I take runtime pattern matching over TypeScript any day of the week, I work with data across boundaries, compile time checking means very little to me (and I'm sick and tired of the "await request.json() as SomeTypeThatMostDefinitelyIsNotTheRightOneButMakesForFancyAutoComplete;" that seems to riddle every TS code base). Sure, you can add runtime dependencies with the additional code bloat to have it runtime check types with TypeScript too, but you still don't get any fault tolerance, and you have to write explicit code to handle errors that according to the type shouldn't exist.