[core] make style/conversion.hpp implementation privateupstream/conversion-private

92 files changed, 616 insertions, 431 deletions

diff --git a/benchmark/function/camera_function.benchmark.cpp b/benchmark/function/camera_function.benchmark.cpp
index 51d2e22293..0ce7d7c763 100644
--- a/benchmark/function/camera_function.benchmark.cpp
+++ b/benchmark/function/camera_function.benchmark.cpp
@@ -1,9 +1,9 @@
 #include <benchmark/benchmark.h>
 
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/json.hpp>
 #include <mbgl/style/conversion/function.hpp>
 #include <mbgl/style/conversion/property_value.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 
 using namespace mbgl;
 using namespace mbgl::style;
diff --git a/benchmark/function/composite_function.benchmark.cpp b/benchmark/function/composite_function.benchmark.cpp
index f16254641f..8064d548fa 100644
--- a/benchmark/function/composite_function.benchmark.cpp
+++ b/benchmark/function/composite_function.benchmark.cpp
@@ -2,10 +2,10 @@
 
 #include <mbgl/benchmark/stub_geometry_tile_feature.hpp>
 
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/json.hpp>
 #include <mbgl/style/conversion/function.hpp>
 #include <mbgl/style/conversion/property_value.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 
 using namespace mbgl;
 using namespace mbgl::style;
diff --git a/benchmark/function/source_function.benchmark.cpp b/benchmark/function/source_function.benchmark.cpp
index 2164b2a418..b75cc143d2 100644
--- a/benchmark/function/source_function.benchmark.cpp
+++ b/benchmark/function/source_function.benchmark.cpp
@@ -2,9 +2,9 @@
 
 #include <mbgl/benchmark/stub_geometry_tile_feature.hpp>
 
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/json.hpp>
 #include <mbgl/style/conversion/property_value.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 
 using namespace mbgl;
 using namespace mbgl::style;
diff --git a/benchmark/parse/filter.benchmark.cpp b/benchmark/parse/filter.benchmark.cpp
index 4e39237138..1ae2b0f2bc 100644
--- a/benchmark/parse/filter.benchmark.cpp
+++ b/benchmark/parse/filter.benchmark.cpp
@@ -1,9 +1,9 @@
 #include <benchmark/benchmark.h>
 
 #include <mbgl/style/filter.hpp>
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/json.hpp>
 #include <mbgl/style/conversion/filter.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/tile/geometry_tile_data.hpp>
 #include <mbgl/benchmark/stub_geometry_tile_feature.hpp>
 
diff --git a/cmake/core-files.cmake b/cmake/core-files.cmake
index 02335fef7a..2d0bd003c7 100644
--- a/cmake/core-files.cmake
+++ b/cmake/core-files.cmake
@@ -363,6 +363,7 @@ set(MBGL_CORE_FILES
     # style
     include/mbgl/style/color_ramp_property_value.hpp
     include/mbgl/style/conversion.hpp
+    include/mbgl/style/conversion_impl.hpp
     include/mbgl/style/filter.hpp
     include/mbgl/style/image.hpp
     include/mbgl/style/layer.hpp
@@ -437,6 +438,7 @@ set(MBGL_CORE_FILES
     src/mbgl/style/conversion/layer.cpp
     src/mbgl/style/conversion/light.cpp
     src/mbgl/style/conversion/position.cpp
+    src/mbgl/style/conversion/property_value.cpp
     src/mbgl/style/conversion/source.cpp
     src/mbgl/style/conversion/stringify.hpp
     src/mbgl/style/conversion/tileset.cpp
diff --git a/include/mbgl/style/conversion.hpp b/include/mbgl/style/conversion.hpp
index 71c2cec237..2c83d1561b 100644
--- a/include/mbgl/style/conversion.hpp
+++ b/include/mbgl/style/conversion.hpp
@@ -1,306 +1,26 @@
 #pragma once
 
-#include <mbgl/util/optional.hpp>
-#include <mbgl/util/feature.hpp>
-#include <mbgl/util/geojson.hpp>
-
 #include <string>
 
 namespace mbgl {
 namespace style {
 namespace conversion {
 
-/*
-   The `conversion` namespace defines conversions from JSON structures conforming to the schema defined by
-   the Mapbox Style Specification, to the various C++ types that form the C++ model of that domain:
-
-       * `std::unique_ptr<Source>`
-       * `std::unique_ptr<Layer>`
-       * `Filter`
-       * `PropertyValue<T>`
-
-   A single template function serves as the public interface:
-
-       template <class T>
-       optional<T> convert(const Convertible& input, Error& error);
-
-   Where `T` is one of the above types. If the conversion fails, the result is empty, and the
-   error parameter includes diagnostic text suitable for presentation to a library user. Otherwise,
-   a filled optional is returned.
-
-   `Convertible` is a type that encapsulates a special form of polymorphism over various underlying types that
-   can serve as input to the conversion algorithm. For instance, on macOS, we need to support
-   conversion from both RapidJSON types, and a JSON structure represented with `NSArray`/`NSDictionary`/etc.
-   On Qt, we need to support conversion from RapidJSON types and QVariant.
-
-   We don't want to use traditional forms of polymorphism to accomplish this:
-
-     * Compile time polymorphism using a template parameter for the actual value type leads to
-       excessive code bloat and long compile times.
-     * Runtime polymorphism using virtual methods requires extra heap allocation and ubiquitous
-       use of std::unique_ptr, unsuitable for this performance-sensitive code.
-
-   Therefore, we're using a custom implementation of runtime polymorphism where we manually create and
-   dispatch through a table of function pointers (vtable), while keeping the storage for any of the possible
-   underlying types inline on the stack, using `std::aligned_storage`.
-
-   For a given underlying type T, an explicit specialization of `ConversionTraits<T>` must be provided. This
-   specialization must provide the following static methods:
-
-      * `isUndefined(v)` -- returns a boolean indication whether `v` is undefined or a JSON null
-
-      * `isArray(v)` -- returns a boolean indicating whether `v` represents a JSON array
-      * `arrayLength(v)` -- called only if `isArray(v)`; returns a size_t length
-      * `arrayMember(v)` -- called only if `isArray(v)`; returns `V` or `V&`
-
-      * `isObject(v)` -- returns a boolean indicating whether `v` represents a JSON object
-      * `objectMember(v, name)` -- called only if `isObject(v)`; `name` is `const char *`; return value:
-         * is true when evaluated in a boolean context iff the named member exists
-         * is convertable to a `V` or `V&` when dereferenced
-      * `eachMember(v, [] (const std::string&, const V&) -> optional<Error> {...})` -- called
-         only if `isObject(v)`; calls the provided lambda once for each key and value of the object;
-         short-circuits if any call returns an `Error`
-
-      * `toBool(v)` -- returns `optional<bool>`, absence indicating `v` is not a JSON boolean
-      * `toNumber(v)` -- returns `optional<float>`, absence indicating `v` is not a JSON number
-      * `toDouble(v)` -- returns `optional<double>`, absence indicating `v` is not a JSON number
-      * `toString(v)` -- returns `optional<std::string>`, absence indicating `v` is not a JSON string
-      * `toValue(v)` -- returns `optional<Value>`, a variant type, for generic conversion,
-        absence indicating `v` is not a boolean, number, or string. Numbers should be converted to
-        unsigned integer, signed integer, or floating point, in descending preference.
-
-   In addition, the type T must be move-constructable. And finally, `Convertible::Storage`, a typedef for
-   `std::aligned_storage_t`, must be large enough to satisfy the memory requirements for any of the
-   possible underlying types. (A static assert will fail if this is not the case.)
-
-   `Convertible` itself is movable, but not copyable. A moved-from `Convertible` is in an invalid state;
-   you must not do anything with it except let it go out of scope.
-*/
+// This is a forward-declaration only header intended to minimize dependencies and to improve
+// compilation speed. In order to specialize implementations and get access to the actual
+// implementation, include <mbgl/style/conversion_impl.hpp>.
 
 struct Error { std::string message; };
 
 template <typename T>
 class ConversionTraits;
 
-class Convertible {
-public:
-    template <typename T>
-    Convertible(T&& value) : vtable(vtableForType<std::decay_t<T>>()) {
-        static_assert(sizeof(Storage) >= sizeof(std::decay_t<T>), "Storage must be large enough to hold value type");
-        new (static_cast<void*>(&storage)) std::decay_t<T>(std::forward<T>(value));
-    }
-
-    Convertible(Convertible&& v)
-        : vtable(v.vtable)
-    {
-        if (vtable) {
-            vtable->move(std::move(v.storage), this->storage);
-        }
-    }
-
-    ~Convertible() {
-        if (vtable) {
-            vtable->destroy(storage);
-        }
-    }
-
-    Convertible& operator=(Convertible&& v) {
-        if (vtable) {
-            vtable->destroy(storage);
-        }
-        vtable = v.vtable;
-        if (vtable) {
-            vtable->move(std::move(v.storage), this->storage);
-        }
-        v.vtable = nullptr;
-        return *this;
-    }
-
-    Convertible()                              = delete;
-    Convertible(const Convertible&)            = delete;
-    Convertible& operator=(const Convertible&) = delete;
-
-    friend inline bool isUndefined(const Convertible& v) {
-        assert(v.vtable);
-        return v.vtable->isUndefined(v.storage);
-    }
-
-    friend inline bool isArray(const Convertible& v) {
-        assert(v.vtable);
-        return v.vtable->isArray(v.storage);
-    }
-
-    friend inline std::size_t arrayLength(const Convertible& v) {
-        assert(v.vtable);
-        return v.vtable->arrayLength(v.storage);
-    }
-
-    friend inline Convertible arrayMember(const Convertible& v, std::size_t i) {
-        assert(v.vtable);
-        return v.vtable->arrayMember(v.storage, i);
-    }
-
-    friend inline bool isObject(const Convertible& v) {
-        assert(v.vtable);
-        return v.vtable->isObject(v.storage);
-    }
-
-    friend inline optional<Convertible> objectMember(const Convertible& v, const char * name) {
-        assert(v.vtable);
-        return v.vtable->objectMember(v.storage, name);
-    }
-
-    friend inline optional<Error> eachMember(const Convertible& v, const std::function<optional<Error> (const std::string&, const Convertible&)>& fn) {
-        assert(v.vtable);
-        return v.vtable->eachMember(v.storage, fn);
-    }
-
-    friend inline optional<bool> toBool(const Convertible& v) {
-        assert(v.vtable);
-        return v.vtable->toBool(v.storage);
-    }
-
-    friend inline optional<float> toNumber(const Convertible& v) {
-        assert(v.vtable);
-        return v.vtable->toNumber(v.storage);
-    }
-
-    friend inline optional<double> toDouble(const Convertible& v) {
-        assert(v.vtable);
-        return v.vtable->toDouble(v.storage);
-    }
-
-    friend inline optional<std::string> toString(const Convertible& v) {
-        assert(v.vtable);
-        return v.vtable->toString(v.storage);
-    }
-
-    friend inline optional<Value> toValue(const Convertible& v) {
-        assert(v.vtable);
-        return v.vtable->toValue(v.storage);
-    }
-
-    friend inline optional<GeoJSON> toGeoJSON(const Convertible& v, Error& error) {
-        assert(v.vtable);
-        return v.vtable->toGeoJSON(v.storage, error);
-    }
-
-private:
-#if __ANDROID__
-    // Android:     JSValue* or mbgl::android::Value
-    using Storage = std::aligned_storage_t<32, 8>;
-#elif __QT__
-    // Qt:          JSValue* or QVariant
-    using Storage = std::aligned_storage_t<32, 8>;
-#else
-    // Node:        JSValue* or v8::Local<v8::Value>
-    // iOS/macOS:   JSValue* or id
-    using Storage = std::aligned_storage_t<8, 8>;
-#endif
-
-    struct VTable {
-        void (*move) (Storage&& src, Storage& dest);
-        void (*destroy) (Storage&);
-
-        bool (*isUndefined) (const Storage&);
-
-        bool        (*isArray)     (const Storage&);
-        std::size_t (*arrayLength) (const Storage&);
-        Convertible (*arrayMember) (const Storage&, std::size_t);
-
-        bool                  (*isObject)     (const Storage&);
-        optional<Convertible> (*objectMember) (const Storage&, const char *);
-        optional<Error>       (*eachMember)   (const Storage&, const std::function<optional<Error> (const std::string&, const Convertible&)>&);
-
-        optional<bool>        (*toBool)   (const Storage&);
-        optional<float>       (*toNumber) (const Storage&);
-        optional<double>      (*toDouble) (const Storage&);
-        optional<std::string> (*toString) (const Storage&);
-        optional<Value>       (*toValue)  (const Storage&);
-
-        // https://github.com/mapbox/mapbox-gl-native/issues/5623
-        optional<GeoJSON> (*toGeoJSON) (const Storage&, Error&);
-    };
-
-    // Extracted this function from the table below to work around a GCC bug with differing
-    // visibility settings for capturing lambdas: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80947
-    template <typename T>
-    static auto vtableEachMember(const Storage& s, const std::function<optional<Error>(const std::string&, const Convertible&)>& fn) {
-        return ConversionTraits<T>::eachMember(reinterpret_cast<const T&>(s), [&](const std::string& k, T&& v) {
-            return fn(k, Convertible(std::move(v)));
-        });
-    }
-
-    template <typename T>
-    static VTable* vtableForType() {
-        using Traits = ConversionTraits<T>;
-        static VTable vtable = {
-            [] (Storage&& src, Storage& dest) {
-                auto srcValue = reinterpret_cast<T&&>(src);
-                new (static_cast<void*>(&dest)) T(std::move(srcValue));
-                srcValue.~T();
-            },
-            [] (Storage& s) {
-                reinterpret_cast<T&>(s).~T();
-            },
-            [] (const Storage& s) {
-                return Traits::isUndefined(reinterpret_cast<const T&>(s));
-            },
-            [] (const Storage& s) {
-                return Traits::isArray(reinterpret_cast<const T&>(s));
-            },
-            [] (const Storage& s) {
-                return Traits::arrayLength(reinterpret_cast<const T&>(s));
-            },
-            [] (const Storage& s, std::size_t i) {
-                return Convertible(Traits::arrayMember(reinterpret_cast<const T&>(s), i));
-            },
-            [] (const Storage& s) {
-                return Traits::isObject(reinterpret_cast<const T&>(s));
-            },
-            [] (const Storage& s, const char * key) {
-                optional<T> member = Traits::objectMember(reinterpret_cast<const T&>(s), key);
-                if (member) {
-                    return optional<Convertible>(Convertible(std::move(*member)));
-                } else {
-                    return optional<Convertible>();
-                }
-            },
-            vtableEachMember<T>,
-            [] (const Storage& s) {
-                return Traits::toBool(reinterpret_cast<const T&>(s));
-            },
-            [] (const Storage& s) {
-                return Traits::toNumber(reinterpret_cast<const T&>(s));
-            },
-            [] (const Storage& s) {
-                return Traits::toDouble(reinterpret_cast<const T&>(s));
-            },
-            [] (const Storage& s) {
-                return Traits::toString(reinterpret_cast<const T&>(s));
-            },
-            []  (const Storage& s) {
-                return Traits::toValue(reinterpret_cast<const T&>(s));
-            },
-            [] (const Storage& s, Error& err) {
-                return Traits::toGeoJSON(reinterpret_cast<const T&>(s), err);
-            }
-        };
-        return &vtable;
-    }
-
-    VTable* vtable;
-    Storage storage;
-};
+class Convertible;
 
