Remove now unnecessary !s / TODO-NULLABLE comments (#25749)

* Remove !s and TODO-NULLABLE comments for [DoesNotReturn]

* Remove !s and TODO-NULLABLE comments for [NotNullIfNotNull]

* Remove !s and TODO-NULLABLE comments for writes via Interlocked.CompareExchange

* Remove !s and TODO-NULLABLE comments for Debug.Assert on fields

* Update/add several TODO-NULLABLE comments

60 files changed, 312 insertions, 312 deletions

diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.CreateFile.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.CreateFile.cs
index b1589acff2..0e7519d42f 100644
--- a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.CreateFile.cs
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.CreateFile.cs
@@ -33,7 +33,7 @@ internal partial class Interop
             int dwFlagsAndAttributes,
             IntPtr hTemplateFile)
         {
-            lpFileName = PathInternal.EnsureExtendedPrefixIfNeeded(lpFileName)!; // TODO-NULLABLE: Remove ! when [NotNullIfNotNull] respected
+            lpFileName = PathInternal.EnsureExtendedPrefixIfNeeded(lpFileName);
             return CreateFilePrivate(lpFileName, dwDesiredAccess, dwShareMode, ref securityAttrs, dwCreationDisposition, dwFlagsAndAttributes, hTemplateFile);
         }
     }
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.CreateFile2.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.CreateFile2.cs
index 82d62cc4d3..323de99c2a 100644
--- a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.CreateFile2.cs
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.CreateFile2.cs
@@ -26,7 +26,7 @@ internal partial class Interop
             FileMode dwCreationDisposition,
             ref Kernel32.CREATEFILE2_EXTENDED_PARAMETERS pCreateExParams)
         {
-            lpFileName = PathInternal.EnsureExtendedPrefixIfNeeded(lpFileName)!; // TODO-NULLABLE: Remove ! when [NotNullIfNotNull] respected
+            lpFileName = PathInternal.EnsureExtendedPrefixIfNeeded(lpFileName);
             return CreateFile2Private(lpFileName, dwDesiredAccess, dwShareMode, dwCreationDisposition, ref pCreateExParams);
         }
     }
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FindFirstFileEx.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FindFirstFileEx.cs
index 7d5203d44f..bb1ddf7857 100644
--- a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FindFirstFileEx.cs
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FindFirstFileEx.cs
@@ -21,7 +21,7 @@ internal partial class Interop
 
         internal static SafeFindHandle FindFirstFile(string fileName, ref WIN32_FIND_DATA data)
         {
-            fileName = PathInternal.EnsureExtendedPrefixIfNeeded(fileName)!; // TODO-NULLABLE: Remove ! when [NotNullIfNotNull] respected
+            fileName = PathInternal.EnsureExtendedPrefixIfNeeded(fileName);
 
             // use FindExInfoBasic since we don't care about short name and it has better perf
             return FindFirstFileExPrivate(fileName, FINDEX_INFO_LEVELS.FindExInfoBasic, ref data, FINDEX_SEARCH_OPS.FindExSearchNameMatch, IntPtr.Zero, 0);
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetFileAttributesEx.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetFileAttributesEx.cs
index 65649e497d..ee2370038f 100644
--- a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetFileAttributesEx.cs
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetFileAttributesEx.cs
@@ -21,7 +21,7 @@ internal partial class Interop
 
         internal static bool GetFileAttributesEx(string name, GET_FILEEX_INFO_LEVELS fileInfoLevel, ref WIN32_FILE_ATTRIBUTE_DATA lpFileInformation)
         {
-            name = PathInternal.EnsureExtendedPrefixIfNeeded(name)!; // TODO-NULLABLE: Remove ! when [NotNullIfNotNull] respected
+            name = PathInternal.EnsureExtendedPrefixIfNeeded(name);
             return GetFileAttributesExPrivate(name, fileInfoLevel, ref lpFileInformation);
         }
     }
diff --git a/src/System.Private.CoreLib/shared/System/AppContext.cs b/src/System.Private.CoreLib/shared/System/AppContext.cs
index 8601d3f26b..605326ca1f 100644
--- a/src/System.Private.CoreLib/shared/System/AppContext.cs
+++ b/src/System.Private.CoreLib/shared/System/AppContext.cs
@@ -63,12 +63,12 @@ namespace System
         }
 
 #pragma warning disable CS0067 // events raised by the VM
-        public static event UnhandledExceptionEventHandler UnhandledException;
+        public static event UnhandledExceptionEventHandler UnhandledException; // TODO-NULLABLE: Should all events use nullable delegate types?
 
-        public static event System.EventHandler<FirstChanceExceptionEventArgs> FirstChanceException;
+        public static event System.EventHandler<FirstChanceExceptionEventArgs> FirstChanceException; // TODO-NULLABLE: Should all events use nullable delegate types?
 #pragma warning restore CS0067
 
-        public static event System.EventHandler ProcessExit;
+        public static event System.EventHandler ProcessExit; // TODO-NULLABLE: Should all events use nullable delegate types?
 
         internal static void OnProcessExit()
         {
@@ -126,7 +126,7 @@ namespace System
                 Interlocked.CompareExchange(ref s_switches, new Dictionary<string, bool>(), null);
             }
 
-            lock (s_switches!) // TODO-NULLABLE: Remove ! when compiler specially-recognizes CompareExchange for nullability
+            lock (s_switches)
             {
                 s_switches[switchName] = isEnabled;
             }
diff --git a/src/System.Private.CoreLib/shared/System/AppDomain.cs b/src/System.Private.CoreLib/shared/System/AppDomain.cs
index d48d34922f..6795e556f3 100644
--- a/src/System.Private.CoreLib/shared/System/AppDomain.cs
+++ b/src/System.Private.CoreLib/shared/System/AppDomain.cs
@@ -41,7 +41,7 @@ namespace System
 
         public PermissionSet PermissionSet => new PermissionSet(PermissionState.Unrestricted);
 
-        public event UnhandledExceptionEventHandler UnhandledException
+        public event UnhandledExceptionEventHandler UnhandledException // TODO-NULLABLE: Should all events use nullable delegate types?
         {
             add { AppContext.UnhandledException += value; }
             remove { AppContext.UnhandledException -= value; }
@@ -67,15 +67,15 @@ namespace System
 
         public bool IsHomogenous => true;
 
-        public event EventHandler DomainUnload = null!;
+        public event EventHandler DomainUnload = null!; // TODO-NULLABLE: Should all events use nullable delegate types?
 
-        public event EventHandler<FirstChanceExceptionEventArgs> FirstChanceException
+        public event EventHandler<FirstChanceExceptionEventArgs> FirstChanceException // TODO-NULLABLE: Should all events use nullable delegate types?
         {
             add { AppContext.FirstChanceException += value; }
             remove { AppContext.FirstChanceException -= value; }
         }
 
-        public event EventHandler ProcessExit
+        public event EventHandler ProcessExit // TODO-NULLABLE: Should all events use nullable delegate types?
         {
             add { AppContext.ProcessExit += value; }
             remove { AppContext.ProcessExit -= value; }
@@ -232,27 +232,27 @@ namespace System
 
         public Assembly[] GetAssemblies() => AssemblyLoadContext.GetLoadedAssemblies();
 
-        public event AssemblyLoadEventHandler AssemblyLoad
+        public event AssemblyLoadEventHandler AssemblyLoad // TODO-NULLABLE: Should all events use nullable delegate types?
         {
             add { AssemblyLoadContext.AssemblyLoad += value; }
             remove { AssemblyLoadContext.AssemblyLoad -= value; }
         }
 
-        public event ResolveEventHandler AssemblyResolve
+        public event ResolveEventHandler AssemblyResolve // TODO-NULLABLE: Should all events use nullable delegate types?
         {
             add { AssemblyLoadContext.AssemblyResolve += value; }
             remove { AssemblyLoadContext.AssemblyResolve -= value; }
         }
 
-        public event ResolveEventHandler ReflectionOnlyAssemblyResolve = null!;
+        public event ResolveEventHandler ReflectionOnlyAssemblyResolve = null!; // TODO-NULLABLE: Should all events use nullable delegate types?
 
-        public event ResolveEventHandler TypeResolve
+        public event ResolveEventHandler TypeResolve // TODO-NULLABLE: Should all events use nullable delegate types?
         {
             add { AssemblyLoadContext.TypeResolve += value; }
             remove { AssemblyLoadContext.TypeResolve -= value; }
         }
 
-        public event ResolveEventHandler ResourceResolve
+        public event ResolveEventHandler ResourceResolve // TODO-NULLABLE: Should all events use nullable delegate types?
         {
             add { AssemblyLoadContext.ResourceResolve += value; }
             remove { AssemblyLoadContext.ResourceResolve -= value; }
@@ -409,7 +409,7 @@ namespace System
                                 (Func<IPrincipal>)mi.CreateDelegate(typeof(Func<IPrincipal>)));
                         }
 
-                        principal = s_getUnauthenticatedPrincipal!(); // TODO-NULLABLE: Remove ! when [NotNullIfNotNull] respected
+                        principal = s_getUnauthenticatedPrincipal();
                         break;
 
                     case PrincipalPolicy.WindowsPrincipal:
@@ -425,7 +425,7 @@ namespace System
                                 (Func<IPrincipal>)mi.CreateDelegate(typeof(Func<IPrincipal>)));
                         }
 
-                        principal = s_getWindowsPrincipal!(); // TODO-NULLABLE: Remove ! when [NotNullIfNotNull] respected
+                        principal = s_getWindowsPrincipal();
                         break;
                 }
             }
diff --git a/src/System.Private.CoreLib/shared/System/Array.cs b/src/System.Private.CoreLib/shared/System/Array.cs
index 11479d88e2..0613abeb0e 100644
--- a/src/System.Private.CoreLib/shared/System/Array.cs
+++ b/src/System.Private.CoreLib/shared/System/Array.cs
@@ -37,7 +37,7 @@ namespace System
             }
 
             // T[] implements IList<T>.
-            return new ReadOnlyCollection<T>(array!); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            return new ReadOnlyCollection<T>(array);
         }
 
         public static void Resize<T>([NotNull] ref T[]? array, int newSize)
@@ -66,7 +66,7 @@ namespace System
             {
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.lengths);
             }
-            if (lengths!.Length == 0) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (lengths.Length == 0)
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_NeedAtLeast1Rank);
 
             int[] intLengths = new int[lengths.Length];
@@ -150,7 +150,7 @@ namespace System
         {
             if (indices == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.indices);
-            if (Rank != indices!.Length) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (Rank != indices.Length)
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RankIndices);
 
             int[] intIndices = new int[indices.Length];
@@ -210,7 +210,7 @@ namespace System
         {
             if (indices == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.indices);
-            if (Rank != indices!.Length) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (Rank != indices.Length)
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RankIndices);
 
             int[] intIndices = new int[indices.Length];
@@ -325,7 +325,7 @@ namespace System
             int i = 0;
             int c = 0;
 
-            while (i < o!.Length && c == 0) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            while (i < o.Length && c == 0)
             {
                 object? left = GetValue(i);
                 object? right = o.GetValue(i);
@@ -384,7 +384,7 @@ namespace System
 
             for (int i = (this.Length >= 8 ? this.Length - 8 : 0); i < this.Length; i++)
             {
-                ret = CombineHashCodes(ret, comparer!.GetHashCode(GetValue(i)!)); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                ret = CombineHashCodes(ret, comparer.GetHashCode(GetValue(i)!));
             }
 
             return ret;
@@ -407,7 +407,7 @@ namespace System
         {
             if (array == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
-            return BinarySearch(array!, array!.GetLowerBound(0), array.Length, value, null); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            return BinarySearch(array, array.GetLowerBound(0), array.Length, value, null);
         }
 
         // Searches a section of an array for a given element using a binary search
@@ -446,7 +446,7 @@ namespace System
         {
             if (array == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
-            return BinarySearch(array!, array!.GetLowerBound(0), array.Length, value, comparer); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            return BinarySearch(array, array.GetLowerBound(0), array.Length, value, comparer);
         }
 
         // Searches a section of an array for a given element using a binary search
@@ -468,7 +468,7 @@ namespace System
         {
             if (array == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
-            int lb = array!.GetLowerBound(0); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            int lb = array.GetLowerBound(0);
             if (index < lb)
                 ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
             if (length < 0)
@@ -553,14 +553,14 @@ namespace System
         {
             if (array == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
-            return BinarySearch<T>(array!, 0, array!.Length, value, null); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            return BinarySearch<T>(array, 0, array.Length, value, null);
         }
 
         public static int BinarySearch<T>(T[] array, T value, System.Collections.Generic.IComparer<T>? comparer)
         {
             if (array == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
-            return BinarySearch<T>(array!, 0, array!.Length, value, comparer); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            return BinarySearch<T>(array, 0, array.Length, value, comparer);
         }
 
         public static int BinarySearch<T>(T[] array, int index, int length, T value)
@@ -577,7 +577,7 @@ namespace System
             if (length < 0)
                 ThrowHelper.ThrowLengthArgumentOutOfRange_ArgumentOutOfRange_NeedNonNegNum();
 
-            if (array!.Length - index < length) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (array.Length - index < length)
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen);
 
             return ArraySortHelper<T>.Default.BinarySearch(array, index, length, value, comparer);
@@ -595,10 +595,10 @@ namespace System
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.converter);
             }
 
-            TOutput[] newArray = new TOutput[array!.Length]; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            TOutput[] newArray = new TOutput[array.Length];
             for (int i = 0; i < array.Length; i++)
             {
-                newArray[i] = converter!(array[i]); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                newArray[i] = converter(array[i]);
             }
             return newArray;
         }
@@ -615,7 +615,7 @@ namespace System
             if (array != null && array.Rank != 1)
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RankMultiDimNotSupported);
             // Note: Array.Copy throws a RankException and we want a consistent ArgumentException for all the IList CopyTo methods.
-            Array.Copy(this, GetLowerBound(0), array!, index, Length); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            Array.Copy(this, GetLowerBound(0), array!, index, Length);
         }
 
         public void CopyTo(Array array, long index)
@@ -649,7 +649,7 @@ namespace System
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
             }
 
-            for (int i = 0; i < array!.Length; i++) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            for (int i = 0; i < array.Length; i++)
             {
                 array[i] = value;
             }
@@ -662,19 +662,19 @@ namespace System
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
             }
 
-            if (startIndex < 0 || startIndex > array!.Length) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (startIndex < 0 || startIndex > array.Length)
             {
                 ThrowHelper.ThrowStartIndexArgumentOutOfRange_ArgumentOutOfRange_Index();
             }
 
-            if (count < 0 || startIndex > array!.Length - count) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (count < 0 || startIndex > array.Length - count)
             {
                 ThrowHelper.ThrowCountArgumentOutOfRange_ArgumentOutOfRange_Count();
             }
 
             for (int i = startIndex; i < startIndex + count; i++)
             {
-                array![i] = value; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                array[i] = value;
             }
         }
 
@@ -691,9 +691,9 @@ namespace System
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match);
             }
 
-            for (int i = 0; i < array!.Length; i++) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            for (int i = 0; i < array.Length; i++)
             {
-                if (match!(array[i])) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                if (match(array[i]))
                 {
                     return array[i];
                 }
@@ -714,9 +714,9 @@ namespace System
             }
 
             List<T> list = new List<T>();
-            for (int i = 0; i < array!.Length; i++) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            for (int i = 0; i < array.Length; i++)
             {
-                if (match!(array[i])) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                if (match(array[i]))
                 {
                     list.Add(array[i]);
                 }
@@ -731,7 +731,7 @@ namespace System
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
             }
 
-            return FindIndex(array!, 0, array!.Length, match); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            return FindIndex(array, 0, array.Length, match);
         }
 
         public static int FindIndex<T>(T[] array, int startIndex, Predicate<T> match)
@@ -741,7 +741,7 @@ namespace System
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
             }
 
-            return FindIndex(array!, startIndex, array!.Length - startIndex, match); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            return FindIndex(array, startIndex, array.Length - startIndex, match);
         }
 
         public static int FindIndex<T>(T[] array, int startIndex, int count, Predicate<T> match)
@@ -751,12 +751,12 @@ namespace System
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
             }
 
