Rule
<boost/url/grammar/type_traits.hpp>
template<class T>
using is_rule = /* implementation-defined */;
This is an alias for std::true_type if T meets the requirements, otherwise it is an alias for std::false_type.
struct U
{
struct value_type;
auto
parse(
char const*& it,
char const* end) const ->
system::result
};
static_assert( is_rule::value, "Requirements not met" );