 template <class T, class Enable = void>
 struct Converter;
 
-template <class T, class...Args>
-optional<T> convert(const Convertible& value, Error& error, Args&&...args) {
-    return Converter<T>()(value, error, std::forward<Args>(args)...);
-}
-
 } // namespace conversion
 } // namespace style
 } // namespace mbgl
+
diff --git a/include/mbgl/style/conversion/constant.hpp b/include/mbgl/style/conversion/constant.hpp
index 7d74ec42ce..40657528c4 100644
--- a/include/mbgl/style/conversion/constant.hpp
+++ b/include/mbgl/style/conversion/constant.hpp
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <mbgl/style/conversion.hpp>
+#include <mbgl/style/types.hpp>
 #include <mbgl/util/color.hpp>
 #include <mbgl/util/enum.hpp>
 #include <mbgl/util/string.hpp>
@@ -30,21 +31,7 @@ struct Converter<std::string> {
 
 template <class T>
 struct Converter<T, typename std::enable_if_t<std::is_enum<T>::value>> {
-    optional<T> operator()(const Convertible& value, Error& error) const {
-        optional<std::string> string = toString(value);
-        if (!string) {
-            error.message = "value must be a string";
-            return nullopt;
-        }
-
-        const auto result = Enum<T>::toEnum(*string);
-        if (!result) {
-            error.message = "value must be a valid enumeration value";
-            return nullopt;
-        }
-
-        return *result;
-    }
+    optional<T> operator()(const Convertible& value, Error& error) const;
 };
 
 template <>
@@ -54,23 +41,7 @@ struct Converter<Color> {
 
 template <size_t N>
 struct Converter<std::array<float, N>> {
-    optional<std::array<float, N>> operator()(const Convertible& value, Error& error) const {
-        if (!isArray(value) || arrayLength(value) != N) {
-            error.message = "value must be an array of " + util::toString(N) + " numbers";
-            return nullopt;
-        }
-
-        std::array<float, N> result;
-        for (size_t i = 0; i < N; i++) {
-            optional<float> n = toNumber(arrayMember(value, i));
-            if (!n) {
-                error.message = "value must be an array of " + util::toString(N) + " numbers";
-                return nullopt;
-            }
-            result[i] = *n;
-        }
-        return result;
-    }
+    optional<std::array<float, N>> operator()(const Convertible& value, Error& error) const;
 };
 
 template <>
diff --git a/include/mbgl/style/conversion/coordinate.hpp b/include/mbgl/style/conversion/coordinate.hpp
index e11db5e32f..1346ed738a 100644
--- a/include/mbgl/style/conversion/coordinate.hpp
+++ b/include/mbgl/style/conversion/coordinate.hpp
@@ -2,6 +2,7 @@
 
 #include <mbgl/style/conversion.hpp>
 #include <mbgl/util/geo.hpp>
+#include <mbgl/util/optional.hpp>
 
 namespace mbgl {
 namespace style {
diff --git a/include/mbgl/style/conversion/custom_geometry_source_options.hpp b/include/mbgl/style/conversion/custom_geometry_source_options.hpp
index f0f505e54f..090e5b6239 100644
--- a/include/mbgl/style/conversion/custom_geometry_source_options.hpp
+++ b/include/mbgl/style/conversion/custom_geometry_source_options.hpp
@@ -2,6 +2,7 @@
 
 #include <mbgl/style/conversion.hpp>
 #include <mbgl/style/sources/custom_geometry_source.hpp>
+#include <mbgl/util/optional.hpp>
 
 namespace mbgl {
 namespace style {
diff --git a/include/mbgl/style/conversion/filter.hpp b/include/mbgl/style/conversion/filter.hpp
index 9daf6ea7a4..2d7ad0afc7 100644
--- a/include/mbgl/style/conversion/filter.hpp
+++ b/include/mbgl/style/conversion/filter.hpp
@@ -2,6 +2,7 @@
 
 #include <mbgl/style/filter.hpp>
 #include <mbgl/style/conversion.hpp>
+#include <mbgl/util/optional.hpp>
 
 namespace mbgl {
 namespace style {
diff --git a/include/mbgl/style/conversion/function.hpp b/include/mbgl/style/conversion/function.hpp
index 49825a3410..ba9acd7a3b 100644
--- a/include/mbgl/style/conversion/function.hpp
+++ b/include/mbgl/style/conversion/function.hpp
@@ -1,8 +1,8 @@
 #pragma once
 
 #include <mbgl/style/property_expression.hpp>
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/constant.hpp>
+#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/expression/expression.hpp>
 #include <mbgl/style/expression/value.hpp>
 
@@ -16,25 +16,7 @@ std::unique_ptr<expression::Expression> convertTokenStringToExpression(const std
 optional<std::unique_ptr<expression::Expression>> convertFunctionToExpression(expression::type::Type, const Convertible&, Error&, bool convertTokens);
 
 template <class T>
-optional<PropertyExpression<T>> convertFunctionToExpression(const Convertible& value, Error& error, bool convertTokens) {
-    auto expression = convertFunctionToExpression(expression::valueTypeToExpressionType<T>(), value, error, convertTokens);
-    if (!expression) {
-        return nullopt;
-    }
-
-    optional<T> defaultValue;
-
-    auto defaultValueValue = objectMember(value, "default");
-    if (defaultValueValue) {
-        defaultValue = convert<T>(*defaultValueValue, error);
-        if (!defaultValue) {
-            error.message = R"(wrong type for "default": )" + error.message;
-            return nullopt;
-        }
-    }
-
-    return PropertyExpression<T>(std::move(*expression), defaultValue);
-}
+optional<PropertyExpression<T>> convertFunctionToExpression(const Convertible& value, Error& error, bool convertTokens);
 
 } // namespace conversion
 } // namespace style
diff --git a/include/mbgl/style/conversion/geojson.hpp b/include/mbgl/style/conversion/geojson.hpp
index 403c5f953b..90c1d64197 100644
--- a/include/mbgl/style/conversion/geojson.hpp
+++ b/include/mbgl/style/conversion/geojson.hpp
@@ -1,7 +1,8 @@
 #pragma once
 
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/util/geojson.hpp>
+#include <mbgl/style/conversion.hpp>
+#include <mbgl/util/optional.hpp>
 
 namespace mbgl {
 namespace style {
diff --git a/include/mbgl/style/conversion/geojson_options.hpp b/include/mbgl/style/conversion/geojson_options.hpp
index 3f625babb6..89511848dd 100644
--- a/include/mbgl/style/conversion/geojson_options.hpp
+++ b/include/mbgl/style/conversion/geojson_options.hpp
@@ -1,7 +1,8 @@
 #pragma once
 
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/sources/geojson_source.hpp>
+#include <mbgl/style/conversion.hpp>
+#include <mbgl/util/optional.hpp>
 
 namespace mbgl {
 namespace style {
diff --git a/include/mbgl/style/conversion/layer.hpp b/include/mbgl/style/conversion/layer.hpp
index 2df6c9e381..9cf019378b 100644
--- a/include/mbgl/style/conversion/layer.hpp
+++ b/include/mbgl/style/conversion/layer.hpp
@@ -2,6 +2,7 @@
 
 #include <mbgl/style/layer.hpp>
 #include <mbgl/style/conversion.hpp>
+#include <mbgl/util/optional.hpp>
 
 #include <memory>
 
diff --git a/include/mbgl/style/conversion/light.hpp b/include/mbgl/style/conversion/light.hpp
index 289fca2e31..2f6f8628b8 100644
--- a/include/mbgl/style/conversion/light.hpp
+++ b/include/mbgl/style/conversion/light.hpp
@@ -2,6 +2,7 @@
 
 #include <mbgl/style/light.hpp>
 #include <mbgl/style/conversion.hpp>
+#include <mbgl/util/optional.hpp>
 
 namespace mbgl {
 namespace style {
diff --git a/include/mbgl/style/conversion/position.hpp b/include/mbgl/style/conversion/position.hpp
index 044c45862d..10db5c6ec1 100644
--- a/include/mbgl/style/conversion/position.hpp
+++ b/include/mbgl/style/conversion/position.hpp
@@ -1,7 +1,8 @@
 #pragma once
 
