Remove stale TODO-NULLABLE comments from code

src/coreclr/src/System.Private.CoreLib/src/System/Attribute.CoreCLR.cs

@@ -287,9 +287,9 @@ private static Attribute[] InternalParamGetCustomAttributes(ParameterInfo param,
                 count = 0;
                 for (int i = 0; i < objAttr.Length; i++)
                 {
-                    if (objAttr[i] != null)
+                    if (objAttr[i] is object attr)
                     {
-                        attributes[count] = (Attribute)objAttr[i]!; // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+                        attributes[count] = (Attribute)attr;
                         count++;
                     }
                 }

src/coreclr/src/System.Private.CoreLib/src/System/Collections/Generic/EqualityComparer.CoreCLR.cs

@@ -116,7 +116,7 @@ internal override int IndexOf(T[] array, T value, int startIndex, int count)
             {
                 for (int i = startIndex; i < endIndex; i++)
                 {
-                    if (array[i] != null && array[i]!.Equals(value)) return i; // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+                    if (array[i] != null && array[i]!.Equals(value)) return i;
                 }
             }
             return -1;
@@ -136,7 +136,7 @@ internal override int LastIndexOf(T[] array, T value, int startIndex, int count)
             {
                 for (int i = startIndex; i >= endIndex; i--)
                 {
-                    if (array[i] != null && array[i]!.Equals(value)) return i; // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+                    if (array[i] != null && array[i]!.Equals(value)) return i;
                 }
             }
             return -1;

src/coreclr/src/System.Private.CoreLib/src/System/MulticastDelegate.cs

@@ -160,10 +160,10 @@ private static bool TrySetSlot(object?[] a, int index, object o)
 
             // The slot may be already set because we have added and removed the same method before.
             // Optimize this case, because it's cheaper than copying the array.
-            if (a[index] != null)
+            if (a[index] is object ai)
             {
                 MulticastDelegate d = (MulticastDelegate)o;
-                MulticastDelegate dd = (MulticastDelegate)a[index]!; // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+                MulticastDelegate dd = (MulticastDelegate)ai;
 
                 if (dd._methodPtr == d._methodPtr &&
                     dd._target == d._target &&

src/coreclr/src/System.Private.CoreLib/src/System/Reflection/Emit/ILGenerator.cs

@@ -1622,14 +1622,14 @@ internal void AddLocalSymInfoToCurrentScope(
         {
             int i = GetCurrentActiveScopeIndex();
             m_localSymInfos[i] ??= new LocalSymInfo();
-            m_localSymInfos[i]!.AddLocalSymInfo(strName, signature, slot, startOffset, endOffset); // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+            m_localSymInfos[i]!.AddLocalSymInfo(strName, signature, slot, startOffset, endOffset);
         }
 
         internal void AddUsingNamespaceToCurrentScope(string strNamespace)
         {
             int i = GetCurrentActiveScopeIndex();
             m_localSymInfos[i] ??= new LocalSymInfo();
-            m_localSymInfos[i]!.AddUsingNamespace(strNamespace); // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+            m_localSymInfos[i]!.AddUsingNamespace(strNamespace);
         }
 
         internal void AddScopeInfo(ScopeAction sa, int iOffset)
@@ -1693,9 +1693,9 @@ internal void EmitScopeTree(ISymbolWriter symWriter)
                 {
                     symWriter.CloseScope(m_iOffsets[i]);
                 }
-                if (m_localSymInfos[i] != null)
+                if (m_localSymInfos[i] is LocalSymInfo lsi)
                 {
-                    m_localSymInfos[i]!.EmitLocalSymInfo(symWriter); // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+                    lsi.EmitLocalSymInfo(symWriter);
                 }
             }
         }

src/coreclr/src/System.Private.CoreLib/src/System/RuntimeType.CoreCLR.cs

@@ -3900,9 +3900,9 @@ private void CreateInstanceCheckThis()
                 Type[] argsType = new Type[args.Length];
                 for (int i = 0; i < args.Length; i++)
                 {
-                    if (args[i] != null)
+                    if (args[i] is object arg)
                     {
-                        argsType[i] = args[i]!.GetType(); // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+                        argsType[i] = arg.GetType();
                     }
                 }
 

src/libraries/Common/src/System/Runtime/InteropServices/ComEventsMethod.cs

@@ -57,9 +57,9 @@ public DelegateWrapper(Delegate d, bool wrapArgs)
                 {
                     for (int i = 0; i < _expectedParamsCount; i++)
                     {
-                        if (_cachedTargetTypes[i] != null)
+                        if (_cachedTargetTypes[i] is Type t)
                         {
-                            args[i] = Enum.ToObject(_cachedTargetTypes[i]!, args[i]); // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+                            args[i] = Enum.ToObject(t, args[i]);
                         }
                     }
                 }

src/libraries/System.Collections.Concurrent/src/System/Collections/Concurrent/BlockingCollection.cs

