[core] Convert legacy functions directly to expressions

5 files changed, 708 insertions, 170 deletions

diff --git a/src/mbgl/style/conversion/function.cpp b/src/mbgl/style/conversion/function.cpp
new file mode 100644
index 0000000000..64adf522a1
--- /dev/null
+++ b/src/mbgl/style/conversion/function.cpp
@@ -0,0 +1,699 @@
+#include <mbgl/style/conversion/function.hpp>
+#include <mbgl/style/expression/dsl.hpp>
+#include <mbgl/style/expression/step.hpp>
+#include <mbgl/style/expression/interpolate.hpp>
+#include <mbgl/style/expression/match.hpp>
+#include <mbgl/style/expression/case.hpp>
+#include <mbgl/style/expression/array_assertion.hpp>
+#include <mbgl/util/string.hpp>
+
+#include <cassert>
+
+namespace mbgl {
+namespace style {
+namespace conversion {
+
+using namespace expression;
+using namespace expression::dsl;
+
+// 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).
+template <>
+struct Converter<double> {
+    optional<double> operator()(const Convertible& value, Error& error) const {
+        auto converted = convert<float>(value, error);
+        if (!converted) {
+            return {};
+        }
+        return *converted;
+    }
+};
+
+template <>
+struct Converter<int64_t> {
+    optional<int64_t> operator()(const Convertible& value, Error& error) const {
+        auto converted = convert<float>(value, error);
+        if (!converted) {
+            return {};
+        }
+        return *converted;
+    }
+};
+
+enum class FunctionType {
+    Interval,
+    Exponential,
+    Categorical,
+    Identity,
+    Invalid
+};
+
+static bool interpolatable(type::Type type) {
+    return type.match(
+        [&] (const type::NumberType&) {
+            return true;
+        },
+        [&] (const type::ColorType&) {
+            return true;
+        },
+        [&] (const type::Array& array) {
+            return array.N && array.itemType == type::Number;
+        },
+        [&] (const auto&) {
+            return false;
+        }
+    );
+}
+
+static FunctionType functionType(type::Type type, const Convertible& value) {
+    auto typeValue = objectMember(value, "type");
+    if (!typeValue) {
+        return interpolatable(type) ? FunctionType::Exponential : FunctionType::Interval;
+    }
+
+    optional<std::string> string = toString(*typeValue);
+    if (!string) {
+        return FunctionType::Invalid;
+    }
+
+    if (*string == "interval")
+        return FunctionType::Interval;
+    if (*string == "exponential" && interpolatable(type))
+        return FunctionType::Exponential;
+    if (*string == "categorical")
+        return FunctionType::Categorical;
+    if (*string == "identity")
+        return FunctionType::Identity;
+
+    return FunctionType::Invalid;
+}
+
+static optional<std::unique_ptr<Expression>> convertLiteral(type::Type type, const Convertible& value, Error& error) {
+    return type.match(
+        [&] (const type::NumberType&) -> optional<std::unique_ptr<Expression>> {
+            auto result = convert<float>(value, error);
+            if (!result) {
+                return {};
+            }
+            return literal(double(*result));
+        },
+        [&] (const type::BooleanType&) -> optional<std::unique_ptr<Expression>> {
+            auto result = convert<bool>(value, error);
+            if (!result) {
+                return {};
+            }
+            return literal(*result);
+        },
+        [&] (const type::StringType&) -> optional<std::unique_ptr<Expression>> {
+            auto result = convert<std::string>(value, error);
+            if (!result) {
+                return {};
+            }
+            return literal(*result);
+        },
+        [&] (const type::ColorType&) -> optional<std::unique_ptr<Expression>> {
+            auto result = convert<Color>(value, error);
+            if (!result) {
+                return {};
+            }
+            return literal(*result);
+        },
+        [&] (const type::Array& array) -> optional<std::unique_ptr<Expression>> {
+            if (!isArray(value)) {
+                error = { "value must be an array" };
+                return {};
+            }
+            if (array.N && arrayLength(value) != *array.N) {
+                error = { "value must be an array of length " + util::toString(*array.N) };
+                return {};
+            }
+            return array.itemType.match(
+                [&] (const type::NumberType&) -> optional<std::unique_ptr<Expression>> {
+                    std::vector<expression::Value> result;
+                    result.reserve(arrayLength(value));
+                    for (std::size_t i = 0; i < arrayLength(value); ++i) {
+                        optional<float> number = toNumber(arrayMember(value, i));
+                        if (!number) {
+                            error = { "value must be an array of numbers" };
+                            return {};
+                        }
+                        result.push_back(double(*number));
+                    }
+                    return literal(result);
+                },
+                [&] (const type::StringType&) -> optional<std::unique_ptr<Expression>> {
+                    std::vector<expression::Value> result;
+                    result.reserve(arrayLength(value));
+                    for (std::size_t i = 0; i < arrayLength(value); ++i) {
+                        optional<std::string> string = toString(arrayMember(value, i));
+                        if (!string) {
+                            error = { "value must be an array of strings" };
+                            return {};
+                        }
+                        result.push_back(*string);
+                    }
+                    return literal(result);
+                },
+                [&] (const auto&) -> optional<std::unique_ptr<Expression>> {
+                    assert(false); // No properties use this type.