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/position.hpp>
+#include <mbgl/style/conversion.hpp>
+#include <mbgl/util/optional.hpp>
 
 namespace mbgl {
 namespace style {
diff --git a/include/mbgl/style/conversion/property_value.hpp b/include/mbgl/style/conversion/property_value.hpp
index fa6752867b..f6f36db983 100644
--- a/include/mbgl/style/conversion/property_value.hpp
+++ b/include/mbgl/style/conversion/property_value.hpp
@@ -1,9 +1,9 @@
 #pragma once
 
 #include <mbgl/style/property_value.hpp>
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/constant.hpp>
 #include <mbgl/style/conversion/function.hpp>
+#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/expression/value.hpp>
 #include <mbgl/style/expression/is_constant.hpp>
 #include <mbgl/style/expression/is_expression.hpp>
@@ -16,53 +16,7 @@ namespace conversion {
 
 template <class T>
 struct Converter<PropertyValue<T>> {
-    optional<PropertyValue<T>> operator()(const Convertible& value, Error& error, bool allowDataExpressions, bool convertTokens) const {
-        using namespace mbgl::style::expression;
-
-        if (isUndefined(value)) {
-            return PropertyValue<T>();
-        }
-
-        optional<PropertyExpression<T>> expression;
-
-        if (isExpression(value)) {
-            ParsingContext ctx(valueTypeToExpressionType<T>());
-            ParseResult parsed = ctx.parseLayerPropertyExpression(value);
-            if (!parsed) {
-                error.message = ctx.getCombinedErrors();
-                return nullopt;
-            }
-            expression = PropertyExpression<T>(std::move(*parsed));
-        } else if (isObject(value)) {
-            expression = convertFunctionToExpression<T>(value, error, convertTokens);
-        } else {
-            optional<T> constant = convert<T>(value, error);
-            if (!constant) {
-                return nullopt;
-            }
-            return convertTokens ? maybeConvertTokens(*constant) : PropertyValue<T>(*constant);
-        }
-
-        if (!expression) {
-            return nullopt;
-        } else if (!allowDataExpressions && !(*expression).isFeatureConstant()) {
-            error.message = "data expressions not supported";
-            return nullopt;
-        } else if (!(*expression).isFeatureConstant() || !(*expression).isZoomConstant()) {
-            return { std::move(*expression) };
-        } else if ((*expression).getExpression().getKind() == Kind::Literal) {
-            optional<T> constant = fromExpressionValue<T>(
-                static_cast<const Literal&>((*expression).getExpression()).getValue());
-            if (!constant) {
-                return nullopt;
-            }
-            return PropertyValue<T>(*constant);
-        } else {
-            assert(false);
-            error.message = "expected a literal expression";
-            return nullopt;
-        }
-    }
+    optional<PropertyValue<T>> operator()(const Convertible& value, Error& error, bool allowDataExpressions, bool convertTokens) const;
 
     template <class S>
     PropertyValue<T> maybeConvertTokens(const S& t) const {
diff --git a/include/mbgl/style/conversion/source.hpp b/include/mbgl/style/conversion/source.hpp
index 2cf2e36da4..19bc1ce6b6 100644
--- a/include/mbgl/style/conversion/source.hpp
+++ b/include/mbgl/style/conversion/source.hpp
@@ -1,7 +1,8 @@
 #pragma once
 
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/source.hpp>
+#include <mbgl/style/conversion.hpp>
+#include <mbgl/util/optional.hpp>
 
 #include <memory>
 
diff --git a/include/mbgl/style/conversion/tileset.hpp b/include/mbgl/style/conversion/tileset.hpp
index 1fb4acf70d..88661c358c 100644
--- a/include/mbgl/style/conversion/tileset.hpp
+++ b/include/mbgl/style/conversion/tileset.hpp
@@ -2,6 +2,7 @@
 
 #include <mbgl/util/tileset.hpp>
 #include <mbgl/style/conversion.hpp>
+#include <mbgl/util/optional.hpp>
 
 namespace mbgl {
 namespace style {
diff --git a/include/mbgl/style/conversion/transition_options.hpp b/include/mbgl/style/conversion/transition_options.hpp
index 0563f39ac3..a72d757d3c 100644
--- a/include/mbgl/style/conversion/transition_options.hpp
+++ b/include/mbgl/style/conversion/transition_options.hpp
@@ -2,6 +2,7 @@
 
 #include <mbgl/style/transition_options.hpp>
 #include <mbgl/style/conversion.hpp>
+#include <mbgl/util/optional.hpp>
 
 namespace mbgl {
 namespace style {
diff --git a/include/mbgl/style/conversion_impl.hpp b/include/mbgl/style/conversion_impl.hpp
new file mode 100644
index 0000000000..27b2ee1917
--- /dev/null
+++ b/include/mbgl/style/conversion_impl.hpp
@@ -0,0 +1,302 @@
+#pragma once
+
+#include <mbgl/style/conversion.hpp>
+#include <mbgl/util/optional.hpp>
+#include <mbgl/util/feature.hpp>
+#include <mbgl/util/geojson.hpp>
+
+#include <string>
+
+namespace mbgl {
+namespace style {
+namespace conversion {
+
+/*
+   The `conversion` namespace defines conversions from JSON structures conforming to the schema defined by
+   the Mapbox Style Specification, to the various C++ types that form the C++ model of that domain:
+
+       * `std::unique_ptr<Source>`
+       * `std::unique_ptr<Layer>`
+       * `Filter`
+       * `PropertyValue<T>`
+
+   A single template function serves as the public interface:
+
+       template <class T>
+       optional<T> convert(const Convertible& input, Error& error);
+
+   Where `T` is one of the above types. If the conversion fails, the result is empty, and the
+   error parameter includes diagnostic text suitable for presentation to a library user. Otherwise,
+   a filled optional is returned.
+
+   `Convertible` is a type that encapsulates a special form of polymorphism over various underlying types that
+   can serve as input to the conversion algorithm. For instance, on macOS, we need to support
+   conversion from both RapidJSON types, and a JSON structure represented with `NSArray`/`NSDictionary`/etc.
+   On Qt, we need to support conversion from RapidJSON types and QVariant.
+
+   We don't want to use traditional forms of polymorphism to accomplish this:
+
+     * Compile time polymorphism using a template parameter for the actual value type leads to
+       excessive code bloat and long compile times.
+     * Runtime polymorphism using virtual methods requires extra heap allocation and ubiquitous
+       use of std::unique_ptr, unsuitable for this performance-sensitive code.
+
+   Therefore, we're using a custom implementation of runtime polymorphism where we manually create and
+   dispatch through a table of function pointers (vtable), while keeping the storage for any of the possible
+   underlying types inline on the stack, using `std::aligned_storage`.
+
+   For a given underlying type T, an explicit specialization of `ConversionTraits<T>` must be provided. This
+   specialization must provide the following static methods:
+
+      * `isUndefined(v)` -- returns a boolean indication whether `v` is undefined or a JSON null
+
+      * `isArray(v)` -- returns a boolean indicating whether `v` represents a JSON array
+      * `arrayLength(v)` -- called only if `isArray(v)`; returns a size_t length
+      * `arrayMember(v)` -- called only if `isArray(v)`; returns `V` or `V&`
+
+      * `isObject(v)` -- returns a boolean indicating whether `v` represents a JSON object
+      * `objectMember(v, name)` -- called only if `isObject(v)`; `name` is `const char *`; return value:
+         * is true when evaluated in a boolean context iff the named member exists
+         * is convertable to a `V` or `V&` when dereferenced
+      * `eachMember(v, [] (const std::string&, const V&) -> optional<Error> {...})` -- called
+         only if `isObject(v)`; calls the provided lambda once for each key and value of the object;
+         short-circuits if any call returns an `Error`
+
+      * `toBool(v)` -- returns `optional<bool>`, absence indicating `v` is not a JSON boolean
+      * `toNumber(v)` -- returns `optional<float>`, absence indicating `v` is not a JSON number
+      * `toDouble(v)` -- returns `optional<double>`, absence indicating `v` is not a JSON number
+      * `toString(v)` -- returns `optional<std::string>`, absence indicating `v` is not a JSON string
+      * `toValue(v)` -- returns `optional<Value>`, a variant type, for generic conversion,
+        absence indicating `v` is not a boolean, number, or string. Numbers should be converted to
+        unsigned integer, signed integer, or floating point, in descending preference.
+
+   In addition, the type T must be move-constructable. And finally, `Convertible::Storage`, a typedef for
+   `std::aligned_storage_t`, must be large enough to satisfy the memory requirements for any of the
+   possible underlying types. (A static assert will fail if this is not the case.)
+
+   `Convertible` itself is movable, but not copyable. A moved-from `Convertible` is in an invalid state;
+   you must not do anything with it except let it go out of scope.
+*/
+
+template <typename T>
+class ConversionTraits;
+
+class Convertible {
+public:
+    template <typename T>
+    Convertible(T&& value) : vtable(vtableForType<std::decay_t<T>>()) {
+        static_assert(sizeof(Storage) >= sizeof(std::decay_t<T>), "Storage must be large enough to hold value type");
+        new (static_cast<void*>(&storage)) std::decay_t<T>(std::forward<T>(value));
+    }
+
+    Convertible(Convertible&& v)
+        : vtable(v.vtable)
+    {
+        if (vtable) {
+            vtable->move(std::move(v.storage), this->storage);
+        }
+    }
+
+    ~Convertible() {
+        if (vtable) {
+            vtable->destroy(storage);
+        }
+    }
+
+    Convertible& operator=(Convertible&& v) {
+        if (vtable) {
+            vtable->destroy(storage);
+        }
+        vtable = v.vtable;
+        if (vtable) {
+            vtable->move(std::move(v.storage), this->storage);
+        }
+        v.vtable = nullptr;
+        return *this;
+    }
+
+    Convertible()                              = delete;
+    Convertible(const Convertible&)            = delete;
+    Convertible& operator=(const Convertible&) = delete;
+
+    friend inline bool isUndefined(const Convertible& v) {
+        assert(v.vtable);
+        return v.vtable->isUndefined(v.storage);
+    }
+
+    friend inline bool isArray(const Convertible& v) {
+        assert(v.vtable);
+        return v.vtable->isArray(v.storage);
+    }
+
+    friend inline std::size_t arrayLength(const Convertible& v) {
+        assert(v.vtable);
+        return v.vtable->arrayLength(v.storage);
+    }
+
+    friend inline Convertible arrayMember(const Convertible& v, std::size_t i) {
+        assert(v.vtable);
+        return v.vtable->arrayMember(v.storage, i);
+    }
+
+    friend inline bool isObject(const Convertible& v) {
+        assert(v.vtable);
+        return v.vtable->isObject(v.storage);
+    }
+
+    friend inline optional<Convertible> objectMember(const Convertible& v, const char * name) {
+        assert(v.vtable);
+        return v.vtable->objectMember(v.storage, name);
+    }
+
+    friend inline optional<Error> eachMember(const Convertible& v, const std::function<optional<Error> (const std::string&, const Convertible&)>& fn) {
+        assert(v.vtable);
+        return v.vtable->eachMember(v.storage, fn);
+    }
+
+    friend inline optional<bool> toBool(const Convertible& v) {
+        assert(v.vtable);
+        return v.vtable->toBool(v.storage);
+    }
+
+    friend inline optional<float> toNumber(const Convertible& v) {
+        assert(v.vtable);
+        return v.vtable->toNumber(v.storage);
+    }
+
+    friend inline optional<double> toDouble(const Convertible& v) {
+        assert(v.vtable);
+        return v.vtable->toDouble(v.storage);
+    }
+
+    friend inline optional<std::string> toString(const Convertible& v) {
+        assert(v.vtable);
+        return v.vtable->toString(v.storage);
+    }
+
+    friend inline optional<Value> toValue(const Convertible& v) {
+        assert(v.vtable);
+        return v.vtable->toValue(v.storage);
+    }
+
+    friend inline optional<GeoJSON> toGeoJSON(const Convertible& v, Error& error) {
+        assert(v.vtable);
+        return v.vtable->toGeoJSON(v.storage, error);
+    }
+
+private:
+#if __ANDROID__
+    // Android:     JSValue* or mbgl::android::Value
+    using Storage = std::aligned_storage_t<32, 8>;
+#elif __QT__
+    // Qt:          JSValue* or QVariant
+    using Storage = std::aligned_storage_t<32, 8>;
+#else
+    // Node:        JSValue* or v8::Local<v8::Value>
+    // iOS/macOS:   JSValue* or id
+    using Storage = std::aligned_storage_t<8, 8>;
+#endif
+
+    struct VTable {
+        void (*move) (Storage&& src, Storage& dest);
+        void (*destroy) (Storage&);
+
+        bool (*isUndefined) (const Storage&);
+
+        bool        (*isArray)     (const Storage&);
+        std::size_t (*arrayLength) (const Storage&);
+        Convertible (*arrayMember) (const Storage&, std::size_t);
+
+        bool                  (*isObject)     (const Storage&);
+        optional<Convertible> (*objectMember) (const Storage&, const char *);
+        optional<Error>       (*eachMember)   (const Storage&, const std::function<optional<Error> (const std::string&, const Convertible&)>&);
+
+        optional<bool>        (*toBool)   (const Storage&);
+        optional<float>       (*toNumber) (const Storage&);
+        optional<double>      (*toDouble) (const Storage&);
+        optional<std::string> (*toString) (const Storage&);
+        optional<Value>       (*toValue)  (const Storage&);
+
+        // https://github.com/mapbox/mapbox-gl-native/issues/5623
+        optional<GeoJSON> (*toGeoJSON) (const Storage&, Error&);
+    };
+
+    // Extracted this function from the table below to work around a GCC bug with differing
+    // visibility settings for capturing lambdas: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80947
+    template <typename T>
+    static auto vtableEachMember(const Storage& s, const std::function<optional<Error>(const std::string&, const Convertible&)>& fn) {
+        return ConversionTraits<T>::eachMember(reinterpret_cast<const T&>(s), [&](const std::string& k, T&& v) {
+            return fn(k, Convertible(std::move(v)));
+        });
+    }
+
+    template <typename T>
+    static VTable* vtableForType() {
+        using Traits = ConversionTraits<T>;
+        static VTable vtable = {
+            [] (Storage&& src, Storage& dest) {
+                auto srcValue = reinterpret_cast<T&&>(src);
+                new (static_cast<void*>(&dest)) T(std::move(srcValue));
+                srcValue.~T();
+            },
+            [] (Storage& s) {
+                reinterpret_cast<T&>(s).~T();
+            },
+            [] (const Storage& s) {
+                return Traits::isUndefined(reinterpret_cast<const T&>(s));
+            },
+            [] (const Storage& s) {
+                return Traits::isArray(reinterpret_cast<const T&>(s));
+            },
+            [] (const Storage& s) {
+                return Traits::arrayLength(reinterpret_cast<const T&>(s));
+            },
+            [] (const Storage& s, std::size_t i) {
+                return Convertible(Traits::arrayMember(reinterpret_cast<const T&>(s), i));
+            },
+            [] (const Storage& s) {
+                return Traits::isObject(reinterpret_cast<const T&>(s));
+            },
+            [] (const Storage& s, const char * key) {
+                optional<T> member = Traits::objectMember(reinterpret_cast<const T&>(s), key);
+                if (member) {
+                    return optional<Convertible>(Convertible(std::move(*member)));
+                } else {
+                    return optional<Convertible>();
+                }
+            },
+            vtableEachMember<T>,
+            [] (const Storage& s) {
+                return Traits::toBool(reinterpret_cast<const T&>(s));
+            },
+            [] (const Storage& s) {
+                return Traits::toNumber(reinterpret_cast<const T&>(s));
+            },
+            [] (const Storage& s) {
+                return Traits::toDouble(reinterpret_cast<const T&>(s));
+            },
+            [] (const Storage& s) {
+                return Traits::toString(reinterpret_cast<const T&>(s));
+            },
+            []  (const Storage& s) {
+                return Traits::toValue(reinterpret_cast<const T&>(s));
+            },
+            [] (const Storage& s, Error& err) {
+                return Traits::toGeoJSON(reinterpret_cast<const T&>(s), err);
+            }
+        };
+        return &vtable;
+    }
+
+    VTable* vtable;
+    Storage storage;
+};
+
+template <class T, class...Args>
+optional<T> convert(const Convertible& value, Error& error, Args&&...args) {
+    return Converter<T>()(value, error, std::forward<Args>(args)...);
+}
+
+} // namespace conversion
+} // namespace style
+} // namespace mbgl
diff --git a/include/mbgl/style/expression/assertion.hpp b/include/mbgl/style/expression/assertion.hpp
index 90da16b068..239cdf2ea6 100644
--- a/include/mbgl/style/expression/assertion.hpp
+++ b/include/mbgl/style/expression/assertion.hpp
@@ -1,8 +1,8 @@
 #pragma once
 
