Address PR feedback

src/System.Private.CoreLib/shared/System/Collections/Concurrent/ConcurrentQueueSegment.cs

@@ -323,7 +323,7 @@ public bool TryEnqueue(T item)
         internal struct Slot
         {
             /// <summary>The item.</summary>
-            [AllowNull,MaybeNull] public T Item; // SOS's ThreadPool command depends on this being at the beginning of the struct when T is a reference type
+            [AllowNull, MaybeNull] public T Item; // SOS's ThreadPool command depends on this being at the beginning of the struct when T is a reference type
             /// <summary>The sequence number for this slot, used to synchronize between enqueuers and dequeuers.</summary>
             public int SequenceNumber;
         }

src/System.Private.CoreLib/shared/System/Collections/Generic/Dictionary.cs

@@ -1405,7 +1405,7 @@ public struct Enumerator : IEnumerator<TKey>, IEnumerator
                 private readonly Dictionary<TKey, TValue> _dictionary;
                 private int _index;
                 private readonly int _version;
-                [AllowNull,MaybeNull] private TKey _currentKey;
+                [AllowNull, MaybeNull] private TKey _currentKey;
 
                 internal Enumerator(Dictionary<TKey, TValue> dictionary)
                 {
@@ -1588,7 +1588,7 @@ public struct Enumerator : IEnumerator<TValue>, IEnumerator
                 private readonly Dictionary<TKey, TValue> _dictionary;
                 private int _index;
                 private readonly int _version;
-                [AllowNull,MaybeNull] private TValue _currentValue;
+                [AllowNull, MaybeNull] private TValue _currentValue;
 
                 internal Enumerator(Dictionary<TKey, TValue> dictionary)
                 {

src/System.Private.CoreLib/shared/System/Collections/Generic/List.cs

@@ -1085,7 +1085,7 @@ public struct Enumerator : IEnumerator<T>, IEnumerator
             private readonly List<T> _list;
             private int _index;
             private readonly int _version;
-            [AllowNull,MaybeNull] private T _current;
+            [AllowNull, MaybeNull] private T _current;
 
             internal Enumerator(List<T> list)
             {

src/System.Private.CoreLib/shared/System/Diagnostics/CodeAnalysis/NullableAttributes.cs

@@ -70,9 +70,9 @@ public sealed class DoesNotReturnAttribute : Attribute { }
     [AttributeUsage(AttributeTargets.Parameter, Inherited = false)]
     public sealed class DoesNotReturnIfAttribute : Attribute
     {
-        /// <summary>Initializes the attribute.</summary>
+        /// <summary>Initializes the attribute with the specified parameter value.</summary>
         /// <param name="parameterValue">
-        /// The condition parameter value.  Code after the method will be considered unreachable by diagnostics if the argument to
+        /// The condition parameter value. Code after the method will be considered unreachable by diagnostics if the argument to
         /// the associated parameter matches this value.
         /// </param>
         public DoesNotReturnIfAttribute(bool parameterValue) => ParameterValue = parameterValue;

src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/Statics.cs

@@ -422,11 +422,10 @@ public static bool HasCustomAttribute(
             return result;
         }
 
-        [return: MaybeNull]
-        public static AttributeType GetCustomAttribute<AttributeType>(PropertyInfo propInfo)
-            where AttributeType : Attribute?
+        public static AttributeType? GetCustomAttribute<AttributeType>(PropertyInfo propInfo)
+            where AttributeType : Attribute
         {
-            AttributeType result = null!;
+            AttributeType? result = null;
 #if (ES_BUILD_PCL || ES_BUILD_PN)
             foreach (var attrib in propInfo.GetCustomAttributes<AttributeType>(false))
             {
@@ -443,11 +442,10 @@ public static AttributeType GetCustomAttribute<AttributeType>(PropertyInfo propI
             return result;
         }
 
-        [return: MaybeNull]
-        public static AttributeType GetCustomAttribute<AttributeType>(Type type)
-            where AttributeType : Attribute?
+        public static AttributeType? GetCustomAttribute<AttributeType>(Type type)
+            where AttributeType : Attribute
         {
-            AttributeType result = null!;
+            AttributeType? result = null;
 #if (ES_BUILD_PCL || ES_BUILD_PN)
             foreach (var attrib in type.GetTypeInfo().GetCustomAttributes<AttributeType>(false))
             {
@@ -540,9 +538,9 @@ public static TraceLoggingTypeInfo CreateDefaultTypeInfo(
 
             recursionCheck.Add(dataType);
 
