[core] Remove stops-based *Function constructors

7 files changed, 122 insertions, 155 deletions

diff --git a/cmake/core-files.cmake b/cmake/core-files.cmake
index 09c12897b0..a06f3a59f5 100644
--- a/cmake/core-files.cmake
+++ b/cmake/core-files.cmake
@@ -504,6 +504,7 @@ set(MBGL_CORE_FILES
     include/mbgl/style/function/interval_stops.hpp
     include/mbgl/style/function/source_function.hpp
     src/mbgl/style/function/categorical_stops.cpp
+    src/mbgl/style/function/convert.cpp
     src/mbgl/style/function/expression.cpp
     src/mbgl/style/function/identity_stops.cpp
 
diff --git a/include/mbgl/style/conversion/function.hpp b/include/mbgl/style/conversion/function.hpp
index e230884944..932925c53c 100644
--- a/include/mbgl/style/conversion/function.hpp
+++ b/include/mbgl/style/conversion/function.hpp
@@ -3,9 +3,18 @@
 #include <mbgl/style/function/camera_function.hpp>
 #include <mbgl/style/function/source_function.hpp>
 #include <mbgl/style/function/composite_function.hpp>
+#include <mbgl/style/function/convert.hpp>
+#include <mbgl/style/function/categorical_stops.hpp>
+#include <mbgl/style/function/exponential_stops.hpp>
+#include <mbgl/style/function/interval_stops.hpp>
+#include <mbgl/style/function/identity_stops.hpp>
+#include <mbgl/style/function/composite_exponential_stops.hpp>
+#include <mbgl/style/function/composite_interval_stops.hpp>
+#include <mbgl/style/function/composite_categorical_stops.hpp>
 #include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/constant.hpp>
 #include <mbgl/util/ignore.hpp>
+#include <mbgl/util/variant.hpp>
 
 namespace mbgl {
 namespace style {
@@ -193,12 +202,22 @@ struct Converter<CameraFunction<T>> {
             return {};
         }
 
-        auto stops = StopsConverter<T, typename CameraFunction<T>::Stops>()(value, error);
+        using Stops = std::conditional_t<
+            util::Interpolatable<T>::value,
+            variant<
+                ExponentialStops<T>,
+                IntervalStops<T>>,
+            variant<
+                IntervalStops<T>>>;
+
+        auto stops = StopsConverter<T, Stops>()(value, error);
         if (!stops) {
             return {};
         }
 
-        return CameraFunction<T>(*stops);
+        return CameraFunction<T>((*stops).match([&] (const auto& s) {
+            return expression::Convert::toExpression(s);
+        }), false);
     }
 };
 
@@ -238,7 +257,19 @@ struct Converter<SourceFunction<T>> {
             return {};
         }
 
-        auto stops = StopsConverter<T, typename SourceFunction<T>::Stops>()(value, error);
+        using Stops = std::conditional_t<
+            util::Interpolatable<T>::value,
+            variant<
+                ExponentialStops<T>,
+                IntervalStops<T>,
+                CategoricalStops<T>,
+                IdentityStops<T>>,
+            variant<
+                IntervalStops<T>,
+                CategoricalStops<T>,
+                IdentityStops<T>>>;
+
+        auto stops = StopsConverter<T, Stops>()(value, error);
         if (!stops) {
             return {};
         }
@@ -248,7 +279,9 @@ struct Converter<SourceFunction<T>> {
             return {};
         }
 
-        return SourceFunction<T>(*propertyString, *stops, *defaultValue);
+        return SourceFunction<T>((*stops).match([&] (const auto& s) {
+            return expression::Convert::toExpression(*propertyString, s);
+        }), *defaultValue);
     }
 };
 
@@ -374,7 +407,17 @@ struct Converter<CompositeFunction<T>> {
             return {};
         }
 
-        auto stops = StopsConverter<T, typename CompositeFunction<T>::Stops>()(value, error);
+        using Stops = std::conditional_t<
+            util::Interpolatable<T>::value,
+            variant<
+                CompositeExponentialStops<T>,
+                CompositeIntervalStops<T>,
+                CompositeCategoricalStops<T>>,
+            variant<
+                CompositeIntervalStops<T>,
+                CompositeCategoricalStops<T>>>;
+
+        auto stops = StopsConverter<T, Stops>()(value, error);
         if (!stops) {
             return {};
         }
@@ -384,7 +427,9 @@ struct Converter<CompositeFunction<T>> {
             return {};
         }
 
