> On Jul 29, 2016, at 5:55 PM, Jacob Bandes-Storch <jtban...@gmail.com> wrote: > > Here are a few thoughts: > -swift=4 > -swift-version=4
-swift-version seems like the best option to me, but Jordan will have a strong opinion. I think he’s crazy busy with Swift 3 work until late next week. -Chris > -language-version=4 > a top-of-file "shebang"-style comment indicating the version, something like > //#swift(4), mirroring the "#if swift" syntax > > On Fri, Jul 29, 2016 at 5:27 PM, Chris Lattner <clatt...@apple.com > <mailto:clatt...@apple.com>> wrote: > >> On Jul 29, 2016, at 5:20 PM, Jacob Bandes-Storch via swift-evolution >> <swift-evolut...@swift.org <mailto:swift-evolut...@swift.org>> wrote: >> >> Chris writes: >> - Source stability features: These should be relatively small, but >> important. For example, we need a “-std=swift3” sort of compiler flag. We >> may also add a way to conditionally enable larger efforts that are under >> development but not yet stable - in order to make it easier to experiment >> with them. >> >> >> I am curious whether the team has thoughts on how to organize the compiler >> codebase in such a way that new features can be added, and possibly >> source-breaking changes made, while still keeping the old functionality >> around. >> >> Are any obvious areas that will need refactoring to make this feasible? >> (Perhaps they could be turned into StarterBugs.) > > I think this would be a great thing to do. We need a few things: > > - The actual compiler flag. It is worth bikeshedding how it is spelled. > “-std=“ is good inspiration, but clearly the wrong specific name. > > - The implementation should be straight forward: the flag should get plumbed > through to a field in swift::LangOptions. Code that diverges can then check > it. > > - Handling divergence in the standard library is another big issue. We have > some ideas here, but it depends on having the compiler work done anyway to > hook into. > >> How many versions back would the compiler be expected to support? Should the >> Swift 5 compiler still support Swift 3 code? > > To be determined. Swift 4 should definitely support Swift 3, but Swift 5 > perhaps not. We can decide that when Swift 4 is winding down. > > -Chris >
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