narrowing in switch doesn't work with ambient enums

[zpdDG4gta8XKpMCd]

declare global {
    module g.m {
        enum E { A, B }
    }
}
declare var x: g.m.E;
declare function never(never: never): never;
function fn() {
    switch (x) {
        case g.m.E.A: return 1;
        case g.m.E.B: return 2;
        default: return never(x); // <-- x expected to be never, actual g.m.E
    }
}

[zpdDG4gta8XKpMCd]

might be related: #20375

[Goodwine]

The compiler is happy if you declare what possible numbers can these enum have.

module g.m {
  enum E { A = 3, B = 7}
}

Test code

I also found this to be annoying and I wish the compiler could at least do this for switches :(
I first thought this could be a bug on but I guess it's not angular/clutz#663

IIUC when this bug gets fixed, then it should be fixed for any kind of enums, not just numeric enums, right?