911799 - We need a cross-module manner of finding out which exceptions we are handling

Status: RESOLVED WONTFIX

(Core :: JavaScript Engine, defect)

Description

[David Teller [:Yoric] - still alive but not very active]

Consider the following code:

try {
  f();
} catch (ex if ex instanceof TypeError) {
  handleError(ex);
} catch (ex if ex instanceof StopIteration) {
  handleStopIteration();
}

At the moment, throwing a TypeError, StopIteration, etc. in f() may or may trigger the expected branch of the try/case depending on whether the error has been thrown from the same compartment.

While this is certainly a desirable property, it would be quite useful to have a way to determine whether a TypeError (respectively a StopIteration) has been thrown in f(), e.g. something along the lines of Array.isArray.

Comment 1

[Boris Zbarsky [:bzbarsky]]

Posted about this to public-script-coord, though maybe es-discuss is a better forum for it....

Comment 2

[Mark S. Miller]

You need another example to motivate this. StopIteration is dead.

Comment 3

[David Teller [:Yoric] - still alive but not very active]

(In reply to Mark S. Miller from comment #2)
> You need another example to motivate this. StopIteration is dead.

Is it? I haven't been informed.
Well, regardless of StopIteration, take a look at bug 908955 - we use the .name hack to find out whether an exception is a coding error, so as to report it eagerly. It works-ish, but that's very fragile.

Comment 4

[André Bargull [:anba]]

A related proposal to ecma-262 has been rejected [1], so let's resolve this stale bug as WONTFIX.

[1] "Builtins.typeOf() and Builtins.is()" at https://github.com/tc39/proposals/blob/master/inactive-proposals.md