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

This metafunction is derived from `bsl::true_type` if `t_TYPE` is an allocator‐aware const type, and if `t_ANY_TYPE` is the same as `t_TYPE`, minus the cv qualification. This trait is used to enable a constructor overload for a const qualified allocator‐aware `ValueType` taking an rvalue of Optional_Base of the non‐const qualified `ValueType`. Such an overload needs to propagate the allocator.

== Synopsis

Declared in `<bslstl_optional.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    class t_TYPE,
    class t_ANY_TYPE>
struct Optional_PropagatesAllocator
    : xref:bsl/integral_constant-02.adoc[bsl::integral_constant<bool, bslma::UsesBslmaAllocator<t_TYPE>::value && bsl::is_const<t_TYPE>::value && bsl::is_same<t_ANY_TYPE, typename bsl::remove_cv<t_TYPE>::type>::value>]
----

== Base Classes

[cols="1,4"]
|===
| Name| Description
| `xref:bsl/integral_constant-02.adoc[bsl::integral_constant<bool, bslma::UsesBslmaAllocator<t_TYPE>::value && bsl::is_const<t_TYPE>::value && bsl::is_same<t_ANY_TYPE, typename bsl::remove_cv<t_TYPE>::type>::value>]`
| Metafunction representing a compile‐time constant of the specified (template parameter) `t_TYPE` with the specified (template parameter) `t_VALUE`.
|===

== Type Aliases

[cols="1,4"]
|===
| Name| Description
| xref:bsl/integral_constant-02/type.adoc[`type`] 
| Alias for this `integral_constant` specialization.
| xref:bsl/integral_constant-02/value_type.adoc[`value_type`] 
| 
|===


== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:bsl/integral_constant-02/operator_call.adoc[`operator()`] 
| Return a copy of the template argument `t_VALUE`.
| xref:bsl/integral_constant-02/2conversion.adoc[`operator value_type`] 
| 
|===


== Static Data Members

[cols="1"]
|===
| Name
| xref:bsl/integral_constant-02/value.adoc[`value`] 
|===



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