calling a __host__ function from a __host__ __device__ when using gather with zip_iterator for vector of vectors

[fkallen]

I would like to gather data from a struct of arrays, which contains some vector of vectors. thrust::zip_iterator is used to fuse the calls of individual arrays. This causes a series of warnings.

#include <thrust/iterator/zip_iterator.h>
#include <thrust/gather.h>
#include <thrust/host_vector.h>


int main(){
    thrust::host_vector<int> map(42);
    thrust::host_vector<thrust::host_vector<char>> vecvec(42); 
    thrust::host_vector<thrust::host_vector<char>> outvecvec(42); 

    auto in = thrust::make_zip_iterator(thrust::make_tuple(
        vecvec.begin()
    ));

    auto out = thrust::make_zip_iterator(thrust::make_tuple(
        outvecvec.begin()
    ));

    #if 1
   // warning calling a __host__ function from a __host__ __device__
    thrust::gather(
        map.begin(),
        map.end(),
        in,
        out
    );

    #else
    // no warning
    thrust::gather(
        map.begin(),
        map.end(),
        vecvec.begin(),
        outvecvec.begin()
    );

    #endif
}

https://cuda.godbolt.org/z/4Ebo6Yn57

/opt/compiler-explorer/libs/thrustcub/trunk/thrust/detail/tuple.inl(458): warning: calling a __host__ function from a __host__ __device__ function is not allowed
          detected during:
            instantiation of "thrust::detail::cons<HT, thrust::null_type>::cons(const thrust::detail::cons<HT2, thrust::null_type> &) [with HT=thrust::host_vector<char, std::allocator<char>>, HT2=thrust::host_vector<char, std::allocator<char>> &]" 
/opt/compiler-explorer/libs/thrustcub/trunk/thrust/tuple.h(346): here

/opt/compiler-explorer/libs/thrustcub/trunk/thrust/detail/function.h(118): warning: calling a __host__ function("thrust::host_vector<char, ::std::allocator<char> > ::~host_vector()") from a __host__ __device__ function("thrust::detail::cons< ::thrust::host_vector<char, ::std::allocator<char> > ,  ::thrust::null_type> ::~cons") is not allowed

/opt/compiler-explorer/libs/thrustcub/trunk/thrust/detail/tuple.inl(458): warning: calling a __host__ function("thrust::host_vector<char, ::std::allocator<char> > ::host_vector(const thrust::host_vector<char, ::std::allocator<char> > &)") from a __host__ __device__ function("thrust::detail::cons< ::thrust::host_vector<char, ::std::allocator<char> > ,  ::thrust::null_type> ::cons< ::thrust::host_vector<char, ::std::allocator<char> >  &> ") is not allowed