Nullable: Exception, SystemException, Argument*Exception (#23515)

* Nullable: Exception, SystemException, Argument*Exception

* Add Debug.Assert rather than comment

5 files changed, 30 insertions, 25 deletions

diff --git a/src/System.Private.CoreLib/shared/System/ArgumentException.cs b/src/System.Private.CoreLib/shared/System/ArgumentException.cs
index 5a918063e7..be7ffbe7fa 100644
--- a/src/System.Private.CoreLib/shared/System/ArgumentException.cs
+++ b/src/System.Private.CoreLib/shared/System/ArgumentException.cs
@@ -11,6 +11,7 @@
 **
 =============================================================================*/
 
+#nullable enable
 using System.Globalization;
 using System.Runtime.Serialization;
 
@@ -23,7 +24,7 @@ namespace System
     [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
     public class ArgumentException : SystemException
     {
-        private string _paramName;
+        private string? _paramName;
 
         // Creates a new ArgumentException with its message 
         // string set to the empty string. 
@@ -36,26 +37,26 @@ namespace System
         // Creates a new ArgumentException with its message 
         // string set to message. 
         // 
-        public ArgumentException(string message)
+        public ArgumentException(string? message)
             : base(message)
         {
             HResult = HResults.COR_E_ARGUMENT;
         }
 
-        public ArgumentException(string message, Exception innerException)
+        public ArgumentException(string? message, Exception? innerException)
             : base(message, innerException)
         {
             HResult = HResults.COR_E_ARGUMENT;
         }
 
-        public ArgumentException(string message, string paramName, Exception innerException)
+        public ArgumentException(string? message, string? paramName, Exception? innerException)
             : base(message, innerException)
         {
             _paramName = paramName;
             HResult = HResults.COR_E_ARGUMENT;
         }
 
-        public ArgumentException(string message, string paramName)
+        public ArgumentException(string? message, string? paramName)
             : base(message)
         {
             _paramName = paramName;
@@ -89,7 +90,7 @@ namespace System
             }
         }
 
-        public virtual string ParamName
+        public virtual string? ParamName
         {
             get { return _paramName; }
         }
diff --git a/src/System.Private.CoreLib/shared/System/ArgumentNullException.cs b/src/System.Private.CoreLib/shared/System/ArgumentNullException.cs
index edc38f2a4c..206c1a055b 100644
--- a/src/System.Private.CoreLib/shared/System/ArgumentNullException.cs
+++ b/src/System.Private.CoreLib/shared/System/ArgumentNullException.cs
@@ -11,6 +11,7 @@
 **
 =============================================================================*/
 
+#nullable enable
 using System.Runtime.Serialization;
 
 namespace System
@@ -30,19 +31,19 @@ namespace System
             HResult = HResults.E_POINTER;
         }
 
-        public ArgumentNullException(string paramName)
+        public ArgumentNullException(string? paramName)
             : base(SR.ArgumentNull_Generic, paramName)
         {
             HResult = HResults.E_POINTER;
         }
 
-        public ArgumentNullException(string message, Exception innerException)
+        public ArgumentNullException(string? message, Exception? innerException)
             : base(message, innerException)
         {
             HResult = HResults.E_POINTER;
         }
 
-        public ArgumentNullException(string paramName, string message)
+        public ArgumentNullException(string? paramName, string? message)
             : base(message, paramName)
         {
             HResult = HResults.E_POINTER;
diff --git a/src/System.Private.CoreLib/shared/System/ArgumentOutOfRangeException.cs b/src/System.Private.CoreLib/shared/System/ArgumentOutOfRangeException.cs
index 2c1941b62b..7ca9085c63 100644
--- a/src/System.Private.CoreLib/shared/System/ArgumentOutOfRangeException.cs
+++ b/src/System.Private.CoreLib/shared/System/ArgumentOutOfRangeException.cs
@@ -11,6 +11,7 @@
 **
 =============================================================================*/
 
+#nullable enable
 using System.Globalization;
 using System.Runtime.Serialization;
 
@@ -22,7 +23,7 @@ namespace System
     [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
     public class ArgumentOutOfRangeException : ArgumentException
     {
-        private object _actualValue;
+        private object? _actualValue;
 
         // Creates a new ArgumentOutOfRangeException with its message 
         // string set to a default message explaining an argument was out of range.
@@ -32,19 +33,19 @@ namespace System
             HResult = HResults.COR_E_ARGUMENTOUTOFRANGE;
         }
 
-        public ArgumentOutOfRangeException(string paramName)
+        public ArgumentOutOfRangeException(string? paramName)
             : base(SR.Arg_ArgumentOutOfRangeException, paramName)
         {
             HResult = HResults.COR_E_ARGUMENTOUTOFRANGE;
         }
 
