Yes, and it's covered in those previous threads. In brief, not all retroactive modeling involves extending a type:
* A vendor supplies you with a closed-source library with a struct S that conforms to standard library protocol P. * Protocol P requires a method named foo(), so struct S has its own implementation of foo(). * You extend protocol P by adding a new default implementation of foo(). This cannot be done if a keyword is required for overriding a default implementation. There is also nowhere for you to append any sort of "retro" keyword anywhere, because no part of your own code extends S in any way. Please, please take the time to study the previous threads; we should not be re-playing existing discussions four or five times on this list. On Thu, Aug 25, 2016 at 10:06 PM, Charles Srstka <cocoa...@charlessoft.com> wrote: > Is there a reason that adding a “retro” keyword on extensions meant to > retroactively apply a protocol is unacceptable? > > Charles > > On Aug 25, 2016, at 6:44 PM, Xiaodi Wu via swift-evolution < > swift-evolution@swift.org> wrote: > > Chris, as I wrote above, this idea has been discussed previously on > several occasions, and the principal reason why it has been abandoned each > time is that it cannot accommodate retroactive modeling. I'll refer you > again to three previous threads discussing this and closely related matters: > > >
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