[swift-evolution] Availability checking of libraries (weak linking?)

[Ben Rimmington]

> On 19 Jan 2017, at 00:24, Swizzlr wrote:
> 
> Say I have an awesome type, and I provide some extensions that makes it work really well with a few other packages.
> 
> I don't want to force those packages on my users, but if they have them, I want to extend them with my awesome type/function/whatever convenience.
> 
> What can be done in code and package manager to weakly link (not literally, I just mean have that behaviour) my awesome type with all these other libraries?
> 
> This is a prelude to a pitch, if there isn't a decent alternative.
> 
> Tom

<https://github.com/apple/swift-evolution/blob/master/proposals/0075-import-test.md>

#if canImport(...) should be available in Swift 4, thanks to Robert Widmann.

<https://github.com/apple/swift/pull/5778>
<https://github.com/apple/swift/pull/6547>

-- Ben