1) Assigns by copying the state ofrhs, as if byany(rhs).swap(*this).

2) Assigns by moving the state ofrhs, as if byany(std::move(rhs)).swap(*this).rhs is left in a valid but unspecified state after the assignment.

3) Assigns the type and value ofrhs, as if byany(std::forward<ValueType>(rhs)).swap(*this). Ifstd::is_copy_constructible<std::decay_t<ValueType>>::value isfalse, the program is ill-formed. This overload participates in overload resolution only ifstd::decay_t<ValueType> is not the same type asany.

1,3) Throwsbad_alloc or any exception thrown by the constructor of the contained type. If an exception is thrown, there are no effects (strong exception guarantee).