anchor.diff:              let methodBuilder = defineMethod typeBuilder abstractMethod
               /// IL generator
               let il = methodBuilder.GetILGenerator()
  +            // Record invocation
  +            generateRecordInvocation il invocationsField abstractMethod
               /// Method overloads defined for current method
               let overloads = groupedMethods |> Seq.tryFind (fst >> (=) abstractMethod)
               match overloads with
  
positive.code:             emitReturnValueLookup exnValue
              il.Emit(OpCodes.Throw)
  
      /// Generates method overload
      let generateOverload 
          (il:ILGenerator)
  
negative.code:                         let x = il.DeclareLocal(abstractMethod.ReturnType)
                          il.Emit(OpCodes.Ldloca_S, x.LocalIndex)
                          il.Emit(OpCodes.Initobj, abstractMethod.ReturnType)
                          il.Emit(OpCodes.Ldloc, x.LocalIndex)
                          il.Emit(OpCodes.Ret)
              if abstractType.IsInterface then
                  typeBuilder.DefineMethodOverride(methodBuilder, abstractMethod)
  