result_core.hpp

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#pragma once
 
#include <yaclib/algo/detail/base_core.hpp>
#include <yaclib/util/intrusive_ptr.hpp>
#include <yaclib/util/result.hpp>
 
#include <utility>
 
namespace yaclib::detail {
 
struct Callback {
  IRef* caller = nullptr;
  char unwrapping = 0;
};
 
template <typename V, typename E>
class ResultCore : public BaseCore {
  template <bool SymmetricTransfer>
  [[nodiscard]] YACLIB_INLINE auto Impl(InlineCore& /*caller*/) noexcept {
    YACLIB_PURE_VIRTUAL();
    return Noop<SymmetricTransfer>();
  }
 
 public:
  [[nodiscard]] InlineCore* Here(InlineCore& caller) noexcept override {
    return Impl<false>(caller);
  }
#if YACLIB_SYMMETRIC_TRANSFER != 0
  [[nodiscard]] yaclib_std::coroutine_handle<> Next(InlineCore& caller) noexcept override {
    return Impl<true>(caller);
  }
#endif
 
  ResultCore() noexcept : BaseCore{kEmpty} {
  }
 
  template <typename... Args>
  explicit ResultCore(Args&&... args) noexcept(std::is_nothrow_constructible_v<Result<V, E>, Args&&...>)
    : BaseCore{kResult}, _result{std::forward<Args>(args)...} {
  }
 
  ~ResultCore() noexcept override {
    _result.~Result<V, E>();
  }
 
  template <typename... Args>
  void Store(Args&&... args) noexcept(std::is_nothrow_constructible_v<Result<V, E>, Args&&...>) {
    new (&_result) Result<V, E>{std::forward<Args>(args)...};
  }
 
  [[nodiscard]] Result<V, E>& Get() noexcept {
    return _result;
  }
 
  union {
    Result<V, E> _result;
    Callback _self;
  };
};
 
extern template class ResultCore<void, StopError>;
 
template <typename V, typename E>
using ResultCorePtr = IntrusivePtr<ResultCore<V, E>>;
 
}  // namespace yaclib::detail