-            if (startIndex < 0 || startIndex > array!.Length) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (startIndex < 0 || startIndex > array.Length)
             {
                 ThrowHelper.ThrowStartIndexArgumentOutOfRange_ArgumentOutOfRange_Index();
             }
 
-            if (count < 0 || startIndex > array!.Length - count) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (count < 0 || startIndex > array.Length - count)
             {
                 ThrowHelper.ThrowCountArgumentOutOfRange_ArgumentOutOfRange_Count();
             }
@@ -769,7 +769,7 @@ namespace System
             int endIndex = startIndex + count;
             for (int i = startIndex; i < endIndex; i++)
             {
-                if (match!(array![i])) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                if (match!(array[i]))
                     return i;
             }
             return -1;
@@ -788,9 +788,9 @@ namespace System
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match);
             }
 
-            for (int i = array!.Length - 1; i >= 0; i--) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            for (int i = array.Length - 1; i >= 0; i--)
             {
-                if (match!(array[i])) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                if (match(array[i]))
                 {
                     return array[i];
                 }
@@ -805,7 +805,7 @@ namespace System
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
             }
 
-            return FindLastIndex(array!, array!.Length - 1, array.Length, match); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            return FindLastIndex(array, array.Length - 1, array.Length, match);
         }
 
         public static int FindLastIndex<T>(T[] array, int startIndex, Predicate<T> match)
@@ -815,7 +815,7 @@ namespace System
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
             }
 
-            return FindLastIndex(array!, startIndex, startIndex + 1, match); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            return FindLastIndex(array, startIndex, startIndex + 1, match);
         }
 
         public static int FindLastIndex<T>(T[] array, int startIndex, int count, Predicate<T> match)
@@ -830,7 +830,7 @@ namespace System
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match);
             }
 
-            if (array!.Length == 0) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (array.Length == 0)
             {
                 // Special case for 0 length List
                 if (startIndex != -1)
@@ -856,7 +856,7 @@ namespace System
             int endIndex = startIndex - count;
             for (int i = startIndex; i > endIndex; i--)
             {
-                if (match!(array[i])) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                if (match(array[i]))
                 {
                     return i;
                 }
@@ -876,9 +876,9 @@ namespace System
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.action);
             }
 
-            for (int i = 0; i < array!.Length; i++) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            for (int i = 0; i < array.Length; i++)
             {
-                action!(array[i]); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                action(array[i]);
             }
         }
 
@@ -890,7 +890,7 @@ namespace System
         {
             if (array == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
-            return IndexOf(array!, value, array!.GetLowerBound(0), array.Length); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            return IndexOf(array, value, array.GetLowerBound(0), array.Length);
         }
 
         // Returns the index of the first occurrence of a given value in a range of
@@ -903,7 +903,7 @@ namespace System
         {
             if (array == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
-            int lb = array!.GetLowerBound(0); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            int lb = array.GetLowerBound(0);
             return IndexOf(array, value, startIndex, array.Length - startIndex + lb);
         }
 
@@ -917,7 +917,7 @@ namespace System
         {
             if (array == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
-            if (array!.Rank != 1) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (array.Rank != 1)
                 ThrowHelper.ThrowRankException(ExceptionResource.Rank_MultiDimNotSupported);
 
             int lb = array.GetLowerBound(0);
@@ -987,7 +987,7 @@ namespace System
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
             }
 
-            return IndexOf(array!, value, 0, array!.Length); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            return IndexOf(array, value, 0, array.Length);
         }
 
         public static int IndexOf<T>(T[] array, T value, int startIndex)
@@ -997,7 +997,7 @@ namespace System
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
             }
 
-            return IndexOf(array!, value, startIndex, array!.Length - startIndex); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            return IndexOf(array, value, startIndex, array.Length - startIndex);
         }
 
         public static int IndexOf<T>(T[] array, T value, int startIndex, int count)
@@ -1007,7 +1007,7 @@ namespace System
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
             }
 
-            if ((uint)startIndex > (uint)array!.Length) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if ((uint)startIndex > (uint)array.Length)
             {
                 ThrowHelper.ThrowStartIndexArgumentOutOfRange_ArgumentOutOfRange_Index();
             }
@@ -1071,7 +1071,7 @@ namespace System
         {
             if (array == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
-            int lb = array!.GetLowerBound(0); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            int lb = array.GetLowerBound(0);
             return LastIndexOf(array, value, array.Length - 1 + lb, array.Length);
         }
 
@@ -1084,7 +1084,7 @@ namespace System
         {
             if (array == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
-            int lb = array!.GetLowerBound(0); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            int lb = array.GetLowerBound(0);
             return LastIndexOf(array, value, startIndex, startIndex + 1 - lb);
         }
 
@@ -1098,7 +1098,7 @@ namespace System
         {
             if (array == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
-            int lb = array!.GetLowerBound(0); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            int lb = array.GetLowerBound(0);
             if (array.Length == 0)
             {
                 return lb - 1;
@@ -1170,7 +1170,7 @@ namespace System
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
             }
 
-            return LastIndexOf(array!, value, array!.Length - 1, array.Length); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            return LastIndexOf(array, value, array.Length - 1, array.Length);
         }
 
         public static int LastIndexOf<T>(T[] array, T value, int startIndex)
@@ -1180,7 +1180,7 @@ namespace System
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
             }
             // if array is empty and startIndex is 0, we need to pass 0 as count
-            return LastIndexOf(array!, value, startIndex, (array!.Length == 0) ? 0 : (startIndex + 1)); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            return LastIndexOf(array, value, startIndex, (array.Length == 0) ? 0 : (startIndex + 1));
         }
 
         public static int LastIndexOf<T>(T[] array, T value, int startIndex, int count)
@@ -1190,7 +1190,7 @@ namespace System
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
             }
 
-            if (array!.Length == 0) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (array.Length == 0)
             {
                 //
                 // Special case for 0 length List
@@ -1285,7 +1285,7 @@ namespace System
         {
             if (array == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
-            Reverse(array!, array!.GetLowerBound(0), array.Length); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            Reverse(array, array.GetLowerBound(0), array.Length);
         }
 
         // Reverses the elements in a range of an array. Following a call to this
@@ -1298,7 +1298,7 @@ namespace System
         {
             if (array == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
-            int lowerBound = array!.GetLowerBound(0); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            int lowerBound = array.GetLowerBound(0);
             if (index < lowerBound)
                 ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
             if (length < 0)
@@ -1341,7 +1341,7 @@ namespace System
         {
             if (array == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
-            Reverse(array!, 0, array!.Length); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            Reverse(array, 0, array.Length);
         }
 
         public static void Reverse<T>(T[] array, int index, int length)
@@ -1352,7 +1352,7 @@ namespace System
                 ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
             if (length < 0)
                 ThrowHelper.ThrowLengthArgumentOutOfRange_ArgumentOutOfRange_NeedNonNegNum();
-            if (array!.Length - index < length) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (array.Length - index < length)
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen);
 
             if (length <= 1)
@@ -1378,7 +1378,7 @@ namespace System
         {
             if (array == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
-            Sort(array!, null, array!.GetLowerBound(0), array.Length, null); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            Sort(array, null, array.GetLowerBound(0), array.Length, null);
         }
 
         // Sorts the elements of two arrays based on the keys in the first array.
@@ -1391,7 +1391,7 @@ namespace System
         {
             if (keys == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.keys);
-            Sort(keys!, items, keys!.GetLowerBound(0), keys.Length, null); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            Sort(keys, items, keys.GetLowerBound(0), keys.Length, null);
         }
 
         // Sorts the elements in a section of an array. The sort compares the
@@ -1439,7 +1439,7 @@ namespace System
         {
             if (keys == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.keys);
-            Sort(keys!, items, keys!.GetLowerBound(0), keys.Length, comparer); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            Sort(keys, items, keys.GetLowerBound(0), keys.Length, comparer);
         }
 
         // Sorts the elements in a section of an array. The sort compares the
@@ -1465,7 +1465,7 @@ namespace System
         {
             if (keys == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.keys);
-            if (keys!.Rank != 1 || (items != null && items.Rank != 1)) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (keys.Rank != 1 || (items != null && items.Rank != 1))
                 ThrowHelper.ThrowRankException(ExceptionResource.Rank_MultiDimNotSupported);
             int keysLowerBound = keys.GetLowerBound(0);
             if (items != null && keysLowerBound != items.GetLowerBound(0))
@@ -1488,14 +1488,14 @@ namespace System
         {
             if (array == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
-            Sort<T>(array!, 0, array!.Length, null); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            Sort<T>(array, 0, array.Length, null);
         }
 
         public static void Sort<TKey, TValue>(TKey[] keys, TValue[]? items)
         {
             if (keys == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.keys);
-            Sort<TKey, TValue>(keys!, items, 0, keys!.Length, null); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            Sort<TKey, TValue>(keys, items, 0, keys.Length, null);
         }
 
         public static void Sort<T>(T[] array, int index, int length)
@@ -1512,14 +1512,14 @@ namespace System
         {
             if (array == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
-            Sort<T>(array!, 0, array!.Length, comparer); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            Sort<T>(array, 0, array.Length, comparer);
         }
 
         public static void Sort<TKey, TValue>(TKey[] keys, TValue[]? items, System.Collections.Generic.IComparer<TKey>? comparer)
         {
             if (keys == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.keys);
-            Sort<TKey, TValue>(keys!, items, 0, keys!.Length, comparer); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            Sort<TKey, TValue>(keys, items, 0, keys.Length, comparer);
         }
 
         public static void Sort<T>(T[] array, int index, int length, System.Collections.Generic.IComparer<T>? comparer)
@@ -1530,7 +1530,7 @@ namespace System
                 ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
             if (length < 0)
                 ThrowHelper.ThrowLengthArgumentOutOfRange_ArgumentOutOfRange_NeedNonNegNum();
-            if (array!.Length - index < length) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (array.Length - index < length)
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen);
 
             if (length > 1)
@@ -1557,7 +1557,7 @@ namespace System
                 ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
             if (length < 0)
                 ThrowHelper.ThrowLengthArgumentOutOfRange_ArgumentOutOfRange_NeedNonNegNum();
-            if (keys!.Length - index < length || (items != null && index > items.Length - length)) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (keys.Length - index < length || (items != null && index > items.Length - length))
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen);
 
             if (length > 1)
@@ -1594,7 +1594,7 @@ namespace System
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.comparison);
             }
 
-            ArraySortHelper<T>.Sort(array!, 0, array!.Length, comparison!); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            ArraySortHelper<T>.Sort(array, 0, array.Length, comparison!);
         }
 
         public static bool TrueForAll<T>(T[] array, Predicate<T> match)
@@ -1609,9 +1609,9 @@ namespace System
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match);
             }
 
-            for (int i = 0; i < array!.Length; i++) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            for (int i = 0; i < array.Length; i++)
             {
-                if (!match!(array[i])) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                if (!match(array[i]))
                 {
                     return false;
                 }
diff --git a/src/System.Private.CoreLib/shared/System/ArraySegment.cs b/src/System.Private.CoreLib/shared/System/ArraySegment.cs
index 941d73ca11..9c383a0e49 100644
--- a/src/System.Private.CoreLib/shared/System/ArraySegment.cs
+++ b/src/System.Private.CoreLib/shared/System/ArraySegment.cs
@@ -43,7 +43,7 @@ namespace System
 
             _array = array;
             _offset = 0;
-            _count = array!.Length; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            _count = array.Length;
         }
 
         public ArraySegment(T[] array, int offset, int count)
diff --git a/src/System.Private.CoreLib/shared/System/BitConverter.cs b/src/System.Private.CoreLib/shared/System/BitConverter.cs
index f6f6b98379..8841ca9b1c 100644
--- a/src/System.Private.CoreLib/shared/System/BitConverter.cs
+++ b/src/System.Private.CoreLib/shared/System/BitConverter.cs
@@ -236,7 +236,7 @@ namespace System
         {
             if (value == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.value);
-            if (unchecked((uint)startIndex) >= unchecked((uint)value!.Length)) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (unchecked((uint)startIndex) >= unchecked((uint)value.Length))
                 ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.startIndex, ExceptionResource.ArgumentOutOfRange_Index);
             if (startIndex > value.Length - sizeof(short))
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_ArrayPlusOffTooSmall, ExceptionArgument.value);
@@ -257,7 +257,7 @@ namespace System
         {
             if (value == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.value);
-            if (unchecked((uint)startIndex) >= unchecked((uint)value!.Length)) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (unchecked((uint)startIndex) >= unchecked((uint)value.Length))
                 ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.startIndex, ExceptionResource.ArgumentOutOfRange_Index);
             if (startIndex > value.Length - sizeof(int))
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_ArrayPlusOffTooSmall, ExceptionArgument.value);
@@ -278,7 +278,7 @@ namespace System
         {
             if (value == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.value);
-            if (unchecked((uint)startIndex) >= unchecked((uint)value!.Length)) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (unchecked((uint)startIndex) >= unchecked((uint)value.Length))
                 ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.startIndex, ExceptionResource.ArgumentOutOfRange_Index);
             if (startIndex > value.Length - sizeof(long))
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_ArrayPlusOffTooSmall, ExceptionArgument.value);
@@ -363,11 +363,11 @@ namespace System
         {
             if (value == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.value);
-            if (startIndex < 0 || startIndex >= value!.Length && startIndex > 0) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (startIndex < 0 || startIndex >= value.Length && startIndex > 0)
                 ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.startIndex, ExceptionResource.ArgumentOutOfRange_Index);
             if (length < 0)
                 throw new ArgumentOutOfRangeException(nameof(length), SR.ArgumentOutOfRange_GenericPositive);
-            if (startIndex > value!.Length - length) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (startIndex > value.Length - length)
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_ArrayPlusOffTooSmall, ExceptionArgument.value);
 
             if (length == 0)
@@ -409,7 +409,7 @@ namespace System
         {
             if (value == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.value);
-            return ToString(value!, 0, value!.Length); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            return ToString(value, 0, value.Length);
         }
 
         // Converts an array of bytes into a String.  
@@ -417,7 +417,7 @@ namespace System
         {
             if (value == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.value);
-            return ToString(value!, startIndex, value!.Length - startIndex); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            return ToString(value, startIndex, value.Length - startIndex);
         }
 
         /*==================================ToBoolean===================================
@@ -435,7 +435,7 @@ namespace System
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.value);
             if (startIndex < 0)
                 ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.startIndex, ExceptionResource.ArgumentOutOfRange_Index);
-            if (startIndex > value!.Length - 1) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (startIndex > value.Length - 1)
                 ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.startIndex, ExceptionResource.ArgumentOutOfRange_Index); // differs from other overloads, which throw base ArgumentException
 
             return value[startIndex] != 0;
diff --git a/src/System.Private.CoreLib/shared/System/Collections/Concurrent/ConcurrentQueue.cs b/src/System.Private.CoreLib/shared/System/Collections/Concurrent/ConcurrentQueue.cs
index e62e37272a..adc22effff 100644
--- a/src/System.Private.CoreLib/shared/System/Collections/Concurrent/ConcurrentQueue.cs
+++ b/src/System.Private.CoreLib/shared/System/Collections/Concurrent/ConcurrentQueue.cs
@@ -100,7 +100,7 @@ namespace System.Collections.Concurrent
 
             // Initialize the segment and add all of the data to it.
             _tail = _head = new ConcurrentQueueSegment<T>(length);
-            foreach (T item in collection!) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            foreach (T item in collection)
             {
                 Enqueue(item);
             }
@@ -147,7 +147,7 @@ namespace System.Collections.Concurrent
 
             // Otherwise, fall back to the slower path that first copies the contents
             // to an array, and then uses that array's non-generic CopyTo to do the copy.
-            ToArray().CopyTo(array!, index); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            ToArray().CopyTo(array, index);
         }
 
         /// <summary>
@@ -164,7 +164,7 @@ namespace System.Collections.Concurrent
         /// cref="ICollection"/>. This property is not supported.
         /// </summary>
         /// <exception cref="NotSupportedException">The SyncRoot property is not supported.</exception>
-        object ICollection.SyncRoot { get { ThrowHelper.ThrowNotSupportedException(ExceptionResource.ConcurrentCollection_SyncRoot_NotSupported); return default!; } } // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+        object ICollection.SyncRoot { get { ThrowHelper.ThrowNotSupportedException(ExceptionResource.ConcurrentCollection_SyncRoot_NotSupported); return default; } }
 
