[swift-evolution] Name disambiguation of computed property/function with same type defined in extensions

Paul Cantrell cantrell at pobox.com
Tue Jun 7 11:36:53 CDT 2016

> On Jun 7, 2016, at 10:47 AM, L. Mihalkovic via swift-evolution <swift-evolution at swift.org> wrote:
> On Jun 7, 2016, at 4:53 PM, Tony Allevato <allevato at google.com <mailto:allevato at google.com>> wrote:
>> I like the "from" keyword the best, but I'll take my own stab at a modification:
>>     import ModuleA
>>     import ModuleB
>>     "hello world".(capitalized from ModuleA)()
>>     "hello world".(capitalized from ModuleB)()
>>     "hello world".(someProperty from ModuleA)
>>     "hello world".(someProperty from ModuleB)
> Hmmm... looks like an oxymoron in its own right... I was under the impression so far that the point of extensions was that they are not tied to a source. This brings us back full circle to the very definition of extensions... However you slice it, swift is lacking some scoping bellow modules, and/or arround some of the language features.

IIRC, a member of the core team (Joe Groff, maybe?) indicated several months ago on the list that methods are internally namespaced to their module. Alas, I can’t find that message. It was a long time ago.

You can see this in the fact that two different files can see two different extension methods:


    import ModuleA
    "hello world".capitalized()


    import ModuleB
    "hello world".capitalized()

…even if they end up compiled into the same binary. And that makes sense: A.swift only expected to see ModuleA’s extension, and was presumably coded around that expectation. That ModuleB happened to end up mixed into the same binary shouldn’t change the behavior of A.swift

If my understand is correct, then my "hello world”.ModuleA::capitalized() and your "hello world".(capitalized from ModuleA)() are both just syntax to expose something that Swift already tracks internally.

Cheers, P

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