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<future>
std::is_error_code_enum (future_errc)
template <>struct is_error_code_enum<future_errc> : public true_type {};error_code enum flag for future_errc
This traits specializations identifies future_errc as an error code enum type. Enabling it to be used to construct or assign values of this type to objects of type error_code.
For future_errc it inherits from true_type.