[_nub3]

so when the transpiled typescript is used by the next door 'i know javascript'-1337-hax0r and is fed with some arbitrary data, your wonderful conceptual typed world does not exist anymore and that wonderful code eventually fails, because a simple sanity check was too much.

[nawgz]

This seems like a pretty bad-faith comment. This user is not proposing they're building a library, and if they were, it would be reasonable to assume they also would assume to extend the IO protections they discuss to the "IO" points of library - external user input.

Additionally, I think it is safe to say a JavaScript user who grabs a TypeScript library and uses it without importing the types to be misusing the library. Imagine if someone were to have a whole test suite was available to them while they develop, and they opted to never run it. And then they complained to you the tests didn't catch any errors. You would look at them sideways, no? Misuse and poor application (human error) are of course things TypeScript cannot solve.