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#include <string>
#include <mbgl/style/expression/check_subtype.hpp>
namespace mbgl {
namespace style {
namespace expression {
namespace type {
std::string errorMessage(const Type& expected, const Type& t) {
return {"Expected " + toString(expected) + " but found " + toString(t) + " instead."};
}
optional<std::string> checkSubtype(const Type& expected, const Type& t) {
if (t.is<ErrorType>()) return {};
optional<std::string> result = expected.match(
[&] (const Array& expectedArray) -> optional<std::string> {
if (!t.is<Array>()) { return {errorMessage(expected, t)}; }
const auto& actualArray = t.get<Array>();
const auto err = checkSubtype(expectedArray.itemType, actualArray.itemType);
if (err) return { errorMessage(expected, t) };
if (expectedArray.N && expectedArray.N != actualArray.N) return { errorMessage(expected, t) };
return {};
},
[&] (const ValueType&) -> optional<std::string> {
if (t.is<ValueType>()) return {};
const Type members[] = {
Null,
Boolean,
Number,
String,
Object,
Color,
Array(Value)
};
for (const auto& member : members) {
const auto err = checkSubtype(member, t);
if (!err) {
return {};
}
}
return { errorMessage(expected, t) };
},
[&] (const auto&) -> optional<std::string> {
if (expected != t) {
return { errorMessage(expected, t) };
}
return {};
}
);
return result;
}
} // namespace type
} // namespace expression
} // namespace style
} // namespace mbgl
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