[#BSLSTL_VARIANT_DEFINE_IF_CONSTRUCTS_FROM]
= BSLSTL_VARIANT_DEFINE_IF_CONSTRUCTS_FROM
:mrdocs:

Constrain a function definition to when `VARIANT` constructs from `TYPE`.

== Synopsis

Declared in `<bslstl_variant.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
#define BSLSTL_VARIANT_DEFINE_IF_CONSTRUCTS_FROM(VARIANT, TYPE)

----

== Description

This component‐private macro is used as a constraint in function definitions which require the specified `VARIANT` to be constructible from the specified `TYPE`.

== Parameters

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


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