsBuckets;
+                T[]?[]? tlsBuckets = t_tlsBuckets;
                 if (tlsBuckets != null)
                 {
                     buffer = tlsBuckets[bucketIndex];
@@ -119,7 +122,7 @@ namespace System.Buffers
                 }
 
                 // We couldn't get a buffer from TLS, so try the global stack.
-                PerCoreLockedStacks b = _buckets[bucketIndex];
+                PerCoreLockedStacks? b = _buckets[bucketIndex];
                 if (b != null)
                 {
                     buffer = b.TryPop();
@@ -185,13 +188,14 @@ namespace System.Buffers
                 // if there was a previous one there, push that to the global stack.  This
                 // helps to keep LIFO access such that the most recently pushed stack will
                 // be in TLS and the first to be popped next.
-                T[][] tlsBuckets = t_tlsBuckets;
+                T[]?[]? tlsBuckets = t_tlsBuckets;
                 if (tlsBuckets == null)
                 {
                     t_tlsBuckets = tlsBuckets = new T[NumBuckets][];
                     tlsBuckets[bucketIndex] = array;
                     if (s_trimBuffers)
                     {
+                        Debug.Assert(s_allTlsBuckets != null, "Should be non-null iff s_trimBuffers is true");
                         s_allTlsBuckets.Add(tlsBuckets, null);
                         if (Interlocked.Exchange(ref _callbackCreated, 1) != 1)
                         {
@@ -201,7 +205,7 @@ namespace System.Buffers
                 }
                 else
                 {
-                    T[] prev = tlsBuckets[bucketIndex];
+                    T[]? prev = tlsBuckets[bucketIndex];
                     tlsBuckets[bucketIndex] = array;
 
                     if (prev != null)
@@ -222,6 +226,9 @@ namespace System.Buffers
 
         public bool Trim()
         {
+            Debug.Assert(s_trimBuffers);
+            Debug.Assert(s_allTlsBuckets != null);
+
             int milliseconds = Environment.TickCount;
             MemoryPressure pressure = GetMemoryPressure();
 
@@ -229,7 +236,7 @@ namespace System.Buffers
             if (log.IsEnabled())
                 log.BufferTrimPoll(milliseconds, (int)pressure);
 
-            PerCoreLockedStacks[] perCoreBuckets = _buckets;
+            PerCoreLockedStacks?[] perCoreBuckets = _buckets;
             for (int i = 0; i < perCoreBuckets.Length; i++)
             {
                 perCoreBuckets[i]?.Trim((uint)milliseconds, Id, pressure, _bucketArraySizes[i]);
@@ -240,12 +247,12 @@ namespace System.Buffers
                 // Under high pressure, release all thread locals
                 if (log.IsEnabled())
                 {
-                    foreach (KeyValuePair<T[][], object> tlsBuckets in s_allTlsBuckets)
+                    foreach (KeyValuePair<T[]?[], object> tlsBuckets in s_allTlsBuckets)
                     {
-                        T[][] buckets = tlsBuckets.Key;
+                        T[]?[] buckets = tlsBuckets.Key;
                         for (int i = 0; i < buckets.Length; i++)
                         {
-                            T[] buffer = Interlocked.Exchange(ref buckets[i], null);
+                            T[]? buffer = Interlocked.Exchange(ref buckets[i], null);
                             if (buffer != null)
                             {
                                 // As we don't want to take a perf hit in the rent path it
@@ -257,9 +264,9 @@ namespace System.Buffers
                 }
                 else
                 {
-                    foreach (KeyValuePair<T[][], object> tlsBuckets in s_allTlsBuckets)
+                    foreach (KeyValuePair<T[]?[], object?> tlsBuckets in s_allTlsBuckets)
                     {
-                        T[][] buckets = tlsBuckets.Key;
+                        T[]?[] buckets = tlsBuckets.Key;
                         Array.Clear(buckets, 0, buckets.Length);
                     }
                 }
@@ -355,11 +362,11 @@ namespace System.Buffers
 
             /// <summary>Try to get an array from the stacks.  If each is empty when it's tested, null will be returned.</summary>
             [MethodImpl(MethodImplOptions.AggressiveInlining)]
-            public T[] TryPop()
+            public T[]? TryPop()
             {
                 // Try to pop from the associated stack first.  If that fails,
                 // round-robin through the other stacks.
-                T[] arr;
+                T[]? arr;
                 LockedStack[] stacks = _perCoreStacks;
                 int index = Thread.GetCurrentProcessorId() % stacks.Length;
                 for (int i = 0; i < stacks.Length; i++)
@@ -383,7 +390,7 @@ namespace System.Buffers
         /// <summary>Provides a simple stack of arrays, protected by a lock.</summary>
         private sealed class LockedStack
         {
-            private readonly T[][] _arrays = new T[MaxBuffersPerArraySizePerCore][];
+            private readonly T[]?[] _arrays = new T[MaxBuffersPerArraySizePerCore][];
             private int _count;
             private uint _firstStackItemMS;
 
@@ -408,9 +415,9 @@ namespace System.Buffers
             }
 
             [MethodImpl(MethodImplOptions.AggressiveInlining)]
-            public T[] TryPop()
+            public T[]? TryPop()
             {
-                T[] arr = null;
+                T[]? arr = null;
                 Monitor.Enter(this);
                 if (_count > 0)
                 {
@@ -473,7 +480,8 @@ namespace System.Buffers
 
                         while (_count > 0 && trimCount-- > 0)
                         {
-                            T[] array = _arrays[--_count];
+                            T[]? array = _arrays[--_count];
+                            Debug.Assert(array != null, "No nulls should have been present in slots < _count.");
                             _arrays[_count] = null;
 
                             if (log.IsEnabled())
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Utilities.cs b/src/System.Private.CoreLib/shared/System/Buffers/Utilities.cs
index 7e1caa039b..c49555a6e5 100644
--- a/src/System.Private.CoreLib/shared/System/Buffers/Utilities.cs
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Utilities.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.Diagnostics;
 using System.Numerics;
 using System.Runtime.CompilerServices;