+                    return {};
+                }
+            );
+        },
+        [&] (const type::NullType&) -> optional<std::unique_ptr<Expression>> {
+            assert(false); // No properties use this type.
+            return {};
+        },
+        [&] (const type::ObjectType&) -> optional<std::unique_ptr<Expression>> {
+            assert(false); // No properties use this type.
+            return {};
+        },
+        [&] (const type::ErrorType&) -> optional<std::unique_ptr<Expression>> {
+            assert(false); // No properties use this type.
+            return {};
+        },
+        [&] (const type::ValueType&) -> optional<std::unique_ptr<Expression>> {
+            assert(false); // No properties use this type.
+            return {};
+        },
+        [&] (const type::CollatorType&) -> optional<std::unique_ptr<Expression>> {
+            assert(false); // No properties use this type.
+            return {};
+        }
+    );
+}
+
+static optional<std::map<double, std::unique_ptr<Expression>>> convertStops(type::Type type,
+                                                                            const Convertible& value,
+                                                                            Error& error) {
+    auto stopsValue = objectMember(value, "stops");
+    if (!stopsValue) {
+        error = { "function value must specify stops" };
+        return {};
+    }
+
+    if (!isArray(*stopsValue)) {
+        error = { "function stops must be an array" };
+        return {};
+    }
+
+    if (arrayLength(*stopsValue) == 0) {
+        error = { "function must have at least one stop" };
+        return {};
+    }
+
+    std::map<double, std::unique_ptr<Expression>> stops;
+    for (std::size_t i = 0; i < arrayLength(*stopsValue); ++i) {
+        const auto& stopValue = arrayMember(*stopsValue, i);
+
+        if (!isArray(stopValue)) {
+            error = { "function stop must be an array" };
+            return {};
+        }
+
+        if (arrayLength(stopValue) != 2) {
+            error = { "function stop must have two elements" };
+            return {};
+        }
+
+        optional<float> t = convert<float>(arrayMember(stopValue, 0), error);
+        if (!t) {
+            return {};
+        }
+
+        optional<std::unique_ptr<Expression>> e = convertLiteral(type, arrayMember(stopValue, 1), error);
+        if (!e) {
+            return {};
+        }
+
+        stops.emplace(*t, std::move(*e));
+    }
+
+    return { std::move(stops) };
+}
+
+template <class T>
+optional<std::map<T, std::unique_ptr<Expression>>> convertBranches(type::Type type,
+                                                                   const Convertible& value,
+                                                                   Error& error) {
+    auto stopsValue = objectMember(value, "stops");
+    if (!stopsValue) {
+        error = { "function value must specify stops" };
+        return {};
+    }
+
+    if (!isArray(*stopsValue)) {
+        error = { "function stops must be an array" };
+        return {};
+    }
+
+    if (arrayLength(*stopsValue) == 0) {
+        error = { "function must have at least one stop" };
+        return {};
+    }
+
+    std::map<T, std::unique_ptr<Expression>> stops;
+    for (std::size_t i = 0; i < arrayLength(*stopsValue); ++i) {
+        const auto& stopValue = arrayMember(*stopsValue, i);
+
+        if (!isArray(stopValue)) {
+            error = { "function stop must be an array" };
+            return {};
+        }
+
+        if (arrayLength(stopValue) != 2) {
+            error = { "function stop must have two elements" };
+            return {};
+        }
+
+        optional<T> t = convert<T>(arrayMember(stopValue, 0), error);
+        if (!t) {
+            return {};
+        }
+
+        optional<std::unique_ptr<Expression>> e = convertLiteral(type, arrayMember(stopValue, 1), error);
+        if (!e) {
+            return {};
+        }
+
+        stops.emplace(*t, std::move(*e));
+    }
+
+    return { std::move(stops) };
+}
+
+static optional<double> convertBase(const Convertible& value, Error& error) {
