I started diving into the Swift code base in December to see if I could wire together generic subscripts (https://bugs.swift.org/browse/SR-115), but I didn't have the time or know-how to get very far. I jumped back in again this past week and some of my earlier work was made obsolete by Chris's DeclContext plumbing at the end of last year
Michael Ilseman (cc'd) also started working on this but I don't think he had time to get much farther.
Last weekend I rebased, updated my code, and pushed a branch that seems to satisfy the general lexer:
I am, however, having a bit of trouble finding my way around the type checker and constraint generator. Trying to compile a simple example fails with this assertion: https://gist.github.com/stephencelis/10f9210a5409ee9bd79b
I know that I need to handle the generic type earlier, but I'm not sure where and I'm not sure where function decls are similarly handled.
I might be biting off more than I can chew, and it's possible that I should dive into some smaller, starter issues to get my feet wet to more gradually understand the code base. If you have the time, though, I'd be grateful for a little push in the right direction!