 #include <mbgl/style/expression/expression.hpp>
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/expression/parsing_context.hpp>
+#include <mbgl/style/conversion.hpp>
 
 #include <memory>
 #include <vector>
diff --git a/include/mbgl/style/expression/case.hpp b/include/mbgl/style/expression/case.hpp
index 02dc3bc4c2..7cd007d3c7 100644
--- a/include/mbgl/style/expression/case.hpp
+++ b/include/mbgl/style/expression/case.hpp
@@ -1,8 +1,8 @@
 #pragma once
 
 #include <mbgl/style/expression/expression.hpp>
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/expression/parsing_context.hpp>
+#include <mbgl/style/conversion.hpp>
 
 #include <memory>
 #include <vector>
diff --git a/include/mbgl/style/expression/coalesce.hpp b/include/mbgl/style/expression/coalesce.hpp
index cd60cee02e..c4216f234f 100644
--- a/include/mbgl/style/expression/coalesce.hpp
+++ b/include/mbgl/style/expression/coalesce.hpp
@@ -1,8 +1,8 @@
 #pragma once
 
 #include <mbgl/style/expression/expression.hpp>
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/expression/parsing_context.hpp>
+#include <mbgl/style/conversion.hpp>
 
 #include <memory>
 #include <map>
diff --git a/include/mbgl/style/expression/compound_expression.hpp b/include/mbgl/style/expression/compound_expression.hpp
index ef10dadb55..b54720a258 100644
--- a/include/mbgl/style/expression/compound_expression.hpp
+++ b/include/mbgl/style/expression/compound_expression.hpp
@@ -1,10 +1,10 @@
 #pragma once
 
 #include <mbgl/style/expression/expression.hpp>
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/expression/parsing_context.hpp>
 #include <mbgl/style/expression/type.hpp>
 #include <mbgl/style/expression/value.hpp>
+#include <mbgl/style/conversion.hpp>
 #include <mbgl/util/optional.hpp>
 
 #include <memory>
diff --git a/include/mbgl/style/expression/parsing_context.hpp b/include/mbgl/style/expression/parsing_context.hpp
index c19974a4f7..66014e33d4 100644
--- a/include/mbgl/style/expression/parsing_context.hpp
+++ b/include/mbgl/style/expression/parsing_context.hpp
@@ -7,6 +7,7 @@
 
 #include <iterator>
 #include <map>
+#include <unordered_map>
 #include <string>
 #include <vector>
 #include <memory>
diff --git a/include/mbgl/style/layer.hpp b/include/mbgl/style/layer.hpp
index e0f71d2689..3b7969ea79 100644
--- a/include/mbgl/style/layer.hpp
+++ b/include/mbgl/style/layer.hpp
@@ -3,6 +3,7 @@
 #include <mbgl/util/noncopyable.hpp>
 #include <mbgl/util/peer.hpp>
 #include <mbgl/util/immutable.hpp>
+#include <mbgl/util/optional.hpp>
 #include <mbgl/style/layer_type.hpp>
 #include <mbgl/style/types.hpp>
 #include <mbgl/style/conversion.hpp>
diff --git a/platform/android/config.cmake b/platform/android/config.cmake
index e76a447c88..be9d95ef0a 100644
--- a/platform/android/config.cmake
+++ b/platform/android/config.cmake
@@ -345,6 +345,11 @@ add_library(example-custom-layer SHARED
     platform/android/src/example_custom_layer.cpp
 )
 
+target_include_directories(example-custom-layer
+    PRIVATE include
+)
+
 target_link_libraries(example-custom-layer
-    PRIVATE mbgl-core
+    PRIVATE -llog
+    PRIVATE -lGLESv2
 )
diff --git a/platform/android/src/native_map_view.cpp b/platform/android/src/native_map_view.cpp
index 8da44c10cb..8c76332b39 100755
--- a/platform/android/src/native_map_view.cpp
+++ b/platform/android/src/native_map_view.cpp
@@ -30,8 +30,8 @@
 
 // Java -> C++ conversion
 #include "style/android_conversion.hpp"
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/filter.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 
 // C++ -> Java conversion
 #include "conversion/conversion.hpp"
diff --git a/platform/android/src/style/android_conversion.hpp b/platform/android/src/style/android_conversion.hpp
index 510a9f8444..8559720b2f 100644
--- a/platform/android/src/style/android_conversion.hpp
+++ b/platform/android/src/style/android_conversion.hpp
@@ -5,8 +5,8 @@
 #include <mbgl/util/feature.hpp>
 #include <mbgl/util/logging.hpp>
 #include <mbgl/util/optional.hpp>
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/geojson.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 
 #include <jni/jni.hpp>
 
diff --git a/platform/android/src/style/conversion/filter.hpp b/platform/android/src/style/conversion/filter.hpp
index c154e88e7c..241c98713a 100644
--- a/platform/android/src/style/conversion/filter.hpp
+++ b/platform/android/src/style/conversion/filter.hpp
@@ -1,8 +1,8 @@
 #pragma once
 
 #include "../android_conversion.hpp"
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/filter.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 
 #include <jni/jni.hpp>
 
diff --git a/platform/android/src/style/conversion/latlngquad.hpp b/platform/android/src/style/conversion/latlngquad.hpp
index 9d1a83e164..9588336855 100644
--- a/platform/android/src/style/conversion/latlngquad.hpp
+++ b/platform/android/src/style/conversion/latlngquad.hpp
@@ -1,8 +1,8 @@
 #pragma once
 
 #include <mapbox/geojson.hpp>
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/geojson.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <jni/jni.hpp>
 
 namespace mbgl {
diff --git a/platform/android/src/style/conversion/url_or_tileset.hpp b/platform/android/src/style/conversion/url_or_tileset.hpp
index 92c1182a63..d6bf86639c 100644
--- a/platform/android/src/style/conversion/url_or_tileset.hpp
+++ b/platform/android/src/style/conversion/url_or_tileset.hpp
@@ -4,8 +4,8 @@
 #include <mbgl/util/variant.hpp>
 
 #include <mbgl/util/tileset.hpp>
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/tileset.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 
 #include <jni/jni.hpp>
 
diff --git a/platform/android/src/style/layers/layer.cpp b/platform/android/src/style/layers/layer.cpp
index c3ae9e40cd..6c08893411 100644
--- a/platform/android/src/style/layers/layer.cpp
+++ b/platform/android/src/style/layers/layer.cpp
@@ -18,10 +18,10 @@
 #include <mbgl/util/logging.hpp>
 
