[#beman-optional-optional-06-2constructor-01a]
= xref:beman.adoc[beman]::xref:beman/optional.adoc[optional]::xref:beman/optional/optional-06.adoc[optional<T&>]::optional
:relfileprefix: ../../../
:mrdocs:

Construct from a U

== Synopsis

Declared in `<beman/optional/optional.hpp>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<class U>
requires (std::is_constructible_v<T&, U> && !(std::is_same_v<std::remove_cvref_t<U>, in_place_t>) &&
                 !(std::is_same_v<std::remove_cvref_t<U>, optional>) &&
                 !detail::reference_constructs_from_temporary_v<T&, U>)
constexpr
explicit(!std::is_convertible_v<U, T &>)
optional(U&& u) noexcept(std::is_nothrow_constructible_v<T &, U>);
----

== Description

Constructs the stored value from `u` if it is convertible to `T&`. If `T&` can be constructed from a temporary, this constructor is deleted to prevent binding a temporary to a reference.


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