I figured if I start using Flow I may as well go all the way. My previous setup was to have JSDoc and Closure compiler style (inline) type annotations everywher

I figured if I start using Flow I may as well go all the way. My previous setup was to have JSDoc and Closure compiler style (inline) type annotations everywhere. The IDE - WebStorm - picked up on that. I filed tons of tickets with Jetbrains and got more and more issues resolved over time, but with the latest Webstorm there were some regressions and it seemed like they had difficulties with all of this. For example, I kept getting suggestions for properties picked up in clearly impossible places, autocompletion for the JSDoc types stopped working lately, etc. So I had enough and started with Flow on one file, then two - then I spent a week converting everything to Flow. I actually found a few subtle bugs in my code, but also two or three minor ones in Flow (issues submitted). I also found clear limits for this type system, for example, when you clearly know 100% sure that a value cannot be undefined but Flow insists you add a type check before using the property because it does not follow your dynamic logic, only its types.