Boo.Lang.Compiler.Steps.ProcessMethodBodies.CheckGeneratorReturnType C# (CSharp) Метод

        void CheckGeneratorReturnType(Method method, IType returnType)
        {
            bool validReturnType =
                (TypeSystemServices.IEnumerableType == returnType ||
                 TypeSystemServices.IEnumeratorType == returnType ||
                 TypeSystemServices.IsSystemObject(returnType) ||
                 TypeSystemServices.IsGenericGeneratorReturnType(returnType));

            if (!validReturnType)
            {
                Error(CompilerErrorFactory.InvalidGeneratorReturnType(method.ReturnType, returnType));
            }
        }