I have to admit I have strong preference to available editor/IDE or REPL rather than language itself. I can adapt on any language if the language has enough fe

I have to admit I have strong preference to available editor/IDE or REPL rather than language itself. I can adapt on any language if the language has enough feature set, but lack of fine toolset support is unacceptable. For instance, these features are highly expected 1. Syntax and scope based accurate auto-completion. 2. REPL debugger with accurate break-point and stepping. These features are optional but make it awesome if exists. 3. Fully featured REPL. 4. A lot of proven libraries. 5. Exceptional linguistic features. 6. Fast build - compiled or interpreted for fast iteration. 7. ... Of course, the language itself needs to be designed to support those toolset features.