1 files changed, 45 insertions, 0 deletions
diff --git a/include/mbgl/style/expression/parse/coalesce.hpp b/include/mbgl/style/expression/parse/coalesce.hpp
new file mode 100644
index 0000000000..fd368fd5ec
--- /dev/null
+++ b/include/mbgl/style/expression/parse/coalesce.hpp
@@ -0,0 +1,45 @@
+#pragma once
+
+#include <vector>
+#include <memory>
+#include <mbgl/style/expression/coalesce.hpp>
+#include <mbgl/style/expression/parsing_context.hpp>
+#include <mbgl/style/expression/type.hpp>
+#include <mbgl/style/conversion.hpp>
+
+namespace mbgl {
+namespace style {
+namespace expression {
+
+struct ParseCoalesce {
+    template <typename V>
+    static ParseResult parse(const V& value, ParsingContext ctx) {
+        using namespace mbgl::style::conversion;
+        assert(isArray(value));
+        auto length = arrayLength(value);
+        if (length < 2) {
+            ctx.error("Expected at least one argument.");
+            return ParseResult();
+        }
+        
+        Coalesce::Args args;
+        optional<type::Type> outputType = ctx.expected;
+        for (std::size_t i = 1; i < length; i++) {
+            auto parsed = parseExpression(arrayMember(value, i), ParsingContext(ctx, i, outputType));
+            if (!parsed) {
+                return parsed;
+            }
+            if (!outputType) {
+                outputType = (*parsed)->getType();
+            }
+            args.push_back(std::move(*parsed));
+        }
+        
+        assert(outputType);
+        return ParseResult(std::make_unique<Coalesce>(*outputType, std::move(args)));
+    }
+};
+
+} // namespace expression
+} // namespace style
+} // namespace mbgl