 // Java -> C++ conversion
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/filter.hpp>
 #include <mbgl/style/conversion/layer.hpp>
 #include <mbgl/style/conversion/source.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 
 // C++ -> Java conversion
 #include "../conversion/property_value.hpp"
diff --git a/platform/android/src/style/sources/geojson_source.cpp b/platform/android/src/style/sources/geojson_source.cpp
index 6d9ab9e22c..14067503f1 100644
--- a/platform/android/src/style/sources/geojson_source.cpp
+++ b/platform/android/src/style/sources/geojson_source.cpp
@@ -5,9 +5,9 @@
 // Java -> C++ conversion
 #include "../android_conversion.hpp"
 #include "../conversion/filter.hpp"
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/geojson.hpp>
 #include <mbgl/style/conversion/geojson_options.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 
 // C++ -> Java conversion
 #include "../../conversion/conversion.hpp"
diff --git a/platform/android/src/style/sources/image_source.cpp b/platform/android/src/style/sources/image_source.cpp
index 249387ea51..278564485d 100644
--- a/platform/android/src/style/sources/image_source.cpp
+++ b/platform/android/src/style/sources/image_source.cpp
@@ -5,7 +5,7 @@
 
 // C++ -> Java conversion
 #include "../../conversion/conversion.hpp"
-#include <mbgl/style/conversion.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/util/premultiply.hpp>
 
 #include "../../bitmap.hpp"
diff --git a/platform/android/src/style/sources/source.cpp b/platform/android/src/style/sources/source.cpp
index 8f14ebc43e..d2e2426c0b 100644
--- a/platform/android/src/style/sources/source.cpp
+++ b/platform/android/src/style/sources/source.cpp
@@ -7,8 +7,8 @@
 #include <mbgl/util/logging.hpp>
 
 // Java -> C++ conversion
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/source.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 
 // C++ -> Java conversion
 #include "../conversion/property_value.hpp"
diff --git a/platform/darwin/src/MGLConversion.h b/platform/darwin/src/MGLConversion.h
index 92a6720e6a..9057ed7824 100644
--- a/platform/darwin/src/MGLConversion.h
+++ b/platform/darwin/src/MGLConversion.h
@@ -1,4 +1,4 @@
-#include <mbgl/style/conversion.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 
 NS_ASSUME_NONNULL_BEGIN
 
diff --git a/platform/node/src/node_conversion.hpp b/platform/node/src/node_conversion.hpp
index 7c5bbf4386..ea6652c5e2 100644
--- a/platform/node/src/node_conversion.hpp
+++ b/platform/node/src/node_conversion.hpp
@@ -8,8 +8,8 @@
 
 #include <mbgl/util/optional.hpp>
 #include <mbgl/util/feature.hpp>
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/geojson.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 
 namespace mbgl {
 namespace style {
diff --git a/platform/node/src/node_expression.hpp b/platform/node/src/node_expression.hpp
index 05af217bde..a53f8c18db 100644
--- a/platform/node/src/node_expression.hpp
+++ b/platform/node/src/node_expression.hpp
@@ -1,6 +1,6 @@
 #pragma once
 
-#include <mbgl/style/conversion.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/style/expression/expression.hpp>
 #include <exception>
 #include <memory>
diff --git a/platform/qt/src/qmapboxgl.cpp b/platform/qt/src/qmapboxgl.cpp
index 480174810c..d584012830 100644
--- a/platform/qt/src/qmapboxgl.cpp
+++ b/platform/qt/src/qmapboxgl.cpp
@@ -13,11 +13,11 @@
 #include <mbgl/math/log2.hpp>
 #include <mbgl/math/minmax.hpp>
 #include <mbgl/style/style.hpp>
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/layer.hpp>
 #include <mbgl/style/conversion/source.hpp>
 #include <mbgl/style/conversion/filter.hpp>
 #include <mbgl/style/conversion/geojson.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/style/filter.hpp>
 #include <mbgl/style/layers/custom_layer.hpp>
 #include <mbgl/style/layers/background_layer.hpp>
diff --git a/platform/qt/src/qt_conversion.hpp b/platform/qt/src/qt_conversion.hpp
index 19b0cb54fc..99a262be54 100644
--- a/platform/qt/src/qt_conversion.hpp
+++ b/platform/qt/src/qt_conversion.hpp
@@ -1,7 +1,7 @@
 #pragma once
 
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/geojson.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/util/optional.hpp>
 
 #include <QVariant>
diff --git a/src/mbgl/style/conversion/color_ramp_property_value.cpp b/src/mbgl/style/conversion/color_ramp_property_value.cpp
index f29438b6a2..0da16c67ee 100644
--- a/src/mbgl/style/conversion/color_ramp_property_value.cpp
+++ b/src/mbgl/style/conversion/color_ramp_property_value.cpp
@@ -1,6 +1,6 @@
 #include <mbgl/style/conversion/color_ramp_property_value.hpp>
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/constant.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/style/expression/value.hpp>
 #include <mbgl/style/expression/is_constant.hpp>
 #include <mbgl/style/expression/is_expression.hpp>
diff --git a/src/mbgl/style/conversion/constant.cpp b/src/mbgl/style/conversion/constant.cpp
index d432b5f051..de4ab22269 100644
--- a/src/mbgl/style/conversion/constant.cpp
+++ b/src/mbgl/style/conversion/constant.cpp
@@ -1,4 +1,5 @@
 #include <mbgl/style/conversion/constant.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 
 namespace mbgl {
 namespace style {
@@ -31,6 +32,38 @@ optional<std::string> Converter<std::string>::operator()(const Convertible& valu
     return *converted;
 }
 
+template <class T>
+optional<T> Converter<T, typename std::enable_if_t<std::is_enum<T>::value>>::operator()(const Convertible& value, Error& error) const {
+    optional<std::string> string = toString(value);
+    if (!string) {
+        error.message = "value must be a string";
+        return nullopt;
+    }
+
+    const auto result = Enum<T>::toEnum(*string);
+    if (!result) {
+        error.message = "value must be a valid enumeration value";
+        return nullopt;
+    }
+
+    return *result;
+}
+
+template optional<AlignmentType> Converter<AlignmentType>::operator()(const Convertible&, Error&) const;
+template optional<CirclePitchScaleType> Converter<CirclePitchScaleType>::operator()(const Convertible&, Error&) const;
+template optional<HillshadeIlluminationAnchorType> Converter<HillshadeIlluminationAnchorType>::operator()(const Convertible&, Error&) const;
+template optional<IconTextFitType> Converter<IconTextFitType>::operator()(const Convertible&, Error&) const;
+template optional<LightAnchorType> Converter<LightAnchorType>::operator()(const Convertible&, Error&) const;
+template optional<LineCapType> Converter<LineCapType>::operator()(const Convertible&, Error&) const;
+template optional<LineJoinType> Converter<LineJoinType>::operator()(const Convertible&, Error&) const;
+template optional<RasterResamplingType> Converter<RasterResamplingType>::operator()(const Convertible&, Error&) const;
+template optional<SymbolAnchorType> Converter<SymbolAnchorType>::operator()(const Convertible&, Error&) const;
+template optional<SymbolPlacementType> Converter<SymbolPlacementType>::operator()(const Convertible&, Error&) const;
+template optional<TextJustifyType> Converter<TextJustifyType>::operator()(const Convertible&, Error&) const;
+template optional<TextTransformType> Converter<TextTransformType>::operator()(const Convertible&, Error&) const;
+template optional<TranslateAnchorType> Converter<TranslateAnchorType>::operator()(const Convertible&, Error&) const;
+template optional<VisibilityType> Converter<VisibilityType>::operator()(const Convertible&, Error&) const;
+
 optional<Color> Converter<Color>::operator()(const Convertible& value, Error& error) const {
     optional<std::string> string = toString(value);
     if (!string) {
@@ -47,6 +80,29 @@ optional<Color> Converter<Color>::operator()(const Convertible& value, Error& er
     return *color;
 }
 
+template <size_t N>
+optional<std::array<float, N>> Converter<std::array<float, N>>::operator()(const Convertible& value, Error& error) const {
+    if (!isArray(value) || arrayLength(value) != N) {
+        error.message = "value must be an array of " + util::toString(N) + " numbers";
+        return nullopt;
+    }
+
+    std::array<float, N> result;
+    for (size_t i = 0; i < N; i++) {
+        optional<float> n = toNumber(arrayMember(value, i));
+        if (!n) {
+            error.message = "value must be an array of " + util::toString(N) + " numbers";
+            return nullopt;
+        }
+        result[i] = *n;
+    }
+    return result;
+}
+
+template optional<std::array<float, 2>> Converter<std::array<float, 2>>::operator()(const Convertible&, Error&) const;
+template optional<std::array<float, 3>> Converter<std::array<float, 3>>::operator()(const Convertible&, Error&) const;
+template optional<std::array<float, 4>> Converter<std::array<float, 4>>::operator()(const Convertible&, Error&) const;
+
 optional<std::vector<float>> Converter<std::vector<float>>::operator()(const Convertible& value, Error& error) const {
     if (!isArray(value)) {
         error.message = "value must be an array";
diff --git a/src/mbgl/style/conversion/coordinate.cpp b/src/mbgl/style/conversion/coordinate.cpp
index 20abd45e26..ee03bffb30 100644
--- a/src/mbgl/style/conversion/coordinate.cpp
+++ b/src/mbgl/style/conversion/coordinate.cpp
@@ -1,4 +1,5 @@
 #include <mbgl/style/conversion/coordinate.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 
 namespace mbgl {
 namespace style {
diff --git a/src/mbgl/style/conversion/custom_geometry_source_options.cpp b/src/mbgl/style/conversion/custom_geometry_source_options.cpp
index 8983f9f479..491509c28f 100644
--- a/src/mbgl/style/conversion/custom_geometry_source_options.cpp
+++ b/src/mbgl/style/conversion/custom_geometry_source_options.cpp
@@ -1,4 +1,5 @@
 #include <mbgl/style/conversion/custom_geometry_source_options.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 
 namespace mbgl {
 namespace style {
diff --git a/src/mbgl/style/conversion/filter.cpp b/src/mbgl/style/conversion/filter.cpp
index 5114c61778..fc25ab0b0d 100644
--- a/src/mbgl/style/conversion/filter.cpp
+++ b/src/mbgl/style/conversion/filter.cpp
@@ -1,10 +1,11 @@
 #include <mbgl/style/conversion/filter.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/style/expression/literal.hpp>
-#include <mbgl/util/geometry.hpp>
 #include <mbgl/style/expression/expression.hpp>
 #include <mbgl/style/expression/type.hpp>
 #include <mbgl/style/expression/compound_expression.hpp>
 #include <mbgl/style/expression/boolean_operator.hpp>
+#include <mbgl/util/geometry.hpp>
 
 namespace mbgl {
 namespace style {
diff --git a/src/mbgl/style/conversion/function.cpp b/src/mbgl/style/conversion/function.cpp
index 1cc49e483a..6aadaad3b3 100644
--- a/src/mbgl/style/conversion/function.cpp
+++ b/src/mbgl/style/conversion/function.cpp
@@ -1,4 +1,6 @@
 #include <mbgl/style/conversion/function.hpp>
+#include <mbgl/style/conversion/position.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/style/expression/dsl.hpp>
 #include <mbgl/style/expression/step.hpp>
 #include <mbgl/style/expression/interpolate.hpp>
@@ -70,6 +72,72 @@ std::unique_ptr<Expression> convertTokenStringToExpression(const std::string& so
     }
 }
 