-        public ArgumentOutOfRangeException(string paramName, string message)
+        public ArgumentOutOfRangeException(string? paramName, string? message)
             : base(message, paramName)
         {
             HResult = HResults.COR_E_ARGUMENTOUTOFRANGE;
         }
 
-        public ArgumentOutOfRangeException(string message, Exception innerException)
+        public ArgumentOutOfRangeException(string? message, Exception? innerException)
             : base(message, innerException)
         {
             HResult = HResults.COR_E_ARGUMENTOUTOFRANGE;
@@ -53,7 +54,7 @@ namespace System
         // We will not use this in the classlibs, but we'll provide it for
         // anyone that's really interested so they don't have to stick a bunch
         // of printf's in their code.
-        public ArgumentOutOfRangeException(string paramName, object actualValue, string message)
+        public ArgumentOutOfRangeException(string? paramName, object? actualValue, string? message)
             : base(message, paramName)
         {
             _actualValue = actualValue;
@@ -92,7 +93,7 @@ namespace System
         // Note - we don't set this anywhere in the class libraries in 
         // version 1, but it might come in handy for other developers who
         // want to avoid sticking printf's in their code.
-        public virtual object ActualValue
+        public virtual object? ActualValue
         {
             get { return _actualValue; }
         }
diff --git a/src/System.Private.CoreLib/shared/System/Exception.cs b/src/System.Private.CoreLib/shared/System/Exception.cs
index 764f36a2fc..c2522d558b 100644
--- a/src/System.Private.CoreLib/shared/System/Exception.cs
+++ b/src/System.Private.CoreLib/shared/System/Exception.cs
@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
 using System.Collections;
 using System.Runtime.Serialization;
 
@@ -16,7 +17,7 @@ namespace System
             _HResult = HResults.COR_E_EXCEPTION;
         }
 
-        public Exception(string message)
+        public Exception(string? message)
             : this()
         {
             _message = message;
@@ -27,7 +28,7 @@ namespace System
         // Note: the stack trace is not started until the exception 
         // is thrown
         // 
-        public Exception(string message, Exception innerException)
+        public Exception(string? message, Exception? innerException)
             : this()
         {
             _message = message;
@@ -72,7 +73,7 @@ namespace System
         // This will traverse exceptions using the innerException property.
         public virtual Exception GetBaseException()
         {
-            Exception inner = InnerException;
+            Exception? inner = InnerException;
             Exception back = this;
 
             while (inner != null)
@@ -84,12 +85,12 @@ namespace System
             return back;
         }
 
-        public Exception InnerException => _innerException;
+        public Exception? InnerException => _innerException;
 
         // Sets the help link for this exception.
         // This should be in a URL/URN form, such as:
         // "file:///C:/Applications/Bazzal/help.html#ErrorNum42"
-        public virtual string HelpLink
+        public virtual string? HelpLink
         {
             get
             {
@@ -101,7 +102,7 @@ namespace System
             }
         }
 
-        public virtual string Source
+        public virtual string? Source
         {
             get
             {
@@ -148,7 +149,7 @@ namespace System
         {
             string s = GetClassName();
 
-            string message = (needMessage ? Message : null);
+            string? message = (needMessage ? Message : null);
             if (!string.IsNullOrEmpty(message))
             {
                 s += ": " + message;
@@ -160,7 +161,7 @@ namespace System
                 "   " + SR.Exception_EndOfInnerExceptionStack;
             }
 
-            string stackTrace = GetStackTrace(needFileLineInfo);
+            string? stackTrace = GetStackTrace(needFileLineInfo);
             if (stackTrace != null)
             {
                 s += Environment.NewLine + stackTrace;
diff --git a/src/System.Private.CoreLib/shared/System/SystemException.cs b/src/System.Private.CoreLib/shared/System/SystemException.cs
index 9a1daf2104..8d8484de16 100644
--- a/src/System.Private.CoreLib/shared/System/SystemException.cs
+++ b/src/System.Private.CoreLib/shared/System/SystemException.cs
@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
 using System.Runtime.Serialization;
 
 namespace System
@@ -16,13 +17,13 @@ namespace System
             HResult = HResults.COR_E_SYSTEM;
         }
 
-        public SystemException(string message)
+        public SystemException(string? message)
             : base(message)
         {
             HResult = HResults.COR_E_SYSTEM;
         }
 
-        public SystemException(string message, Exception innerException)
+        public SystemException(string? message, Exception? innerException)
             : base(message, innerException)
         {
             HResult = HResults.COR_E_SYSTEM;