[swift-evolution] [swift-evolution-announce] [Review] SE-0156: Class and Subtype existentials

Hooman Mehr hooman at mac.com
Wed Mar 1 14:23:14 CST 2017

Similar observation on my side as well. Certainly it is better to specify the class constrain (or the type alias that has the class constrain) first because (sub)class constrain is the most determining factor about the nature of the declaration, but I think it is too hard to enforce properly when we have left type alias door wide open.

> On Mar 1, 2017, at 12:01 PM, Matthew Johnson via swift-evolution <swift-evolution at swift.org> wrote:
>> On Mar 1, 2017, at 1:59 PM, Brent Royal-Gordon via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> A good and necessary enhancement. My only objection is to the ordering rules—I'm not convinced that they pull their weight, especially given that typealiases can be used to introduce class constraints that aren't in the leftmost position. It's a lot of rules and strictures for a dubious benefit. 
> I made a similar comment in the discussion thread.  I don’t feel strongly enough to argue over it, but it does feel like a rather arbitrary limitation.
>> -- 
>> Brent Royal-Gordon
>> Sent from my iPhone
>> On Feb 28, 2017, at 1:11 PM, Douglas Gregor <dgregor at apple.com <mailto:dgregor at apple.com>> wrote:
>>> Hello Swift community,
>>> The review of SE-0156 "Class and Subtype existentials" begins now and runs through March 7, 2017. The proposal is available here:
>>> https://github.com/apple/swift-evolution/blob/master/proposals/0156-subclass-existentials.md <https://github.com/apple/swift-evolution/blob/master/proposals/0156-subclass-existentials.md>
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