AFAIK, there was an optimization for literal string concatenation that was broken in Xcode 8.3 (and the Swift version that comes with it), but is now fixed in master.
https://bugs.swift.org/browse/SR-4348 <https://bugs.swift.org/browse/SR-4348> > On May 16, 2017, at 10:47 PM, Ben Rimmington via swift-evolution > <swift-evolution@swift.org> wrote: > > >> On 16 May 2017, at 21:27, Tony Allevato <tony.allev...@gmail.com> wrote: >> >>> On Tue, May 16, 2017 at 1:25 PM David Hart <da...@hartbit.com> wrote: >>> The problem I see is that + is an operator of the Standard Library and not >>> part of the core language. I wouldn’t want + to sometimes to be a runtime >>> operation and other times a compile-time operation. No, I really think we >>> need strong language support here. >> >> Why not? Compile-time concatenation of string literals delimited by `+` >> sounds like a perfectly reasonable compiler optimization. >> >> Your argument would also state that the compiler should not do constant >> folding like turning `5 + 7` into `12`, would it not? What makes that >> situation different? > > When does the compiler do constant folding? > > Welcome to Apple Swift version 3.1 (swiftlang-802.0.53 clang-802.0.42). > Type :help for assistance. > 1> import Foundation > 2> let x: NSNumber = 12 > x: __NSCFNumber = Int64(12) > 3> let y: NSNumber = 5 + 7 > error: repl.swift:3:21: error: cannot convert value of type 'Int' to > specified type 'NSNumber' > let y: NSNumber = 5 + 7 > ~~^~~ > NSNumber( ) > > -- Ben > > _______________________________________________ > swift-evolution mailing list > swift-evolution@swift.org > https://lists.swift.org/mailman/listinfo/swift-evolution
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