It’s been 2 months since the new version of Swift 5.9 has been released. This is a major new release that adds an expressive macro system to the language and introduces support for integrating Swift into C++ codebases through bidirectional interoperability. It also introduces parameter packs, an improved expression evaluator while debugging, enhanced crash handling, Windows platform improvements.

Macros help developers reduce repetitive boilerplate and create more expressive libraries that can be distributed as a Swift package. The CompilerPluginSupport module enables defining macro targets. Macro targets allow authoring and distributing custom Swift macros as APIs in a library.