Interpolation forvector-valued element (e.g. Raviart-Thomas) inconsistent

The interpolation of the vector-valued Raviart-Thomas functions is somehow inconsistent.

For H(div) functions, it is only meaningful to assign values in the normal direction of a vector valued function. Therefore dune-localfunctions projects the original function in normal direction. There is two possibilities to define such an original function: scalar-valued or vector-valued. Let's distinguish:

• In the interpolation process of dune-functions, scalar-valued functions will be automatically transformed to vectors. I think this trick is rather dirty as in the end, if thinking of BCs, it would be natural that the original function is projected in outer normal direction first and then interpolated. However, this is not the case, as e.g. orientation of normal vectors is not taken into account
• Assuming, a vector-valued function is used, the produced result is actually wrong. And I believe it is due to an implementation of interpolate.hh in dune-functions. In particular, if I understand correctly, in the LocalInterpolateVisitor, a local view of a grid function is addressed component-wise (here component j):

auto localFj = [&](const LocalDomain& x){

const auto& y = localF_(x); // still correct

return FiniteElementRange(flatVectorView(nodeToRangeEntry_(node, treePath, y))[j]);

};

The problem for the vector-valued Raviart-Thomas elements is that the subsequent code does not lead to increasing j such that always only the first component of the _original function _ is utilized for interpolation. This leads to errors. So far I used very simple output messages to analyze this.

After all, maybe vector-valued local finite elements have not been considered when implementing interpolate?