Hazel: A live functional programming environment featuring typed holes

This is semi-related to one of the killer features of Eclipse that never really made it into any large-scale systems: the ability to run incomplete or broken code. The Eclipse Compiler for Java had a special feature that it could generate bytecode for nearly any file, including those that were utterly broken. It would mostly work, and you could incrementally work on unit tests alongside the code being developed. It was honestly one of the most productive environments I ever…

Great! I'm convinced designing a functional language and IDE side-by-side will result in greatly improved ergonomics. The Hazel playground breaks for me (Safari), but the direction looks promising. One of my own (nearly abandoned) toy projects is something similar. It's not easy — at least to me it wasn't — to design a language that is forgiving on as many aspects as possible. Both syntactically and semantically. Turning every error into a warning during development time and keep the impact…