src/tint/utils/rtti/ignore.h

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#ifndef SRC_TINT_UTILS_RTTI_IGNORE_H_
#define SRC_TINT_UTILS_RTTI_IGNORE_H_

#include <type_traits>

namespace tint {

/// Ignore is used as a special type used for skipping over types for trait helper functions.
class Ignore {};

}  // namespace tint

namespace std {

/// A specialization of std::common_type where the first template argument is tint::Ignore.
/// Used so that std::common_type will ignore template arguments of type tint::Ignore.
template <typename T>
struct common_type<tint::Ignore, T> {
    /// The second template type.
    using type = T;
};

/// A specialization of std::common_type where the second template argument is tint::Ignore.
/// Used so that std::common_type will ignore template arguments of type tint::Ignore.
template <typename T>
struct common_type<T, tint::Ignore> {
    /// The first template type.
    using type = T;
};

}  // namespace std

#endif  // SRC_TINT_UTILS_RTTI_IGNORE_H_