No, I'm not. You're way overthinking this and your attitude is weirdly gatekeepy. I'm asking TypeScript to implement a shortcut feature for the tedious, boilerplate code we already write to use type guards to inspect objects from APIs before passing them on.
I'm not sure where the "gatekeeping" accusation comes from. In your original comment, you wrote:
> There are a number of ways that TypeScript's type-checking can be subverted at runtime, ... As a developer, in the case of an API change that violated my assumptions, I would personally prefer my applications to fail-hard at the point of the API call
I interpreted that to mean that you would prefer TypeScript's type system to be sound: If a function expects a Foo, you want a guarantee that you'll never get into the body of the function at runtime with an argument whose type isn't Foo.
I can understand that that seems like a fairly simple request. But when you dig into soundness, you discover that it is anything but. Optionally-typed languages like TypeScript are unsound by design because soundness is a difficult requirement with very severe trade-offs around interop, runtime performance, and usability. Making TypeScript sound would give you a language that felt very little like TypeScript does today.