         /// <summary>Returns an enumerator that iterates through a collection.</summary>
         /// <returns>An <see cref="IEnumerator"/> that can be used to iterate through the collection.</returns>
@@ -462,7 +462,7 @@ namespace System.Collections.Concurrent
 
             // Get the number of items to be enumerated
             long count = GetCount(head, headHead, tail, tailTail);
-            if (index > array!.Length - count) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (index > array.Length - count)
             {
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_ArrayPlusOffTooSmall);
             }
diff --git a/src/System.Private.CoreLib/shared/System/Collections/Generic/Dictionary.cs b/src/System.Private.CoreLib/shared/System/Collections/Generic/Dictionary.cs
index a10bb894a8..f2372deeea 100644
--- a/src/System.Private.CoreLib/shared/System/Collections/Generic/Dictionary.cs
+++ b/src/System.Private.CoreLib/shared/System/Collections/Generic/Dictionary.cs
@@ -100,7 +100,7 @@ namespace System.Collections.Generic
             // avoid the enumerator allocation and overhead by looping through the entries array directly.
             // We only do this when dictionary is Dictionary<TKey,TValue> and not a subclass, to maintain
             // back-compat with subclasses that may have overridden the enumerator behavior.
-            if (dictionary!.GetType() == typeof(Dictionary<TKey, TValue>)) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (dictionary.GetType() == typeof(Dictionary<TKey, TValue>))
             {
                 Dictionary<TKey, TValue> d = (Dictionary<TKey, TValue>)dictionary;
                 int count = d._count;
@@ -131,7 +131,7 @@ namespace System.Collections.Generic
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.collection);
             }
 
-            foreach (KeyValuePair<TKey, TValue> pair in collection!) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            foreach (KeyValuePair<TKey, TValue> pair in collection)
             {
                 Add(pair.Key, pair.Value);
             }
@@ -219,7 +219,7 @@ namespace System.Collections.Generic
                 int i = FindEntry(key);
                 if (i >= 0) return _entries![i].value;
                 ThrowHelper.ThrowKeyNotFoundException(key);
-                return default!; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                return default;
             }
             set
             {
@@ -320,7 +320,7 @@ namespace System.Collections.Generic
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
             }
 
-            if ((uint)index > (uint)array!.Length) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if ((uint)index > (uint)array.Length)
             {
                 ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
             }
@@ -354,7 +354,7 @@ namespace System.Collections.Generic
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.info);
             }
 
-            info!.AddValue(VersionName, _version); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            info.AddValue(VersionName, _version);
             info.AddValue(ComparerName, _comparer ?? EqualityComparer<TKey>.Default, typeof(IEqualityComparer<TKey>));
             info.AddValue(HashSizeName, _buckets == null ? 0 : _buckets.Length); // This is the length of the bucket array
 
@@ -383,7 +383,7 @@ namespace System.Collections.Generic
                 IEqualityComparer<TKey>? comparer = _comparer;
                 if (comparer == null)
                 {
-                    uint hashCode = (uint)key!.GetHashCode(); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                    uint hashCode = (uint)key.GetHashCode();
                     // Value in _buckets is 1-based
                     i = buckets[hashCode % (uint)buckets.Length] - 1;
                     if (default(TKey)! != null) // TODO-NULLABLE: default(T) == null warning (https://github.com/dotnet/roslyn/issues/34757)
@@ -492,7 +492,7 @@ namespace System.Collections.Generic
             Debug.Assert(entries != null, "expected entries to be non-null");
 
             IEqualityComparer<TKey>? comparer = _comparer;
-            uint hashCode = (uint)((comparer == null) ? key!.GetHashCode() : comparer.GetHashCode(key)); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            uint hashCode = (uint)((comparer == null) ? key.GetHashCode() : comparer.GetHashCode(key));
 
             int collisionCount = 0;
             ref int bucket = ref _buckets[hashCode % (uint)_buckets.Length];
@@ -700,7 +700,7 @@ namespace System.Collections.Generic
                     ThrowHelper.ThrowSerializationException(ExceptionResource.Serialization_MissingKeys);
                 }
 
-                for (int i = 0; i < array!.Length; i++) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                for (int i = 0; i < array.Length; i++)
                 {
                     if (array[i].Key == null)
                     {
@@ -778,7 +778,7 @@ namespace System.Collections.Generic
             if (buckets != null)
             {
                 Debug.Assert(entries != null, "entries should be non-null");
-                uint hashCode = (uint)(_comparer?.GetHashCode(key) ?? key!.GetHashCode()); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                uint hashCode = (uint)(_comparer?.GetHashCode(key) ?? key.GetHashCode());
                 uint bucket = hashCode % (uint)buckets.Length;
                 int last = -1;
                 // Value in buckets is 1-based
@@ -846,7 +846,7 @@ namespace System.Collections.Generic
             if (buckets != null)
             {
                 Debug.Assert(entries != null, "entries should be non-null");
-                uint hashCode = (uint)(_comparer?.GetHashCode(key) ?? key!.GetHashCode()); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                uint hashCode = (uint)(_comparer?.GetHashCode(key) ?? key.GetHashCode());
                 uint bucket = hashCode % (uint)buckets.Length;
                 int last = -1;
                 // Value in buckets is 1-based
@@ -925,7 +925,7 @@ namespace System.Collections.Generic
         {
             if (array == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
-            if (array!.Rank != 1) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (array.Rank != 1)
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RankMultiDimNotSupported);
             if (array.GetLowerBound(0) != 0)
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_NonZeroLowerBound);
@@ -965,7 +965,7 @@ namespace System.Collections.Generic
                     {
                         if (entries![i].next >= -1)
                         {
-                            objects![index++] = new KeyValuePair<TKey, TValue>(entries[i].key, entries[i].value); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                            objects[index++] = new KeyValuePair<TKey, TValue>(entries[i].key, entries[i].value);
                         }
                     }
                 }
@@ -1089,7 +1089,7 @@ namespace System.Collections.Generic
 
                 try
                 {
-                    TKey tempKey = (TKey)key!; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                    TKey tempKey = (TKey)key;
                     try
                     {
                         this[tempKey] = (TValue)value!;
@@ -1125,7 +1125,7 @@ namespace System.Collections.Generic
 
             try
             {
-                TKey tempKey = (TKey)key!; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                TKey tempKey = (TKey)key;
 
                 try
                 {
@@ -1298,7 +1298,7 @@ namespace System.Collections.Generic
                 {
                     ThrowHelper.ThrowArgumentNullException(ExceptionArgument.dictionary);
                 }
-                _dictionary = dictionary!; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                _dictionary = dictionary;
             }
 
             public Enumerator GetEnumerator()
@@ -1311,12 +1311,12 @@ namespace System.Collections.Generic
                     ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
                 }
 
-                if (index < 0 || index > array!.Length) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                if (index < 0 || index > array.Length)
                 {
                     ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
                 }
 
-                if (array!.Length - index < _dictionary.Count) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                if (array.Length - index < _dictionary.Count)
                 {
                     ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_ArrayPlusOffTooSmall);
                 }
@@ -1358,7 +1358,7 @@ namespace System.Collections.Generic
             {
                 if (array == null)
                     ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
-                if (array!.Rank != 1) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                if (array.Rank != 1)
                     ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RankMultiDimNotSupported);
                 if (array.GetLowerBound(0) != 0)
                     ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_NonZeroLowerBound);
@@ -1385,7 +1385,7 @@ namespace System.Collections.Generic
                     {
                         for (int i = 0; i < count; i++)
                         {
-                            if (entries![i].next >= -1) objects![index++] = entries[i].key; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                            if (entries![i].next >= -1) objects[index++] = entries[i].key;
                         }
                     }
                     catch (ArrayTypeMismatchException)
@@ -1481,7 +1481,7 @@ namespace System.Collections.Generic
                 {
                     ThrowHelper.ThrowArgumentNullException(ExceptionArgument.dictionary);
                 }
-                _dictionary = dictionary!; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                _dictionary = dictionary;
             }
 
             public Enumerator GetEnumerator()
@@ -1494,7 +1494,7 @@ namespace System.Collections.Generic
                     ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
                 }
 
-                if ((uint)index > array!.Length) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                if ((uint)index > array.Length)
                 {
                     ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
                 }
@@ -1541,7 +1541,7 @@ namespace System.Collections.Generic
             {
                 if (array == null)
                     ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
-                if (array!.Rank != 1) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                if (array.Rank != 1)
                     ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RankMultiDimNotSupported);
                 if (array.GetLowerBound(0) != 0)
                     ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_NonZeroLowerBound);
@@ -1568,7 +1568,7 @@ namespace System.Collections.Generic
                     {
                         for (int i = 0; i < count; i++)
                         {
-                            if (entries![i].next >= -1) objects![index++] = entries[i].value!; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                            if (entries![i].next >= -1) objects[index++] = entries[i].value!;
                         }
                     }
                     catch (ArrayTypeMismatchException)
diff --git a/src/System.Private.CoreLib/shared/System/Collections/Generic/List.cs b/src/System.Private.CoreLib/shared/System/Collections/Generic/List.cs
index 5e13e3eb37..46d710a7f7 100644
--- a/src/System.Private.CoreLib/shared/System/Collections/Generic/List.cs
+++ b/src/System.Private.CoreLib/shared/System/Collections/Generic/List.cs
@@ -346,7 +346,7 @@ namespace System.Collections.Generic
             List<TOutput> list = new List<TOutput>(_size);
             for (int i = 0; i < _size; i++)
             {
-                list._items[i] = converter!(_items[i]); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                list._items[i] = converter(_items[i]);
             }
             list._size = _size;
             return list;
@@ -447,7 +447,7 @@ namespace System.Collections.Generic
             List<T> list = new List<T>();
             for (int i = 0; i < _size; i++)
             {
-                if (match!(_items[i])) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                if (match(_items[i]))
                 {
                     list.Add(_items[i]);
                 }
@@ -543,7 +543,7 @@ namespace System.Collections.Generic
             int endIndex = startIndex - count;
             for (int i = startIndex; i > endIndex; i--)
             {
-                if (match!(_items[i])) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                if (match(_items[i]))
                 {
                     return i;
                 }
@@ -747,7 +747,7 @@ namespace System.Collections.Generic
             }
             else
             {
-                using (IEnumerator<T> en = collection!.GetEnumerator()) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                using (IEnumerator<T> en = collection.GetEnumerator())
                 {
                     while (en.MoveNext())
                     {
@@ -867,7 +867,7 @@ namespace System.Collections.Generic
             int freeIndex = 0;   // the first free slot in items array
 
             // Find the first item which needs to be removed.
-            while (freeIndex < _size && !match!(_items[freeIndex])) freeIndex++; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            while (freeIndex < _size && !match(_items[freeIndex])) freeIndex++;
             if (freeIndex >= _size) return 0;
 
             int current = freeIndex + 1;
@@ -1026,7 +1026,7 @@ namespace System.Collections.Generic
 
             if (_size > 1)
             {
-                ArraySortHelper<T>.Sort(_items, 0, _size, comparison!); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                ArraySortHelper<T>.Sort(_items, 0, _size, comparison);
             }
             _version++;
         }
diff --git a/src/System.Private.CoreLib/shared/System/Collections/HashHelpers.SerializationInfoTable.cs b/src/System.Private.CoreLib/shared/System/Collections/HashHelpers.SerializationInfoTable.cs
index 64cf029d1c..0a2fbb90a3 100644
--- a/src/System.Private.CoreLib/shared/System/Collections/HashHelpers.SerializationInfoTable.cs
+++ b/src/System.Private.CoreLib/shared/System/Collections/HashHelpers.SerializationInfoTable.cs
@@ -22,7 +22,7 @@ namespace System.Collections
                 if (s_serializationInfoTable == null)
                     Interlocked.CompareExchange(ref s_serializationInfoTable, new ConditionalWeakTable<object, SerializationInfo>(), null);
 
-                return s_serializationInfoTable!; // TODO-NULLABLE: Remove ! when compiler specially-recognizes CompareExchange for nullability
+                return s_serializationInfoTable;
             }
         }
     }
diff --git a/src/System.Private.CoreLib/shared/System/Collections/ObjectModel/Collection.cs b/src/System.Private.CoreLib/shared/System/Collections/ObjectModel/Collection.cs
index 21af1c3593..0b258b7846 100644
--- a/src/System.Private.CoreLib/shared/System/Collections/ObjectModel/Collection.cs
+++ b/src/System.Private.CoreLib/shared/System/Collections/ObjectModel/Collection.cs
@@ -26,7 +26,7 @@ namespace System.Collections.ObjectModel
             {
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.list);
             }
-            items = list!;  // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            items = list;
         }
 
         public int Count
@@ -195,7 +195,7 @@ namespace System.Collections.ObjectModel
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
             }
 
-            if (array!.Rank != 1) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (array.Rank != 1)
             {
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RankMultiDimNotSupported);
             }
@@ -249,7 +249,7 @@ namespace System.Collections.ObjectModel
                 {
                     for (int i = 0; i < count; i++)
                     {
-                        objects![index++] = items[i];  // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                        objects[index++] = items[i];
                     }
                 }
                 catch (ArrayTypeMismatchException)
diff --git a/src/System.Private.CoreLib/shared/System/Collections/ObjectModel/ReadOnlyCollection.cs b/src/System.Private.CoreLib/shared/System/Collections/ObjectModel/ReadOnlyCollection.cs
index 69b3424169..52a18e891b 100644
--- a/src/System.Private.CoreLib/shared/System/Collections/ObjectModel/ReadOnlyCollection.cs
+++ b/src/System.Private.CoreLib/shared/System/Collections/ObjectModel/ReadOnlyCollection.cs
@@ -21,7 +21,7 @@ namespace System.Collections.ObjectModel
             {
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.list);
             }
-            this.list = list!; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            this.list = list;
         }
 
         public int Count
@@ -127,7 +127,7 @@ namespace System.Collections.ObjectModel
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
             }
 
-            if (array!.Rank != 1)  // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (array.Rank != 1)
             {
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RankMultiDimNotSupported);
             }
@@ -181,7 +181,7 @@ namespace System.Collections.ObjectModel
                 {
                     for (int i = 0; i < count; i++)
                     {
-                        objects![index++] = list[i]; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                        objects[index++] = list[i];
                     }
                 }
                 catch (ArrayTypeMismatchException)
diff --git a/src/System.Private.CoreLib/shared/System/DateTimeOffset.cs b/src/System.Private.CoreLib/shared/System/DateTimeOffset.cs
index 20457028c2..6cc68de64d 100644
--- a/src/System.Private.CoreLib/shared/System/DateTimeOffset.cs
+++ b/src/System.Private.CoreLib/shared/System/DateTimeOffset.cs
@@ -658,7 +658,7 @@ namespace System
         public static DateTimeOffset Parse(string input, IFormatProvider? formatProvider)
         {
             if (input == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.input);
-            return Parse(input!, formatProvider, DateTimeStyles.None); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            return Parse(input, formatProvider, DateTimeStyles.None);
         }
 
         public static DateTimeOffset Parse(string input, IFormatProvider? formatProvider, DateTimeStyles styles)
@@ -689,7 +689,7 @@ namespace System
         {
             if (input == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.input);
             if (format == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.format);
-            return ParseExact(input!, format!, formatProvider, DateTimeStyles.None); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            return ParseExact(input, format, formatProvider, DateTimeStyles.None);
         }
 
