Use extension everything to polyfill ArgumentNullException.ThrowIfNull

src/coreclr/nativeaot/System.Private.CoreLib/src/System/Reflection/MethodInvoker.cs

@@ -29,7 +29,7 @@ internal MethodInvoker(RuntimeConstructorInfo constructor)
 
         public static MethodInvoker Create(MethodBase method)
         {
-            ArgumentNullException.ThrowIfNull(method, nameof(method));
+            ArgumentNullException.ThrowIfNull(method);
 
             if (method is RuntimeMethodInfo rmi)
             {

src/coreclr/nativeaot/System.Private.CoreLib/src/System/Runtime/InteropServices/Marshal.NativeAot.cs

@@ -90,7 +90,7 @@ internal static unsafe void PtrToStructureImpl(IntPtr ptr, object structure)
         public static unsafe void DestroyStructure(IntPtr ptr, Type structuretype)
         {
             ArgumentNullException.ThrowIfNull(ptr);
-            ArgumentNullException.ThrowIfNull(structuretype, nameof(structuretype));
+            ArgumentNullException.ThrowIfNull(structuretype);
 
             RuntimeTypeHandle structureTypeHandle = structuretype.TypeHandle;
 

src/libraries/Common/src/Extensions/NonCapturingTimer/NonCapturingTimer.cs

@@ -13,10 +13,7 @@ internal static class NonCapturingTimer
     {
         public static Timer Create(TimerCallback callback, object state, TimeSpan dueTime, TimeSpan period)
         {
-            if (callback is null)
-            {
-                throw new ArgumentNullException(nameof(callback));
-            }
+            ArgumentNullException.ThrowIfNull(callback);
 
             // Don't capture the current ExecutionContext and its AsyncLocals onto the timer
             bool restoreFlow = false;

src/libraries/Common/src/System/CodeDom/CodeTypeReference.cs

@@ -42,14 +42,7 @@ public CodeTypeReference()
 
         public CodeTypeReference(Type type)
         {
-#if NET
             ArgumentNullException.ThrowIfNull(type);
-#else
-            if (type is null)
-            {
-                throw new ArgumentNullException(nameof(type));
-            }
-#endif
 
             if (type.IsArray)
             {

src/libraries/Common/src/System/CodeDom/CodeTypeReferenceCollection.cs

@@ -41,14 +41,7 @@ public CodeTypeReference this[int index]
 
         public void AddRange(CodeTypeReference[] value)
         {
-#if NET
             ArgumentNullException.ThrowIfNull(value);
-#else
-            if (value is null)
-            {
-                throw new ArgumentNullException(nameof(value));
-            }
-#endif
 
             for (int i = 0; i < value.Length; i++)
             {
@@ -58,14 +51,7 @@ public void AddRange(CodeTypeReference[] value)
 
         public void AddRange(CodeTypeReferenceCollection value)
         {
-#if NET
             ArgumentNullException.ThrowIfNull(value);
-#else
-            if (value is null)
-            {
-                throw new ArgumentNullException(nameof(value));
-            }
-#endif
 
             int currentCount = value.Count;
             for (int i = 0; i < currentCount; i++)

src/libraries/Common/src/System/Composition/Diagnostics/CompositionTrace.cs

@@ -35,14 +35,8 @@ public static void Registration_TypeExportConventionOverridden(Type type)
 
         public static void Registration_MemberExportConventionOverridden(Type type, MemberInfo member)
         {
-            if (type is null)
-            {
-                throw new ArgumentNullException(nameof(type));
-            }
-            if (member is null)
-            {
-                throw new ArgumentNullException(nameof(member));
-            }
+            ArgumentNullException.ThrowIfNull(type);
+            ArgumentNullException.ThrowIfNull(member);
 
             if (CompositionTraceSource.CanWriteWarning)
             {
@@ -54,14 +48,8 @@ public static void Registration_MemberExportConventionOverridden(Type type, Memb
 
         public static void Registration_MemberImportConventionOverridden(Type type, MemberInfo member)
         {
-            if (type is null)
-            {
-                throw new ArgumentNullException(nameof(type));
-            }
-            if (member is null)
-            {
-                throw new ArgumentNullException(nameof(member));
-            }
+            ArgumentNullException.ThrowIfNull(type);
+            ArgumentNullException.ThrowIfNull(member);
 
             if (CompositionTraceSource.CanWriteWarning)
             {
@@ -73,14 +61,8 @@ public static void Registration_MemberImportConventionOverridden(Type type, Memb
 
         public static void Registration_OnSatisfiedImportNotificationOverridden(Type type, MemberInfo member)
         {
-            if (type is null)
-            {
-                throw new ArgumentNullException(nameof(type));
-            }
-            if (member is null)
-            {
-                throw new ArgumentNullException(nameof(member));
-            }
+            ArgumentNullException.ThrowIfNull(type);
+            ArgumentNullException.ThrowIfNull(member);
 
