#include <cstdio>

template<class T0> struct prop {

    T0 operator()() {
      return data;
    }

    void operator()( T0 data_ ) {
      data = static_cast<T0&&>( data_ ); //data_ is always a copy, so move it
    }

    T0 data;
};

struct test {
    prop<int> data;
};

int main() {

  test t0{};

  t0.data( 10 );
  
  printf( "data = %d\n", t0.data() );
  
}