Require a BaseParameters type at compile time via enable_if

src/server/api/parameters_parser.cpp

@@ -3,6 +3,8 @@
 #include "server/api/route_parameters_grammar.hpp"
 #include "server/api/table_parameter_grammar.hpp"
 
+#include <type_traits>
+
 namespace osrm
 {
 namespace server
@@ -10,37 +12,37 @@ namespace server
 namespace api
 {
 
-template<>
-boost::optional<engine::api::RouteParameters> parseParameters(std::string::iterator& iter, std::string::iterator end)
+namespace detail
 {
-    RouteParametersGrammar grammar;
+
+template <typename ParameterT, typename GrammarT>
+boost::optional<ParameterT> parseParameters(std::string::iterator &iter, std::string::iterator end)
+{
+    GrammarT grammar;
     const auto result = boost::spirit::qi::parse(iter, end, grammar);
 
-    boost::optional<engine::api::RouteParameters> parameters;
+    boost::optional<ParameterT> parameters;
     if (result && iter == end)
-    {
         parameters = std::move(grammar.parameters);
-    }
 
     return parameters;
 }
+} // ns detail
 
-template<>
-boost::optional<engine::api::TableParameters> parseParameters(std::string::iterator& iter, std::string::iterator end)
+template <>
+boost::optional<engine::api::RouteParameters> parseParameters(std::string::iterator &iter,
+                                                              std::string::iterator end)
 {
-    TableParametersGrammar grammar;
-    const auto result = boost::spirit::qi::parse(iter, end, grammar);
-
-    boost::optional<engine::api::TableParameters> parameters;
-    if (result && iter == end)
-    {
-        parameters = std::move(grammar.parameters);
-    }
-
-    return parameters;
+    return detail::parseParameters<engine::api::RouteParameters, RouteParametersGrammar>(iter, end);
 }
 
-}
-}
+template <>
+boost::optional<engine::api::TableParameters> parseParameters(std::string::iterator &iter,
+                                                              std::string::iterator end)
+{
+    return detail::parseParameters<engine::api::TableParameters, TableParametersGrammar>(iter, end);
 }
 
+} // ns api
+} // ns server
+} // ns osrm