@@ -1089,15 +1089,16 @@ private static List<WaitHandle> GetHandles(BlockingCollection<T>[] collections,
             List<CancellationToken> tokensList = new List<CancellationToken>(collections.Length + 1); // + 1 for the external token
             tokensList.Add(externalCancellationToken);
 
-            //Read the appropriate WaitHandle based on the operation mode.
+            // Read the appropriate WaitHandle based on the operation mode.
             if (isAddOperation)
             {
                 for (int i = 0; i < collections.Length; i++)
                 {
-                    if (collections[i]._freeNodes != null)
+                    BlockingCollection<T> c = collections[i];
+                    if (c._freeNodes != null)
                     {
-                        handlesList.Add(collections[i]._freeNodes!.AvailableWaitHandle); // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
-                        tokensList.Add(collections[i]._producersCancellationTokenSource.Token);
+                        handlesList.Add(c._freeNodes.AvailableWaitHandle);
+                        tokensList.Add(c._producersCancellationTokenSource.Token);
                     }
                 }
             }

src/libraries/System.ComponentModel.Composition/src/System/ComponentModel/Composition/ReflectionModel/LazyMemberInfo.cs

@@ -97,14 +97,13 @@ public override int GetHashCode()
             {
                 return MemberType.GetHashCode() ^ _accessorsCreator.GetHashCode();
             }
-            else
+
+            if (_accessors != null && _accessors[0] is MemberInfo accessor)
             {
-                if (_accessors == null || _accessors[0] == null)
-                {
-                    throw new Exception(SR.Diagnostic_InternalExceptionMessage);
-                }
-                return MemberType.GetHashCode() ^ _accessors[0]!.GetHashCode(); // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+                return MemberType.GetHashCode() ^ accessor.GetHashCode();
             }
+
+            throw new Exception(SR.Diagnostic_InternalExceptionMessage);
         }
 
         public override bool Equals(object? obj)

src/libraries/System.Drawing.Common/src/System/Drawing/ClientUtils.cs

@@ -109,9 +109,11 @@ public override bool Equals(object? obj)
 
                 for (int i = 0; i < Count; i++)
                 {
-                    if (InnerList[i] != other.InnerList[i])
+                    object? thisObj = InnerList[i];
+                    object? otherObj = other.InnerList[i];
+                    if (thisObj != otherObj)
                     {
-                        if (InnerList[i] == null || !InnerList[i]!.Equals(other.InnerList[i])) // TODO-NULLABLE: https://github.com/dotnet/roslyn/issues/34644
+                        if (thisObj is null || !thisObj.Equals(otherObj))
                         {
                             return false;
                         }

src/libraries/System.Drawing.Common/src/System/Drawing/Printing/PrintingServices.Unix.cs

@@ -664,11 +664,11 @@ internal static void GetPrintDialogInfo(string printer, ref string port, ref str
 
                 NameValueCollection options = LoadPrinterOptions(cups_dests.options, cups_dests.num_options);
 
-                if (options["printer-state"] != null)
-                    state = int.Parse(options["printer-state"]!); // TODO-NULLABLE dotnet/roslyn#34644
+                if (options["printer-state"] is string printerState)
+                    state = int.Parse(printerState);
 
-                if (options["printer-comment"] != null)
-                    comment = options["printer-state"]!; // TODO-NULLABLE dotnet/roslyn#34644
+                if (options["printer-comment"] is string printerComment)
+                    comment = printerComment;
 
                 switch (state)
                 {

src/libraries/System.Net.Http/src/System/Net/Http/Headers/HeaderUtilities.cs

@@ -355,11 +355,11 @@ internal static void DumpHeaders(StringBuilder sb, params HttpHeaders?[] headers
 
             for (int i = 0; i < headers.Length; i++)
             {
-                if (headers[i] != null)
+                if (headers[i] is HttpHeaders hh)
                 {
-                    foreach (var header in headers[i]!) // TODO-NULLABLE: https://github.com/dotnet/roslyn/issues/34644
+                    foreach (KeyValuePair<string, IEnumerable<string>> header in hh)
                     {
-                        foreach (var headerValue in header.Value)
+                        foreach (string headerValue in header.Value)
                         {
                             sb.Append("  ");
                             sb.Append(header.Key);