+template <class T>
+optional<PropertyExpression<T>> convertFunctionToExpression(const Convertible& value, Error& error, bool convertTokens) {
+    auto expression = convertFunctionToExpression(expression::valueTypeToExpressionType<T>(), value, error, convertTokens);
+    if (!expression) {
+        return nullopt;
+    }
+
+    optional<T> defaultValue;
+
+    auto defaultValueValue = objectMember(value, "default");
+    if (defaultValueValue) {
+        defaultValue = convert<T>(*defaultValueValue, error);
+        if (!defaultValue) {
+            error.message = R"(wrong type for "default": )" + error.message;
+            return nullopt;
+        }
+    }
+
+    return PropertyExpression<T>(std::move(*expression), defaultValue);
+}
+
+template optional<PropertyExpression<AlignmentType>>
+    convertFunctionToExpression<AlignmentType>(const Convertible&, Error&, bool);
+template optional<PropertyExpression<bool>>
+    convertFunctionToExpression<bool>(const Convertible&, Error&, bool);
+template optional<PropertyExpression<CirclePitchScaleType>>
+    convertFunctionToExpression<CirclePitchScaleType>(const Convertible&, Error&, bool);
+template optional<PropertyExpression<float>>
+    convertFunctionToExpression<float>(const Convertible&, Error&, bool);
+template optional<PropertyExpression<HillshadeIlluminationAnchorType>>
+    convertFunctionToExpression<HillshadeIlluminationAnchorType>(const Convertible&, Error&, bool);
+template optional<PropertyExpression<IconTextFitType>>
+    convertFunctionToExpression<IconTextFitType>(const Convertible&, Error&, bool);
+template optional<PropertyExpression<LightAnchorType>>
+    convertFunctionToExpression<LightAnchorType>(const Convertible&, Error&, bool);
+template optional<PropertyExpression<LineCapType>>
+    convertFunctionToExpression<LineCapType>(const Convertible&, Error&, bool);
+template optional<PropertyExpression<LineJoinType>>
+    convertFunctionToExpression<LineJoinType>(const Convertible&, Error&, bool);
+template optional<PropertyExpression<Color>>
+    convertFunctionToExpression<Color>(const Convertible&, Error&, bool);
+template optional<PropertyExpression<Position>>
+    convertFunctionToExpression<Position>(const Convertible&, Error&, bool);
+template optional<PropertyExpression<RasterResamplingType>>
+    convertFunctionToExpression<RasterResamplingType>(const Convertible&, Error&, bool);
+template optional<PropertyExpression<std::array<float, 2>>>
+    convertFunctionToExpression<std::array<float, 2>>(const Convertible&, Error&, bool);
+template optional<PropertyExpression<std::array<float, 4>>>
+    convertFunctionToExpression<std::array<float, 4>>(const Convertible&, Error&, bool);
+template optional<PropertyExpression<std::string>>
+    convertFunctionToExpression<std::string>(const Convertible&, Error&, bool);
+template optional<PropertyExpression<std::vector<float>>>
+    convertFunctionToExpression<std::vector<float>>(const Convertible&, Error&, bool);
+template optional<PropertyExpression<std::vector<std::string>>>
+    convertFunctionToExpression<std::vector<std::string>>(const Convertible&, Error&, bool);
+template optional<PropertyExpression<SymbolAnchorType>>
+    convertFunctionToExpression<SymbolAnchorType>(const Convertible&, Error&, bool);
+template optional<PropertyExpression<SymbolPlacementType>>
+    convertFunctionToExpression<SymbolPlacementType>(const Convertible&, Error&, bool);
+template optional<PropertyExpression<TextJustifyType>>
+    convertFunctionToExpression<TextJustifyType>(const Convertible&, Error&, bool);
+template optional<PropertyExpression<TextTransformType>>
+    convertFunctionToExpression<TextTransformType>(const Convertible&, Error&, bool);
+template optional<PropertyExpression<TranslateAnchorType>>
+    convertFunctionToExpression<TranslateAnchorType>(const Convertible&, Error&, bool);
+
 // Ad-hoc Converters for double and int64_t. We should replace float with double wholesale,
 // and promote the int64_t Converter to general use (and it should check that the input is
 // an integer).
diff --git a/src/mbgl/style/conversion/geojson.cpp b/src/mbgl/style/conversion/geojson.cpp
index e39a1a80eb..c2d34c5491 100644
--- a/src/mbgl/style/conversion/geojson.cpp
+++ b/src/mbgl/style/conversion/geojson.cpp
@@ -1,5 +1,6 @@
 #include <mbgl/style/conversion/geojson.hpp>
 #include <mbgl/style/conversion/json.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 
 namespace mbgl {
 namespace style {
diff --git a/src/mbgl/style/conversion/geojson_options.cpp b/src/mbgl/style/conversion/geojson_options.cpp
index 77340e5f1d..11bd7cc507 100644
--- a/src/mbgl/style/conversion/geojson_options.cpp
+++ b/src/mbgl/style/conversion/geojson_options.cpp
@@ -1,4 +1,5 @@
 #include <mbgl/style/conversion/geojson_options.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 
 namespace mbgl {
 namespace style {
diff --git a/src/mbgl/style/conversion/get_json_type.cpp b/src/mbgl/style/conversion/get_json_type.cpp
index cd3b4608b1..2e9d35a957 100644
--- a/src/mbgl/style/conversion/get_json_type.cpp
+++ b/src/mbgl/style/conversion/get_json_type.cpp
@@ -1,4 +1,5 @@
 #include <mbgl/style/conversion/get_json_type.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/util/feature.hpp>
 
 namespace mbgl {
diff --git a/src/mbgl/style/conversion/json.hpp b/src/mbgl/style/conversion/json.hpp
index a823f6d383..3a7bf2b557 100644
--- a/src/mbgl/style/conversion/json.hpp
+++ b/src/mbgl/style/conversion/json.hpp
@@ -1,6 +1,6 @@
 #pragma once
 
-#include <mbgl/style/conversion.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/style/rapidjson_conversion.hpp>
 
 #include <string>
diff --git a/src/mbgl/style/conversion/layer.cpp b/src/mbgl/style/conversion/layer.cpp
index d36ca494da..085d7ae4c6 100644
--- a/src/mbgl/style/conversion/layer.cpp
+++ b/src/mbgl/style/conversion/layer.cpp
@@ -1,6 +1,7 @@
 #include <mbgl/style/conversion/layer.hpp>
 #include <mbgl/style/conversion/constant.hpp>
 #include <mbgl/style/conversion/filter.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/style/layers/background_layer.hpp>
 #include <mbgl/style/layers/circle_layer.hpp>
 #include <mbgl/style/layers/fill_layer.hpp>
diff --git a/src/mbgl/style/conversion/light.cpp b/src/mbgl/style/conversion/light.cpp
index 7b96c89a1c..e8723216ee 100644
--- a/src/mbgl/style/conversion/light.cpp
+++ b/src/mbgl/style/conversion/light.cpp
@@ -2,6 +2,7 @@
 #include <mbgl/style/conversion/position.hpp>
 #include <mbgl/style/conversion/property_value.hpp>
 #include <mbgl/style/conversion/transition_options.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 
 namespace mbgl {
 namespace style {
diff --git a/src/mbgl/style/conversion/position.cpp b/src/mbgl/style/conversion/position.cpp
index a19f57bff3..df6c868ee8 100644
--- a/src/mbgl/style/conversion/position.cpp
+++ b/src/mbgl/style/conversion/position.cpp
@@ -1,5 +1,6 @@
 #include <mbgl/style/conversion/position.hpp>
 #include <mbgl/style/conversion/constant.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 
 #include <array>
 
diff --git a/src/mbgl/style/conversion/property_value.cpp b/src/mbgl/style/conversion/property_value.cpp
new file mode 100644
index 0000000000..8a93c24767
--- /dev/null
+++ b/src/mbgl/style/conversion/property_value.cpp
@@ -0,0 +1,83 @@
+#include <mbgl/style/conversion/property_value.hpp>
+#include <mbgl/style/conversion/position.hpp>
+#include <mbgl/style/conversion_impl.hpp>
+
+namespace mbgl {
+namespace style {
+namespace conversion {
+
+template <class T>
+optional<PropertyValue<T>> Converter<PropertyValue<T>>::operator()(const Convertible& value, Error& error, bool allowDataExpressions, bool convertTokens) const {
+    using namespace mbgl::style::expression;
+
+    if (isUndefined(value)) {
+        return PropertyValue<T>();
+    }
+
+    optional<PropertyExpression<T>> expression;
+
+    if (isExpression(value)) {
+        ParsingContext ctx(valueTypeToExpressionType<T>());
+        ParseResult parsed = ctx.parseLayerPropertyExpression(value);
+        if (!parsed) {
+            error.message = ctx.getCombinedErrors();
+            return nullopt;
+        }
+        expression = PropertyExpression<T>(std::move(*parsed));
+    } else if (isObject(value)) {
+        expression = convertFunctionToExpression<T>(value, error, convertTokens);
+    } else {
+        optional<T> constant = convert<T>(value, error);
+        if (!constant) {
+            return nullopt;
+        }
+        return convertTokens ? maybeConvertTokens(*constant) : PropertyValue<T>(*constant);
+    }
+
+    if (!expression) {
+        return nullopt;
+    } else if (!allowDataExpressions && !(*expression).isFeatureConstant()) {
+        error.message = "data expressions not supported";
+        return nullopt;
+    } else if (!(*expression).isFeatureConstant() || !(*expression).isZoomConstant()) {
+        return { std::move(*expression) };
+    } else if ((*expression).getExpression().getKind() == Kind::Literal) {
+        optional<T> constant = fromExpressionValue<T>(
+            static_cast<const Literal&>((*expression).getExpression()).getValue());
+        if (!constant) {
+            return nullopt;
+        }
+        return PropertyValue<T>(*constant);
+    } else {
+        assert(false);
+        error.message = "expected a literal expression";
+        return nullopt;
+    }
+}
+
+template optional<PropertyValue<bool>> Converter<PropertyValue<bool>>::operator()(conversion::Convertible const&, conversion::Error&, bool, bool) const;
+template optional<PropertyValue<float>> Converter<PropertyValue<float>>::operator()(conversion::Convertible const&, conversion::Error&, bool, bool) const;
+template optional<PropertyValue<std::array<float, 2>>> Converter<PropertyValue<std::array<float, 2>>>::operator()(conversion::Convertible const&, conversion::Error&, bool, bool) const;
+template optional<PropertyValue<std::array<float, 4>>> Converter<PropertyValue<std::array<float, 4>>>::operator()(conversion::Convertible const&, conversion::Error&, bool, bool) const;
+template optional<PropertyValue<std::vector<float>>> Converter<PropertyValue<std::vector<float>>>::operator()(conversion::Convertible const&, conversion::Error&, bool, bool) const;
+template optional<PropertyValue<Color>> Converter<PropertyValue<Color>>::operator()(conversion::Convertible const&, conversion::Error&, bool, bool) const;
+template optional<PropertyValue<std::string>> Converter<PropertyValue<std::string>>::operator()(conversion::Convertible const&, conversion::Error&, bool, bool) const;
+template optional<PropertyValue<std::vector<std::string>>> Converter<PropertyValue<std::vector<std::string>>>::operator()(conversion::Convertible const&, conversion::Error&, bool, bool) const;
+template optional<PropertyValue<AlignmentType>> Converter<PropertyValue<AlignmentType>>::operator()(conversion::Convertible const&, conversion::Error&, bool, bool) const;
+template optional<PropertyValue<CirclePitchScaleType>> Converter<PropertyValue<CirclePitchScaleType>>::operator()(conversion::Convertible const&, conversion::Error&, bool, bool) const;
+template optional<PropertyValue<HillshadeIlluminationAnchorType>> Converter<PropertyValue<HillshadeIlluminationAnchorType>>::operator()(conversion::Convertible const&, conversion::Error&, bool, bool) const;
+template optional<PropertyValue<IconTextFitType>> Converter<PropertyValue<IconTextFitType>>::operator()(conversion::Convertible const&, conversion::Error&, bool, bool) const;
+template optional<PropertyValue<LightAnchorType>> Converter<PropertyValue<LightAnchorType>>::operator()(conversion::Convertible const&, conversion::Error&, bool, bool) const;
+template optional<PropertyValue<LineCapType>> Converter<PropertyValue<LineCapType>>::operator()(conversion::Convertible const&, conversion::Error&, bool, bool) const;
+template optional<PropertyValue<LineJoinType>> Converter<PropertyValue<LineJoinType>>::operator()(conversion::Convertible const&, conversion::Error&, bool, bool) const;
+template optional<PropertyValue<Position>> Converter<PropertyValue<Position>>::operator()(conversion::Convertible const&, conversion::Error&, bool, bool) const;
+template optional<PropertyValue<RasterResamplingType>> Converter<PropertyValue<RasterResamplingType>>::operator()(conversion::Convertible const&, conversion::Error&, bool, bool) const;
+template optional<PropertyValue<SymbolAnchorType>> Converter<PropertyValue<SymbolAnchorType>>::operator()(conversion::Convertible const&, conversion::Error&, bool, bool) const;
+template optional<PropertyValue<SymbolPlacementType>> Converter<PropertyValue<SymbolPlacementType>>::operator()(conversion::Convertible const&, conversion::Error&, bool, bool) const;
+template optional<PropertyValue<TextJustifyType>> Converter<PropertyValue<TextJustifyType>>::operator()(conversion::Convertible const&, conversion::Error&, bool, bool) const;
+template optional<PropertyValue<TextTransformType>> Converter<PropertyValue<TextTransformType>>::operator()(conversion::Convertible const&, conversion::Error&, bool, bool) const;
+template optional<PropertyValue<TranslateAnchorType>> Converter<PropertyValue<TranslateAnchorType>>::operator()(conversion::Convertible const&, conversion::Error&, bool, bool) const;
+
+} // namespace conversion
+} // namespace style
+} // namespace mbgl
diff --git a/src/mbgl/style/conversion/source.cpp b/src/mbgl/style/conversion/source.cpp
index ce0cb24ce0..5ecbd3b474 100644
--- a/src/mbgl/style/conversion/source.cpp
+++ b/src/mbgl/style/conversion/source.cpp
@@ -3,6 +3,7 @@
 #include <mbgl/style/conversion/geojson.hpp>
 #include <mbgl/style/conversion/geojson_options.hpp>
 #include <mbgl/style/conversion/tileset.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/style/sources/geojson_source.hpp>
 #include <mbgl/style/sources/raster_source.hpp>
 #include <mbgl/style/sources/raster_dem_source.hpp>
diff --git a/src/mbgl/style/conversion/tileset.cpp b/src/mbgl/style/conversion/tileset.cpp
index b566af0a18..40575838ea 100644
--- a/src/mbgl/style/conversion/tileset.cpp
+++ b/src/mbgl/style/conversion/tileset.cpp
@@ -1,4 +1,5 @@
 #include <mbgl/style/conversion/tileset.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/util/geo.hpp>
 #include <mbgl/math/clamp.hpp>
 
