1 files changed, 112 insertions, 0 deletions
diff --git a/include/mbgl/style/expression/type.hpp b/include/mbgl/style/expression/type.hpp
new file mode 100644
index 0000000000..513c4bdc17
--- /dev/null
+++ b/include/mbgl/style/expression/type.hpp
@@ -0,0 +1,112 @@
+#pragma once
+
+#include <mbgl/util/optional.hpp>
+#include <mbgl/util/string.hpp>
+#include <mbgl/util/variant.hpp>
+#include <vector>
+
+namespace mbgl {
+namespace style {
+namespace expression {
+namespace type {
+
+template <class T>
+std::string toString(const T& t);
+
+struct NullType {
+    constexpr NullType() {};
+    std::string getName() const { return "null"; }
+    bool operator==(const NullType&) const { return true; }
+};
+
+struct NumberType {
+    constexpr NumberType() {};
+    std::string getName() const { return "number"; }
+    bool operator==(const NumberType&) const { return true; }
+};
+
+struct BooleanType {
+    constexpr BooleanType() {};
+    std::string getName() const { return "boolean"; }
+    bool operator==(const BooleanType&) const { return true; }
+};
+
+struct StringType {
+    constexpr StringType() {};
+    std::string getName() const { return "string"; }
+    bool operator==(const StringType&) const { return true; }
+};
+
+struct ColorType {
+    constexpr ColorType() {};
+    std::string getName() const { return "color"; }
+    bool operator==(const ColorType&) const { return true; }
+};
+
+struct ObjectType {
+    constexpr ObjectType() {};
+    std::string getName() const { return "object"; }
+    bool operator==(const ObjectType&) const { return true; }
+};
+
+struct ErrorType {
+    constexpr ErrorType() {};
+    std::string getName() const { return "error"; }
+    bool operator==(const ErrorType&) const { return true; }
+};
+
+struct ValueType {
+    constexpr ValueType() {};
+    std::string getName() const { return "value"; }
+    bool operator==(const ValueType&) const { return true; }
+};
+
+constexpr NullType Null;
+constexpr NumberType Number;
+constexpr StringType String;
+constexpr BooleanType Boolean;
+constexpr ColorType Color;
+constexpr ValueType Value;
+constexpr ObjectType Object;
+constexpr ErrorType Error;
+
+struct Array;
+
+using Type = variant<
+    NullType,
+    NumberType,
+    BooleanType,
+    StringType,
+    ColorType,
+    ObjectType,
+    ValueType,
+    mapbox::util::recursive_wrapper<Array>,
+    ErrorType>;
+
+struct Array {
+    explicit Array(Type itemType_) : itemType(std::move(itemType_)) {}
+    Array(Type itemType_, std::size_t N_) : itemType(std::move(itemType_)), N(N_) {}
+    Array(Type itemType_, optional<std::size_t> N_) : itemType(std::move(itemType_)), N(std::move(N_)) {}
+    std::string getName() const {
+        if (N) {
+            return "array<" + toString(itemType) + ", " + util::toString(*N) + ">";
+        } else if (itemType == Value) {
+            return "array";
+        } else {
+            return "array<" + toString(itemType) + ">";
+        }
+    }
+
+    bool operator==(const Array& rhs) const { return itemType == rhs.itemType && N == rhs.N; }
+    
+    Type itemType;
+    optional<std::size_t> N;
+};
+    
+template <class T>
+std::string toString(const T& type) { return type.match([&] (const auto& t) { return t.getName(); }); }
+
+} // namespace type
+} // namespace expression
+} // namespace style
+} // namespace mbgl