[#BSLSTL_VARIANT_DECLARE_IF_CONSTRUCTS_FROM]
= BSLSTL&lowbar;VARIANT&lowbar;DECLARE&lowbar;IF&lowbar;CONSTRUCTS&lowbar;FROM
:mrdocs:

Enable a constructor when `VARIANT` can construct from `TYPE`&period;

== Synopsis

Declared in `&lt;bslstl&lowbar;variant&period;h&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
#define BSLSTL&lowbar;VARIANT&lowbar;DECLARE&lowbar;IF&lowbar;CONSTRUCTS&lowbar;FROM(VARIANT, TYPE)

----

== Description

This component&hyphen;private macro is used as a constraint in function declarations which require the specified `VARIANT` to be constructible from the specified `TYPE`&period;

== Parameters

[cols="1,4"]
|===
| Name| Description
| *VARIANT*
| variant specialization under consideration
| *TYPE*
| candidate alternative or converting type
|===


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