[#BloombergLP-bslstl-Variant_CheckForP1957R2-0e0]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bslstl.adoc[bslstl]::Variant_CheckForP1957R2
:relfileprefix: ../../
:mrdocs:

This component‐private metafunction checks whether a conversion from a pointer type to (template parameter) `t_TYPE` is narrowing. It is instantiated only for `bool`, and its behavior depends on whether the compiler has implemented P1957R2.

== Synopsis

Declared in `<bslstl_variant.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    class t_TYPE,
    class = void>
struct Variant_CheckForP1957R2
    : xref:bsl/true_type.adoc[bsl::true_type]
----

== Base Classes

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

== Specializations

[cols="1"]
|===
| Name
| xref:BloombergLP/bslstl/Variant_CheckForP1957R2-0ed.adoc[`Variant_CheckForP1957R2<t_TYPE, bsl::void_t<decltype(Variant_ArrayHelper<t_TYPE>{{"bc"}})>>`] 
|===



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