instanceof Error typeguard not functioning

[basarat]

Wonder if this is something that should work. I think it should:

    try {
         throw new Error('awesome');
    } catch (ex) {
        if (ex instanceof Error) {
            console.log(ex.foo);  // compiles. Should be error
        }
    }

The reason is that ex is still of type any. I suspect its in the spec that instanceof guard will not work on type any (I haven't checked).

Would be great if we could have this though.

[RyanCavanaugh]

See #1426. We do not narrow values of type any.

The first version of type guards did narrow any values, but there was too much code in the wild that did stuff like

var x: any; // x is a string or an HTML element I know is an image
if(x instanceof HTMLElement) {
  x.width = 100;
}

[basarat]

@RyanCavanaugh sure its #1425 ?

[RyanCavanaugh]

Typo'd and updated, meant #1426