Use parser::get() instead of operator[] in the implementation of

param_t::operator().

include/boost/parser/parser.hpp

@@ -843,7 +843,7 @@ namespace boost { namespace parser {
             template<typename Context>
             decltype(auto) operator()(Context const & context) const
             {
-                return parser::_params(context)[llong<I>{}];
+                return parser::get(parser::_params(context), llong<I>{});
             }
         };