> An API call, reading a file, calling less well-behaved libraries or making some system calls can all result in objects that pass compile-time checks but will cause a runtime exception or unexpected behavior.

Seems crazy to me to have this attitude, the whole point of typescript (and indeed many other languages with type checkers) is that we can leave out unecessary checks if proven by the compiler. The burden of compatibility is on the caller to ensure they supply correct values