[swift-evolution] [Swift 4] Organizing source stability

[Graydon Hoare]

> On Jul 29, 2016, at 5:20 PM, Jacob Bandes-Storch via swift-evolution <swift-evolution at swift.org> wrote:
> 
> 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.

Picking up on a slightly cold thread...

Yes, I've lately been sketching an extension to build-configuration (#if ..) statements, to support feature-at-a-time evolution. There are a bunch of edge issues to work through around compiler release channels, name scoping, diagnostics, parser control and so forth. I'll post a draft proposal in a bit.

-Graydon