[core] Prepare Filter and FilterEvaluator for extraction (#5366)

benchmark/parse/filter.cpp

@@ -13,32 +13,6 @@ using namespace mbgl;
 
 typedef std::multimap<std::string, Value> Properties;
 
-class StubFeature : public GeometryTileFeature {
-public:
-    inline StubFeature(const Properties& properties_, FeatureType type_)
-        : properties(properties_), type(type_) {
-    }
-
-    optional<Value> getValue(const std::string& key) const override {
-        auto it = properties.find(key);
-        if (it == properties.end())
-            return optional<Value>();
-        return it->second;
-    }
-
-    FeatureType getType() const override {
-        return type;
-    }
-
-    GeometryCollection getGeometries() const override {
-        return GeometryCollection();
-    }
-
-private:
-    const Properties properties;
-    FeatureType type;
-};
-
 style::Filter parse(const char* expression) {
     rapidjson::GenericDocument<rapidjson::UTF8<>, rapidjson::CrtAllocator> doc;
     doc.Parse<0>(expression);
@@ -54,10 +28,14 @@ static void Parse_Filter(benchmark::State& state) {
 static void Parse_EvaluateFilter(benchmark::State& state) {
     const style::Filter filter = parse(R"FILTER(["==", "foo", "bar"])FILTER");
     const Properties properties = { { "foo", std::string("bar") } };
-    const StubFeature feature(properties, FeatureType::Unknown);
 
     while (state.KeepRunning()) {
-        style::Filter::visit(filter, style::FilterEvaluator{ feature });
+        filter(FeatureType::Unknown, [&] (const std::string& key) -> optional<Value> {
+            auto it = properties.find(key);
+            if (it == properties.end())
+                return {};
+            return it->second;
+        });
     }
 }