> Right but the instant you annotate a, it knows and gives you a good error unless you annotate it with :any > Neither Flow nor Typescript can actually projec

> Right but the instant you annotate a, it knows and gives you a good error unless you annotate it with :any > Neither Flow nor Typescript can actually project soundness onto Javascript. Mentioning that is a giant red herring. So long as compatibility with base ecmascript is offered there is code which cannot be verified as sound or unsound without the execution context at hand. I don't see how you can say that. Flow can absolutely create a 'sound' type system on top of javascript. Elm transpiles to javascript and has a sound type system that doesn't produce runtime errors. Flow has different syntax but it restricts the type system in a similar way.