-        return CompositeFunction<T>(*propertyString, *stops, *defaultValue);
+        return CompositeFunction<T>((*stops).match([&] (const auto& s) {
+            return expression::Convert::toExpression(*propertyString, s);
+        }), *defaultValue);
     }
 };
 
diff --git a/include/mbgl/style/function/camera_function.hpp b/include/mbgl/style/function/camera_function.hpp
index 479deb20df..65b7991849 100644
--- a/include/mbgl/style/function/camera_function.hpp
+++ b/include/mbgl/style/function/camera_function.hpp
@@ -1,16 +1,12 @@
 #pragma once
 
 #include <mbgl/style/expression/expression.hpp>
+#include <mbgl/style/expression/value.hpp>
+#include <mbgl/style/expression/is_constant.hpp>
 #include <mbgl/style/expression/interpolate.hpp>
 #include <mbgl/style/expression/step.hpp>
 #include <mbgl/style/expression/find_zoom_curve.hpp>
-#include <mbgl/style/expression/value.hpp>
-#include <mbgl/style/expression/is_constant.hpp>
-#include <mbgl/style/function/convert.hpp>
-#include <mbgl/style/function/exponential_stops.hpp>
-#include <mbgl/style/function/interval_stops.hpp>
-#include <mbgl/util/interpolate.hpp>
-#include <mbgl/util/variant.hpp>
+#include <mbgl/util/range.hpp>
 
 namespace mbgl {
 namespace style {
@@ -18,31 +14,15 @@ namespace style {
 template <class T>
 class CameraFunction {
 public:
-    using Stops = std::conditional_t<
-        util::Interpolatable<T>::value,
-        variant<
-            ExponentialStops<T>,
-            IntervalStops<T>>,
-        variant<
-            IntervalStops<T>>>;
-    
-    CameraFunction(std::unique_ptr<expression::Expression> expression_)
-         : isExpression(true),
+    // The second parameter should be used only for conversions from legacy functions.
+    CameraFunction(std::unique_ptr<expression::Expression> expression_, bool isExpression_ = true)
+         : isExpression(isExpression_),
            expression(std::move(expression_)),
-           zoomCurve(expression::findZoomCurveChecked(expression.get()))
-    {
+           zoomCurve(expression::findZoomCurveChecked(expression.get())) {
         assert(!expression::isZoomConstant(*expression));
         assert(expression::isFeatureConstant(*expression));
     }
 
-    CameraFunction(const Stops& stops)
-        : isExpression(false),
-          expression(stops.match([&] (const auto& s) {
-            return expression::Convert::toExpression(s);
-          })),
-          zoomCurve(expression::findZoomCurveChecked(expression.get()))
-    {}
-
     T evaluate(float zoom) const {
         const expression::EvaluationResult result = expression->evaluate(expression::EvaluationContext(zoom, nullptr));
         if (result) {
@@ -82,7 +62,7 @@ public:
     const expression::Expression& getExpression() const { return *expression; }
 
 private:
-    std::shared_ptr<expression::Expression> expression;
+    std::shared_ptr<const expression::Expression> expression;
     const variant<const expression::Interpolate*, const expression::Step*> zoomCurve;
 };
 
diff --git a/include/mbgl/style/function/composite_function.hpp b/include/mbgl/style/function/composite_function.hpp
index f99fc973ed..3b63bd005d 100644
--- a/include/mbgl/style/function/composite_function.hpp
+++ b/include/mbgl/style/function/composite_function.hpp
@@ -1,74 +1,29 @@
 #pragma once
 
 #include <mbgl/style/expression/expression.hpp>
+#include <mbgl/style/expression/value.hpp>
+#include <mbgl/style/expression/is_constant.hpp>
 #include <mbgl/style/expression/interpolate.hpp>
 #include <mbgl/style/expression/step.hpp>
 #include <mbgl/style/expression/find_zoom_curve.hpp>
-#include <mbgl/style/expression/value.hpp>
-#include <mbgl/style/expression/is_constant.hpp>
-#include <mbgl/style/function/convert.hpp>
-#include <mbgl/style/function/composite_exponential_stops.hpp>
-#include <mbgl/style/function/composite_interval_stops.hpp>
-#include <mbgl/style/function/composite_categorical_stops.hpp>
-#include <mbgl/util/interpolate.hpp>
 #include <mbgl/util/range.hpp>
-#include <mbgl/util/variant.hpp>
-
-#include <string>
-#include <tuple>
 