+    auto baseValue = objectMember(value, "base");
+
+    if (!baseValue) {
+        return 1.0;
+    }
+
+    auto base = toNumber(*baseValue);
+    if (!base) {
+        error = { "function base must be a number" };
+        return {};
+    }
+
+    return *base;
+}
+
+static std::unique_ptr<Expression> step(type::Type type, std::unique_ptr<Expression> input, std::map<double, std::unique_ptr<Expression>> stops) {
+    return std::make_unique<Step>(type, std::move(input), std::move(stops));
+}
+
+static std::unique_ptr<Expression> interpolate(type::Type type, Interpolator interpolator, std::unique_ptr<Expression> input, std::map<double, std::unique_ptr<Expression>> stops) {
+    ParsingContext ctx;
+    auto result = createInterpolate(type, std::move(interpolator), std::move(input), std::move(stops), ctx);
+    if (!result) {
+        assert(false);
+        return {};
+    }
+    return std::move(*result);
+}
+
+template <class T>
+std::unique_ptr<Expression> categorical(type::Type type, const std::string& property, std::map<T, std::unique_ptr<Expression>> branches) {
+    std::unordered_map<T, std::shared_ptr<Expression>> convertedBranches;
+    for (auto& b : branches) {
+        convertedBranches[b.first] = std::move(b.second);
+    }
+    return std::make_unique<Match<T>>(type, get(literal(property)), std::move(convertedBranches), error("replaced with default"));
+}
+
+template <>
+std::unique_ptr<Expression> categorical<bool>(type::Type type, const std::string& property, std::map<bool, std::unique_ptr<Expression>> branches) {
+    auto it = branches.find(true);
+    std::unique_ptr<Expression> trueCase = it == branches.end() ?
+        error("replaced with default") :
+        std::move(it->second);
+
+    it = branches.find(false);
+    std::unique_ptr<Expression> falseCase = it == branches.end() ?
+        error("replaced with default") :
+        std::move(it->second);
+
+    std::vector<typename Case::Branch> trueBranch;
+    trueBranch.emplace_back(get(literal(property)), std::move(trueCase));
+
+    return std::make_unique<Case>(type, std::move(trueBranch), std::move(falseCase));
+}
+
+static optional<std::unique_ptr<Expression>> convertIntervalFunction(type::Type type,
+                                                                     const Convertible& value,
+                                                                     Error& error,
+                                                                     std::unique_ptr<Expression> input) {
+    auto stops = convertStops(type, value, error);
+    if (!stops) {
+        return {};
+    }
+    return step(type, std::move(input), std::move(*stops));
+}
+
+static optional<std::unique_ptr<Expression>> convertExponentialFunction(type::Type type,
+                                                                        const Convertible& value,
+                                                                        Error& error,
+                                                                        std::unique_ptr<Expression> input) {
+    auto stops = convertStops(type, value, error);
+    if (!stops) {
+        return {};
+    }
+    auto base = convertBase(value, error);
+    if (!base) {
+        return {};
+    }
+    return interpolate(type, exponential(*base), std::move(input), std::move(*stops));
+}
+
+static optional<std::unique_ptr<Expression>> convertCategoricalFunction(type::Type type,
+                                                                        const Convertible& value,
+                                                                        Error& err,
+                                                                        const std::string& property) {
+    auto stopsValue = objectMember(value, "stops");
+    if (!stopsValue) {
+        err = { "function value must specify stops" };
+        return {};
+    }
+
+    if (!isArray(*stopsValue)) {
+        err = { "function stops must be an array" };
+        return {};
+    }
+
+    if (arrayLength(*stopsValue) == 0) {
+        err = { "function must have at least one stop" };
