[discretefunction.default] modernize static checks

dune/gdt/discretefunction/default.hh

@@ -34,14 +34,8 @@ class ConstDiscreteFunction
                                                  SpaceImp::dimDomain, typename SpaceImp::RangeFieldType,
                                                  SpaceImp::dimRange, SpaceImp::dimRangeCols>
 {
-  static_assert(std::is_base_of<SpaceInterface<typename SpaceImp::Traits, SpaceImp::dimDomain, SpaceImp::dimRange,
-                                               SpaceImp::dimRangeCols>,
-                                SpaceImp>::value,
-                "SpaceImp has to be derived from SpaceInterface!");
-  static_assert(std::is_base_of<Dune::Stuff::LA::VectorInterface<typename VectorImp::Traits,
-                                                                 typename VectorImp::Traits::ScalarType>,
-                                VectorImp>::value,
-                "VectorImp has to be derived from Stuff::LA::VectorInterface!");
+  static_assert(is_space<SpaceImp>::value, "SpaceImp has to be derived from SpaceInterface!");
+  static_assert(Stuff::LA::is_vector<VectorImp>::value, "VectorImp has to be derived from Stuff::LA::VectorInterface!");
   static_assert(std::is_same<typename SpaceImp::RangeFieldType, typename VectorImp::ScalarType>::value,
                 "Types do not match!");
   typedef Stuff::LocalizableFunctionInterface<typename SpaceImp::EntityType, typename SpaceImp::DomainFieldType,