std::experimental::nonesuch (3) Linux Manual Page

std::experimental::nonesuch – std::experimental::nonesuch

Synopsis

Defined in header<experimental / type_traits>

    struct nonesuch {

    ~nonesuch() = delete;

    nonesuch(nonesuch const &) = delete;
    (library fundamentals TS v2)

        void
        operator=(nonesuch const &) = delete;
};

std::experimental::nonesuch is a class type used by std::experimental::detected_t to indicate detection failure.
nonesuch has no default constructor or initializer-list constructor, and is not an aggregate.

Notes

nonesuch cannot be constructed, destroyed, or copied.
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR Applied to Behavior as published Correct behavior
LWG_2960 LFTSv2 nonesuch may be an aggregate and has an implicit conversion sequence from {} made non-aggregate and removed ICS