         // Constructs a DateTimeOffset from a string. The string must specify a
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Contracts/Contracts.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Contracts/Contracts.cs
index af6c1a333f..df338d16fb 100644
--- a/src/System.Private.CoreLib/shared/System/Diagnostics/Contracts/Contracts.cs
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Contracts/Contracts.cs
@@ -703,7 +703,7 @@ namespace System.Diagnostics.Contracts
         /// full trust, because it will inform you of bugs in the appdomain and because the event handler
         /// could allow you to continue execution.
         /// </summary>
-        public static event EventHandler<ContractFailedEventArgs> ContractFailed
+        public static event EventHandler<ContractFailedEventArgs> ContractFailed // TODO-NULLABLE: Should all events use nullable delegate types?
         {
             add
             {
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/EventSource.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/EventSource.cs
index b7492347a8..58e74a12eb 100644
--- a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/EventSource.cs
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/EventSource.cs
@@ -479,7 +479,7 @@ namespace System.Diagnostics.Tracing
         /// <summary>
         /// Fires when a Command (e.g. Enable) comes from a an EventListener.  
         /// </summary>
-        public event EventHandler<EventCommandEventArgs> EventCommandExecuted
+        public event EventHandler<EventCommandEventArgs> EventCommandExecuted // TODO-NULLABLE: Should all events use nullable delegate types?
         {
             add
             {
@@ -4042,7 +4042,7 @@ namespace System.Diagnostics.Tracing
         /// In a multi-threaded environment, it is possible that 'EventSourceEventWrittenCallback' 
         /// events for a particular eventSource to occur BEFORE the EventSourceCreatedCallback is issued.
         /// </summary>
-        public event EventHandler<EventSourceCreatedEventArgs> EventSourceCreated
+        public event EventHandler<EventSourceCreatedEventArgs> EventSourceCreated // TODO-NULLABLE: Should all events use nullable delegate types?
         {
             add
             {
@@ -4060,7 +4060,7 @@ namespace System.Diagnostics.Tracing
         /// This event is raised whenever an event has been written by a EventSource for which 
         /// the EventListener has enabled events.  
         /// </summary>
-        public event EventHandler<EventWrittenEventArgs> EventWritten = null!;
+        public event EventHandler<EventWrittenEventArgs> EventWritten = null!; // TODO-NULLABLE: Should all events use nullable delegate types?
 
         static EventListener()
         {
@@ -4479,7 +4479,7 @@ namespace System.Diagnostics.Tracing
             {
                 if (s_EventSources == null)
                     Interlocked.CompareExchange(ref s_EventSources, new List<WeakReference>(2), null);
-                return s_EventSources!; // TODO-NULLABLE: Remove ! when compiler specially-recognizes CompareExchange for nullability
+                return s_EventSources;
             }
         }
 
diff --git a/src/System.Private.CoreLib/shared/System/Environment.Win32.cs b/src/System.Private.CoreLib/shared/System/Environment.Win32.cs
index 3cad6fbf8c..78d49b1bcc 100644
--- a/src/System.Private.CoreLib/shared/System/Environment.Win32.cs
+++ b/src/System.Private.CoreLib/shared/System/Environment.Win32.cs
@@ -80,7 +80,7 @@ namespace System
                 {
                     foreach (string name in environmentKey.GetValueNames())
                     {
-                        string? value = environmentKey.GetValue(name, "")!.ToString(); // TODO-NULLABLE: Remove ! when [NotNullIfNotNull] respected
+                        string? value = environmentKey.GetValue(name, "").ToString();
                         try
                         {
                             results.Add(name, value);
diff --git a/src/System.Private.CoreLib/shared/System/Environment.cs b/src/System.Private.CoreLib/shared/System/Environment.cs
index d99a5a667a..2b638fde9e 100644
--- a/src/System.Private.CoreLib/shared/System/Environment.cs
+++ b/src/System.Private.CoreLib/shared/System/Environment.cs
@@ -122,7 +122,7 @@ namespace System
                 {
                     Interlocked.CompareExchange(ref s_osVersion, GetOSVersion(), null);
                 }
-                return s_osVersion!; // TODO-NULLABLE: Remove ! when compiler specially-recognizes CompareExchange for nullability
+                return s_osVersion;
             }
         }
 
diff --git a/src/System.Private.CoreLib/shared/System/Exception.cs b/src/System.Private.CoreLib/shared/System/Exception.cs
index cb13645192..80dec57b10 100644
--- a/src/System.Private.CoreLib/shared/System/Exception.cs
+++ b/src/System.Private.CoreLib/shared/System/Exception.cs
@@ -166,7 +166,7 @@ namespace System
             return s;
         }
 
-        protected event EventHandler<SafeSerializationEventArgs> SerializeObjectState
+        protected event EventHandler<SafeSerializationEventArgs> SerializeObjectState // TODO-NULLABLE: Should all events use nullable delegate types?
         {
             add { throw new PlatformNotSupportedException(SR.PlatformNotSupported_SecureBinarySerialization); }
             remove { throw new PlatformNotSupportedException(SR.PlatformNotSupported_SecureBinarySerialization); }
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/CultureData.Windows.cs b/src/System.Private.CoreLib/shared/System/Globalization/CultureData.Windows.cs
index 8d117ebab1..2e528e69a4 100644
--- a/src/System.Private.CoreLib/shared/System/Globalization/CultureData.Windows.cs
+++ b/src/System.Private.CoreLib/shared/System/Globalization/CultureData.Windows.cs
@@ -432,7 +432,7 @@ namespace System.Globalization
             {
                 for (int i = 0; i < array.Length; i++)
                 {
-                    array[i] = ReescapeWin32String(array[i])!; // TODO-NULLABLE: Remove ! when [NotNullIfNotNull] respected
+                    array[i] = ReescapeWin32String(array[i]);
                 }
             }
 
diff --git a/src/System.Private.CoreLib/shared/System/Progress.cs b/src/System.Private.CoreLib/shared/System/Progress.cs
index 12557da4e9..36095c96c1 100644
--- a/src/System.Private.CoreLib/shared/System/Progress.cs
+++ b/src/System.Private.CoreLib/shared/System/Progress.cs
@@ -56,7 +56,7 @@ namespace System
         /// Handlers registered with this event will be invoked on the 
         /// <see cref="System.Threading.SynchronizationContext"/> captured when the instance was constructed.
         /// </remarks>
-        public event EventHandler<T> ProgressChanged = null!;
+        public event EventHandler<T> ProgressChanged = null!; // TODO-NULLABLE: Should all events use nullable delegate types?
 
         /// <summary>Reports a progress change.</summary>
         /// <param name="value">The value of the updated progress.</param>
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/Assembly.cs b/src/System.Private.CoreLib/shared/System/Reflection/Assembly.cs
index 69820dea99..0b7a189219 100644
--- a/src/System.Private.CoreLib/shared/System/Reflection/Assembly.cs
+++ b/src/System.Private.CoreLib/shared/System/Reflection/Assembly.cs
@@ -117,7 +117,7 @@ namespace System.Reflection
             return Activator.CreateInstance(t, bindingAttr, binder, args, culture, activationAttributes);
         }
 
-        public virtual event ModuleResolveEventHandler ModuleResolve { add { throw NotImplemented.ByDesign; } remove { throw NotImplemented.ByDesign; } }
+        public virtual event ModuleResolveEventHandler ModuleResolve { add { throw NotImplemented.ByDesign; } remove { throw NotImplemented.ByDesign; } } // TODO-NULLABLE: Should all events use nullable delegate types?
 
         public virtual Module ManifestModule { get { throw NotImplemented.ByDesign; } }
         public virtual Module? GetModule(string name) { throw NotImplemented.ByDesign; }
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/AsyncMethodBuilder.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/AsyncMethodBuilder.cs
index 35f9702327..3c9ecc3a12 100644
--- a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/AsyncMethodBuilder.cs
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/AsyncMethodBuilder.cs
@@ -132,7 +132,7 @@ namespace System.Runtime.CompilerServices
                 // and decrement its outstanding operation count.
                 try
                 {
-                    System.Threading.Tasks.Task.ThrowAsync(exception!, targetContext: _synchronizationContext); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                    System.Threading.Tasks.Task.ThrowAsync(exception, targetContext: _synchronizationContext);
                 }
                 finally
                 {
@@ -144,7 +144,7 @@ namespace System.Runtime.CompilerServices
                 // Otherwise, queue the exception to be thrown on the ThreadPool.  This will
                 // result in a crash unless legacy exception behavior is enabled by a config
                 // file or a CLR host.
-                System.Threading.Tasks.Task.ThrowAsync(exception!, targetContext: null); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                System.Threading.Tasks.Task.ThrowAsync(exception, targetContext: null);
             }
 
             // The exception was propagated already; we don't need or want to fault the builder, just mark it as completed.
@@ -602,7 +602,7 @@ namespace System.Runtime.CompilerServices
                 if (context == null)
                 {
                     Debug.Assert(StateMachine != null);
-                    StateMachine!.MoveNext(); // TODO-NULLABLE: remove ! when Debug.Assert on fields is respected (https://github.com/dotnet/roslyn/issues/36830)
+                    StateMachine.MoveNext();
                 }
                 else
                 {
@@ -788,7 +788,7 @@ namespace System.Runtime.CompilerServices
             // If the exception represents cancellation, cancel the task.  Otherwise, fault the task.
             bool successfullySet = exception is OperationCanceledException oce ?
                 task.TrySetCanceled(oce.CancellationToken, oce) :
-                task.TrySetException(exception!); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                task.TrySetException(exception);
 
             // Unlike with TaskCompletionSource, we do not need to spin here until _taskAndStateMachine is completed,
             // since AsyncTaskMethodBuilder.SetException should not be immediately followed by any code
@@ -1017,7 +1017,7 @@ namespace System.Runtime.CompilerServices
 
             try
             {
-                stateMachine!.MoveNext(); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                stateMachine.MoveNext();
             }
             finally
             {
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/ConditionalWeakTable.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/ConditionalWeakTable.cs
index a916d719fc..b1a760af8c 100644
--- a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/ConditionalWeakTable.cs
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/ConditionalWeakTable.cs
@@ -59,7 +59,7 @@ namespace System.Runtime.CompilerServices
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.key);
             }
 
-            return _container.TryGetValueWorker(key!, out value); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            return _container.TryGetValueWorker(key, out value);
         }
 
         /// <summary>Adds a key to the table.</summary>
@@ -80,13 +80,13 @@ namespace System.Runtime.CompilerServices
 
             lock (_lock)
             {
-                int entryIndex = _container.FindEntry(key!, out _); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                int entryIndex = _container.FindEntry(key, out _);
                 if (entryIndex != -1)
                 {
                     ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_AddingDuplicate);
                 }
 
-                CreateEntry(key!, value); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                CreateEntry(key, value);
             }
         }
 
@@ -102,7 +102,7 @@ namespace System.Runtime.CompilerServices
 
             lock (_lock)
             {
-                int entryIndex = _container.FindEntry(key!, out _); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                int entryIndex = _container.FindEntry(key, out _);
 
                 // if we found a key we should just update, if no we should create a new entry.
                 if (entryIndex != -1)
@@ -111,7 +111,7 @@ namespace System.Runtime.CompilerServices
                 }
                 else
                 {
-                    CreateEntry(key!, value); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                    CreateEntry(key, value);
                 }
             }
         }
@@ -133,7 +133,7 @@ namespace System.Runtime.CompilerServices
 
             lock (_lock)
             {
-                return _container.Remove(key!); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                return _container.Remove(key);
             }
         }
 
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/ContractHelper.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/ContractHelper.cs
index 4cb70c052e..e654458cc8 100644
--- a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/ContractHelper.cs
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/ContractHelper.cs
@@ -17,7 +17,7 @@ namespace System.Runtime.CompilerServices
         /// event handlers sets the Cancel flag in the ContractFailedEventArgs, then the Contract class will
         /// not pop up an assert dialog box or trigger escalation policy.
         /// </summary>
-        internal static event EventHandler<ContractFailedEventArgs> InternalContractFailed;
+        internal static event EventHandler<ContractFailedEventArgs> InternalContractFailed; // TODO-NULLABLE: Should all events use nullable delegate types?
 
         /// <summary>
         /// Rewriter will call this method on a contract failure to allow listeners to be notified.
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/RuntimeHelpers.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/RuntimeHelpers.cs
index b251c0b05d..60fa072752 100644
--- a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/RuntimeHelpers.cs
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/RuntimeHelpers.cs
@@ -23,7 +23,7 @@ namespace System.Runtime.CompilerServices
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
             }
 
-            (int offset, int length) = range.GetOffsetAndLength(array!.Length); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            (int offset, int length) = range.GetOffsetAndLength(array.Length);
 
             if (default(T)! != null || typeof(T[]) == array.GetType()) // TODO-NULLABLE: default(T) == null warning (https://github.com/dotnet/roslyn/issues/34757)
             {
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/NativeLibrary.cs b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/NativeLibrary.cs
index 2062499057..33dee03fb8 100644
--- a/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/NativeLibrary.cs
+++ b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/NativeLibrary.cs
@@ -208,7 +208,7 @@ namespace System.Runtime.InteropServices
 
             try
             {
-                s_nativeDllResolveMap!.Add(assembly, resolver); // TODO-NULLABLE: Remove ! when compiler specially-recognizes CompareExchange for nullability
+                s_nativeDllResolveMap.Add(assembly, resolver);
             }
             catch (ArgumentException)
             {
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/Loader/AssemblyLoadContext.cs b/src/System.Private.CoreLib/shared/System/Runtime/Loader/AssemblyLoadContext.cs
index c952686276..1c19e0971c 100644
--- a/src/System.Private.CoreLib/shared/System/Runtime/Loader/AssemblyLoadContext.cs
+++ b/src/System.Private.CoreLib/shared/System/Runtime/Loader/AssemblyLoadContext.cs
@@ -168,7 +168,7 @@ namespace System.Runtime.Loader
         //
         // Inputs: Invoking assembly, and library name to resolve
         // Returns: A handle to the loaded native library
-        public event Func<Assembly, string, IntPtr> ResolvingUnmanagedDll
+        public event Func<Assembly, string, IntPtr> ResolvingUnmanagedDll // TODO-NULLABLE: Should all events use nullable delegate types?
         {
             add
             {
@@ -186,7 +186,7 @@ namespace System.Runtime.Loader
         //
         // Inputs: The AssemblyLoadContext and AssemblyName to be loaded
         // Returns: The Loaded assembly object.
-        public event Func<AssemblyLoadContext, AssemblyName, Assembly?> Resolving
+        public event Func<AssemblyLoadContext, AssemblyName, Assembly?> Resolving // TODO-NULLABLE: Should all events use nullable delegate types?
         {
             add
             {
@@ -198,7 +198,7 @@ namespace System.Runtime.Loader
             }
         }
 
-        public event Action<AssemblyLoadContext> Unloading
+        public event Action<AssemblyLoadContext> Unloading // TODO-NULLABLE: Should all events use nullable delegate types?
         {
             add
             {
@@ -212,17 +212,17 @@ namespace System.Runtime.Loader
 
 #region AppDomainEvents
         // Occurs when an Assembly is loaded
-        internal static event AssemblyLoadEventHandler AssemblyLoad;
+        internal static event AssemblyLoadEventHandler AssemblyLoad; // TODO-NULLABLE: Should all events use nullable delegate types?
 
         // Occurs when resolution of type fails
-        internal static event ResolveEventHandler TypeResolve;
+        internal static event ResolveEventHandler TypeResolve; // TODO-NULLABLE: Should all events use nullable delegate types?
 
         // Occurs when resolution of resource fails
-        internal static event ResolveEventHandler ResourceResolve;
+        internal static event ResolveEventHandler ResourceResolve; // TODO-NULLABLE: Should all events use nullable delegate types?
 
