I have.

It's when you do

    const dir = "up"; // TS infers type "string"
    test(dir); // error

For mutable variables (let/var), you usually want TS to infer `string` in the first line. IMO the fact that they also infer `string` for constants is a design flaw, that I hope will one day be fixed.

They recently added a feature to make this less painful:

    const dir = "up" as const;
    test(dir); // works

That's the same as `as "up"` bit without having to duplicate the string.