 namespace mbgl {
-
-class GeometryTileFeature;
-
 namespace style {
 
-// A CompositeFunction consists of an outer zoom function whose stop range values are
-// "inner" source functions. It provides the GL Native implementation of
-// "zoom-and-property" functions from the style spec.
-
 template <class T>
 class CompositeFunction {
 public:
-    using InnerStops = std::conditional_t<
-        util::Interpolatable<T>::value,
-        variant<
-            ExponentialStops<T>,
-            IntervalStops<T>,
-            CategoricalStops<T>>,
-        variant<
-            IntervalStops<T>,
-            CategoricalStops<T>>>;
-
-    using Stops = std::conditional_t<
-        util::Interpolatable<T>::value,
-        variant<
-            CompositeExponentialStops<T>,
-            CompositeIntervalStops<T>,
-            CompositeCategoricalStops<T>>,
-        variant<
-            CompositeIntervalStops<T>,
-            CompositeCategoricalStops<T>>>;
-
+    // The second parameter should be used only for conversions from legacy functions.
     CompositeFunction(std::unique_ptr<expression::Expression> expression_, optional<T> defaultValue_ = {})
-    :   isExpression(true),
-        defaultValue(std::move(defaultValue_)),
-        expression(std::move(expression_)),
-        zoomCurve(expression::findZoomCurveChecked(expression.get()))
-    {
+        : isExpression(defaultValue_),
+          expression(std::move(expression_)),
+          defaultValue(std::move(defaultValue_)),
+          zoomCurve(expression::findZoomCurveChecked(expression.get())) {
         assert(!expression::isZoomConstant(*expression));
         assert(!expression::isFeatureConstant(*expression));
     }
 
-    CompositeFunction(const std::string& property, const Stops& stops, optional<T> defaultValue_ = {})
-    :   isExpression(false),
-        defaultValue(std::move(defaultValue_)),
-        expression(stops.match([&] (const auto& s) {
-            return expression::Convert::toExpression(property, s);
-        })),
-        zoomCurve(expression::findZoomCurveChecked(expression.get()))
-    {}
-
     // Return the range obtained by evaluating the function at each of the zoom levels in zoomRange
     template <class Feature>
     Range<T> evaluate(const Range<float>& zoomRange, const Feature& feature, T finalDefaultValue) {
@@ -118,8 +73,8 @@ public:
     bool isExpression;
     
 private:
+    std::shared_ptr<const expression::Expression> expression;
     optional<T> defaultValue;
-    std::shared_ptr<expression::Expression> expression;
     const variant<const expression::Interpolate*, const expression::Step*> zoomCurve;
 };
 
diff --git a/include/mbgl/style/function/convert.hpp b/include/mbgl/style/function/convert.hpp
index e5a5808e1d..a0dae992fa 100644
--- a/include/mbgl/style/function/convert.hpp
+++ b/include/mbgl/style/function/convert.hpp
@@ -306,40 +306,15 @@ struct Convert {
         return std::move(*zoomCurve);
     }
 
-    
-    static std::unique_ptr<Expression> fromIdentityFunction(type::Type type, const std::string& property)
+    template <typename T>
+    static std::unique_ptr<Expression> toExpression(const std::string& property,
+                                                    const IdentityStops<T>&)
     {
-        std::unique_ptr<Expression> input = type.match(
-            [&] (const type::StringType&) {
-                return makeGet(type::String, property);
-            },
-            [&] (const type::NumberType&) {
-                return makeGet(type::Number, property);
-            },
-            [&] (const type::BooleanType&) {
-                return makeGet(type::Boolean, property);
-            },
-            [&] (const type::ColorType&) {
-                std::vector<std::unique_ptr<Expression>> args;
-                args.push_back(makeGet(type::String, property));
-                return std::make_unique<Coercion>(type::Color, std::move(args));
-            },
-            [&] (const type::Array& arr) {
-                std::vector<std::unique_ptr<Expression>> getArgs;
-                getArgs.push_back(makeLiteral(property));
-                ParsingContext ctx;
-                ParseResult get = createCompoundExpression("get", std::move(getArgs), ctx);
-                assert(get);
-                assert(ctx.getErrors().size() == 0);
-                return std::make_unique<ArrayAssertion>(arr, std::move(*get));
-            },
-            [&] (const auto&) -> std::unique_ptr<Expression> {
-                return makeLiteral(Null);
-            }
-        );
-        
-        return input;
+        return fromIdentityFunction(property, expression::valueTypeToExpressionType<T>());
     }
+
+private:
+    static std::unique_ptr<Expression> fromIdentityFunction(const std::string& property, type::Type type);
 };
 
