Fix InvalidOperationException in ProxyGenerator for class with generic non-virtual method (#2620)

Order of operations in ProxyBuilderHelper changed which is relevant for generic methods

Fixes #2619

Author: csharper2010

src/NHibernate.Test/StaticProxyTest/StaticProxyFactoryFixture.cs

@@ -209,6 +209,22 @@ protected virtual void GetObjectData(SerializationInfo info, StreamingContext co
 			}
 		}
 
+		[Serializable]
+		public abstract class ClassWithGenericNonVirtualMethod : IWithGenericMethod
+		{
+			public virtual int Id { get; set; }
+			public virtual string Name { get; set; }
+			public T CopyTo<T>() where T : class, IWithGenericMethod
+			{
+				return null;
+			}
+		}
+
+		public interface IWithGenericMethod
+		{
+			T CopyTo<T>() where T : class, IWithGenericMethod;
+		}
+
 		[Test]
 		public void VerifyProxyForClassWithInternalInterface()
 		{
@@ -550,6 +566,32 @@ public void VerifyProxyForInternalClass()
 
 					Assert.That(factory.GetFieldInterceptionProxy(), Is.InstanceOf<InternalTestClass>());
 
+#if NETFX
+				});
+#endif
+		}
+
+		[Test(Description = "GH2619")]
+		public void VerifyProxyForClassWithGenericNonVirtualMethod()
+		{
+			var factory = new StaticProxyFactory();
+			factory.PostInstantiate(
+				typeof(ClassWithGenericNonVirtualMethod).FullName,
+				typeof(ClassWithGenericNonVirtualMethod),
+				new HashSet<System.Type> { typeof(INHibernateProxy) },
+				null, null, null, true);
+
+#if NETFX
+			VerifyGeneratedAssembly(
+				() =>
+				{
+#endif
+					var proxy = factory.GetProxy(1, null);
+					Assert.That(proxy, Is.Not.Null);
+					Assert.That(proxy, Is.InstanceOf<ClassWithGenericNonVirtualMethod>());
+
+					Assert.That(factory.GetFieldInterceptionProxy(), Is.InstanceOf<ClassWithGenericNonVirtualMethod>());
+
 #if NETFX
 				});
 #endif

src/NHibernate/Proxy/ProxyBuilderHelper.cs

@@ -178,8 +178,6 @@ internal static MethodBuilder GenerateMethodSignature(string name, MethodInfo me
 					CallingConventions.HasThis,
 					method.ReturnType,
 					parameters.ToArray(param => param.ParameterType));
-			if (explicitImplementation)
-				methodBuilder.SetImplementationFlags(MethodImplAttributes.Managed | MethodImplAttributes.IL);
 
 			var typeArgs = method.GetGenericArguments();
 			if (typeArgs.Length > 0)
@@ -208,6 +206,9 @@ internal static MethodBuilder GenerateMethodSignature(string name, MethodInfo me
 				}
 			}
 
+			if (explicitImplementation)
+				methodBuilder.SetImplementationFlags(MethodImplAttributes.Managed | MethodImplAttributes.IL);
+
 			return methodBuilder;
 		}