             if (CompositionTraceSource.CanWriteWarning)
             {
@@ -92,10 +74,7 @@ public static void Registration_OnSatisfiedImportNotificationOverridden(Type typ
 
         public static void Registration_PartCreationConventionOverridden(Type type)
         {
-            if (type is null)
-            {
-                throw new ArgumentNullException(nameof(type));
-            }
+            ArgumentNullException.ThrowIfNull(type);
 
             if (CompositionTraceSource.CanWriteWarning)
             {
@@ -107,14 +86,8 @@ public static void Registration_PartCreationConventionOverridden(Type type)
 
         public static void Registration_MemberImportConventionMatchedTwice(Type type, MemberInfo member)
         {
-            if (type is null)
-            {
-                throw new ArgumentNullException(nameof(type));
-            }
-            if (member is null)
-            {
-                throw new ArgumentNullException(nameof(member));
-            }
+            ArgumentNullException.ThrowIfNull(type);
+            ArgumentNullException.ThrowIfNull(member);
 
             if (CompositionTraceSource.CanWriteWarning)
             {
@@ -126,10 +99,7 @@ public static void Registration_MemberImportConventionMatchedTwice(Type type, Me
 
         public static void Registration_PartMetadataConventionOverridden(Type type)
         {
-            if (type is null)
-            {
-                throw new ArgumentNullException(nameof(type));
-            }
+            ArgumentNullException.ThrowIfNull(type);
 
             if (CompositionTraceSource.CanWriteWarning)
             {
@@ -141,14 +111,8 @@ public static void Registration_PartMetadataConventionOverridden(Type type)
 
         public static void Registration_ParameterImportConventionOverridden(ParameterInfo parameter, ConstructorInfo constructor)
         {
-            if (parameter is null)
-            {
-                throw new ArgumentNullException(nameof(parameter));
-            }
-            if (constructor is null)
-            {
-                throw new ArgumentNullException(nameof(constructor));
-            }
+            ArgumentNullException.ThrowIfNull(parameter);
+            ArgumentNullException.ThrowIfNull(constructor);
 
             if (CompositionTraceSource.CanWriteWarning)
             {

src/libraries/Common/src/System/ExceptionPolyfills.cs

@@ -0,0 +1,27 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Diagnostics.CodeAnalysis;
+using System.Runtime.CompilerServices;
+
+namespace System
+{
+    /// <summary>Provides downlevel polyfills for static methods on Exception-derived types.</summary>
+    internal static class ExceptionPolyfills
+    {
+        extension(ArgumentNullException)
+        {
+            public static void ThrowIfNull([NotNull] object? argument, [CallerArgumentExpression(nameof(argument))] string? paramName = null)
+            {
+                if (argument is null)
+                {
+                    ThrowArgumentNullException(paramName);
+                }
+            }
+        }
+
+        [DoesNotReturn]
+        private static void ThrowArgumentNullException(string? paramName) =>
+            throw new ArgumentNullException(paramName);
+    }
+}

src/libraries/Common/src/System/IO/ReadOnlyMemoryStream.cs

@@ -198,10 +198,7 @@ protected override void Dispose(bool disposing)
 #if NETFRAMEWORK || NETSTANDARD2_0
         private static void ValidateBufferArguments(byte[] buffer, int offset, int count)
         {
-            if (buffer is null)
-            {
-                throw new ArgumentNullException(nameof(buffer));
-            }
+            ArgumentNullException.ThrowIfNull(buffer);
 
             if (offset < 0)
             {

src/libraries/Common/src/System/IO/StreamHelpers.CopyValidation.cs

@@ -9,10 +9,7 @@ internal static partial class StreamHelpers
         /// <summary>Validate the arguments to CopyTo, as would Stream.CopyTo.</summary>
         public static void ValidateCopyToArgs(Stream source, Stream destination, int bufferSize)
         {
-            if (destination is null)
-            {
-                throw new ArgumentNullException(nameof(destination));
-            }
+            ArgumentNullException.ThrowIfNull(destination);
 
             if (bufferSize <= 0)
             {

src/libraries/Common/src/System/Resources/ResourceWriter.cs

@@ -48,10 +48,7 @@ public sealed partial class
         ResourceWriter(string fileName)
 #endif
         {
-            if (fileName is null)
-            {
-                throw new ArgumentNullException(nameof(fileName));
-            }
+            ArgumentNullException.ThrowIfNull(fileName);
 