+        return {};
+    }
+
+    const auto& first = arrayMember(*stopsValue, 0);
+
+    if (!isArray(first)) {
+        err = { "function stop must be an array" };
+        return {};
+    }
+
+    if (arrayLength(first) != 2) {
+        err = { "function stop must have two elements" };
+        return {};
+    }
+
+    if (toBool(arrayMember(first, 0))) {
+        auto branches = convertBranches<bool>(type, value, err);
+        if (!branches) {
+            return {};
+        }
+        return categorical(type, property, std::move(*branches));
+    }
+
+    if (toNumber(arrayMember(first, 0))) {
+        auto branches = convertBranches<int64_t>(type, value, err);
+        if (!branches) {
+            return {};
+        }
+        return categorical(type, property, std::move(*branches));
+    }
+
+    if (toString(arrayMember(first, 0))) {
+        auto branches = convertBranches<std::string>(type, value, err);
+        if (!branches) {
+            return {};
+        }
+        return categorical(type, property, std::move(*branches));
+    }
+
+    err = { "stop domain value must be a number, string, or boolean" };
+    return {};
+}
+
+optional<std::unique_ptr<Expression>> convertCameraFunctionToExpression(type::Type type,
+                                                                        const Convertible& value,
+                                                                        Error& error) {
+    if (!isObject(value)) {
+        error = { "function must be an object" };
+        return {};
+    }
+
+    switch (functionType(type, value)) {
+    case FunctionType::Interval:
+        return convertIntervalFunction(type, value, error, zoom());
+    case FunctionType::Exponential:
+        return convertExponentialFunction(type, value, error, zoom());
+    default:
+        error = { "unsupported function type" };
+        return {};
+    }
+}
+
+optional<std::unique_ptr<Expression>> convertSourceFunctionToExpression(type::Type type,
+                                                                        const Convertible& value,
+                                                                        Error& error) {
+    if (!isObject(value)) {
+        error = { "function must be an object" };
+        return {};
+    }
+
+    auto propertyValue = objectMember(value, "property");
+    if (!propertyValue) {
+        error = { "function must specify property" };
+        return {};
+    }
+
+    auto property = toString(*propertyValue);
+    if (!property) {
+        error = { "function property must be a string" };
+        return {};
+    }
+
+    switch (functionType(type, value)) {
+    case FunctionType::Interval:
+        return convertIntervalFunction(type, value, error, number(get(literal(*property))));
+    case FunctionType::Exponential:
+        return convertExponentialFunction(type, value, error, number(get(literal(*property))));
+    case FunctionType::Categorical:
+        return convertCategoricalFunction(type, value, error, *property);
+    case FunctionType::Identity:
+        return type.match(
+            [&] (const type::StringType&) -> optional<std::unique_ptr<Expression>> {
+                return string(get(literal(*property)));
+            },
+            [&] (const type::NumberType&) -> optional<std::unique_ptr<Expression>> {
+                return number(get(literal(*property)));
+            },
+            [&] (const type::BooleanType&) -> optional<std::unique_ptr<Expression>> {
+                return boolean(get(literal(*property)));
+            },
+            [&] (const type::ColorType&) -> optional<std::unique_ptr<Expression>> {
+                return toColor(get(literal(*property)));
+            },
+            [&] (const type::Array& array) -> optional<std::unique_ptr<Expression>> {
+                return std::unique_ptr<Expression>(
+                    std::make_unique<ArrayAssertion>(array, get(literal(*property))));
+            },
+            [&] (const auto&) -> optional<std::unique_ptr<Expression>>  {
+                assert(false); // No properties use this type.
