[swift-dev] Implementation of Existential Collection (AnySequence and co.)

Pavol Vaskovic pali at pali.sk
Sat Apr 8 15:45:49 CDT 2017

Jordan Rose says in the comment on SR-4499 that Dmitri no longer works on
Swift. Who owns that part of code now?

Also, who is able to answer my original questions from this thread?


On Wed, 5 Apr 2017 at 18:56, Pavol Vaskovic <pali at pali.sk> wrote:

> On Wednesday, 5 April 2017 at 16:04, rintaro ishizaki wrote:
> > Just FYI
> >
> > Implementation of Type Erasers
> >
> https://lists.swift.org/pipermail/swift-dev/Week-of-Mon-20160905/002852.html
> Thanks for that link!
> This looks like a followup to Chris’s question, so I’m pinging Dmitri to
> chime in on this.
> Bug report: https://bugs.swift.org/browse/SR-4499
> For a reproducer, see the benchmark for `run_SuffixAnySequence` - that is
> utterly dominated by wending elements from the underlying sequence using
> generic witness table. There is no specialization occurring at all. As I’ve
> reasoned in my original e-mail, this is understandable - semantics of
> _AnyIteratorBox used in AnyIterator’s `next` method require virtual
> dispatch.
> Closure based approach to type erasure should’t have such a semantic
> barrier for optimization - the limit would probably just be currently
> conservative optimization?
> Best regards
> Pavol Vaskovic
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