Setup: Throw when method inaccessible to proxy generator

Source/Mock.cs

@@ -436,6 +436,7 @@ internal static MethodCall<T> Setup<T>(Mock<T> mock, Expression<Action<T>> expre
 				var args = methodCall.Arguments.ToArray();
 
 				ThrowIfSetupExpressionInvolvesUnsupportedMember(expression, method);
+				ThrowIfSetupMethodNotVisibleToProxyFactory(method);
 				var call = new MethodCall<T>(mock, condition, expression, method, args);
 
 				var targetInterceptor = GetInterceptor(methodCall.Object, mock);
@@ -464,6 +465,7 @@ internal static MethodCallReturn<T, TResult> Setup<T, TResult>(
 				var args = methodCall.Arguments.ToArray();
 
 				ThrowIfSetupExpressionInvolvesUnsupportedMember(expression, method);
+				ThrowIfSetupMethodNotVisibleToProxyFactory(method);
 				var call = new MethodCallReturn<T, TResult>(mock, condition, expression, method, args);
 
 				var targetInterceptor = GetInterceptor(methodCall.Object, mock);
@@ -493,6 +495,7 @@ internal static MethodCallReturn<T, TProperty> SetupGet<T, TProperty>(
 
 				var propGet = prop.GetGetMethod(true);
 				ThrowIfSetupExpressionInvolvesUnsupportedMember(expression, propGet);
+				ThrowIfSetupMethodNotVisibleToProxyFactory(propGet);
 
 				var call = new MethodCallReturn<T, TProperty>(mock, condition, expression, propGet, new Expression[0]);
 				// Directly casting to MemberExpression is fine as ToPropertyInfo would throw if it wasn't
@@ -551,6 +554,7 @@ internal static SetterMethodCall<T, TProperty> SetupSet<T, TProperty>(
 
 			var propSet = prop.GetSetMethod(true);
 			ThrowIfSetupExpressionInvolvesUnsupportedMember(expression, propSet);
+			ThrowIfSetupMethodNotVisibleToProxyFactory(propSet);
 
 			var call = new SetterMethodCall<T, TProperty>(mock, expression, propSet);
 			var targetInterceptor = GetInterceptor(((MemberExpression)expression.Body).Expression, mock);
@@ -802,6 +806,19 @@ private static void ThrowIfPropertyNotReadable(PropertyInfo prop)
 			}
 		}
 
+		private static void ThrowIfSetupMethodNotVisibleToProxyFactory(MethodInfo method)
+		{
+			if (Mock.ProxyFactory.IsMethodVisible(method, out string messageIfNotVisible) == false)
+			{
+				throw new ArgumentException(string.Format(
+					CultureInfo.CurrentCulture,
+					Resources.MethodNotVisibleToProxyFactory,
+					method.DeclaringType.Name,
+					method.Name,
+					messageIfNotVisible));
+			}
+		}
+
 		private static void ThrowIfSetupExpressionInvolvesUnsupportedMember(Expression setup, MethodInfo method)
 		{
 			if (method.IsStatic)

Source/Properties/Resources.resx

@@ -352,4 +352,8 @@ Expected invocation on the mock once, but was {4} times: {1}</value>
 	<data name="UseItExprIsNullRatherThanNullArgumentValue" xml:space="preserve">
 		<value>Use ItExpr.IsNull&lt;TValue&gt; rather than a null argument value, as it prevents proper method lookup.</value>
 	</data>
+	<data name="MethodNotVisibleToProxyFactory" xml:space="preserve">
+		<value>Cannot set up {0}.{1} because it is not accessible to the proxy generator used by Moq:
+{2}</value>
+	</data>
 </root>

Source/Proxy/CastleProxyFactory.cs

@@ -106,6 +106,11 @@ public object CreateProxy(Type mockType, ICallInterceptor interceptor, Type[] in
 			}
 		}
 
+		public bool IsMethodVisible(MethodInfo method, out string messageIfNotVisible)
+		{
+			return Castle.DynamicProxy.ProxyUtil.IsAccessible(method, out messageIfNotVisible);
+		}
+
 		private static readonly Dictionary<Type, Type> delegateInterfaceCache = new Dictionary<Type, Type>();
 		private static readonly ProxyGenerationOptions proxyOptions;
 		private static int delegateInterfaceSuffix;

Source/Proxy/IProxyFactory.cs

@@ -47,6 +47,8 @@ internal interface IProxyFactory
 	{
 		object CreateProxy(Type mockType, ICallInterceptor interceptor, Type[] interfaces, object[] arguments);
 
+		bool IsMethodVisible(MethodInfo method, out string messageIfNotVisible);
+
 		/// <summary>
 		/// Gets an autogenerated interface with a method on it that matches the signature of the specified
 		/// <paramref name="delegateType"/>.