This component‐private metafunction provides a member typedef Index representing the value that should be computed by Variant_ConvertIndex.

Synopsis

Declared in <bslstl_variant.h>

template<
    class t_SRC,
    class t_VARIANT,
    class = void>
struct Variant_OverloadHelper;

Description

This component‐private metafunction provides a member typedef Index representing the value that should be computed by Variant_ConvertIndex. The primary template is instantiated when the partial specialization below is not viable because no viable alternative exists for the conversion or because the best match is not "unique" (see the documentation of Variant_ConvertIndex for an explanation).

Type Aliases

Name

Description

Index

Index constant equal to variant_npos when no unique conversion exists.

Specializations

Name

Description

Variant_OverloadHelper<t_SRC, bsl::variant<t_HEAD, t_TAIL...>, bsl::void_t<decltype(Variant_OverloadSetImp<t_SRC, 0, t_HEAD, t_TAIL...>:: candidate(std::declval<t_SRC>()))>>

Provide Index when a unique best‐match alternative is found.

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