         // Occurs when resolution of assembly fails
         // This event is fired after resolve events of AssemblyLoadContext fails
-        internal static event ResolveEventHandler AssemblyResolve;
+        internal static event ResolveEventHandler AssemblyResolve; // TODO-NULLABLE: Should all events use nullable delegate types?
 #endregion
 
         public static AssemblyLoadContext Default => DefaultAssemblyLoadContext.s_loadContext;
diff --git a/src/System.Private.CoreLib/shared/System/String.Searching.cs b/src/System.Private.CoreLib/shared/System/String.Searching.cs
index ab98daf75d..cce119b1d0 100644
--- a/src/System.Private.CoreLib/shared/System/String.Searching.cs
+++ b/src/System.Private.CoreLib/shared/System/String.Searching.cs
@@ -18,7 +18,7 @@ namespace System
             return SpanHelpers.IndexOf(
                 ref _firstChar,
                 Length,
-                ref value!._firstChar, // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                ref value._firstChar,
                 value.Length) >= 0;
         }
 
diff --git a/src/System.Private.CoreLib/shared/System/StringComparer.cs b/src/System.Private.CoreLib/shared/System/StringComparer.cs
index ef7281f061..3774a713dc 100644
--- a/src/System.Private.CoreLib/shared/System/StringComparer.cs
+++ b/src/System.Private.CoreLib/shared/System/StringComparer.cs
@@ -302,10 +302,10 @@ namespace System
 
             if (_ignoreCase)
             {
-                return obj!.GetHashCodeOrdinalIgnoreCase(); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                return obj.GetHashCodeOrdinalIgnoreCase();
             }
 
-            return obj!.GetHashCode(); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            return obj.GetHashCode();
         }
 
         // Equals method for the comparer itself. 
@@ -342,7 +342,7 @@ namespace System
             {
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.obj);
             }
-            return obj!.GetHashCode(); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            return obj.GetHashCode();
         }
 
         public void GetObjectData(SerializationInfo info, StreamingContext context)
@@ -387,7 +387,7 @@ namespace System
             {
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.obj);
             }
-            return obj!.GetHashCodeOrdinalIgnoreCase(); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            return obj.GetHashCodeOrdinalIgnoreCase();
         }
 
         public void GetObjectData(SerializationInfo info, StreamingContext context)
diff --git a/src/System.Private.CoreLib/shared/System/Text/DecoderBestFitFallback.cs b/src/System.Private.CoreLib/shared/System/Text/DecoderBestFitFallback.cs
index 91226416ab..0501529bdf 100644
--- a/src/System.Private.CoreLib/shared/System/Text/DecoderBestFitFallback.cs
+++ b/src/System.Private.CoreLib/shared/System/Text/DecoderBestFitFallback.cs
@@ -72,7 +72,7 @@ namespace System.Text
                     object o = new object();
                     Interlocked.CompareExchange<object?>(ref s_InternalSyncObject, o, null);
                 }
-                return s_InternalSyncObject!; // TODO-NULLABLE: Remove ! when compiler specially-recognizes CompareExchange for nullability
+                return s_InternalSyncObject;
             }
         }
 
diff --git a/src/System.Private.CoreLib/shared/System/Text/DecoderFallback.cs b/src/System.Private.CoreLib/shared/System/Text/DecoderFallback.cs
index aa3f65bfa9..282baf7590 100644
--- a/src/System.Private.CoreLib/shared/System/Text/DecoderFallback.cs
+++ b/src/System.Private.CoreLib/shared/System/Text/DecoderFallback.cs
@@ -15,11 +15,11 @@ namespace System.Text
         private static DecoderFallback? s_exceptionFallback;
 
         public static DecoderFallback ReplacementFallback =>
-            s_replacementFallback ?? Interlocked.CompareExchange(ref s_replacementFallback, new DecoderReplacementFallback(), null) ?? s_replacementFallback!; // TODO-NULLABLE: Remove ! when compiler specially-recognizes CompareExchange for nullability
+            s_replacementFallback ?? Interlocked.CompareExchange(ref s_replacementFallback, new DecoderReplacementFallback(), null) ?? s_replacementFallback;
 
 
         public static DecoderFallback ExceptionFallback =>
-            s_exceptionFallback ?? Interlocked.CompareExchange<DecoderFallback?>(ref s_exceptionFallback, new DecoderExceptionFallback(), null) ?? s_exceptionFallback!; // TODO-NULLABLE: Remove ! when compiler specially-recognizes CompareExchange for nullability
+            s_exceptionFallback ?? Interlocked.CompareExchange<DecoderFallback?>(ref s_exceptionFallback, new DecoderExceptionFallback(), null) ?? s_exceptionFallback;
 
         // Fallback
         //
diff --git a/src/System.Private.CoreLib/shared/System/Text/EncoderBestFitFallback.cs b/src/System.Private.CoreLib/shared/System/Text/EncoderBestFitFallback.cs
index 518ceb7056..2e9cd69d8c 100644
--- a/src/System.Private.CoreLib/shared/System/Text/EncoderBestFitFallback.cs
+++ b/src/System.Private.CoreLib/shared/System/Text/EncoderBestFitFallback.cs
@@ -72,7 +72,7 @@ namespace System.Text
                     object o = new object();
                     Interlocked.CompareExchange<object?>(ref s_InternalSyncObject, o, null);
                 }
-                return s_InternalSyncObject!; // TODO-NULLABLE: Remove ! when compiler specially-recognizes CompareExchange for nullability
+                return s_InternalSyncObject;
             }
         }
 
diff --git a/src/System.Private.CoreLib/shared/System/Text/EncoderFallback.cs b/src/System.Private.CoreLib/shared/System/Text/EncoderFallback.cs
index 8fa9e6d27a..fd32a19517 100644
--- a/src/System.Private.CoreLib/shared/System/Text/EncoderFallback.cs
+++ b/src/System.Private.CoreLib/shared/System/Text/EncoderFallback.cs
@@ -23,7 +23,7 @@ namespace System.Text
                 if (s_replacementFallback == null)
                     Interlocked.CompareExchange<EncoderFallback?>(ref s_replacementFallback, new EncoderReplacementFallback(), null);
 
-                return s_replacementFallback!; // TODO-NULLABLE: Remove ! when compiler specially-recognizes CompareExchange for nullability
+                return s_replacementFallback;
             }
         }
 
@@ -35,7 +35,7 @@ namespace System.Text
                 if (s_exceptionFallback == null)
                     Interlocked.CompareExchange<EncoderFallback?>(ref s_exceptionFallback, new EncoderExceptionFallback(), null);
 
-                return s_exceptionFallback!; // TODO-NULLABLE: Remove ! when compiler specially-recognizes CompareExchange for nullability
+                return s_exceptionFallback;
             }
         }
 
diff --git a/src/System.Private.CoreLib/shared/System/Text/EncodingTable.cs b/src/System.Private.CoreLib/shared/System/Text/EncodingTable.cs
index 4c0bd4a87c..3927ce6c0e 100644
--- a/src/System.Private.CoreLib/shared/System/Text/EncodingTable.cs
+++ b/src/System.Private.CoreLib/shared/System/Text/EncodingTable.cs
@@ -159,7 +159,7 @@ namespace System.Text
                     return null;
             }
 
-            CodePageDataItem? data = s_codePageToCodePageData![index]; // TODO-NULLABLE: Remove ! when compiler specially-recognizes CompareExchange for nullability
+            CodePageDataItem? data = s_codePageToCodePageData[index];
             if (data == null)
             {
                 Interlocked.CompareExchange<CodePageDataItem?>(ref s_codePageToCodePageData[index], InternalGetCodePageDataItem(codePage, index), null);
diff --git a/src/System.Private.CoreLib/shared/System/Text/StringBuilder.cs b/src/System.Private.CoreLib/shared/System/Text/StringBuilder.cs
index 81cd160bdc..6cb56c8f5f 100644
--- a/src/System.Private.CoreLib/shared/System/Text/StringBuilder.cs
+++ b/src/System.Private.CoreLib/shared/System/Text/StringBuilder.cs
@@ -644,7 +644,7 @@ namespace System.Text
                         ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumOpCantHappen();
                     }
 
-                    return new ReadOnlyMemory<char>(_currentChunk!.m_ChunkChars, 0, _currentChunk.m_ChunkLength); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                    return new ReadOnlyMemory<char>(_currentChunk.m_ChunkChars, 0, _currentChunk.m_ChunkLength);
                 }
             }
 
diff --git a/src/System.Private.CoreLib/shared/System/Text/UTF8Encoding.cs b/src/System.Private.CoreLib/shared/System/Text/UTF8Encoding.cs
index 89bd8c58b4..eccf905a00 100644
--- a/src/System.Private.CoreLib/shared/System/Text/UTF8Encoding.cs
+++ b/src/System.Private.CoreLib/shared/System/Text/UTF8Encoding.cs
@@ -138,7 +138,7 @@ namespace System.Text
                 ThrowHelper.ThrowArgumentOutOfRangeException((index < 0) ? ExceptionArgument.index : ExceptionArgument.count, ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
             }
 
-            if (chars!.Length - index < count) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (chars.Length - index < count)
             {
                 ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.chars, ExceptionResource.ArgumentOutOfRange_IndexCountBuffer);
             }
@@ -165,7 +165,7 @@ namespace System.Text
 
             fixed (char* pChars = chars)
             {
-                return GetByteCountCommon(pChars, chars!.Length); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                return GetByteCountCommon(pChars, chars.Length);
             }
         }
 
@@ -275,12 +275,12 @@ namespace System.Text
                     resource: ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
             }
 
-            if (s!.Length - charIndex < charCount) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (s.Length - charIndex < charCount)
             {
                 ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.s, ExceptionResource.ArgumentOutOfRange_IndexCount);
             }
 
-            if ((uint)byteIndex > bytes!.Length) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if ((uint)byteIndex > bytes.Length)
             {
                 ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.byteIndex, ExceptionResource.ArgumentOutOfRange_Index);
             }
@@ -325,12 +325,12 @@ namespace System.Text
                     resource: ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
             }
 
-            if (chars!.Length - charIndex < charCount) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (chars.Length - charIndex < charCount)
             {
                 ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.chars, ExceptionResource.ArgumentOutOfRange_IndexCount);
             }
 
-            if ((uint)byteIndex > bytes!.Length) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if ((uint)byteIndex > bytes.Length)
             {
                 ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.byteIndex, ExceptionResource.ArgumentOutOfRange_Index);
             }
@@ -443,7 +443,7 @@ namespace System.Text
                 ThrowHelper.ThrowArgumentOutOfRangeException((index < 0) ? ExceptionArgument.index : ExceptionArgument.count, ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
             }
 
-            if (bytes!.Length - index < count) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (bytes.Length - index < count)
             {
                 ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.bytes, ExceptionResource.ArgumentOutOfRange_IndexCountBuffer);
             }
@@ -510,12 +510,12 @@ namespace System.Text
                     resource: ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
             }
 
-            if (bytes!.Length - byteIndex < byteCount) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (bytes.Length - byteIndex < byteCount)
             {
                 ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.bytes, ExceptionResource.ArgumentOutOfRange_IndexCountBuffer);
             }
 
-            if ((uint)charIndex > (uint)chars!.Length) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if ((uint)charIndex > (uint)chars.Length)
             {
                 ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.charIndex, ExceptionResource.ArgumentOutOfRange_Index);
             }
@@ -672,7 +672,7 @@ namespace System.Text
                     resource: ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
             }
 
-            if (bytes!.Length - index < count) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (bytes.Length - index < count)
             {
                 ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.bytes, ExceptionResource.ArgumentOutOfRange_IndexCountBuffer);
             }
diff --git a/src/System.Private.CoreLib/shared/System/Threading/CancellationTokenSource.cs b/src/System.Private.CoreLib/shared/System/Threading/CancellationTokenSource.cs
index 4c1705641d..513f6f05bb 100644
--- a/src/System.Private.CoreLib/shared/System/Threading/CancellationTokenSource.cs
+++ b/src/System.Private.CoreLib/shared/System/Threading/CancellationTokenSource.cs
@@ -133,10 +133,10 @@ namespace System.Threading
                 //   2. if IsCancellationRequested = false, then NotifyCancellation will see that the event exists, and will call Set().
                 if (IsCancellationRequested)
                 {
-                    _kernelEvent!.Set(); // TODO-NULLABLE: Remove ! when compiler specially-recognizes CompareExchange for nullability
+                    _kernelEvent.Set();
                 }
 
-                return _kernelEvent!; // TODO-NULLABLE: Remove ! when compiler specially-recognizes CompareExchange for nullability
+                return _kernelEvent;
             }
         }
 
diff --git a/src/System.Private.CoreLib/shared/System/Threading/LazyInitializer.cs b/src/System.Private.CoreLib/shared/System/Threading/LazyInitializer.cs
index 4a80c4f361..f8fdf6791a 100644
--- a/src/System.Private.CoreLib/shared/System/Threading/LazyInitializer.cs
+++ b/src/System.Private.CoreLib/shared/System/Threading/LazyInitializer.cs
@@ -272,7 +272,7 @@ namespace System.Threading
                 }
             }
 
-            return target!; // TODO-NULLABLE: Remove ! when [NotNullIfNotNull] respected
+            return target!; // TODO-NULLABLE: Compiler can't infer target's non-nullness (https://github.com/dotnet/roslyn/issues/37300)
         }
 
         /// <summary>
@@ -284,6 +284,6 @@ namespace System.Threading
         private static object EnsureLockInitialized([NotNull] ref object? syncLock) =>
             syncLock ??
             Interlocked.CompareExchange(ref syncLock, new object(), null) ??
-            syncLock!; // TODO-NULLABLE: Remove ! when compiler specially-recognizes CompareExchange for nullability
+            syncLock;
     }
 }
diff --git a/src/System.Private.CoreLib/shared/System/Threading/Tasks/Future.cs b/src/System.Private.CoreLib/shared/System/Threading/Tasks/Future.cs
index bed2f81a91..48a5ee4a06 100644
--- a/src/System.Private.CoreLib/shared/System/Threading/Tasks/Future.cs
+++ b/src/System.Private.CoreLib/shared/System/Threading/Tasks/Future.cs
@@ -339,7 +339,7 @@ namespace System.Threading.Tasks
             }
 
             // Create and schedule the future.
-            Task<TResult> f = new Task<TResult>(function!, parent, cancellationToken, creationOptions, internalOptions | InternalTaskOptions.QueuedByRuntime, scheduler); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            Task<TResult> f = new Task<TResult>(function, parent, cancellationToken, creationOptions, internalOptions | InternalTaskOptions.QueuedByRuntime, scheduler);
 
             f.ScheduleAndStart(false);
             return f;
@@ -359,7 +359,7 @@ namespace System.Threading.Tasks
             }
 
             // Create and schedule the future.
-            Task<TResult> f = new Task<TResult>(function!, state, parent, cancellationToken, creationOptions, internalOptions | InternalTaskOptions.QueuedByRuntime, scheduler); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            Task<TResult> f = new Task<TResult>(function, state, parent, cancellationToken, creationOptions, internalOptions | InternalTaskOptions.QueuedByRuntime, scheduler);
 
             f.ScheduleAndStart(false);
             return f;
@@ -727,13 +727,13 @@ namespace System.Threading.Tasks
                 out internalOptions);
 
             Task continuationTask = new ContinuationTaskFromResultTask<TResult>(
-                this, continuationAction!, null, // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                this, continuationAction, null,
                 creationOptions, internalOptions
             );
 
             // Register the continuation.  If synchronous execution is requested, this may
             // actually invoke the continuation before returning.
-            ContinueWithCore(continuationTask, scheduler!, cancellationToken, continuationOptions); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            ContinueWithCore(continuationTask, scheduler, cancellationToken, continuationOptions);
 
             return continuationTask;
         }
@@ -920,13 +920,13 @@ namespace System.Threading.Tasks
                 out internalOptions);
 
             Task continuationTask = new ContinuationTaskFromResultTask<TResult>(
-                this, continuationAction!, state, // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                this, continuationAction, state,
                 creationOptions, internalOptions
             );
 
             // Register the continuation.  If synchronous execution is requested, this may
             // actually invoke the continuation before returning.
-            ContinueWithCore(continuationTask, scheduler!, cancellationToken, continuationOptions); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            ContinueWithCore(continuationTask, scheduler, cancellationToken, continuationOptions);
 
             return continuationTask;
         }
@@ -1136,13 +1136,13 @@ namespace System.Threading.Tasks
                 out internalOptions);
 
             Task<TNewResult> continuationFuture = new ContinuationResultTaskFromResultTask<TResult, TNewResult>(
-                this, continuationFunction!, null, // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                this, continuationFunction, null,
                 creationOptions, internalOptions
             );
 
             // Register the continuation.  If synchronous execution is requested, this may
             // actually invoke the continuation before returning.
-            ContinueWithCore(continuationFuture, scheduler!, cancellationToken, continuationOptions); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            ContinueWithCore(continuationFuture, scheduler, cancellationToken, continuationOptions);
 
             return continuationFuture;
         }
@@ -1359,13 +1359,13 @@ namespace System.Threading.Tasks
                 out internalOptions);
 
             Task<TNewResult> continuationFuture = new ContinuationResultTaskFromResultTask<TResult, TNewResult>(
-                this, continuationFunction!, state, // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                this, continuationFunction, state,
                 creationOptions, internalOptions
             );
 