diff --git a/src/mbgl/style/conversion/transition_options.cpp b/src/mbgl/style/conversion/transition_options.cpp
index 924032a0c0..6e39dca24f 100644
--- a/src/mbgl/style/conversion/transition_options.cpp
+++ b/src/mbgl/style/conversion/transition_options.cpp
@@ -1,4 +1,5 @@
 #include <mbgl/style/conversion/transition_options.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 
 namespace mbgl {
 namespace style {
diff --git a/src/mbgl/style/expression/array_assertion.cpp b/src/mbgl/style/expression/array_assertion.cpp
index 4049301b0b..9df586bdc3 100644
--- a/src/mbgl/style/expression/array_assertion.cpp
+++ b/src/mbgl/style/expression/array_assertion.cpp
@@ -1,5 +1,6 @@
 #include <mbgl/style/expression/array_assertion.hpp>
 #include <mbgl/style/expression/check_subtype.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/util/string.hpp>
 
 namespace mbgl {
diff --git a/src/mbgl/style/expression/assertion.cpp b/src/mbgl/style/expression/assertion.cpp
index 2434d7a2f8..7e93003ac3 100644
--- a/src/mbgl/style/expression/assertion.cpp
+++ b/src/mbgl/style/expression/assertion.cpp
@@ -1,5 +1,6 @@
 #include <mbgl/style/expression/assertion.hpp>
 #include <mbgl/style/expression/check_subtype.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 
 namespace mbgl {
 namespace style {
diff --git a/src/mbgl/style/expression/at.cpp b/src/mbgl/style/expression/at.cpp
index 725e5ddb51..648f247830 100644
--- a/src/mbgl/style/expression/at.cpp
+++ b/src/mbgl/style/expression/at.cpp
@@ -1,4 +1,5 @@
 #include <mbgl/style/expression/at.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/util/string.hpp>
 
 
diff --git a/src/mbgl/style/expression/boolean_operator.cpp b/src/mbgl/style/expression/boolean_operator.cpp
index 68e96129aa..fa472270ce 100644
--- a/src/mbgl/style/expression/boolean_operator.cpp
+++ b/src/mbgl/style/expression/boolean_operator.cpp
@@ -1,4 +1,5 @@
 #include <mbgl/style/expression/boolean_operator.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 
 namespace mbgl {
 namespace style {
diff --git a/src/mbgl/style/expression/case.cpp b/src/mbgl/style/expression/case.cpp
index e885c0ce6b..0c2ff0d7cd 100644
--- a/src/mbgl/style/expression/case.cpp
+++ b/src/mbgl/style/expression/case.cpp
@@ -1,4 +1,5 @@
 #include <mbgl/style/expression/case.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/util/string.hpp>
 
 namespace mbgl {
diff --git a/src/mbgl/style/expression/coalesce.cpp b/src/mbgl/style/expression/coalesce.cpp
index 0090f16009..cdbf452f7f 100644
--- a/src/mbgl/style/expression/coalesce.cpp
+++ b/src/mbgl/style/expression/coalesce.cpp
@@ -1,5 +1,6 @@
 #include <mbgl/style/expression/coalesce.hpp>
 #include <mbgl/style/expression/check_subtype.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 
 namespace mbgl {
 namespace style {
diff --git a/src/mbgl/style/expression/coercion.cpp b/src/mbgl/style/expression/coercion.cpp
index f5a4d70f66..486658ddda 100644
--- a/src/mbgl/style/expression/coercion.cpp
+++ b/src/mbgl/style/expression/coercion.cpp
@@ -1,6 +1,7 @@
 #include <mbgl/style/expression/coercion.hpp>
 #include <mbgl/style/expression/check_subtype.hpp>
 #include <mbgl/style/expression/util.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/util/string.hpp>
 
 namespace mbgl {
diff --git a/src/mbgl/style/expression/collator_expression.cpp b/src/mbgl/style/expression/collator_expression.cpp
index b27eedbc76..07346633a2 100644
--- a/src/mbgl/style/expression/collator_expression.cpp
+++ b/src/mbgl/style/expression/collator_expression.cpp
@@ -1,6 +1,7 @@
 #include <mbgl/style/expression/collator.hpp>
 #include <mbgl/style/expression/collator_expression.hpp>
 #include <mbgl/style/expression/literal.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/util/string.hpp>
 
 namespace mbgl {
diff --git a/src/mbgl/style/expression/comparison.cpp b/src/mbgl/style/expression/comparison.cpp
index 6179c3ce88..cdcdb5d59c 100644
--- a/src/mbgl/style/expression/comparison.cpp
+++ b/src/mbgl/style/expression/comparison.cpp
@@ -1,6 +1,7 @@
 #include <mbgl/style/expression/collator.hpp>
 #include <mbgl/style/expression/comparison.hpp>
 #include <mbgl/style/expression/dsl.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 
 namespace mbgl {
 namespace style {
diff --git a/src/mbgl/style/expression/compound_expression.cpp b/src/mbgl/style/expression/compound_expression.cpp
index 4c476a3749..f8c2376cb3 100644
--- a/src/mbgl/style/expression/compound_expression.cpp
+++ b/src/mbgl/style/expression/compound_expression.cpp
@@ -3,6 +3,7 @@
 #include <mbgl/style/expression/compound_expression.hpp>
 #include <mbgl/style/expression/check_subtype.hpp>
 #include <mbgl/style/expression/util.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/tile/geometry_tile_data.hpp>
 #include <mbgl/math/log2.hpp>
 #include <mbgl/util/i18n.hpp>
diff --git a/src/mbgl/style/expression/interpolate.cpp b/src/mbgl/style/expression/interpolate.cpp
index 54fbc6e1d7..8725e9e86d 100644
--- a/src/mbgl/style/expression/interpolate.cpp
+++ b/src/mbgl/style/expression/interpolate.cpp
@@ -1,4 +1,5 @@
 #include <mbgl/style/expression/interpolate.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/util/string.hpp>
 
 namespace mbgl {
diff --git a/src/mbgl/style/expression/is_expression.cpp b/src/mbgl/style/expression/is_expression.cpp
index 77212f6a1e..acf074c25b 100644
--- a/src/mbgl/style/expression/is_expression.cpp
+++ b/src/mbgl/style/expression/is_expression.cpp
@@ -1,8 +1,7 @@
 #include <mbgl/style/expression/is_expression.hpp>
 #include <mbgl/style/expression/compound_expression.hpp>
 #include <mbgl/style/expression/parsing_context.hpp>
-
-#include <mbgl/style/conversion.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 
 #include <unordered_set>
 
diff --git a/src/mbgl/style/expression/length.cpp b/src/mbgl/style/expression/length.cpp
index ad7a15675a..f1b58d7952 100644
--- a/src/mbgl/style/expression/length.cpp
+++ b/src/mbgl/style/expression/length.cpp
@@ -1,4 +1,5 @@
 #include <mbgl/style/expression/length.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/util/string.hpp>
 
 namespace mbgl {
diff --git a/src/mbgl/style/expression/let.cpp b/src/mbgl/style/expression/let.cpp
index 242a995b0b..592ceed58a 100644
--- a/src/mbgl/style/expression/let.cpp
+++ b/src/mbgl/style/expression/let.cpp
@@ -1,5 +1,6 @@
 #include <mbgl/style/expression/let.hpp>
 #include <mbgl/style/conversion/get_json_type.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/util/string.hpp>
 
 namespace mbgl {
diff --git a/src/mbgl/style/expression/literal.cpp b/src/mbgl/style/expression/literal.cpp
index 345a52de9b..c69341d298 100644
--- a/src/mbgl/style/expression/literal.cpp
+++ b/src/mbgl/style/expression/literal.cpp
@@ -1,4 +1,5 @@
 #include <mbgl/style/expression/literal.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/util/string.hpp>
 
 namespace mbgl {
diff --git a/src/mbgl/style/expression/match.cpp b/src/mbgl/style/expression/match.cpp
index 4b4984811f..0f05001a97 100644
--- a/src/mbgl/style/expression/match.cpp
+++ b/src/mbgl/style/expression/match.cpp
@@ -1,6 +1,7 @@
 #include <mbgl/style/expression/match.hpp>
 #include <mbgl/style/expression/check_subtype.hpp>
 #include <mbgl/style/expression/parsing_context.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/util/string.hpp>
 
 namespace mbgl {
diff --git a/src/mbgl/style/expression/parsing_context.cpp b/src/mbgl/style/expression/parsing_context.cpp
index b3f6b1acee..ef17caed33 100644
--- a/src/mbgl/style/expression/parsing_context.cpp
+++ b/src/mbgl/style/expression/parsing_context.cpp
@@ -24,6 +24,7 @@
 #include <mbgl/style/expression/find_zoom_curve.hpp>
 
 #include <mbgl/style/conversion/get_json_type.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 
 #include <mbgl/util/string.hpp>
 
diff --git a/src/mbgl/style/expression/step.cpp b/src/mbgl/style/expression/step.cpp
index a1ca0a702e..39b04c04a0 100644
--- a/src/mbgl/style/expression/step.cpp
+++ b/src/mbgl/style/expression/step.cpp
@@ -1,5 +1,6 @@
 #include <mbgl/style/expression/step.hpp>
 #include <mbgl/style/expression/get_covering_stops.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/util/string.hpp>
 
