[#BloombergLP-bslstl-variant_constructsFromStd]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bslstl.adoc[bslstl]::variant_constructsFromStd
:relfileprefix: ../../
:mrdocs:

This component‐private constexpr variable template is `true` if `t_VARIANT` is a specialization of `bsl::variant`, and `t_STD_VARIANT` is the `std::variant` type (possibly with added cvref‐qualification) that has the same sequence of alternatives, and each alternative of `t_VARIANT` is constructible from the corresponding alternative of `t_STD_VARIANT` (with cv‐qualification and value category matching that of `t_STD_VARIANT`). Note that we use `bsl::conjunction_v` for its short‐circuiting properties: if `t_STD_VARIANT` isn`t a `std::variant` (for example, if it`s a `bsl::variant`) we avoid recursing into the constraints of `bsl::variant`.

== Synopsis

Declared in `<bslstl_variant.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    class t_VARIANT,
    class t_STD_VARIANT>
constexpr bool variant_constructsFromStd = bsl::conjunction_v<
      bsl::is_same<typename Variant_CorrespondingStdVariant<t_VARIANT>::type,
                   bsl::remove_cvref_t<t_STD_VARIANT>>,
      std::is_constructible<bsl::remove_cvref_t<t_STD_VARIANT>,
                            t_STD_VARIANT>>;
----


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