I love Swift for iOS and macOS apps and I want to use it for everything else on my Mac. So I made a prototype that I call "Swift Light":
I posted a demo video here » https://underplot.com/light
This is not an Xcode alternative — Xcode is obviously aready really good at what it does, also it's first-party and it's free.
Swift Light is an alternative of you having to use scripts from the command line and fall back on weird languages to do so. It could be really good for local automation, experiments, and highly specialized computations like statistical work, graphing, and more.
Please let me know what you think once you've watched the video, I'm curious to get everyone's thoughts!