Copy generic type parameter constraints more precisely

Author: stakx

src/Castle.Core/DynamicProxy/Generators/Emitters/GenericUtil.cs

@@ -1,4 +1,4 @@
-// Copyright 2004-2021 Castle Project - http://www.castleproject.org/
+// Copyright 2004-2025 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.
@@ -121,9 +121,25 @@ private static GenericTypeParameterBuilder[] CopyGenericArguments(
 				{
 					var attributes = originalGenericArguments[i].GenericParameterAttributes;
 					newGenericParameters[i].SetGenericParameterAttributes(attributes);
-					var constraints = AdjustGenericConstraints(methodToCopyGenericsFrom, newGenericParameters, originalGenericArguments, originalGenericArguments[i].GetGenericParameterConstraints());
 
-					newGenericParameters[i].SetInterfaceConstraints(constraints);
+					var constraints = originalGenericArguments[i].GetGenericParameterConstraints();
+					if (constraints.Length > 0)
+					{
+						constraints = AdjustGenericConstraints(methodToCopyGenericsFrom, newGenericParameters, originalGenericArguments, constraints);
+
+						var baseTypeConstraint = Array.Find(constraints, static c => c.IsClass);
+						if (baseTypeConstraint != null)
+						{
+							newGenericParameters[i].SetBaseTypeConstraint(baseTypeConstraint);
+						}
+
+						var interfaceConstraints = Array.FindAll(constraints, static c => c.IsInterface);
+						if (interfaceConstraints.Length > 0)
+						{
+							newGenericParameters[i].SetInterfaceConstraints(interfaceConstraints);
+						}
+					}
+
 					CopyNonInheritableAttributes(newGenericParameters[i], originalGenericArguments[i]);
 				}
 				catch (NotSupportedException)