+                return {};
+            }
+        );
+    default:
+        error = { "unsupported function type" };
+        return {};
+    }
+}
+
+template <class T>
+optional<std::unique_ptr<Expression>> composite(type::Type type,
+                                                const Convertible& value,
+                                                Error& error,
+                                                std::unique_ptr<Expression> (*makeInnerExpression) (type::Type type,
+                                                                                                    double base,
+                                                                                                    const std::string& property,
+                                                                                                    std::map<T, std::unique_ptr<Expression>>)) {
+    auto propertyValue = objectMember(value, "property");
+    if (!propertyValue) {
+        error = { "function must specify property" };
+        return {};
+    }
+
+    auto base = convertBase(value, error);
+    if (!base) {
+        return {};
+    }
+
+    auto propertyString = toString(*propertyValue);
+    if (!propertyString) {
+        error = { "function property must be a string" };
+        return {};
+    }
+
+    auto stopsValue = objectMember(value, "stops");
+
+    // Checked by caller.
+    assert(stopsValue);
+    assert(isArray(*stopsValue));
+
+    std::map<float, std::map<T, std::unique_ptr<Expression>>> map;
+
+    for (std::size_t i = 0; i < arrayLength(*stopsValue); ++i) {
+        const auto& stopValue = arrayMember(*stopsValue, i);
+
+        if (!isArray(stopValue)) {
+            error = { "function stop must be an array" };
+            return {};
+        }
+
+        if (arrayLength(stopValue) != 2) {
+            error = { "function stop must have two elements" };
+            return {};
+        }
+
+        const auto& stopInput = arrayMember(stopValue, 0);
+
+        if (!isObject(stopInput)) {
+            error = { "stop input must be an object" };
+            return {};
+        }
+
+        auto zoomValue = objectMember(stopInput, "zoom");
+        if (!zoomValue) {
+            error = { "stop input must specify zoom" };
+            return {};
+        }
+
+        auto sourceValue = objectMember(stopInput, "value");
+        if (!sourceValue) {
+            error = { "stop input must specify value" };
+            return {};
+        }
+
+        optional<float> z = convert<float>(*zoomValue, error);
+        if (!z) {
+            return {};
+        }
+
+        optional<T> d = convert<T>(*sourceValue, error);
+        if (!d) {
+            return {};
+        }
+
+        optional<std::unique_ptr<Expression>> r = convertLiteral(type, arrayMember(stopValue, 1), error);
+        if (!r) {
+            return {};
+        }
+
+        map[*z].emplace(*d, std::move(*r));
+    }
+
+    std::map<double, std::unique_ptr<Expression>> stops;
+
+    for (auto& e : map) {
+        stops.emplace(e.first, makeInnerExpression(type, *base, *propertyString, std::move(e.second)));
+    }
+
+    if (interpolatable(type)) {
+        return interpolate(type, linear(), zoom(), std::move(stops));
+    } else {
+        return step(type, zoom(), std::move(stops));
+    }
+}
+
+optional<std::unique_ptr<Expression>> convertCompositeFunctionToExpression(type::Type type,
+                                                                           const Convertible& value,
+                                                                           Error& err) {
+    if (!isObject(value)) {
+        err = { "function must be an object" };
+        return {};
+    }
+
+    auto stopsValue = objectMember(value, "stops");
+    if (!stopsValue) {
+        err = { "function value must specify stops" };
+        return {};
+    }
+
+    if (!isArray(*stopsValue)) {
+        err = { "function stops must be an array" };
+        return {};
+    }
+
+    if (arrayLength(*stopsValue) == 0) {
+        err = { "function must have at least one stop" };
+        return {};
+    }
+
+    const auto& first = arrayMember(*stopsValue, 0);
+
+    if (!isArray(first)) {
+        err = { "function stop must be an array" };
