Does such a thing exist for Flow? Could it? If it did that would go a lot further to push me to flow than that it just catches more errors. I get huge productivity gains from my editor helping me with API completions etc...
Aside: I tend to do much more with higher order functions than with classes, so Typescript and the like really don't excite me very much. I'm happier to skip the whole transpile and source-map shuffle. Also, I tend to put at least partial JSDoc comments on just about everything, so that an open documentation panel explains things as I move the cursor down the file. Any type annotation is also shown on the function names/params in the structure tree browser.
Finally, autocomplete is not as useful when not using "Enterprise" style naming conventions. E.g. - "inv_acct.load()" vs "checkoutInvoicePayableAccount.asynchronousLazyLoadFromRemoteServer()". Hopefully, between context and comments, such ridiculous names aren't really necesary - like, how many "account" type values do you have floating around in the current scope/context???
[0]: http://ternjs.net/