[core] Add expression filter support (#11251)

* WIP

* WIP

* WIP

* Remove Filter::operator()(const Feature&)

* WIP

* WIP

* WIP

* WIP

* Hook up expression filter evaluator

* Replace `shared_ptr` with &reference

* Fill in implementation of `void operator()(const ExpressionFilter&)`

* Fix failing tests

* Switch back to a shared_ptr per chat with @anandthakker

* Fix benchmark compilation

* Shot in the dark to fix CI

* Shot in the dark to fix CI (part 2)

* Shot in the dark to fix CI (part 3)

* In src/mbgl/style/conversion/filter.cpp, add a port of isExpressionFilter and use it to decide in Converter<Filter>::operator() whether to parse the incoming JSON as an ExpressionFilter or one of the legacy filter types

* Remove bool Filter::operator()(const GeometryTileFeature&) const

*  Ensure the map zoom is passed into filtering operations wherever applicable

* Add expression filter tests

* Addressed PR feedback

* Implement `NSPredicate *operator()(mbgl::style::ExpressionFilter filter)`

* Fix formatting& nit

1 files changed, 13 insertions, 9 deletions

diff --git a/include/mbgl/style/filter.hpp b/include/mbgl/style/filter.hpp
index a204a2b17a..ccf8dce188 100644
--- a/include/mbgl/style/filter.hpp
+++ b/include/mbgl/style/filter.hpp
@@ -3,6 +3,7 @@
 #include <mbgl/util/variant.hpp>
 #include <mbgl/util/feature.hpp>
 #include <mbgl/util/geometry.hpp>
+#include <mbgl/style/expression/expression.hpp>
 
 #include <string>
 #include <vector>
@@ -232,6 +233,15 @@ public:
         return true;
     }
 };
+    
+class ExpressionFilter {
+public:
+    std::shared_ptr<const expression::Expression> expression;
+    
+    friend bool operator==(const ExpressionFilter& lhs, const ExpressionFilter& rhs) {
+        return *(lhs.expression) == *(rhs.expression);
+    }
+};
 
 
 using FilterBase = variant<
@@ -258,19 +268,13 @@ using FilterBase = variant<
     class IdentifierInFilter,
     class IdentifierNotInFilter,
     class HasIdentifierFilter,
-    class NotHasIdentifierFilter>;
+    class NotHasIdentifierFilter,
+    class ExpressionFilter>;
 
 class Filter : public FilterBase {
 public:
     using FilterBase::FilterBase;
-
-    bool operator()(const Feature&) const;
-
-    template <class GeometryTileFeature>
-    bool operator()(const GeometryTileFeature&) const;
-
-    template <class PropertyAccessor>
-    bool operator()(FeatureType type, optional<FeatureIdentifier> id, PropertyAccessor accessor) const;
+    bool operator()(const expression::EvaluationContext& context) const;
 };
 
 } // namespace style