src/libraries/System.Private.CoreLib/src/System/Collections/ArrayList.cs

@@ -262,7 +262,7 @@ public virtual bool Contains(object? item)
             else
             {
                 for (int i = 0; i < _size; i++)
-                    if ((_items[i] != null) && (_items[i]!.Equals(item))) // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+                    if (_items[i] is object o && o.Equals(item))
                         return true;
                 return false;
             }
@@ -916,7 +916,7 @@ public override int IndexOf(object? value, int startIndex, int count)
                 else
                 {
                     for (int i = startIndex; i < endIndex; i++)
-                        if (_list[i] != null && _list[i]!.Equals(value)) // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+                        if (_list[i] is object o && o.Equals(value))
                             return i;
                     return -1;
                 }
@@ -984,7 +984,7 @@ public override int LastIndexOf(object? value, int startIndex, int count)
                 else
                 {
                     for (int i = startIndex; i >= endIndex; i--)
-                        if (_list[i] != null && _list[i]!.Equals(value)) // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+                        if (_list[i] is object o && o.Equals(value))
                             return i;
                     return -1;
                 }
@@ -2311,7 +2311,7 @@ public override bool Contains(object? item)
                 else
                 {
                     for (int i = 0; i < _baseSize; i++)
-                        if (_baseList[_baseIndex + i] != null && _baseList[_baseIndex + i]!.Equals(item)) // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+                        if (_baseList[_baseIndex + i] is object o && o.Equals(item))
                             return true;
                     return false;
                 }

src/libraries/System.Private.CoreLib/src/System/DefaultBinder.cs

@@ -104,15 +104,15 @@ public sealed override MethodBase BindToMethod(
                     continue;
 
                 // Validate the parameters.
-                ParameterInfo[] par = candidates[i]!.GetParametersNoCopy(); // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+                ParameterInfo[] par = candidates[i]!.GetParametersNoCopy();
 
 #region Match method by parameter count
                 if (par.Length == 0)
                 {
 #region No formal parameters
                     if (args.Length != 0)
                     {
-                        if ((candidates[i]!.CallingConvention & CallingConventions.VarArgs) == 0) // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+                        if ((candidates[i]!.CallingConvention & CallingConventions.VarArgs) == 0)
                             continue;
                     }
 

src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/TraceLogging/XplatEventLogger.cs

@@ -131,9 +131,9 @@ private static string Serialize(ReadOnlyCollection<string>? payloadName, ReadOnl
                     }
                     default:
                     {
-                        if (payload[i] != null)
+                        if (payload[i] is object o)
                         {
-                            sb.Append(payload[i]!.ToString()); // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+                            sb.Append(o.ToString());
                         }
                         break;
                     }

src/libraries/System.Private.CoreLib/src/System/Globalization/DateTimeParse.cs

@@ -194,23 +194,26 @@ internal static bool TryParseExactMultiple(ReadOnlySpan<char> s, string?[]? form
             //
             for (int i = 0; i < formats.Length; i++)
             {
-                if (formats[i] == null || formats[i]!.Length == 0) // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+                string? format = formats[i];
+                if (string.IsNullOrEmpty(format))
                 {
                     result.SetBadFormatSpecifierFailure();
                     return false;
                 }
+
                 // Create a new result each time to ensure the runs are independent. Carry through
                 // flags from the caller and return the result.
                 DateTimeResult innerResult = default;       // The buffer to store the parsing result.
                 innerResult.Init(s);
                 innerResult.flags = result.flags;
-                if (TryParseExact(s, formats[i], dtfi, style, ref innerResult))
+                if (TryParseExact(s, format, dtfi, style, ref innerResult))
                 {
                     result.parsedDate = innerResult.parsedDate;
                     result.timeZoneOffset = innerResult.timeZoneOffset;
                     return true;
                 }
             }
+
             result.SetBadDateTimeFailure();
             return false;
         }

src/libraries/System.Private.CoreLib/src/System/Resources/ResourceReader.cs

@@ -956,7 +956,7 @@ private Type FindType(int typeIndex)
                 }
             }
             Debug.Assert(_typeTable[typeIndex] != null, "Should have found a type!");
-            return _typeTable[typeIndex]!; // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+            return _typeTable[typeIndex]!;
         }
 
         private string TypeNameFromTypeCode(ResourceTypeCode typeCode)