+        return {};
+    }
+
+    if (arrayLength(first) != 2) {
+        err = { "function stop must have two elements" };
+        return {};
+    }
+
+    const auto& stop = arrayMember(first, 0);
+
+    if (!isObject(stop)) {
+        err = { "stop must be an object" };
+        return {};
+    }
+
+    auto sourceValue = objectMember(stop, "value");
+    if (!sourceValue) {
+        err = { "stop must specify value" };
+        return {};
+    }
+
+    if (toBool(*sourceValue)) {
+        switch (functionType(type, value)) {
+        case FunctionType::Categorical:
+            return composite<bool>(type, value, err, [] (type::Type type_, double, const std::string& property, std::map<bool, std::unique_ptr<Expression>> stops) {
+                return categorical<bool>(type_, property, std::move(stops));
+            });
+        default:
+            err = { "unsupported function type" };
+            return {};
+        }
+    }
+
+    if (toNumber(*sourceValue)) {
+        switch (functionType(type, value)) {
+        case FunctionType::Interval:
+            return composite<double>(type, value, err, [] (type::Type type_, double, const std::string& property, std::map<double, std::unique_ptr<Expression>> stops) {
+                return step(type_, number(get(literal(property))), std::move(stops));
+            });
+        case FunctionType::Exponential:
+            return composite<double>(type, value, err, [] (type::Type type_, double base, const std::string& property, std::map<double, std::unique_ptr<Expression>> stops) {
+                return interpolate(type_, exponential(base), number(get(literal(property))), std::move(stops));
+            });
+        case FunctionType::Categorical:
+            return composite<int64_t>(type, value, err, [] (type::Type type_, double, const std::string& property, std::map<int64_t, std::unique_ptr<Expression>> stops) {
+                return categorical<int64_t>(type_, property, std::move(stops));
+            });
+        default:
+            err = { "unsupported function type" };
+            return {};
+        }
+    }
+
+    if (toString(*sourceValue)) {
+        switch (functionType(type, value)) {
+        case FunctionType::Categorical:
+            return composite<std::string>(type, value, err, [] (type::Type type_, double, const std::string& property, std::map<std::string, std::unique_ptr<Expression>> stops) {
+                return categorical<std::string>(type_, property, std::move(stops));
+            });
+        default:
+            err = { "unsupported function type" };
+            return {};
+        }
+    }
+
+    err = { "stop domain value must be a number, string, or boolean" };
+    return {};
+}
+
+} // namespace conversion
+} // namespace style
+} // namespace mbgl
diff --git a/src/mbgl/style/expression/dsl.cpp b/src/mbgl/style/expression/dsl.cpp
index 2298bdf8d3..5532e0a520 100644
--- a/src/mbgl/style/expression/dsl.cpp
+++ b/src/mbgl/style/expression/dsl.cpp
@@ -1,4 +1,5 @@
 #include <mbgl/style/expression/dsl.hpp>
+#include <mbgl/style/expression/error.hpp>
 #include <mbgl/style/expression/literal.hpp>
 #include <mbgl/style/expression/assertion.hpp>
 #include <mbgl/style/expression/coercion.hpp>
@@ -28,6 +29,10 @@ static std::unique_ptr<Expression> compound(const char* op, Args... args) {
     return std::move(*result);
 }
 
+std::unique_ptr<Expression> error(std::string message) {
+    return std::make_unique<Error>(std::move(message));
+}
+
 std::unique_ptr<Expression> literal(const char* value) {
     return literal(std::string(value));
 }
@@ -60,6 +65,10 @@ std::unique_ptr<Expression> string(std::unique_ptr<Expression> value) {
     return std::make_unique<Assertion>(type::String, vec(std::move(value)));
 }
 
+std::unique_ptr<Expression> boolean(std::unique_ptr<Expression> value) {
+    return std::make_unique<Assertion>(type::Boolean, vec(std::move(value)));
+}
+
 std::unique_ptr<Expression> toColor(const char* value) {
     return toColor(literal(value));
 }
diff --git a/src/mbgl/style/function/categorical_stops.cpp b/src/mbgl/style/function/categorical_stops.cpp
deleted file mode 100644
index dd179f5376..0000000000
--- a/src/mbgl/style/function/categorical_stops.cpp
+++ /dev/null
@@ -1,41 +0,0 @@