 } // namespace expression
diff --git a/include/mbgl/style/function/source_function.hpp b/include/mbgl/style/function/source_function.hpp
index bc4e3b9c7d..a83e73a5d0 100644
--- a/include/mbgl/style/function/source_function.hpp
+++ b/include/mbgl/style/function/source_function.hpp
@@ -1,15 +1,8 @@
 #pragma once
 
+#include <mbgl/style/expression/expression.hpp>
+#include <mbgl/style/expression/value.hpp>
 #include <mbgl/style/expression/is_constant.hpp>
-#include <mbgl/style/function/convert.hpp>
-#include <mbgl/style/function/exponential_stops.hpp>
-#include <mbgl/style/function/interval_stops.hpp>
-#include <mbgl/style/function/categorical_stops.hpp>
-#include <mbgl/style/function/identity_stops.hpp>
-#include <mbgl/util/interpolate.hpp>
-#include <mbgl/util/variant.hpp>
-
-#include <string>
 
 namespace mbgl {
 namespace style {
@@ -17,37 +10,15 @@ namespace style {
 template <class T>
 class SourceFunction {
 public:
-    using Stops = std::conditional_t<
-        util::Interpolatable<T>::value,
-        variant<
-            ExponentialStops<T>,
-            IntervalStops<T>,
-            CategoricalStops<T>,
-            IdentityStops<T>>,
-        variant<
-            IntervalStops<T>,
-            CategoricalStops<T>,
-            IdentityStops<T>>>;
-
+    // The second parameter should be used only for conversions from legacy functions.
     SourceFunction(std::unique_ptr<expression::Expression> expression_, optional<T> defaultValue_ = {})
-        : isExpression(true),
-          defaultValue(std::move(defaultValue_)),
-          expression(std::move(expression_))
-    {
+        : isExpression(defaultValue_),
+          expression(std::move(expression_)),
+          defaultValue(std::move(defaultValue_)) {
         assert(expression::isZoomConstant(*expression));
         assert(!expression::isFeatureConstant(*expression));
     }
     
-    SourceFunction(const std::string& property, const Stops& stops, optional<T> defaultValue_ = {})
-        : isExpression(false),
-          defaultValue(std::move(defaultValue_)),
-          expression(stops.match([&] (const IdentityStops<T>&) {
-              return expression::Convert::fromIdentityFunction(expression::valueTypeToExpressionType<T>(), property);
-          }, [&] (const auto& s) {
-              return expression::Convert::toExpression(property, s);
-          }))
-    {}
-
     template <class Feature>
     T evaluate(const Feature& feature, T finalDefaultValue) const {
         const expression::EvaluationResult result = expression->evaluate(expression::EvaluationContext(&feature));
@@ -73,8 +44,8 @@ public:
     const expression::Expression& getExpression() const { return *expression; }
 
 private:
+    std::shared_ptr<const expression::Expression> expression;
     optional<T> defaultValue;
-    std::shared_ptr<expression::Expression> expression;
 };
 
 } // namespace style
diff --git a/src/mbgl/style/function/convert.cpp b/src/mbgl/style/function/convert.cpp
new file mode 100644
index 0000000000..a3b19f287b
--- /dev/null
+++ b/src/mbgl/style/function/convert.cpp
@@ -0,0 +1,40 @@
+#include <mbgl/style/function/convert.hpp>
+
+namespace mbgl {
+namespace style {
+namespace expression {
+
+std::unique_ptr<Expression> Convert::fromIdentityFunction(const std::string& property, type::Type type) {
+    return type.match(
+        [&] (const type::StringType&) {
+            return makeGet(type::String, property);
+        },
+        [&] (const type::NumberType&) {
+            return makeGet(type::Number, property);
+        },
+        [&] (const type::BooleanType&) {
+            return makeGet(type::Boolean, property);
+        },
+        [&] (const type::ColorType&) {
+            std::vector<std::unique_ptr<Expression>> args;
+            args.push_back(makeGet(type::String, property));
+            return std::make_unique<Coercion>(type::Color, std::move(args));
+        },
+        [&] (const type::Array& arr) {
+            std::vector<std::unique_ptr<Expression>> getArgs;
+            getArgs.push_back(makeLiteral(property));
+            ParsingContext ctx;
+            ParseResult get = createCompoundExpression("get", std::move(getArgs), ctx);
+            assert(get);
+            assert(ctx.getErrors().size() == 0);
+            return std::make_unique<ArrayAssertion>(arr, std::move(*get));
+        },
+        [&] (const auto&) -> std::unique_ptr<Expression> {
+            return makeLiteral(Null);
+        }
+    );
+}
+
+} // namespace expression
+} // namespace style
+} // namespace mbgl