Typescript is great, but it is ultimately a gradually typed language that is built around compiling to Javascript, and that has extensive interaction with untyp

Typescript is great, but it is ultimately a gradually typed language that is built around compiling to Javascript, and that has extensive interaction with untyped Javascript code. You often end up with obscure issues that a good type system should prevent. Maybe because the third party typings for a package are faulty or incomplete, maybe because the compiler just gave up on a complex expression and fell back to any, or because the developer just gave up and used `as any`. Typescript is also really constrained by keeping JS compatibility. A prime example is the lack of real sumtypes. Instead you have to use objects with a string tag and do if/switch on that tag to disambiguate the concrete type, which is incredibly awkward when compared to proper compiler sum type support. I'd much rather use Typescript than Javascript, but it's far from perfect.