             _output = new FileStream(fileName, FileMode.Create, FileAccess.Write, FileShare.None);
             _resourceList = new SortedDictionary<string, object?>(FastResourceComparer.Default);
@@ -65,10 +62,7 @@ public sealed partial class
         ResourceWriter(Stream stream)
 #endif
         {
-            if (stream is null)
-            {
-                throw new ArgumentNullException(nameof(stream));
-            }
+            ArgumentNullException.ThrowIfNull(stream);
 
             if (!stream.CanWrite)
             {
@@ -85,10 +79,7 @@ public sealed partial class
         //
         public void AddResource(string name, string? value)
         {
-            if (name is null)
-            {
-                throw new ArgumentNullException(nameof(name));
-            }
+            ArgumentNullException.ThrowIfNull(name);
 
             if (_resourceList == null)
             {
@@ -105,10 +96,7 @@ public void AddResource(string name, string? value)
         //
         public void AddResource(string name, object? value)
         {
-            if (name is null)
-            {
-                throw new ArgumentNullException(nameof(name));
-            }
+            ArgumentNullException.ThrowIfNull(name);
 
             if (_resourceList == null)
             {
@@ -134,10 +122,7 @@ public void AddResource(string name, object? value)
         //
         public void AddResource(string name, Stream? value, bool closeAfterWrite = false)
         {
-            if (name is null)
-            {
-                throw new ArgumentNullException(nameof(name));
-            }
+            ArgumentNullException.ThrowIfNull(name);
 
             if (_resourceList == null)
             {
@@ -174,10 +159,7 @@ private void AddResourceInternal(string name, Stream? value, bool closeAfterWrit
         //
         public void AddResource(string name, byte[]? value)
         {
-            if (name is null)
-            {
-                throw new ArgumentNullException(nameof(name));
-            }
+            ArgumentNullException.ThrowIfNull(name);
 
             if (_resourceList == null)
             {

src/libraries/Common/src/System/Security/Cryptography/AesGcm.cs

@@ -156,24 +156,10 @@ private partial void EncryptCore(
         /// <exception cref="CryptographicException">The encryption operation failed.</exception>
         public void Encrypt(byte[] nonce, byte[] plaintext, byte[] ciphertext, byte[] tag, byte[]? associatedData = null)
         {
-#if NET
             ArgumentNullException.ThrowIfNull(nonce);
             ArgumentNullException.ThrowIfNull(plaintext);
             ArgumentNullException.ThrowIfNull(ciphertext);
             ArgumentNullException.ThrowIfNull(tag);
-#else
-            if (nonce is null)
-                throw new ArgumentNullException(nameof(nonce));
-
-            if (plaintext is null)
-                throw new ArgumentNullException(nameof(plaintext));
-
-            if (ciphertext is null)
-                throw new ArgumentNullException(nameof(ciphertext));
-
-            if (tag is null)
-                throw new ArgumentNullException(nameof(tag));
-#endif
 
             Encrypt((ReadOnlySpan<byte>)nonce, plaintext, ciphertext, tag, associatedData);
         }
@@ -249,24 +235,10 @@ public void Encrypt(
         /// <exception cref="AuthenticationTagMismatchException">The tag value could not be verified.</exception>
         public void Decrypt(byte[] nonce, byte[] ciphertext, byte[] tag, byte[] plaintext, byte[]? associatedData = null)
         {
-#if NET
             ArgumentNullException.ThrowIfNull(nonce);
             ArgumentNullException.ThrowIfNull(ciphertext);
             ArgumentNullException.ThrowIfNull(tag);
             ArgumentNullException.ThrowIfNull(plaintext);
-#else
-            if (nonce is null)
-                throw new ArgumentNullException(nameof(nonce));
-
-            if (ciphertext is null)
-                throw new ArgumentNullException(nameof(ciphertext));
-
-            if (tag is null)
-                throw new ArgumentNullException(nameof(tag));
-
-            if (plaintext is null)
-                throw new ArgumentNullException(nameof(plaintext));
-#endif
 
             Decrypt((ReadOnlySpan<byte>)nonce, ciphertext, tag, plaintext, associatedData);
         }

src/libraries/Common/src/System/Security/Cryptography/Asn1/AttributeAsn.manual.cs

@@ -1,20 +1,18 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+#pragma warning disable CA1510
+
 namespace System.Security.Cryptography.Asn1
 {
     internal partial struct AttributeAsn
     {
         public AttributeAsn(AsnEncodedData attribute)
         {
-#if NET
-            ArgumentNullException.ThrowIfNull(attribute);
-#else
             if (attribute is null)
             {
                 throw new ArgumentNullException(nameof(attribute));
             }
-#endif
 
             AttrType = attribute.Oid!.Value!;
             AttrValues = new[] { new ReadOnlyMemory<byte>(attribute.RawData) };

src/libraries/Common/src/System/Security/Cryptography/Asn1/X509ExtensionAsn.manual.cs

@@ -9,14 +9,7 @@ internal partial struct X509ExtensionAsn
     {
         public X509ExtensionAsn(X509Extension extension)
         {
-#if NET
             ArgumentNullException.ThrowIfNull(extension);
-#else
-            if (extension is null)
-            {
-                throw new ArgumentNullException(nameof(extension));
-            }
-#endif
 
             ExtnId = extension.Oid!.Value!;
             Critical = extension.Critical;