             // Register the continuation.  If synchronous execution is requested, this may
             // actually invoke the continuation before returning.
-            ContinueWithCore(continuationFuture, scheduler!, cancellationToken, continuationOptions); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            ContinueWithCore(continuationFuture, scheduler, cancellationToken, continuationOptions);
 
             return continuationFuture;
         }
diff --git a/src/System.Private.CoreLib/shared/System/Threading/Tasks/FutureFactory.cs b/src/System.Private.CoreLib/shared/System/Threading/Tasks/FutureFactory.cs
index 904bf531a7..f8db2bac0b 100644
--- a/src/System.Private.CoreLib/shared/System/Threading/Tasks/FutureFactory.cs
+++ b/src/System.Private.CoreLib/shared/System/Threading/Tasks/FutureFactory.cs
@@ -661,7 +661,7 @@ namespace System.Threading.Tasks
             // RespectParentCancellation.
             Task t = new Task(new Action<object>(delegate
             {
-                FromAsyncCoreLogic(asyncResult!, endFunction, endAction, promise, requiresSynchronization: true); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                FromAsyncCoreLogic(asyncResult, endFunction, endAction, promise, requiresSynchronization: true);
             }),
                 (object?)null, null,
                 default, TaskCreationOptions.None, InternalTaskOptions.None, null);
@@ -672,9 +672,9 @@ namespace System.Threading.Tasks
             if (Task.s_asyncDebuggingEnabled)
                 Task.AddToActiveTasks(t);
 
-            if (asyncResult!.IsCompleted) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (asyncResult.IsCompleted)
             {
-                try { t.InternalRunSynchronously(scheduler!, waitForCompletion: false); } // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                try { t.InternalRunSynchronously(scheduler, waitForCompletion: false); }
                 catch (Exception e) { promise.TrySetException(e); } // catch and log any scheduler exceptions
             }
             else
@@ -683,7 +683,7 @@ namespace System.Threading.Tasks
                     asyncResult.AsyncWaitHandle,
                     delegate
                     {
-                        try { t.InternalRunSynchronously(scheduler!, waitForCompletion: false); } // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                        try { t.InternalRunSynchronously(scheduler, waitForCompletion: false); }
                         catch (Exception e) { promise.TrySetException(e); } // catch and log any scheduler exceptions
                     },
                     null,
@@ -766,7 +766,7 @@ namespace System.Threading.Tasks
             Task<TResult> promise = new Task<TResult>(state, creationOptions);
 
             if (AsyncCausalityTracer.LoggingOn)
-                AsyncCausalityTracer.TraceOperationCreation(promise, "TaskFactory.FromAsync: " + beginMethod!.Method.Name); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                AsyncCausalityTracer.TraceOperationCreation(promise, "TaskFactory.FromAsync: " + beginMethod.Method.Name);
 
             if (Task.s_asyncDebuggingEnabled)
                 Task.AddToActiveTasks(promise);
@@ -774,7 +774,7 @@ namespace System.Threading.Tasks
             try
             {
                 //if we don't require synchronization, a faster set result path is taken
-                var asyncResult = beginMethod!(iar => // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                var asyncResult = beginMethod(iar =>
                 {
                     if (!iar.CompletedSynchronously)
                         FromAsyncCoreLogic(iar, endFunction, endAction, promise, requiresSynchronization: true);
@@ -883,7 +883,7 @@ namespace System.Threading.Tasks
             Task<TResult> promise = new Task<TResult>(state, creationOptions);
 
             if (AsyncCausalityTracer.LoggingOn)
-                AsyncCausalityTracer.TraceOperationCreation(promise, "TaskFactory.FromAsync: " + beginMethod!.Method.Name); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                AsyncCausalityTracer.TraceOperationCreation(promise, "TaskFactory.FromAsync: " + beginMethod.Method.Name);
 
             if (Task.s_asyncDebuggingEnabled)
                 Task.AddToActiveTasks(promise);
@@ -891,7 +891,7 @@ namespace System.Threading.Tasks
             try
             {
                 //if we don't require synchronization, a faster set result path is taken
-                var asyncResult = beginMethod!(arg1, iar => // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                var asyncResult = beginMethod(arg1, iar =>
                 {
                     if (!iar.CompletedSynchronously)
                         FromAsyncCoreLogic(iar, endFunction, endAction, promise, requiresSynchronization: true);
@@ -1008,7 +1008,7 @@ namespace System.Threading.Tasks
             Task<TResult> promise = new Task<TResult>(state, creationOptions);
 
             if (AsyncCausalityTracer.LoggingOn)
-                AsyncCausalityTracer.TraceOperationCreation(promise, "TaskFactory.FromAsync: " + beginMethod!.Method.Name); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                AsyncCausalityTracer.TraceOperationCreation(promise, "TaskFactory.FromAsync: " + beginMethod.Method.Name);
 
             if (Task.s_asyncDebuggingEnabled)
                 Task.AddToActiveTasks(promise);
@@ -1016,7 +1016,7 @@ namespace System.Threading.Tasks
             try
             {
                 //if we don't require synchronization, a faster set result path is taken
-                var asyncResult = beginMethod!(arg1, arg2, iar => // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                var asyncResult = beginMethod(arg1, arg2, iar =>
                 {
                     if (!iar.CompletedSynchronously)
                         FromAsyncCoreLogic(iar, endFunction, endAction, promise, requiresSynchronization: true);
@@ -1141,7 +1141,7 @@ namespace System.Threading.Tasks
             Task<TResult> promise = new Task<TResult>(state, creationOptions);
 
             if (AsyncCausalityTracer.LoggingOn)
-                AsyncCausalityTracer.TraceOperationCreation(promise, "TaskFactory.FromAsync: " + beginMethod!.Method.Name); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                AsyncCausalityTracer.TraceOperationCreation(promise, "TaskFactory.FromAsync: " + beginMethod.Method.Name);
 
             if (Task.s_asyncDebuggingEnabled)
                 Task.AddToActiveTasks(promise);
@@ -1149,7 +1149,7 @@ namespace System.Threading.Tasks
             try
             {
                 //if we don't require synchronization, a faster set result path is taken
-                var asyncResult = beginMethod!(arg1, arg2, arg3, iar => // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                var asyncResult = beginMethod(arg1, arg2, arg3, iar =>
                 {
                     if (!iar.CompletedSynchronously)
                         FromAsyncCoreLogic(iar, endFunction, endAction, promise, requiresSynchronization: true);
@@ -1254,11 +1254,11 @@ namespace System.Threading.Tasks
                 // Validate argument
                 if (asyncResult == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.asyncResult);
 
-                var promise = asyncResult!.AsyncState as FromAsyncTrimPromise<TInstance>; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                var promise = asyncResult.AsyncState as FromAsyncTrimPromise<TInstance>;
                 if (promise == null) ThrowHelper.ThrowArgumentException(ExceptionResource.InvalidOperation_WrongAsyncResultOrEndCalledMultiple, ExceptionArgument.asyncResult);
 
                 // Grab the relevant state and then null it out so that the task doesn't hold onto the state unnecessarily
-                var thisRef = promise!.m_thisRef; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                var thisRef = promise.m_thisRef;
                 var endMethod = promise.m_endMethod;
                 promise.m_thisRef = default;
                 promise.m_endMethod = null;
@@ -1269,7 +1269,7 @@ namespace System.Threading.Tasks
                 if (!asyncResult.CompletedSynchronously)
                 {
                     Debug.Assert(thisRef != null);
-                    promise.Complete(thisRef, endMethod!, asyncResult, requiresSynchronization: true); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                    promise.Complete(thisRef, endMethod, asyncResult, requiresSynchronization: true);
                 }
             }
 
@@ -1612,7 +1612,7 @@ namespace System.Threading.Tasks
             if (scheduler == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.scheduler);
 
             // Check tasks array and make defensive copy
-            Task<TAntecedentResult>[] tasksCopy = TaskFactory.CheckMultiContinuationTasksAndCopy<TAntecedentResult>(tasks!); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            Task<TAntecedentResult>[] tasksCopy = TaskFactory.CheckMultiContinuationTasksAndCopy<TAntecedentResult>(tasks);
 
             // Bail early if cancellation has been requested.
             if (cancellationToken.IsCancellationRequested
@@ -1631,7 +1631,7 @@ namespace System.Threading.Tasks
                 return starter.ContinueWith<TResult>(
                    // use a cached delegate
                    GenericDelegateCache<TAntecedentResult, TResult>.CWAllFuncDelegate,
-                   continuationFunction, scheduler!, cancellationToken, continuationOptions); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                   continuationFunction, scheduler, cancellationToken, continuationOptions);
             }
             else
             {
@@ -1640,7 +1640,7 @@ namespace System.Threading.Tasks
                 return starter.ContinueWith<TResult>(
                    // use a cached delegate
                    GenericDelegateCache<TAntecedentResult, TResult>.CWAllActionDelegate,
-                   continuationAction, scheduler!, cancellationToken, continuationOptions); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                   continuationAction, scheduler, cancellationToken, continuationOptions);
             }
         }
 
@@ -1658,7 +1658,7 @@ namespace System.Threading.Tasks
             if (scheduler == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.scheduler);
 
             // Check tasks array and make defensive copy
-            Task[] tasksCopy = TaskFactory.CheckMultiContinuationTasksAndCopy(tasks!); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            Task[] tasksCopy = TaskFactory.CheckMultiContinuationTasksAndCopy(tasks);
 
             // Bail early if cancellation has been requested.
             if (cancellationToken.IsCancellationRequested
@@ -1684,7 +1684,7 @@ namespace System.Threading.Tasks
                         Debug.Assert(state is Func<Task[], TResult>);
                         return ((Func<Task[], TResult>)state)(completedTasks.Result);
                     },
-                    continuationFunction, scheduler!, cancellationToken, continuationOptions); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                    continuationFunction, scheduler, cancellationToken, continuationOptions);
             }
             else
             {
@@ -1699,7 +1699,7 @@ namespace System.Threading.Tasks
                         Debug.Assert(state is Action<Task[]>);
                        ((Action<Task[]>)state)(completedTasks.Result); return default!;
                    },
-                   continuationAction, scheduler!, cancellationToken, continuationOptions); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                   continuationAction, scheduler, cancellationToken, continuationOptions);
             }
         }
 
@@ -1982,7 +1982,7 @@ namespace System.Threading.Tasks
             // check arguments
             TaskFactory.CheckMultiTaskContinuationOptions(continuationOptions);
             if (tasks == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.tasks);
-            if (tasks!.Length == 0) ThrowHelper.ThrowArgumentException(ExceptionResource.Task_MultiTaskContinuation_EmptyTaskList, ExceptionArgument.tasks); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (tasks.Length == 0) ThrowHelper.ThrowArgumentException(ExceptionResource.Task_MultiTaskContinuation_EmptyTaskList, ExceptionArgument.tasks);
 
             //ArgumentNullException of continuationFunction or continuationAction is checked by the caller
             Debug.Assert((continuationFunction != null) != (continuationAction != null), "Expected exactly one of endFunction/endAction to be non-null");
@@ -2010,7 +2010,7 @@ namespace System.Threading.Tasks
                          Debug.Assert(state is Func<Task, TResult>);
                          return ((Func<Task, TResult>)state)(completedTask.Result);
                      },
-                     continuationFunction, scheduler!, cancellationToken, continuationOptions); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                     continuationFunction, scheduler, cancellationToken, continuationOptions);
             }
             else
             {
@@ -2024,7 +2024,7 @@ namespace System.Threading.Tasks
                         ((Action<Task>)state)(completedTask.Result);
                         return default!;
                     },
-                    continuationAction, scheduler!, cancellationToken, continuationOptions); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                    continuationAction, scheduler, cancellationToken, continuationOptions);
             }
         }
 
@@ -2038,7 +2038,7 @@ namespace System.Threading.Tasks
             // check arguments
             TaskFactory.CheckMultiTaskContinuationOptions(continuationOptions);
             if (tasks == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.tasks);
-            if (tasks!.Length == 0) ThrowHelper.ThrowArgumentException(ExceptionResource.Task_MultiTaskContinuation_EmptyTaskList, ExceptionArgument.tasks); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (tasks.Length == 0) ThrowHelper.ThrowArgumentException(ExceptionResource.Task_MultiTaskContinuation_EmptyTaskList, ExceptionArgument.tasks);
             //ArgumentNullException of continuationFunction or continuationAction is checked by the caller
             Debug.Assert((continuationFunction != null) != (continuationAction != null), "Expected exactly one of endFunction/endAction to be non-null");
             if (scheduler == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.scheduler);
@@ -2060,7 +2060,7 @@ namespace System.Threading.Tasks
                 return starter.ContinueWith<TResult>(
                     // Use a cached delegate
                     GenericDelegateCache<TAntecedentResult, TResult>.CWAnyFuncDelegate,
-                    continuationFunction, scheduler!, cancellationToken, continuationOptions); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                    continuationFunction, scheduler, cancellationToken, continuationOptions);
             }
             else
             {
@@ -2068,7 +2068,7 @@ namespace System.Threading.Tasks
                 return starter.ContinueWith<TResult>(
                     // Use a cached delegate
                     GenericDelegateCache<TAntecedentResult, TResult>.CWAnyActionDelegate,
-                    continuationAction, scheduler!, cancellationToken, continuationOptions); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                    continuationAction, scheduler, cancellationToken, continuationOptions);
             }
         }
     }
diff --git a/src/System.Private.CoreLib/shared/System/Threading/Tasks/Task.cs b/src/System.Private.CoreLib/shared/System/Threading/Tasks/Task.cs
index 6f25d4ccb9..705f196fb7 100644
--- a/src/System.Private.CoreLib/shared/System/Threading/Tasks/Task.cs
+++ b/src/System.Private.CoreLib/shared/System/Threading/Tasks/Task.cs
@@ -1037,7 +1037,7 @@ namespace System.Threading.Tasks
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.scheduler);
             }
 
-            InternalRunSynchronously(scheduler!, waitForCompletion: true); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            InternalRunSynchronously(scheduler, waitForCompletion: true);
         }
 
         //
@@ -1512,7 +1512,7 @@ namespace System.Threading.Tasks
                     }
                 }
 
-                return contingentProps.m_completionEvent!; // TODO-NULLABLE: Remove ! when compiler specially-recognizes CompareExchange for nullability
+                return contingentProps.m_completionEvent;
             }
         }
 
@@ -1802,7 +1802,7 @@ namespace System.Threading.Tasks
 
             lock (props)
             {
-                props.m_exceptionsHolder!.Add(exceptionObject, representsCancellation); // TODO-NULLABLE: Remove ! when compiler specially-recognizes CompareExchange for nullability
+                props.m_exceptionsHolder.Add(exceptionObject, representsCancellation);
             }
         }
 
@@ -3634,13 +3634,13 @@ namespace System.Threading.Tasks
             CreationOptionsFromContinuationOptions(continuationOptions, out creationOptions, out internalOptions);
 
             Task continuationTask = new ContinuationTaskFromTask(
-                this, continuationAction!, null, // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                this, continuationAction, null,
                 creationOptions, internalOptions
             );
 
             // Register the continuation.  If synchronous execution is requested, this may
             // actually invoke the continuation before returning.
-            ContinueWithCore(continuationTask, scheduler!, cancellationToken, continuationOptions); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            ContinueWithCore(continuationTask, scheduler, cancellationToken, continuationOptions);
 
             return continuationTask;
         }
@@ -3824,13 +3824,13 @@ namespace System.Threading.Tasks
             CreationOptionsFromContinuationOptions(continuationOptions, out creationOptions, out internalOptions);
 
             Task continuationTask = new ContinuationTaskFromTask(
-                this, continuationAction!, state, // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                this, continuationAction, state,
                 creationOptions, internalOptions
             );
 
             // Register the continuation.  If synchronous execution is requested, this may
             // actually invoke the continuation before returning.
-            ContinueWithCore(continuationTask, scheduler!, cancellationToken, continuationOptions); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            ContinueWithCore(continuationTask, scheduler, cancellationToken, continuationOptions);
 
             return continuationTask;
         }
@@ -4027,13 +4027,13 @@ namespace System.Threading.Tasks
             CreationOptionsFromContinuationOptions(continuationOptions, out creationOptions, out internalOptions);
 
             Task<TResult> continuationTask = new ContinuationResultTaskFromTask<TResult>(
-                this, continuationFunction!, null, // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                this, continuationFunction, null,
                 creationOptions, internalOptions
             );
 
             // Register the continuation.  If synchronous execution is requested, this may
             // actually invoke the continuation before returning.
-            ContinueWithCore(continuationTask, scheduler!, cancellationToken, continuationOptions); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            ContinueWithCore(continuationTask, scheduler, cancellationToken, continuationOptions);
 
             return continuationTask;
         }
@@ -4234,13 +4234,13 @@ namespace System.Threading.Tasks
             CreationOptionsFromContinuationOptions(continuationOptions, out creationOptions, out internalOptions);
 
             Task<TResult> continuationTask = new ContinuationResultTaskFromTask<TResult>(
-                this, continuationFunction!, state, // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                this, continuationFunction, state,
                 creationOptions, internalOptions
             );
 
             // Register the continuation.  If synchronous execution is requested, this may
             // actually invoke the continuation before returning.
-            ContinueWithCore(continuationTask, scheduler!, cancellationToken, continuationOptions); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            ContinueWithCore(continuationTask, scheduler, cancellationToken, continuationOptions);
 
             return continuationTask;
         }
@@ -4745,7 +4745,7 @@ namespace System.Threading.Tasks
             bool returnValue = true;
 
             // Collects incomplete tasks in "waitedOnTaskList"
-            for (int i = tasks!.Length - 1; i >= 0; i--) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            for (int i = tasks.Length - 1; i >= 0; i--)
             {
                 Task task = tasks[i];
 
@@ -4754,7 +4754,7 @@ namespace System.Threading.Tasks
                     ThrowHelper.ThrowArgumentException(ExceptionResource.Task_WaitMulti_NullTask, ExceptionArgument.tasks);
                 }
 
-                bool taskIsCompleted = task!.IsCompleted; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                bool taskIsCompleted = task.IsCompleted;
                 if (!taskIsCompleted)
                 {
                     // try inlining the task only if we have an infinite timeout and an empty cancellation token
@@ -5110,7 +5110,7 @@ namespace System.Threading.Tasks
             // Make a pass through the loop to check for any tasks that may have
             // already been completed, and to verify that no tasks are null.
 
