[#absl-optional_ref-0c-2constructor-0e0]
= xref:absl.adoc[absl]::xref:absl/optional_ref-0c.adoc[optional&lowbar;ref]::optional&lowbar;ref
:relfileprefix: ../../
:mrdocs:

Converts from an `optional&lowbar;ref&lt;U&gt;` when `U&ast;` converts to `T&ast;`&period;

== Synopsis

Declared in `&lt;absl&sol;types&sol;optional&lowbar;ref&period;h&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template&lt;
    typename U,
    typename = xref:absl/optional_ref-0c.adoc[EnableIfConvertibleFrom&lt;U&gt;]&gt;
constexpr
optional&lowbar;ref(xref:absl/optional_ref-0c.adoc[optional&lowbar;ref&lt;U&gt;] input);
----

== Parameters

[cols="1,4"]
|===
| Name| Description
| *input*
| The source reference to convert from&period;
|===


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