chromium/third_party/dawn/src/tint/utils/result/result.h

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#ifndef SRC_TINT_UTILS_RESULT_RESULT_H_
#define SRC_TINT_UTILS_RESULT_RESULT_H_

#include <utility>
#include <variant>

#include "src/tint/utils/diagnostic/diagnostic.h"
#include "src/tint/utils/ice/ice.h"
#include "src/tint/utils/text/string_stream.h"
#include "src/tint/utils/traits/traits.h"

namespace tint {

/// Empty structure that can be used as the SUCCESS_TYPE for a Result.
struct SuccessType { … };

/// An instance of SuccessType that can be used as a generic success value for a Result.
static constexpr const SuccessType Success;

/// The default Result error type.
struct Failure { … };

/// Write the Failure to the given stream
/// @param out the output stream
/// @param failure the Failure
/// @returns the output stream
template <typename STREAM, typename = traits::EnableIfIsOStream<STREAM>>
auto& operator<<(STREAM& out, const Failure& failure) { … }

/// Result is a helper for functions that need to return a value, or an failure value.
/// Result can be constructed with either a 'success' or 'failure' value.
/// @tparam SUCCESS_TYPE the 'success' value type.
/// @tparam FAILURE_TYPE the 'failure' value type. Defaults to FailureType which provides no
///         information about the failure, except that something failed. Must not be the same type
///         as SUCCESS_TYPE.
template <typename SUCCESS_TYPE, typename FAILURE_TYPE = Failure>
struct [[nodiscard]] Result { … };

/// Writes the result to the stream.
/// @param out the stream to write to
/// @param res the result
/// @return the stream so calls can be chained
template <typename STREAM,
          typename SUCCESS,
          typename FAILURE,
          typename = traits::EnableIfIsOStream<STREAM>>
auto& operator<<(STREAM& out, const Result<SUCCESS, FAILURE>& res) { … }

}  // namespace tint

#endif  // SRC_TINT_UTILS_RESULT_RESULT_H_