If you think of languages like tools I find Haskell particularly productive. The type checker gives me a whole program view of every branch and I can interactiv

If you think of languages like tools I find Haskell particularly productive. The type checker gives me a whole program view of every branch and I can interactively query my program thanks to strong inference and good tooling. Mastering a good emacs setup has boosted my productivity with git and having OS-agnostic tooling for linting, debugging, shell, document publishing, email, etc.