Add nullable reference type annotations to DynamicProxy's public API

CHANGELOG.md

@@ -6,6 +6,7 @@ Enhancements:
 - Two new generic method overloads `proxyGenerator.CreateClassProxy<TClass>([options], constructorArguments, interceptors)` (@backstromjoel, #636)
 - Allow specifying which attributes should always be copied to proxy class by adding attribute type to `AttributesToAlwaysReplicate`. Previously only non-inherited, with `Inherited=false`, attributes were copied. (@shoaibshakeel381, #633)
 - Support for C# 8+ [default interface methods](https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/proposals/csharp-8.0/default-interface-methods) in interface and class proxies without target (@stakx, #661)
+- DynamicProxy's public API has been augmented with nullable reference type annotations (@stakx, #668)
 
 Bugfixes:
 - `ArgumentException`: "Could not find method overriding method" with overridden class method having generic by-ref parameter (@stakx, #657)

src/Castle.Core/Compatibility/NullStateStaticAnalysisAttributes.cs

@@ -0,0 +1,51 @@
+// Copyright 2004-2023 Castle Project - http://www.castleproject.org/
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+namespace System.Diagnostics.CodeAnalysis
+{
+	using System;
+
+#if !NETSTANDARD2_1_OR_GREATER && !NETCOREAPP3_0_OR_GREATER
+	[AttributeUsage(AttributeTargets.Method, Inherited = false)]
+	internal sealed class DoesNotReturnAttribute : Attribute
+	{
+	}
+#endif
+
+#if !NET5_0_OR_GREATER
+	[AttributeUsage(AttributeTargets.Method | AttributeTargets.Property, AllowMultiple = true, Inherited = false)]
+	internal sealed class MemberNotNullAttribute : Attribute
+	{
+		public MemberNotNullAttribute(string member)
+		{
+			Members = new[] { member };
+		}
+
+		public string[] Members { get; }
+	}
+#endif
+
+#if !NETSTANDARD2_1_OR_GREATER && !NETCOREAPP3_0_OR_GREATER
+	[AttributeUsage(AttributeTargets.Parameter, Inherited = false)]
+	internal sealed class NotNullWhenAttribute : Attribute
+	{
+		public NotNullWhenAttribute(bool returnValue)
+		{
+			ReturnValue = returnValue;
+		}
+
+		public bool ReturnValue { get; }
+	}
+#endif
+}

src/Castle.Core/DynamicProxy/AbstractInvocation.cs

@@ -12,28 +12,30 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#nullable enable
+
 namespace Castle.DynamicProxy
 {
 	using System;
 	using System.Diagnostics;
+	using System.Diagnostics.CodeAnalysis;
 	using System.Reflection;
 
 	public abstract class AbstractInvocation : IInvocation
 	{
 		private readonly IInterceptor[] interceptors;
-		private readonly object[] arguments;
+		private readonly object?[] arguments;
 		private int currentInterceptorIndex = -1;
-		private Type[] genericMethodArguments;
+		private Type[]? genericMethodArguments;
 		private readonly MethodInfo proxiedMethod;
 		protected readonly object proxyObject;
 
 		protected AbstractInvocation(
 			object proxy,
 			IInterceptor[] interceptors,
 			MethodInfo proxiedMethod,
-			object[] arguments)
+			object?[] arguments)
 		{
-			Debug.Assert(proxiedMethod != null);
 			proxyObject = proxy;
 			this.interceptors = interceptors;
 			this.proxiedMethod = proxiedMethod;
@@ -45,13 +47,13 @@ public void SetGenericMethodArguments(Type[] arguments)
 			genericMethodArguments = arguments;
 		}
 
-		public abstract object InvocationTarget { get; }
+		public abstract object? InvocationTarget { get; }
 
-		public abstract Type TargetType { get; }
+		public abstract Type? TargetType { get; }
 
-		public abstract MethodInfo MethodInvocationTarget { get; }
+		public abstract MethodInfo? MethodInvocationTarget { get; }
 
-		public Type[] GenericArguments
+		public Type[]? GenericArguments
 		{
 			get { return genericMethodArguments; }
 		}
@@ -71,7 +73,7 @@ public MethodInfo GetConcreteMethod()
 			return EnsureClosedMethod(Method);
 		}
 
-		public MethodInfo GetConcreteMethodInvocationTarget()
+		public MethodInfo? GetConcreteMethodInvocationTarget()
 		{
 			// it is ensured by the InvocationHelper that method will be closed
 			var method = MethodInvocationTarget;
@@ -80,19 +82,19 @@ public MethodInfo GetConcreteMethodInvocationTarget()
 			return method;
 		}
 
-		public object ReturnValue { get; set; }
+		public object? ReturnValue { get; set; }
 
-		public object[] Arguments
+		public object?[] Arguments
 		{
 			get { return arguments; }
 		}
 
-		public void SetArgumentValue(int index, object value)
+		public void SetArgumentValue(int index, object? value)
 		{
 			arguments[index] = value;
 		}
 
-		public object GetArgumentValue(int index)
+		public object? GetArgumentValue(int index)
 		{
 			return arguments[index];
 		}
@@ -137,6 +139,7 @@ public IInvocationProceedInfo CaptureProceedInfo()
 
 		protected abstract void InvokeMethodOnTarget();
 
+		[DoesNotReturn]
 		protected void ThrowOnNoTarget()
 		{
 			// let's try to build as friendly message as we can
@@ -152,7 +155,7 @@ protected void ThrowOnNoTarget()
 
 			string methodKindIs;
 			string methodKindDescription;
-			if (Method.DeclaringType.IsClass && Method.IsAbstract)
+			if (Method.DeclaringType!.IsClass && Method.IsAbstract)
 			{
 				methodKindIs = "is abstract";
 				methodKindDescription = "an abstract method";

src/Castle.Core/DynamicProxy/AllMethodsHook.cs

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#nullable enable
+
 namespace Castle.DynamicProxy
 {
 	using System;
@@ -32,7 +34,7 @@ public class AllMethodsHook : IProxyGenerationHook
 
 		public virtual bool ShouldInterceptMethod(Type type, MethodInfo methodInfo)
 		{
-			return SkippedTypes.Contains(methodInfo.DeclaringType) == false;
+			return SkippedTypes.Contains(methodInfo.DeclaringType!) == false;
 		}
 
 		public virtual void NonProxyableMemberNotification(Type type, MemberInfo memberInfo)
@@ -43,7 +45,7 @@ public virtual void MethodsInspected()
 		{
 		}
 
-		public override bool Equals(object obj)
+		public override bool Equals(object? obj)
 		{
 			return obj != null && obj.GetType() == GetType();
 		}