[#BloombergLP-bslstl-Variant_OverloadSetImp-07]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bslstl.adoc[bslstl]::Variant_OverloadSetImp
:relfileprefix: ../../
:mrdocs:

This component‐private metafunction computes an overload set consisting of one function, named `candidate`, for each type in (template parameters) `t_HEAD, t_TAIL...`, having one parameter of that type. Each such function participates in overload resolution only when `std::declval<t_SRC>()` is convertible to the alternative without narrowing, and returns `bsl::integral_constant<t_INDEX + i>`, where `i` is the zero‐based index of the corresponding alternative. Note that a type that occurs multiple times in `t_HEAD, t_TAIL...` (possibly with varying cv‐qualifications) will only result in the generation of a single candidate. This implementation relies on expression SFINAE, `decltype`, `std::declval`, and P1957R2; since these features are not available in C++03, the C++03 version requires an exact match modulo cv‐qualification.

== Synopsis

Declared in `<bslstl_variant.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    class t_SRC,
    size_t t_INDEX,
    class t_HEAD,
    class... t_TAIL>
struct Variant_OverloadSetImp
    : Variant_OverloadSetImp<t_SRC, t_INDEX + 1, t_TAIL...>
----

== Base Classes

[cols="1,4"]
|===
| Name| Description
| `Variant_OverloadSetImp<t_SRC, t_INDEX + 1, t_TAIL...>`
| This component‐private metafunction computes an overload set consisting of one function, named `candidate`, for each type in (template parameters) `t_HEAD, t_TAIL...`, having one parameter of that type. Each such function participates in overload resolution only when `std::declval<t_SRC>()` is convertible to the alternative without narrowing, and returns `bsl::integral_constant<t_INDEX + i>`, where `i` is the zero‐based index of the corresponding alternative. Note that a type that occurs multiple times in `t_HEAD, t_TAIL...` (possibly with varying cv‐qualifications) will only result in the generation of a single candidate. This implementation relies on expression SFINAE, `decltype`, `std::declval`, and P1957R2; since these features are not available in C++03, the C++03 version requires an exact match modulo cv‐qualification.
|===

== Static Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bslstl/Variant_OverloadSetImp-07/candidate-01.adoc[`candidate`] 
| Overload candidate selecting alternative `t_INDEX` for source type `t_SRC`.
|===


== Using Declarations

[cols="1"]
|===
| Name
| xref:BloombergLP/bslstl/Variant_OverloadSetImp-07/candidate-02.adoc[`candidate`] 
|===


== Specializations

[cols="1"]
|===
| Name
| xref:BloombergLP/bslstl/Variant_OverloadSetImp-03.adoc[`Variant_OverloadSetImp<t_SRC, t_INDEX, t_HEAD>`] 
|===


== Derived Classes

[cols="1,4"]
|===
| Name| Description
| `Variant_OverloadSetImp` 
| This component‐private metafunction computes an overload set consisting of one function, named `candidate`, for each type in (template parameters) `t_HEAD, t_TAIL...`, having one parameter of that type. Each such function participates in overload resolution only when `std::declval<t_SRC>()` is convertible to the alternative without narrowing, and returns `bsl::integral_constant<t_INDEX + i>`, where `i` is the zero‐based index of the corresponding alternative. Note that a type that occurs multiple times in `t_HEAD, t_TAIL...` (possibly with varying cv‐qualifications) will only result in the generation of a single candidate. This implementation relies on expression SFINAE, `decltype`, `std::declval`, and P1957R2; since these features are not available in C++03, the C++03 version requires an exact match modulo cv‐qualification.
|===


[.small]#Created with https://www.mrdocs.com[MrDocs]#