[swift-evolution] Proposal Idea : Library (third party) Importable Checking

[Joe Groff]

> On Jan 14, 2016, at 11:17 PM, Félix Cloutier <felixcca at yahoo.ca> wrote:
> 
> If it's meant to be included in a library, don't we need a linkage mechanism that will expose these symbols only if another library is linked in?

I see, that's the part I missed. If you wanted these symbols to be conditionally available, that would indeed require a new language, and probably dynamic linker, feature. You could however manage this without any new features, by adding the extensions in a third library dependent on the two base libraries.

-Joe

> Félix
> 
>> Le 15 janv. 2016 à 01:43:16, Jo Albright via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> a écrit :
>> 
>>> Interesting idea. Unless I'm misunderstanding something, it seems to me you could kill both birds with one stone. If we add an 'importable' predicate to the '#if' language, then you can already use that to conditionalize the import:
>>> 
>>> #if importable(ThirdPartyLibrary)
>>> import ThirdPartyLibrary
>>> /* decls that depend on library */
>>> #endif
>>> 
>>> -Joe
>> 
>> 
>> I am totally on board with that idea… since you could declare a type outside of the “#if importable” scope and add an extension inside the scope.
>> 
>> Designer . Developer .  Nerd 
>> Jo Albright
>> 
>> 
>> 
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