Typescript compiler architecture is quite different to flows. Typescript was written from the get go to provide really fast and accurate intellisense to IDEs. The newer refactoring powers are super nice too. Most ides just ask typescripts language service “hey, my user’s cursor is here, what should I show for code completion?”

I think that’s what differentiates TS from flow. Typescript thought about the whole developers workflow while flow is just a compile time typechecker.