[#BloombergLP-bslstl-Variant_CheckForP1957R2-0e0]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bslstl.adoc[bslstl]::Variant&lowbar;CheckForP1957R2
:relfileprefix: ../../
:mrdocs:

This component&hyphen;private metafunction checks whether a conversion from a pointer type to (template parameter) `t&lowbar;TYPE` is narrowing&period; It is instantiated only for `bool`, and its behavior depends on whether the compiler has implemented P1957R2&period;

== Synopsis

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

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template&lt;
    class t&lowbar;TYPE,
    class = void&gt;
struct Variant&lowbar;CheckForP1957R2
    : xref:bsl/true_type.adoc[bsl::true&lowbar;type]
----

== Base Classes

[cols="1,4"]
|===
| Name| Description
| `xref:bsl/true_type.adoc[bsl::true&lowbar;type]`
| Metafunction representing the boolean constant `true`&period;
|===

== Specializations

[cols="1"]
|===
| Name
| xref:BloombergLP/bslstl/Variant_CheckForP1957R2-0ed.adoc[`Variant&lowbar;CheckForP1957R2&lt;t&lowbar;TYPE, bsl::void&lowbar;t&lt;decltype(Variant&lowbar;ArrayHelper&lt;t&lowbar;TYPE&gt;&lcub;&lcub;&quot;bc&quot;&rcub;&rcub;)&gt;&gt;`] 
|===



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