-            for (int taskIndex = 0; taskIndex < tasks!.Length; taskIndex++) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            for (int taskIndex = 0; taskIndex < tasks.Length; taskIndex++)
             {
                 Task task = tasks[taskIndex];
 
@@ -5119,7 +5119,7 @@ namespace System.Threading.Tasks
                     ThrowHelper.ThrowArgumentException(ExceptionResource.Task_WaitMulti_NullTask, ExceptionArgument.tasks);
                 }
 
-                if (signaledTaskIndex == -1 && task!.IsCompleted) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                if (signaledTaskIndex == -1 && task.IsCompleted)
                 {
                     // We found our first completed task.  Store it, but we can't just return here,
                     // as we still need to validate the whole array for nulls.
@@ -5171,7 +5171,7 @@ namespace System.Threading.Tasks
             if (exception == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.exception);
 
             var task = new Task();
-            bool succeeded = task.TrySetException(exception!); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            bool succeeded = task.TrySetException(exception);
             Debug.Assert(succeeded, "This should always succeed on a new task.");
             return task;
         }
@@ -5185,7 +5185,7 @@ namespace System.Threading.Tasks
             if (exception == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.exception);
 
             var task = new Task<TResult>();
-            bool succeeded = task.TrySetException(exception!); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            bool succeeded = task.TrySetException(exception);
             Debug.Assert(succeeded, "This should always succeed on a new task.");
             return task;
         }
@@ -5345,7 +5345,7 @@ namespace System.Threading.Tasks
                 return Task.FromCanceled(cancellationToken);
 
             // Kick off initial Task, which will call the user-supplied function and yield a Task.
-            Task<Task?> task1 = Task<Task?>.Factory.StartNew(function!, cancellationToken, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            Task<Task?> task1 = Task<Task?>.Factory.StartNew(function, cancellationToken, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
 
             // Create a promise-style Task to be used as a proxy for the operation
             // Set lookForOce == true so that unwrap logic can be on the lookout for OCEs thrown as faults from task1, to support in-delegate cancellation.
@@ -5390,7 +5390,7 @@ namespace System.Threading.Tasks
                 return Task.FromCanceled<TResult>(cancellationToken);
 
             // Kick off initial Task, which will call the user-supplied function and yield a Task.
-            Task<Task<TResult>?> task1 = Task<Task<TResult>?>.Factory.StartNew(function!, cancellationToken, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            Task<Task<TResult>?> task1 = Task<Task<TResult>?>.Factory.StartNew(function, cancellationToken, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
 
             // Create a promise-style Task to be used as a proxy for the operation
             // Set lookForOce == true so that unwrap logic can be on the lookout for OCEs thrown as faults from task1, to support in-delegate cancellation.
@@ -5617,7 +5617,7 @@ namespace System.Threading.Tasks
                 foreach (var task in tasks)
                 {
                     if (task == null) ThrowHelper.ThrowArgumentException(ExceptionResource.Task_MultiTaskContinuation_NullTask, ExceptionArgument.tasks);
-                    taskArray[index++] = task!; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                    taskArray[index++] = task;
                 }
                 return InternalWhenAll(taskArray);
             }
@@ -5625,10 +5625,10 @@ namespace System.Threading.Tasks
             // Do some argument checking and convert tasks to a List (and later an array).
             if (tasks == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.tasks);
             List<Task> taskList = new List<Task>();
-            foreach (Task task in tasks!) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            foreach (Task task in tasks)
             {
                 if (task == null) ThrowHelper.ThrowArgumentException(ExceptionResource.Task_MultiTaskContinuation_NullTask, ExceptionArgument.tasks);
-                taskList.Add(task!); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                taskList.Add(task);
             }
 
             // Delegate the rest to InternalWhenAll()
@@ -5667,7 +5667,7 @@ namespace System.Threading.Tasks
             // Do some argument checking and make a defensive copy of the tasks array
             if (tasks == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.tasks);
 
-            int taskCount = tasks!.Length; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            int taskCount = tasks.Length;
             if (taskCount == 0) return InternalWhenAll(tasks); // Small optimization in the case of an empty array.
 
             Task[] tasksCopy = new Task[taskCount];
@@ -5675,7 +5675,7 @@ namespace System.Threading.Tasks
             {
                 Task task = tasks[i];
                 if (task == null) ThrowHelper.ThrowArgumentException(ExceptionResource.Task_MultiTaskContinuation_NullTask, ExceptionArgument.tasks);
-                tasksCopy[i] = task!; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                tasksCopy[i] = task;
             }
 
             // The rest can be delegated to InternalWhenAll()
@@ -5861,7 +5861,7 @@ namespace System.Threading.Tasks
                 foreach (var task in tasks)
                 {
                     if (task == null) ThrowHelper.ThrowArgumentException(ExceptionResource.Task_MultiTaskContinuation_NullTask, ExceptionArgument.tasks);
-                    taskArray[index++] = task!; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                    taskArray[index++] = task;
                 }
                 return InternalWhenAll<TResult>(taskArray);
             }
@@ -5869,10 +5869,10 @@ namespace System.Threading.Tasks
             // Do some argument checking and convert tasks into a List (later an array)
             if (tasks == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.tasks);
             List<Task<TResult>> taskList = new List<Task<TResult>>();
-            foreach (Task<TResult> task in tasks!) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            foreach (Task<TResult> task in tasks)
             {
                 if (task == null) ThrowHelper.ThrowArgumentException(ExceptionResource.Task_MultiTaskContinuation_NullTask, ExceptionArgument.tasks);
-                taskList.Add(task!); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                taskList.Add(task);
             }
 
             // Delegate the rest to InternalWhenAll<TResult>().
@@ -5914,7 +5914,7 @@ namespace System.Threading.Tasks
             // Do some argument checking and make a defensive copy of the tasks array
             if (tasks == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.tasks);
 
-            int taskCount = tasks!.Length; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            int taskCount = tasks.Length;
             if (taskCount == 0) return InternalWhenAll<TResult>(tasks); // small optimization in the case of an empty task array
 
             Task<TResult>[] tasksCopy = new Task<TResult>[taskCount];
@@ -5922,7 +5922,7 @@ namespace System.Threading.Tasks
             {
                 Task<TResult> task = tasks[i];
                 if (task == null) ThrowHelper.ThrowArgumentException(ExceptionResource.Task_MultiTaskContinuation_NullTask, ExceptionArgument.tasks);
-                tasksCopy[i] = task!; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                tasksCopy[i] = task;
             }
 
             // Delegate the rest to InternalWhenAll<TResult>()
@@ -6081,7 +6081,7 @@ namespace System.Threading.Tasks
         public static Task<Task> WhenAny(params Task[] tasks)
         {
             if (tasks == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.tasks);
-            if (tasks!.Length == 0) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (tasks.Length == 0)
             {
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Task_MultiTaskContinuation_EmptyTaskList, ExceptionArgument.tasks);
             }
@@ -6094,7 +6094,7 @@ namespace System.Threading.Tasks
             {
                 Task task = tasks[i];
                 if (task == null) ThrowHelper.ThrowArgumentException(ExceptionResource.Task_MultiTaskContinuation_NullTask, ExceptionArgument.tasks);
-                tasksCopy[i] = task!; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                tasksCopy[i] = task;
             }
 
             // Previously implemented CommonCWAnyLogic() can handle the rest
@@ -6123,10 +6123,10 @@ namespace System.Threading.Tasks
             // Make a defensive copy, as the user may manipulate the tasks collection
             // after we return but before the WhenAny asynchronously completes.
             List<Task> taskList = new List<Task>();
-            foreach (Task task in tasks!) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            foreach (Task task in tasks)
             {
                 if (task == null) ThrowHelper.ThrowArgumentException(ExceptionResource.Task_MultiTaskContinuation_NullTask, ExceptionArgument.tasks);
-                taskList.Add(task!); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                taskList.Add(task);
             }
 
             if (taskList.Count == 0)
diff --git a/src/System.Private.CoreLib/shared/System/Threading/Tasks/TaskCompletionSource.cs b/src/System.Private.CoreLib/shared/System/Threading/Tasks/TaskCompletionSource.cs
index b0c79e61ba..71a7e22ebd 100644
--- a/src/System.Private.CoreLib/shared/System/Threading/Tasks/TaskCompletionSource.cs
+++ b/src/System.Private.CoreLib/shared/System/Threading/Tasks/TaskCompletionSource.cs
@@ -150,7 +150,7 @@ namespace System.Threading.Tasks
         {
             if (exception == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.exception);
 
-            bool rval = _task.TrySetException(exception!); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            bool rval = _task.TrySetException(exception);
             if (!rval && !_task.IsCompleted) SpinUntilCompleted();
             return rval;
         }
@@ -180,11 +180,11 @@ namespace System.Threading.Tasks
             if (exceptions == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.exceptions);
 
             List<Exception> defensiveCopy = new List<Exception>();
-            foreach (Exception e in exceptions!) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            foreach (Exception e in exceptions)
             {
                 if (e == null)
                     ThrowHelper.ThrowArgumentException(ExceptionResource.TaskCompletionSourceT_TrySetException_NullException, ExceptionArgument.exceptions);
-                defensiveCopy.Add(e!); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                defensiveCopy.Add(e);
             }
 
             if (defensiveCopy.Count == 0)
@@ -216,7 +216,7 @@ namespace System.Threading.Tasks
         {
             if (exception == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.exception);
 
-            if (!TrySetException(exception!)) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (!TrySetException(exception))
             {
                 ThrowHelper.ThrowInvalidOperationException(ExceptionResource.TaskT_TransitionToFinal_AlreadyCompleted);
             }
diff --git a/src/System.Private.CoreLib/shared/System/Threading/Tasks/TaskScheduler.cs b/src/System.Private.CoreLib/shared/System/Threading/Tasks/TaskScheduler.cs
index f79a87ac06..4c7a3c4ea2 100644
--- a/src/System.Private.CoreLib/shared/System/Threading/Tasks/TaskScheduler.cs
+++ b/src/System.Private.CoreLib/shared/System/Threading/Tasks/TaskScheduler.cs
@@ -298,7 +298,7 @@ namespace System.Threading.Tasks
                 Interlocked.CompareExchange(ref s_activeTaskSchedulers, new ConditionalWeakTable<TaskScheduler, object?>(), null);
                 activeTaskSchedulers = s_activeTaskSchedulers;
             }
-            activeTaskSchedulers!.Add(this, null); // TODO-NULLABLE: Remove ! when compiler specially-recognizes CompareExchange for nullability
+            activeTaskSchedulers.Add(this, null);
         }
 
         /// <summary>
@@ -445,7 +445,7 @@ namespace System.Threading.Tasks
         /// Each handler is passed a <see cref="T:System.Threading.Tasks.UnobservedTaskExceptionEventArgs"/>
         /// instance, which may be used to examine the exception and to mark it as observed.
         /// </remarks>
-        public static event EventHandler<UnobservedTaskExceptionEventArgs> UnobservedTaskException;
+        public static event EventHandler<UnobservedTaskExceptionEventArgs> UnobservedTaskException; // TODO-NULLABLE: Should all events use nullable delegate types?
 
         ////////////////////////////////////////////////////////////
         //
diff --git a/src/System.Private.CoreLib/shared/System/Threading/Thread.cs b/src/System.Private.CoreLib/shared/System/Threading/Thread.cs
index eeb2f413ce..28b2e6eb8f 100644
--- a/src/System.Private.CoreLib/shared/System/Threading/Thread.cs
+++ b/src/System.Private.CoreLib/shared/System/Threading/Thread.cs
@@ -152,7 +152,7 @@ namespace System.Threading
                     }
                     Interlocked.CompareExchange(ref s_asyncLocalPrincipal, new AsyncLocal<IPrincipal?>(), null);
                 }
-                s_asyncLocalPrincipal!.Value = value; // TODO-NULLABLE: Remove ! when compiler specially-recognizes CompareExchange for nullability
+                s_asyncLocalPrincipal.Value = value;
             }
         }
 
diff --git a/src/System.Private.CoreLib/shared/System/TimeZone.cs b/src/System.Private.CoreLib/shared/System/TimeZone.cs
index 0775e5b1fa..841ba76132 100644
--- a/src/System.Private.CoreLib/shared/System/TimeZone.cs
+++ b/src/System.Private.CoreLib/shared/System/TimeZone.cs
@@ -42,7 +42,7 @@ namespace System
                     object o = new object();
                     Interlocked.CompareExchange<object?>(ref s_InternalSyncObject, o, null);
                 }
-                return s_InternalSyncObject!; // TODO-NULLABLE: Remove ! when compiler specially-recognizes CompareExchange for nullability
+                return s_InternalSyncObject;
             }
         }
 
diff --git a/src/System.Private.CoreLib/shared/System/TimeZoneInfo.Win32.cs b/src/System.Private.CoreLib/shared/System/TimeZoneInfo.Win32.cs
index 0ec94702df..8cff79351c 100644
--- a/src/System.Private.CoreLib/shared/System/TimeZoneInfo.Win32.cs
+++ b/src/System.Private.CoreLib/shared/System/TimeZoneInfo.Win32.cs
@@ -563,8 +563,8 @@ namespace System
                     // read LastEntry   {(yearN, 1, 1) - MaxValue       }
 
                     // read the FirstEntry and LastEntry key values (ex: "1980", "2038")
-                    int first = (int)dynamicKey.GetValue(FirstEntryValue, -1)!; // TODO-NULLABLE: Remove ! when [NotNullIfNotNull] respected
-                    int last = (int)dynamicKey.GetValue(LastEntryValue, -1)!; // TODO-NULLABLE: Remove ! when [NotNullIfNotNull] respected
+                    int first = (int)dynamicKey.GetValue(FirstEntryValue, -1);
+                    int last = (int)dynamicKey.GetValue(LastEntryValue, -1);
 
                     if (first == -1 || last == -1 || first > last)
                     {
diff --git a/src/System.Private.CoreLib/src/System/Array.CoreCLR.cs b/src/System.Private.CoreLib/src/System/Array.CoreCLR.cs
index d2c04156fd..8eadef1a03 100644
--- a/src/System.Private.CoreLib/src/System/Array.CoreCLR.cs
+++ b/src/System.Private.CoreLib/src/System/Array.CoreCLR.cs
@@ -29,10 +29,10 @@ namespace System
             if (length < 0)
                 ThrowHelper.ThrowLengthArgumentOutOfRange_ArgumentOutOfRange_NeedNonNegNum();
 
