So this proposal would not only change the meaning of “as”, but would require changing all bridged Objective-C API to remove any implicit conversions?
-Kenny > On Mar 4, 2017, at 3:45 PM, Charles Srstka <cocoa...@charlessoft.com> wrote: > >> On Mar 4, 2017, at 5:12 PM, Kenny Leung via swift-evolution >> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote: >> >> Speaking from a position of total ignorance here, but I’ll do it anyway :-) >> >> How is the implicit dynamic bridging any different from implicit static >> bridging? If I have an Objective-C method like >> >> - (NSArray<SuctionBall>)getAllSuctionBalls >> >> It would get translated into >> >> func getAllSuctionBalls() -> [SuctionBall] >> >> Where an NSArray is being implicitly bridged to a Swift array. Since such an >> implicit conversion exists anyway, what’s the harm in it happening when you >> do >> >> let swiftSuctionBalls = getSomething() as [SuctionBall] > > 1. The bridging described above is necessary, because you’re calling an API > in another language. Some kind of bridging has to be involved for that to > work at all, and we all understand that. > > 2. The bridging above doesn’t abuse a language construct that typically has a > completely different meaning (“as” as compile-time type coercion, with no > runtime effects). > > 3. If we fix “as” so that it only means type coercion, we could finally have > a way to avoid the bridging behavior above; i.e. ‘getAllSuctionBalls() as > NSArray’ to leave the returned value in its original form as an NSArray, > rather than bridging it to Swift and then back. This would be really useful > for certain situations like NSURL’s -fileReferenceURL which gets mangled by > the bridge, and it could also provide a potential performance optimization > when getting values that are just going to get passed to other Objective-C > APIs afterward. > > Charles
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