 #include <cmath>
diff --git a/src/mbgl/style/layer.cpp b/src/mbgl/style/layer.cpp
index 31ff5bf47a..e08b71e6b3 100644
--- a/src/mbgl/style/layer.cpp
+++ b/src/mbgl/style/layer.cpp
@@ -2,6 +2,7 @@
 #include <mbgl/style/layer_impl.hpp>
 #include <mbgl/style/layer_observer.hpp>
 #include <mbgl/style/conversion/constant.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 
 namespace mbgl {
 namespace style {
diff --git a/src/mbgl/style/layers/background_layer.cpp b/src/mbgl/style/layers/background_layer.cpp
index e47b41daa8..f2e85ce7e7 100644
--- a/src/mbgl/style/layers/background_layer.cpp
+++ b/src/mbgl/style/layers/background_layer.cpp
@@ -3,12 +3,12 @@
 #include <mbgl/style/layers/background_layer.hpp>
 #include <mbgl/style/layers/background_layer_impl.hpp>
 #include <mbgl/style/layer_observer.hpp>
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/color_ramp_property_value.hpp>
 #include <mbgl/style/conversion/constant.hpp>
 #include <mbgl/style/conversion/property_value.hpp>
 #include <mbgl/style/conversion/transition_options.hpp>
 #include <mbgl/style/conversion/json.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/util/fnv_hash.hpp>
 
 namespace mbgl {
diff --git a/src/mbgl/style/layers/circle_layer.cpp b/src/mbgl/style/layers/circle_layer.cpp
index 1dae77547b..c301a83c9e 100644
--- a/src/mbgl/style/layers/circle_layer.cpp
+++ b/src/mbgl/style/layers/circle_layer.cpp
@@ -3,12 +3,12 @@
 #include <mbgl/style/layers/circle_layer.hpp>
 #include <mbgl/style/layers/circle_layer_impl.hpp>
 #include <mbgl/style/layer_observer.hpp>
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/color_ramp_property_value.hpp>
 #include <mbgl/style/conversion/constant.hpp>
 #include <mbgl/style/conversion/property_value.hpp>
 #include <mbgl/style/conversion/transition_options.hpp>
 #include <mbgl/style/conversion/json.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/util/fnv_hash.hpp>
 
 namespace mbgl {
diff --git a/src/mbgl/style/layers/fill_extrusion_layer.cpp b/src/mbgl/style/layers/fill_extrusion_layer.cpp
index db90415daa..74cdb9abe6 100644
--- a/src/mbgl/style/layers/fill_extrusion_layer.cpp
+++ b/src/mbgl/style/layers/fill_extrusion_layer.cpp
@@ -3,12 +3,12 @@
 #include <mbgl/style/layers/fill_extrusion_layer.hpp>
 #include <mbgl/style/layers/fill_extrusion_layer_impl.hpp>
 #include <mbgl/style/layer_observer.hpp>
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/color_ramp_property_value.hpp>
 #include <mbgl/style/conversion/constant.hpp>
 #include <mbgl/style/conversion/property_value.hpp>
 #include <mbgl/style/conversion/transition_options.hpp>
 #include <mbgl/style/conversion/json.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/util/fnv_hash.hpp>
 
 namespace mbgl {
diff --git a/src/mbgl/style/layers/fill_layer.cpp b/src/mbgl/style/layers/fill_layer.cpp
index 2da131b6b2..bdfc000736 100644
--- a/src/mbgl/style/layers/fill_layer.cpp
+++ b/src/mbgl/style/layers/fill_layer.cpp
@@ -3,12 +3,12 @@
 #include <mbgl/style/layers/fill_layer.hpp>
 #include <mbgl/style/layers/fill_layer_impl.hpp>
 #include <mbgl/style/layer_observer.hpp>
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/color_ramp_property_value.hpp>
 #include <mbgl/style/conversion/constant.hpp>
 #include <mbgl/style/conversion/property_value.hpp>
 #include <mbgl/style/conversion/transition_options.hpp>
 #include <mbgl/style/conversion/json.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/util/fnv_hash.hpp>
 
 namespace mbgl {
diff --git a/src/mbgl/style/layers/heatmap_layer.cpp b/src/mbgl/style/layers/heatmap_layer.cpp
index df00558135..a90aab7009 100644
--- a/src/mbgl/style/layers/heatmap_layer.cpp
+++ b/src/mbgl/style/layers/heatmap_layer.cpp
@@ -3,12 +3,12 @@
 #include <mbgl/style/layers/heatmap_layer.hpp>
 #include <mbgl/style/layers/heatmap_layer_impl.hpp>
 #include <mbgl/style/layer_observer.hpp>
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/color_ramp_property_value.hpp>
 #include <mbgl/style/conversion/constant.hpp>
 #include <mbgl/style/conversion/property_value.hpp>
 #include <mbgl/style/conversion/transition_options.hpp>
 #include <mbgl/style/conversion/json.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/util/fnv_hash.hpp>
 
 namespace mbgl {
diff --git a/src/mbgl/style/layers/hillshade_layer.cpp b/src/mbgl/style/layers/hillshade_layer.cpp
index fb96c681cc..aed49f6441 100644
--- a/src/mbgl/style/layers/hillshade_layer.cpp
+++ b/src/mbgl/style/layers/hillshade_layer.cpp
@@ -3,12 +3,12 @@
 #include <mbgl/style/layers/hillshade_layer.hpp>
 #include <mbgl/style/layers/hillshade_layer_impl.hpp>
 #include <mbgl/style/layer_observer.hpp>
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/color_ramp_property_value.hpp>
 #include <mbgl/style/conversion/constant.hpp>
 #include <mbgl/style/conversion/property_value.hpp>
 #include <mbgl/style/conversion/transition_options.hpp>
 #include <mbgl/style/conversion/json.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/util/fnv_hash.hpp>
 
 namespace mbgl {
diff --git a/src/mbgl/style/layers/layer.cpp.ejs b/src/mbgl/style/layers/layer.cpp.ejs
index 4e80a7bf74..b5fb1a97a4 100644
--- a/src/mbgl/style/layers/layer.cpp.ejs
+++ b/src/mbgl/style/layers/layer.cpp.ejs
@@ -8,12 +8,12 @@
 #include <mbgl/style/layers/<%- type.replace('-', '_') %>_layer.hpp>
 #include <mbgl/style/layers/<%- type.replace('-', '_') %>_layer_impl.hpp>
 #include <mbgl/style/layer_observer.hpp>
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/color_ramp_property_value.hpp>
 #include <mbgl/style/conversion/constant.hpp>
 #include <mbgl/style/conversion/property_value.hpp>
 #include <mbgl/style/conversion/transition_options.hpp>
 #include <mbgl/style/conversion/json.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/util/fnv_hash.hpp>
 
 namespace mbgl {
diff --git a/src/mbgl/style/layers/line_layer.cpp b/src/mbgl/style/layers/line_layer.cpp
index c744adad95..1b84c2d73e 100644
--- a/src/mbgl/style/layers/line_layer.cpp
+++ b/src/mbgl/style/layers/line_layer.cpp
@@ -3,12 +3,12 @@
 #include <mbgl/style/layers/line_layer.hpp>
 #include <mbgl/style/layers/line_layer_impl.hpp>
 #include <mbgl/style/layer_observer.hpp>
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/color_ramp_property_value.hpp>
 #include <mbgl/style/conversion/constant.hpp>
 #include <mbgl/style/conversion/property_value.hpp>
 #include <mbgl/style/conversion/transition_options.hpp>
 #include <mbgl/style/conversion/json.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/util/fnv_hash.hpp>
 
 namespace mbgl {
diff --git a/src/mbgl/style/layers/raster_layer.cpp b/src/mbgl/style/layers/raster_layer.cpp
index 45d3240833..7bd01c92e1 100644
--- a/src/mbgl/style/layers/raster_layer.cpp
+++ b/src/mbgl/style/layers/raster_layer.cpp
@@ -3,12 +3,12 @@
 #include <mbgl/style/layers/raster_layer.hpp>
 #include <mbgl/style/layers/raster_layer_impl.hpp>
 #include <mbgl/style/layer_observer.hpp>
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/color_ramp_property_value.hpp>
 #include <mbgl/style/conversion/constant.hpp>
 #include <mbgl/style/conversion/property_value.hpp>
 #include <mbgl/style/conversion/transition_options.hpp>
 #include <mbgl/style/conversion/json.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/util/fnv_hash.hpp>
 
 namespace mbgl {
diff --git a/src/mbgl/style/layers/symbol_layer.cpp b/src/mbgl/style/layers/symbol_layer.cpp
index 48af6b13aa..4ea138a7f5 100644
--- a/src/mbgl/style/layers/symbol_layer.cpp
+++ b/src/mbgl/style/layers/symbol_layer.cpp
@@ -3,12 +3,12 @@
 #include <mbgl/style/layers/symbol_layer.hpp>
 #include <mbgl/style/layers/symbol_layer_impl.hpp>
 #include <mbgl/style/layer_observer.hpp>
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/color_ramp_property_value.hpp>
 #include <mbgl/style/conversion/constant.hpp>
 #include <mbgl/style/conversion/property_value.hpp>
 #include <mbgl/style/conversion/transition_options.hpp>
 #include <mbgl/style/conversion/json.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/util/fnv_hash.hpp>
 
 namespace mbgl {
diff --git a/src/mbgl/style/parser.cpp b/src/mbgl/style/parser.cpp
index 0a90919f0b..114a666f08 100644
--- a/src/mbgl/style/parser.cpp
+++ b/src/mbgl/style/parser.cpp
@@ -1,12 +1,12 @@
 #include <mbgl/style/parser.hpp>
 #include <mbgl/style/layer_impl.hpp>
 #include <mbgl/style/rapidjson_conversion.hpp>
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/coordinate.hpp>
 #include <mbgl/style/conversion/source.hpp>
 #include <mbgl/style/conversion/layer.hpp>
 #include <mbgl/style/conversion/light.hpp>
 #include <mbgl/style/conversion/transition_options.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 
 #include <mbgl/util/logging.hpp>
 #include <mbgl/util/string.hpp>
diff --git a/src/mbgl/style/rapidjson_conversion.hpp b/src/mbgl/style/rapidjson_conversion.hpp
index 79bd9c928b..be335101e9 100644
--- a/src/mbgl/style/rapidjson_conversion.hpp
+++ b/src/mbgl/style/rapidjson_conversion.hpp
@@ -1,7 +1,7 @@
 #pragma once
 
 #include <mbgl/util/rapidjson.hpp>
-#include <mbgl/style/conversion.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 
 #include <mapbox/geojson.hpp>
 #include <mapbox/geojson/rapidjson.hpp>
diff --git a/test/style/conversion/light.test.cpp b/test/style/conversion/light.test.cpp
index f111e40ff3..092c476277 100644
--- a/test/style/conversion/light.test.cpp
+++ b/test/style/conversion/light.test.cpp
@@ -1,9 +1,9 @@
 #include <mbgl/test/util.hpp>
 
-#include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/json.hpp>
 #include <mbgl/style/conversion/constant.hpp>
 #include <mbgl/style/conversion/light.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/style/position.hpp>
 #include <mbgl/util/color.hpp>
 #include <mbgl/util/chrono.hpp>
diff --git a/test/style/expression/expression.test.cpp b/test/style/expression/expression.test.cpp
index 0b46facf42..982a769b93 100644
--- a/test/style/expression/expression.test.cpp
+++ b/test/style/expression/expression.test.cpp
@@ -1,6 +1,6 @@
 #include <mbgl/test/util.hpp>
 #include <mbgl/util/io.hpp>
-#include <mbgl/style/conversion.hpp>
+#include <mbgl/style/conversion_impl.hpp>
 #include <mbgl/util/rapidjson.hpp>
 #include <mbgl/style/rapidjson_conversion.hpp>
 #include <mbgl/style/expression/is_expression.hpp>