-            RuntimeType? t = elementType!.UnderlyingSystemType as RuntimeType; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            RuntimeType? t = elementType.UnderlyingSystemType as RuntimeType;
             if (t == null)
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_MustBeType, ExceptionArgument.elementType);
-            return InternalCreate((void*)t!.TypeHandle.Value, 1, &length, null); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            return InternalCreate((void*)t.TypeHandle.Value, 1, &length, null);
         }
 
         public static unsafe Array CreateInstance(Type elementType, int length1, int length2)
@@ -44,13 +44,13 @@ namespace System
             if (length2 < 0)
                 ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.length2, ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
 
-            RuntimeType? t = elementType!.UnderlyingSystemType as RuntimeType; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            RuntimeType? t = elementType.UnderlyingSystemType as RuntimeType;
             if (t == null)
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_MustBeType, ExceptionArgument.elementType);
             int* pLengths = stackalloc int[2];
             pLengths[0] = length1;
             pLengths[1] = length2;
-            return InternalCreate((void*)t!.TypeHandle.Value, 2, pLengths, null); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            return InternalCreate((void*)t.TypeHandle.Value, 2, pLengths, null);
         }
 
         public static unsafe Array CreateInstance(Type elementType, int length1, int length2, int length3)
@@ -64,14 +64,14 @@ namespace System
             if (length3 < 0)
                 ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.length3, ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
 
-            RuntimeType? t = elementType!.UnderlyingSystemType as RuntimeType; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            RuntimeType? t = elementType.UnderlyingSystemType as RuntimeType;
             if (t == null)
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_MustBeType, ExceptionArgument.elementType);
             int* pLengths = stackalloc int[3];
             pLengths[0] = length1;
             pLengths[1] = length2;
             pLengths[2] = length3;
-            return InternalCreate((void*)t!.TypeHandle.Value, 3, pLengths, null); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            return InternalCreate((void*)t.TypeHandle.Value, 3, pLengths, null);
         }
 
         public static unsafe Array CreateInstance(Type elementType, params int[] lengths)
@@ -80,10 +80,10 @@ namespace System
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.elementType);
             if (lengths == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.lengths);
-            if (lengths!.Length == 0) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (lengths.Length == 0)
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_NeedAtLeast1Rank);
 
-            RuntimeType? t = elementType!.UnderlyingSystemType as RuntimeType; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            RuntimeType? t = elementType.UnderlyingSystemType as RuntimeType;
             if (t == null)
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_MustBeType, ExceptionArgument.elementType);
 
@@ -96,7 +96,7 @@ namespace System
                     ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.lengths, i, ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
 
             fixed (int* pLengths = &lengths[0])
-                return InternalCreate((void*)t!.TypeHandle.Value, lengths.Length, pLengths, null); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                return InternalCreate((void*)t.TypeHandle.Value, lengths.Length, pLengths, null);
         }
 
         public static unsafe Array CreateInstance(Type elementType, int[] lengths, int[] lowerBounds)
@@ -107,12 +107,12 @@ namespace System
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.lengths);
             if (lowerBounds == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.lowerBounds);
-            if (lengths!.Length != lowerBounds!.Length) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (lengths.Length != lowerBounds!.Length)
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RanksAndBounds);
             if (lengths.Length == 0)
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_NeedAtLeast1Rank);
 
-            RuntimeType? t = elementType!.UnderlyingSystemType as RuntimeType; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            RuntimeType? t = elementType.UnderlyingSystemType as RuntimeType;
             if (t == null)
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_MustBeType, ExceptionArgument.elementType);
 
@@ -126,7 +126,7 @@ namespace System
 
             fixed (int* pLengths = &lengths[0])
             fixed (int* pLowerBounds = &lowerBounds[0])
-                return InternalCreate((void*)t!.TypeHandle.Value, lengths.Length, pLengths, pLowerBounds); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                return InternalCreate((void*)t.TypeHandle.Value, lengths.Length, pLengths, pLowerBounds);
         }
 
         [MethodImplAttribute(MethodImplOptions.InternalCall)]
@@ -142,7 +142,7 @@ namespace System
             if (destinationArray == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.destinationArray);
 
-            Copy(sourceArray!, sourceArray!.GetLowerBound(0), destinationArray!, destinationArray!.GetLowerBound(0), length, false); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            Copy(sourceArray, sourceArray.GetLowerBound(0), destinationArray, destinationArray.GetLowerBound(0), length, false);
         }
 
         // Copies length elements from sourceArray, starting at sourceIndex, to
@@ -178,7 +178,7 @@ namespace System
             if (array == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
 
-            ref byte p = ref GetRawArrayGeometry(array!, out uint numComponents, out uint elementSize, out int lowerBound, out bool containsGCPointers); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            ref byte p = ref GetRawArrayGeometry(array, out uint numComponents, out uint elementSize, out int lowerBound, out bool containsGCPointers);
 
             int offset = index - lowerBound;
 
@@ -202,7 +202,7 @@ namespace System
         {
             if (indices == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.indices);
-            if (Rank != indices!.Length) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (Rank != indices.Length)
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RankIndices);
 
             TypedReference elemref = new TypedReference();
@@ -293,7 +293,7 @@ namespace System
         {
             if (indices == null)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.indices);
-            if (Rank != indices!.Length) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (Rank != indices.Length)
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RankIndices);
 
             TypedReference elemref = new TypedReference();
diff --git a/src/System.Private.CoreLib/src/System/Attribute.CoreCLR.cs b/src/System.Private.CoreLib/src/System/Attribute.CoreCLR.cs
index 96a04fd502..19ee5e0859 100644
--- a/src/System.Private.CoreLib/src/System/Attribute.CoreCLR.cs
+++ b/src/System.Private.CoreLib/src/System/Attribute.CoreCLR.cs
@@ -294,7 +294,7 @@ namespace System
                 {
                     if (objAttr[i] != null)
                     {
-                        attributes[count] = (Attribute)objAttr[i]!; // TODO-NULLABLE Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+                        attributes[count] = (Attribute)objAttr[i]!; // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
                         count++;
                     }
                 }
diff --git a/src/System.Private.CoreLib/src/System/Collections/ObjectModel/ReadOnlyDictionary.cs b/src/System.Private.CoreLib/src/System/Collections/ObjectModel/ReadOnlyDictionary.cs
index c1de2ae6e0..a6c242fe94 100644
--- a/src/System.Private.CoreLib/src/System/Collections/ObjectModel/ReadOnlyDictionary.cs
+++ b/src/System.Private.CoreLib/src/System/Collections/ObjectModel/ReadOnlyDictionary.cs
@@ -273,7 +273,7 @@ namespace System.Collections.ObjectModel
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
             }
 
-            if (array!.Rank != 1) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (array.Rank != 1)
             {
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RankMultiDimNotSupported);
             }
@@ -318,7 +318,7 @@ namespace System.Collections.ObjectModel
                     {
                         foreach (var item in m_dictionary)
                         {
-                            objects![index++] = new KeyValuePair<TKey, TValue>(item.Key, item.Value); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                            objects[index++] = new KeyValuePair<TKey, TValue>(item.Key, item.Value);
                         }
                     }
                     catch (ArrayTypeMismatchException)
@@ -349,7 +349,7 @@ namespace System.Collections.ObjectModel
                         Interlocked.CompareExchange<object?>(ref m_syncRoot, new object(), null);
                     }
                 }
-                return m_syncRoot!; // TODO-NULLABLE: Remove ! when compiler specially-recognizes CompareExchange for nullability
+                return m_syncRoot;
             }
         }
 
@@ -430,7 +430,7 @@ namespace System.Collections.ObjectModel
                 {
                     ThrowHelper.ThrowArgumentNullException(ExceptionArgument.collection);
                 }
-                m_collection = collection!; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                m_collection = collection;
             }
 
             #region ICollection<T> Members
@@ -518,7 +518,7 @@ namespace System.Collections.ObjectModel
                             Interlocked.CompareExchange<object?>(ref m_syncRoot, new object(), null);
                         }
                     }
-                    return m_syncRoot!; // TODO-NULLABLE: Remove ! when compiler specially-recognizes CompareExchange for nullability
+                    return m_syncRoot;
                 }
             }
 
@@ -538,7 +538,7 @@ namespace System.Collections.ObjectModel
                 {
                     ThrowHelper.ThrowArgumentNullException(ExceptionArgument.collection);
                 }
-                m_collection = collection!; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                m_collection = collection;
             }
 
             #region ICollection<T> Members
@@ -626,7 +626,7 @@ namespace System.Collections.ObjectModel
                             Interlocked.CompareExchange<object?>(ref m_syncRoot, new object(), null);
                         }
                     }
-                    return m_syncRoot!; // TODO-NULLABLE: Remove ! when compiler specially-recognizes CompareExchange for nullability
+                    return m_syncRoot;
                 }
             }
 
@@ -647,7 +647,7 @@ namespace System.Collections.ObjectModel
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
             }
 
-            if (array!.Rank != 1) // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            if (array.Rank != 1)
             {
                 ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RankMultiDimNotSupported);
             }
@@ -707,7 +707,7 @@ namespace System.Collections.ObjectModel
                 {
                     foreach (var item in collection)
                     {
-                        objects![index++] = item; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                        objects[index++] = item;
                     }
                 }
                 catch (ArrayTypeMismatchException)
diff --git a/src/System.Private.CoreLib/src/System/MulticastDelegate.cs b/src/System.Private.CoreLib/src/System/MulticastDelegate.cs
index 311c1629b8..67b3ef443b 100644
--- a/src/System.Private.CoreLib/src/System/MulticastDelegate.cs
+++ b/src/System.Private.CoreLib/src/System/MulticastDelegate.cs
@@ -579,7 +579,7 @@ namespace System
         {
             if (target == null)
                 ThrowNullThisInDelegateToInstance();
-            this._target = target!; // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            this._target = target;
             this._methodPtr = methodPtr;
         }
 
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/ILGenerator.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/ILGenerator.cs
index 4b7c508034..a350c70c27 100644
--- a/src/System.Private.CoreLib/src/System/Reflection/Emit/ILGenerator.cs
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/ILGenerator.cs
@@ -1564,7 +1564,7 @@ namespace System.Reflection.Emit
             {
                 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); // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
         }
 
         internal void AddUsingNamespaceToCurrentScope(
@@ -1575,7 +1575,7 @@ namespace System.Reflection.Emit
             {
                 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); // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
         }
 
         internal void AddScopeInfo(ScopeAction sa, int iOffset)
@@ -1642,7 +1642,7 @@ namespace System.Reflection.Emit
                 }
                 if (m_localSymInfos[i] != null)
                 {
-                    m_localSymInfos[i]!.EmitLocalSymInfo(symWriter); // TODO-NULLABLE Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
+                    m_localSymInfos[i]!.EmitLocalSymInfo(symWriter); // TODO-NULLABLE: Indexer nullability tracked (https://github.com/dotnet/roslyn/issues/34644)
                 }
             }
         }
diff --git a/src/System.Private.CoreLib/src/System/Reflection/RuntimeAssembly.cs b/src/System.Private.CoreLib/src/System/Reflection/RuntimeAssembly.cs
index 92cd2b83ab..e55d46637b 100644
--- a/src/System.Private.CoreLib/src/System/Reflection/RuntimeAssembly.cs
+++ b/src/System.Private.CoreLib/src/System/Reflection/RuntimeAssembly.cs
@@ -50,11 +50,11 @@ namespace System.Reflection
                 {
                     Interlocked.CompareExchange<object?>(ref m_syncRoot, new object(), null);
                 }
-                return m_syncRoot!; // TODO-NULLABLE: Remove ! when compiler specially-recognizes CompareExchange for nullability
+                return m_syncRoot;
             }
         }
 
-        public override event ModuleResolveEventHandler ModuleResolve
+        public override event ModuleResolveEventHandler ModuleResolve // TODO-NULLABLE: Should all events use nullable delegate types?
         {
             add
             {
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComEventsMethod.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComEventsMethod.cs
index 996802013a..10ef6e5db9 100644
--- a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComEventsMethod.cs
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComEventsMethod.cs
@@ -173,7 +173,7 @@ namespace System.Runtime.InteropServices
                 {
                     if (wrapper.Delegate.GetType() == d.GetType())
                     {
-                        wrapper.Delegate = Delegate.Combine(wrapper.Delegate, d)!; // TODO-NULLABLE: Remove ! when [NotNullIfNotNull] respected
+                        wrapper.Delegate = Delegate.Combine(wrapper.Delegate, d);
                         return;
                     }
                 }
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/EventRegistrationTokenTable.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/EventRegistrationTokenTable.cs
index 6714f7b33c..5788afbdd2 100644
--- a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/EventRegistrationTokenTable.cs
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/EventRegistrationTokenTable.cs
@@ -243,7 +243,7 @@ namespace System.Runtime.InteropServices.WindowsRuntime
             {
                 Interlocked.CompareExchange(ref refEventTable, new EventRegistrationTokenTable<T>(), null);
             }
-            return refEventTable!; // TODO-NULLABLE: Remove ! when compiler specially-recognizes CompareExchange for nullability
+            return refEventTable;
         }
     }
 }
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Loader/AssemblyDependencyResolver.cs b/src/System.Private.CoreLib/src/System/Runtime/Loader/AssemblyDependencyResolver.cs
index 8ceeb93b18..d04c8bf23d 100644
--- a/src/System.Private.CoreLib/src/System/Runtime/Loader/AssemblyDependencyResolver.cs
+++ b/src/System.Private.CoreLib/src/System/Runtime/Loader/AssemblyDependencyResolver.cs
@@ -99,7 +99,7 @@ namespace System.Runtime.Loader
             _assemblyPaths = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
             foreach (string assemblyPath in assemblyPaths)
             {
-                _assemblyPaths.Add(Path.GetFileNameWithoutExtension(assemblyPath)!, assemblyPath); // TODO-NULLABLE: Remove ! when [NotNullIfNotNull] respected
+                _assemblyPaths.Add(Path.GetFileNameWithoutExtension(assemblyPath), assemblyPath);
             }
 
             _nativeSearchPaths = SplitPathsList(nativeSearchPathsList);
diff --git a/src/System.Private.CoreLib/src/System/StubHelpers.cs b/src/System.Private.CoreLib/src/System/StubHelpers.cs
index 0f9ee4e4a2..0deff2c84a 100644
--- a/src/System.Private.CoreLib/src/System/StubHelpers.cs
+++ b/src/System.Private.CoreLib/src/System/StubHelpers.cs
@@ -1622,7 +1622,7 @@ namespace System.StubHelpers
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.pHandle, ExceptionResource.ArgumentNull_SafeHandle);
             }
 
-            pHandle!.DangerousAddRef(ref success); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+            pHandle.DangerousAddRef(ref success);
             return pHandle.DangerousGetHandle();
         }
 
@@ -1636,7 +1636,7 @@ namespace System.StubHelpers
 
             try
             {
-                pHandle!.DangerousRelease(); // TODO-NULLABLE: Remove ! when [DoesNotReturn] respected
+                pHandle.DangerousRelease();
             }
             catch
             {
diff --git a/src/System.Private.CoreLib/src/System/Utf8String.Construction.cs b/src/System.Private.CoreLib/src/System/Utf8String.Construction.cs
index 18988b7a20..074cc60003 100644
--- a/src/System.Private.CoreLib/src/System/Utf8String.Construction.cs
+++ b/src/System.Private.CoreLib/src/System/Utf8String.Construction.cs
@@ -49,7 +49,7 @@ namespace System
 
             Utf8String newString = FastAllocate(value.Length);
             Buffer.Memmove(ref newString.DangerousGetMutableReference(), ref MemoryMarshal.GetReference(value), (uint)value.Length);
-            return Utf8Utility.ValidateAndFixupUtf8String(newString)!; // TODO-NULLABLE: Remove ! when [NotNullIfNotNull] respected
+            return Utf8Utility.ValidateAndFixupUtf8String(newString);
         }
 
         /// <summary>