MissingMethodException when mocking interface with sealed default implementation

[pjquirk]

I thought this might fall under the #1148 umbrella, but using the latest 6.0 release (6.0.100-rc.1.21458.32) still results in the error.

I think the expected behavior here should be to use the default implementation if CallBase is true, otherwise, error as cannot be mocked. This repro errors regardless of the value of CallBase.

Repro

using Moq;

namespace moqrepro
{
    class Program
    {
        static void Main(string[] args)
        {
            var mock = new Mock<ILog>();

            // This setup has no effect
            // mock.Setup(p => p.Log(It.IsAny<string>()))
            //     .Callback<string>(msg => Console.WriteLine(msg));

            // XXX: This throws
            mock.Object.Log();
        }
    }

    public interface ILog
    {
        // Remove sealed to avoid exception above
        public sealed void Log()
        {
            Log("Testing");
        }

        void Log(string msg);
    }
}

Full build/run log:

> dotnet restore

Welcome to .NET 6.0!
---------------------
SDK Version: 6.0.100-rc.1.21458.32

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Read more about .NET CLI Tools telemetry: https://aka.ms/dotnet-cli-telemetry

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--------------------------------------------------------------------------------------
  Determining projects to restore...
  Restored /Users/pjquirk/Source/scratch/moqrepro/moqrepro.csproj (in 338 ms).

> dotnet build
Microsoft (R) Build Engine version 17.0.0-preview-21458-01+2c5510013 for .NET
Copyright (C) Microsoft Corporation. All rights reserved.

  Determining projects to restore...
  All projects are up-to-date for restore.
  You are using a preview version of .NET. See: https://aka.ms/dotnet-core-preview
  moqrepro -> /Users/pjquirk/Source/scratch/moqrepro/bin/Debug/net6.0/moqrepro.dll

Build succeeded.
    0 Warning(s)
    0 Error(s)

Time Elapsed 00:00:02.15

> dotnet run
Unhandled exception. System.MissingMethodException: Method not found: 'Void moqrepro.ILog.Log()'.
   at System.Reflection.Emit.TypeBuilder.CreateTypeNoLock()
   at System.Reflection.Emit.TypeBuilder.CreateTypeInfo()
   at Castle.DynamicProxy.Generators.Emitters.AbstractTypeEmitter.CreateType(TypeBuilder type)
   at Castle.DynamicProxy.Generators.Emitters.AbstractTypeEmitter.BuildType()
   at Castle.DynamicProxy.Generators.InterfaceProxyWithoutTargetGenerator.GenerateType(String typeName, Type proxyTargetType, Type[] interfaces, INamingScope namingScope)
   at Castle.DynamicProxy.Generators.InterfaceProxyWithTargetGenerator.<>c__DisplayClass6_0.<GenerateCode>b__0(String n, INamingScope s)
   at Castle.DynamicProxy.Generators.BaseProxyGenerator.<>c__DisplayClass33_0.<ObtainProxyType>b__0(CacheKey _)
   at Castle.Core.Internal.SynchronizedDictionary`2.GetOrAdd(TKey key, Func`2 valueFactory)
   at Castle.DynamicProxy.Generators.BaseProxyGenerator.ObtainProxyType(CacheKey cacheKey, Func`3 factory)
   at Castle.DynamicProxy.Generators.InterfaceProxyWithTargetGenerator.GenerateCode(Type proxyTargetType, Type[] interfaces, ProxyGenerationOptions options)
   at Castle.DynamicProxy.DefaultProxyBuilder.CreateInterfaceProxyTypeWithoutTarget(Type interfaceToProxy, Type[] additionalInterfacesToProxy, ProxyGenerationOptions options)
   at Castle.DynamicProxy.ProxyGenerator.CreateInterfaceProxyTypeWithoutTarget(Type interfaceToProxy, Type[] additionalInterfacesToProxy, ProxyGenerationOptions options)
   at Castle.DynamicProxy.ProxyGenerator.CreateInterfaceProxyWithoutTarget(Type interfaceToProxy, Type[] additionalInterfacesToProxy, ProxyGenerationOptions options, IInterceptor[] interceptors)
   at Moq.CastleProxyFactory.CreateProxy(Type mockType, IInterceptor interceptor, Type[] interfaces, Object[] arguments) in C:\projects\moq4\src\Moq\ProxyFactories\CastleProxyFactory.cs:line 50
   at Moq.Mock`1.InitializeInstance() in C:\projects\moq4\src\Moq\Mock`1.cs:line 311
   at Moq.Mock`1.OnGetObject() in C:\projects\moq4\src\Moq\Mock`1.cs:line 325
   at Moq.Mock.get_Object() in C:\projects\moq4\src\Moq\Mock.cs:line 179
   at Moq.Mock`1.get_Object() in C:\projects\moq4\src\Moq\Mock`1.cs:line 283
   at moqrepro.Program.Main(String[] args) in /Users/pjquirk/Source/scratch/moqrepro/Program.cs:line 15

I'm on MacOS Catalina 10.15.7 (19H1323).

[wzchua]

DynamicProxy fails to check that the method is not virtual here

[stakx]

@pjquirk, I'm just about to release Moq version 4.18.2 to NuGet, which includes a fix for this. Thanks again for reporting.