SourceKit crashes are caused by bugs in the Swift type checker most of the time; it's not SourceKit itself that's at fault usually. We did a lot of work to fix

SourceKit crashes are caused by bugs in the Swift type checker most of the time; it's not SourceKit itself that's at fault usually. We did a lot of work to fix architectural problems in 3.1, especially with generics, and there will be more improvements in 4.0. It's definitely a priority now that the language design has settled down.