src/libraries/System.Private.CoreLib/src/System/Text/StringBuilder.cs

@@ -1340,15 +1340,15 @@ private unsafe StringBuilder AppendJoinCore<T>(char* separator, int separatorLen
 
             if (values[0] != null)
             {
-                Append(values[0]!.ToString()); // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+                Append(values[0]!.ToString());
             }
 
             for (int i = 1; i < values.Length; i++)
             {
                 Append(separator, separatorLength);
                 if (values[i] != null)
                 {
-                    Append(values[i]!.ToString()); // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+                    Append(values[i]!.ToString());
                 }
             }
             return this;

src/libraries/System.Private.CoreLib/src/System/Threading/WaitHandle.cs

@@ -303,9 +303,9 @@ private static int WaitMultiple(ReadOnlySpan<WaitHandle> waitHandles, bool waitA
             {
                 for (int i = 0; i < waitHandles.Length; ++i)
                 {
-                    if (safeWaitHandles[i] != null)
+                    if (safeWaitHandles[i] is SafeWaitHandle swh)
                     {
-                        safeWaitHandles[i]!.DangerousRelease(); // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+                        swh.DangerousRelease();
                         safeWaitHandles[i] = null;
                     }
                 }

src/libraries/System.Private.CoreLib/src/System/Type.Helpers.cs

@@ -135,8 +135,8 @@ public virtual Type[] FindInterfaces(TypeFilter filter, object? filterCriteria)
             cnt = 0;
             for (int i = 0; i < c.Length; i++)
             {
-                if (c[i] != null)
-                    ret[cnt++] = c[i]!; // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+                if (c[i] is Type t)
+                    ret[cnt++] = t!;
             }
             return ret;
         }
@@ -272,47 +272,47 @@ public virtual MemberInfo[] FindMembers(MemberTypes memberType, BindingFlags bin
             {
                 for (i = 0; i < m.Length; i++)
                     if (m[i] != null)
-                        ret[cnt++] = m[i]!;  // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+                        ret[cnt++] = m[i]!;
             }
 
             // Copy the Constructors
             if (c != null)
             {
                 for (i = 0; i < c.Length; i++)
-                    if (c[i] != null)
-                        ret[cnt++] = c[i]!;  // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+                    if (c[i] is ConstructorInfo ci)
+                        ret[cnt++] = ci;
             }
 
             // Copy the Fields
             if (f != null)
             {
                 for (i = 0; i < f.Length; i++)
-                    if (f[i] != null)
-                        ret[cnt++] = f[i]!;  // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+                    if (f[i] is FieldInfo fi)
+                        ret[cnt++] = fi;
             }
 
             // Copy the Properties
             if (p != null)
             {
                 for (i = 0; i < p.Length; i++)
-                    if (p[i] != null)
-                        ret[cnt++] = p[i]!; // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+                    if (p[i] is PropertyInfo pi)
+                        ret[cnt++] = pi;
             }
 
             // Copy the Events
             if (e != null)
             {
                 for (i = 0; i < e.Length; i++)
-                    if (e[i] != null)
-                        ret[cnt++] = e[i]!; // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+                    if (e[i] is EventInfo ei)
+                        ret[cnt++] = ei;
             }
 
             // Copy the Types
             if (t != null)
             {
                 for (i = 0; i < t.Length; i++)
-                    if (t[i] != null)
-                        ret[cnt++] = t[i]!; // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+                    if (t[i] is Type type)
+                        ret[cnt++] = type;
             }
 
             return ret;

src/libraries/System.Private.DataContractSerialization/src/System/Runtime/Serialization/ExtensionDataReader.cs

@@ -105,8 +105,7 @@ internal void Reset()
         public override string XmlLang { get { return IsXmlDataNode ? _xmlNodeReader.XmlLang : base.XmlLang; } }
         public override string this[int i] { get { return IsXmlDataNode ? _xmlNodeReader[i] : GetAttribute(i); } }
         public override string? this[string name] { get { return IsXmlDataNode ? _xmlNodeReader[name] : GetAttribute(name); } }
-        // TODO-NULLABLE - unnecessary namespaceURI! - https://github.com/dotnet/roslyn/issues/47221
-        public override string? this[string name, string? namespaceURI] { get { return IsXmlDataNode ? _xmlNodeReader[name, namespaceURI!] : GetAttribute(name, namespaceURI); } }
+        public override string? this[string name, string? namespaceURI] { get { return IsXmlDataNode ? _xmlNodeReader[name, namespaceURI] : GetAttribute(name, namespaceURI); } }
 
         public override bool MoveToFirstAttribute()
         {