Constructs an optional from another optional of type U.

Synopsis

Declared in <beman/optional/optional.hpp>

template<class U>
requires (std::is_constructible_v<T&, const U&> && !std::is_same_v<std::remove_cv_t<T>, optional<U>> &&
             !std::is_same_v<T&, U> && !detail::reference_constructs_from_temporary_v<T&, const U&>)
constexpr
explicit(!std::is_convertible_v<const U &, T &>)
optional(optional<U> const& rhs) noexcept(std::is_nothrow_constructible_v<T &, const U &>);

Description

Constructs the stored value from the rhs if it has a value, otherwise constructs an empty optional. If T& can be constructed from a temporary, this constructor is deleted to prevent binding a temporary to a reference.

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