-            var eventAttrib = Statics.GetCustomAttribute<EventDataAttribute?>(dataType);
+            var eventAttrib = Statics.GetCustomAttribute<EventDataAttribute>(dataType);
             if (eventAttrib != null ||
-                Statics.GetCustomAttribute<CompilerGeneratedAttribute?>(dataType) != null ||
+                Statics.GetCustomAttribute<CompilerGeneratedAttribute>(dataType) != null ||
                 IsGenericMatch(dataType, typeof(KeyValuePair<,>)))
             {
                 var analysis = new TypeAnalysis(dataType, eventAttrib, recursionCheck);

src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/TypeAnalysis.cs

@@ -59,7 +59,7 @@ public TypeAnalysis(
 
                 var propertyType = propertyInfo.PropertyType;
                 var propertyTypeInfo = TraceLoggingTypeInfo.GetInstance(propertyType, recursionCheck);
-                var fieldAttribute = Statics.GetCustomAttribute<EventFieldAttribute?>(propertyInfo);
+                var fieldAttribute = Statics.GetCustomAttribute<EventFieldAttribute>(propertyInfo);
 
                 string propertyName =
                     fieldAttribute != null && fieldAttribute.Name != null

src/System.Private.CoreLib/shared/System/Enum.cs

@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
 using System.Reflection;
 using System.Runtime.CompilerServices;
@@ -645,7 +646,7 @@ private static bool TryParseUInt64Enum(RuntimeType enumType, string? originalVal
         }
 
         /// <summary>Tries to parse the value of an enum with an underlying type that can't be expressed in C# (e.g. char, bool, double, etc.)</summary>
-        private static bool TryParseRareEnum(RuntimeType enumType, string? originalValueString, ReadOnlySpan<char> value, bool ignoreCase, bool throwOnFailure, out object? result)
+        private static bool TryParseRareEnum(RuntimeType enumType, string? originalValueString, ReadOnlySpan<char> value, bool ignoreCase, bool throwOnFailure, [NotNullWhen(true)] out object? result)
         {
             Debug.Assert(
                 enumType.GetEnumUnderlyingType() != typeof(sbyte) &&

src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/AsyncMethodBuilder.cs

@@ -569,7 +569,7 @@ private static void ExecutionContextCallback(object? s)
             /// <summary>A delegate to the <see cref="MoveNext()"/> method.</summary>
             private Action? _moveNextAction;
             /// <summary>The state machine itself.</summary>
-            [AllowNull,MaybeNull] public TStateMachine StateMachine = default!; // mutable struct; do not make this readonly. SOS DumpAsync command depends on this name.  // TODO-NULLABLE: Remove ! when nullable attributes are respected
+            [AllowNull, MaybeNull] public TStateMachine StateMachine = default!; // mutable struct; do not make this readonly. SOS DumpAsync command depends on this name.  // TODO-NULLABLE: Remove ! when nullable attributes are respected
             /// <summary>Captured ExecutionContext with which to invoke <see cref="MoveNextAction"/>; may be null.</summary>
             public ExecutionContext? Context;
 

src/System.Private.CoreLib/shared/System/Threading/Tasks/FutureFactory.cs

@@ -1229,7 +1229,7 @@ private sealed class FromAsyncTrimPromise<TInstance> : Task<TResult> where TInst
             internal static readonly AsyncCallback s_completeFromAsyncResult = CompleteFromAsyncResult;
 
             /// <summary>A reference to the object on which the begin/end methods are invoked.</summary>
-            [AllowNull,MaybeNull] private TInstance m_thisRef;
+            [AllowNull, MaybeNull] private TInstance m_thisRef;
             /// <summary>The end method.</summary>
             private Func<TInstance, IAsyncResult, TResult>? m_endMethod;
 

src/System.Private.CoreLib/shared/System/Threading/Tasks/Sources/ManualResetValueTaskSourceCore.cs

@@ -32,7 +32,7 @@ public struct ManualResetValueTaskSourceCore<TResult>
         /// <summary>Whether the current operation has completed.</summary>
         private bool _completed;
         /// <summary>The result with which the operation succeeded, or the default value if it hasn't yet completed or failed.</summary>
-        [AllowNull,MaybeNull] private TResult _result;
+        [AllowNull, MaybeNull] private TResult _result;
         /// <summary>The exception with which the operation failed, or null if it hasn't yet completed or completed successfully.</summary>
         private ExceptionDispatchInfo? _error;
         /// <summary>The current version of this value, used to help prevent misuse.</summary>

src/System.Private.CoreLib/shared/System/Threading/ThreadLocal.cs

@@ -675,7 +675,7 @@ internal LinkedSlot(LinkedSlotVolatile[]? slotArray)
             internal volatile LinkedSlotVolatile[]? _slotArray;
 
             // The value for this slot.
-            [AllowNull,MaybeNull] internal T _value = default!; // TODO-NULLABLE: Remove ! when nullable attributes are respected
+            [AllowNull, MaybeNull] internal T _value = default!; // TODO-NULLABLE: Remove ! when nullable attributes are respected
         }
 
         /// <summary>

src/System.Private.CoreLib/shared/System/Version.cs

@@ -320,7 +320,7 @@ public static bool TryParse(string? input, [NotNullWhen(true)] out Version? resu
             return (result = ParseVersion(input.AsSpan(), throwOnFailure: false)) != null;
         }
 
-        public static bool TryParse(ReadOnlySpan<char> input, out Version? result) =>
+        public static bool TryParse(ReadOnlySpan<char> input, [NotNullWhen(true)] out Version? result) =>
             (result = ParseVersion(input, throwOnFailure: false)) != null;
 
         private static Version? ParseVersion(ReadOnlySpan<char> input, bool throwOnFailure)