QMetaType::registerConverter implementation should support custom template converter function

//Proposal
template<typename From, typename To, template <typename ...> typename C>static bool registerConverter(C<From, To> function){ Q_STATIC_ASSERT_X((!QMetaTypeId2<To>::IsBuiltIn || !QMetaTypeId2<From>::IsBuiltIn), "QMetaType::registerConverter: At least one of the types must be a custom type.");  
const int fromTypeId = qMetaTypeId<From>(); 
const int toTypeId = qMetaTypeId<To>(); 
static const QtPrivate::ConverterFunctor<From, To, C<From, To>> f(function); return registerConverterFunction(&f, fromTypeId, toTypeId);
}

//A template custom variant container to custom type container converter
template <typename T>
struct TemplateParameter;

template <template <typename ...> typename C, typename T>
struct TemplateParameter<C<T>>
{
    using type = T;
};

template <typename T>
using type = typename TemplateParameter<T>::type;

template <typename From, typename To>To fromSharedVariantContainer(const From &from){ 
To to; 
for(const auto& it : from){ 
to << qSharedPointerCast<type<To>>(it); 
}  
return to;
}

//Usecase
https://github.com/semlanik/qtprotobuf/blob/master/src/protobuf/qqmllistpropertyconstructor.h
Unusable pertinent methods