TypeScript's type system is intentionally unsound in a handful of places- function parameters are bivariant, for example. I believe Flow is at least closer to b

TypeScript's type system is intentionally unsound in a handful of places- function parameters are bivariant, for example. I believe Flow is at least closer to being sound. I suspect switching from Flow to TypeScript would be relatively straightforward as far as the types go, but going the other direction would not.