-#include <mbgl/style/function/categorical_stops.hpp>
-#include <mbgl/style/types.hpp>
-#include <mbgl/util/color.hpp>
-
-#include <array>
-
-namespace mbgl {
-namespace style {
-
-optional<CategoricalValue> categoricalValue(const Value& value) {
-    return value.match(
-        [] (bool t) { return optional<CategoricalValue>(t); },
-        [] (uint64_t t) { return optional<CategoricalValue>(int64_t(t)); },
-        [] (int64_t t) { return optional<CategoricalValue>(t); },
-        [] (double t) { return optional<CategoricalValue>(int64_t(t)); },
-        [] (const std::string& t) { return optional<CategoricalValue>(t); },
-        [] (const auto&) { return optional<CategoricalValue>(); }
-    );
-}
-
-template <class T>
-optional<T> CategoricalStops<T>::evaluate(const Value& value) const {
-    auto v = categoricalValue(value);
-    if (!v) {
-        return {};
-    }
-    auto it = stops.find(*v);
-    return it == stops.end() ? optional<T>() : it->second;
-}
-
-template class CategoricalStops<float>;
-template class CategoricalStops<Color>;
-template class CategoricalStops<std::array<float, 2>>;
-template class CategoricalStops<std::string>;
-template class CategoricalStops<TextTransformType>;
-template class CategoricalStops<TextJustifyType>;
-template class CategoricalStops<SymbolAnchorType>;
-template class CategoricalStops<LineJoinType>;
-
-} // namespace style
-} // namespace mbgl
diff --git a/src/mbgl/style/function/convert.cpp b/src/mbgl/style/function/convert.cpp
deleted file mode 100644
index a3b19f287b..0000000000
--- a/src/mbgl/style/function/convert.cpp
+++ /dev/null
@@ -1,40 +0,0 @@
-#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
diff --git a/src/mbgl/style/function/identity_stops.cpp b/src/mbgl/style/function/identity_stops.cpp
deleted file mode 100644
index 0ac6fda846..0000000000
--- a/src/mbgl/style/function/identity_stops.cpp
+++ /dev/null
@@ -1,89 +0,0 @@
-#include <mbgl/style/function/identity_stops.hpp>
-#include <mbgl/style/types.hpp>
-#include <mbgl/util/enum.hpp>
-#include <mbgl/util/color.hpp>
-
-#include <array>
-
-namespace mbgl {
-namespace style {
-
-template <>
-optional<float> IdentityStops<float>::evaluate(const Value& value) const {
-    return numericValue<float>(value);
-}
-
-template <>
-optional<std::string> IdentityStops<std::string>::evaluate(const Value& value) const {
-    if (!value.is<std::string>()) {
-        return {};
-    }
-    
-    return value.get<std::string>();
-}
-
-template <>
-optional<Color> IdentityStops<Color>::evaluate(const Value& value) const {
-    if (!value.is<std::string>()) {
-        return {};
-    }
-
-    return Color::parse(value.get<std::string>());
-}
-
-template <>
-optional<TextTransformType> IdentityStops<TextTransformType>::evaluate(const Value& value) const {
-    if (!value.is<std::string>()) {
-        return {};
-    }
-
-    return Enum<TextTransformType>::toEnum(value.get<std::string>());
-}
-
-template <>
-optional<TextJustifyType> IdentityStops<TextJustifyType>::evaluate(const Value& value) const {
-    if (!value.is<std::string>()) {
-        return {};
-    }
-
-    return Enum<TextJustifyType>::toEnum(value.get<std::string>());
-}
-
-template <>
-optional<SymbolAnchorType> IdentityStops<SymbolAnchorType>::evaluate(const Value& value) const {
-    if (!value.is<std::string>()) {
-        return {};
-    }
-
-    return Enum<SymbolAnchorType>::toEnum(value.get<std::string>());
-}
-
-template <>
-optional<LineJoinType> IdentityStops<LineJoinType>::evaluate(const Value& value) const {
-    if (!value.is<std::string>()) {
-        return {};
-    }
-
-    return Enum<LineJoinType>::toEnum(value.get<std::string>());
-}
-
-template <>
-optional<std::array<float, 2>> IdentityStops<std::array<float, 2>>::evaluate(const Value& value) const {
-    if (!value.is<std::vector<Value>>()) {
-        return {};
-    }
-
-    const auto& vector = value.get<std::vector<Value>>();
-    if (vector.size() != 2 || !numericValue<float>(vector[0]) || !numericValue<float>(vector[1])) {
-        return {};
-    }
-
-    std::array<float, 2> array {{
-        *numericValue<float>(vector[0]),
-        *numericValue<float>(vector[1])
-    }};
-    return array;
-}
-
-} // namespace style
-} // namespace mbgl