I'm curious to know how well it performs. I spent the better part of this weekend rewriting 4k lines of Swift in Objective-C because I couldn't deal with the 60-90 second compile times.
I've had to rewrite my approach a few times because of this to avoid certain coding techniques, but once I've rewritten to avoid them, Swift can happily compile my 7-8k LOC code-base in ~6s.
One other example FWIW: having a largish array of Int arrays causes the compiler to either go into an endless loop or simply take too long, UNLESS the type of the array is specified.
var data = [[1,2,3],[4,5,6], ... ] // > 20 elements -> compiler hangs
as opposed to:
var data:[[Int]] = [[1,2,3],[4,5,6], ... ] // compiles quickly
There's a whole repo dedicated to Swift compiler crashes being maintained at: https://github.com/practicalswift/swift-compiler-crashes
I remember on several occasions fighting Visual C++ over code it bombed out on. Having a precompiled header scheme to make up for poor performance. Yes it sucks, but you don't do these things because you think it's acceptable, it's because the alternative is more painful.
It's a shame because Swift is a neat language. But because Xcode doesn't support incremental compilation for Swift, a single character change causes the entire project to rebuild. Couple that with LLDB crashing because I'm including Objective-C frameworks (via Cocoapods), and the whole experience becomes absolutely terrible.
Disclosure: I write Android apps, so I'm only occasionally peeking at how the iOS dev scene is developing. I've already been thinking of trying to write Android apps in Scala, but maybe this Swift to Java compiler is also worth looking at
If you have time for making stuff up and downvoting, then you surely have time to run some benchmarks.