Fix for the js-interop crash

Fix for the js-interop crash
BUG=https://github.com/dart-lang/sdk/issues/24974

[Siggi Cherem (dart-lang), 2015-11-20 00:06:37]

Patchset #1 (id:1) has been deleted

[Siggi Cherem (dart-lang), 2015-11-20 00:07:28]

Patchset #1 (id:20001) has been deleted

[Siggi Cherem (dart-lang), 2015-11-20 00:08:11]

sigmund@google.com changed reviewers:
+ sra@google.com

[Jacob, 2015-11-20 00:50:34]

jacobr@google.com changed reviewers:
+ jacobr@google.com

[Jacob, 2015-11-20 00:50:34]

Siggi. Thanks so much for taking a look at this. A few drive by questions about
what the behavior is with this fix.

https://codereview.chromium.org/1458313002/diff/40001/pkg/compiler/lib/src/ss...
File pkg/compiler/lib/src/ssa/builder.dart (right):

https://codereview.chromium.org/1458313002/diff/40001/pkg/compiler/lib/src/ss...
pkg/compiler/lib/src/ssa/builder.dart:5947: // we want.
I thought in resolution we were treating each of these methods as returning any
js class. Perhaps we should fix the bug in that direction instead of here?

[Siggi Cherem (dart-lang), 2015-11-20 01:06:18]

https://codereview.chromium.org/1458313002/diff/40001/pkg/compiler/lib/src/ss...
File pkg/compiler/lib/src/ssa/builder.dart (right):

https://codereview.chromium.org/1458313002/diff/40001/pkg/compiler/lib/src/ss...
pkg/compiler/lib/src/ssa/builder.dart:5947: // we want.
On 2015/11/20 00:50:34, Jacob wrote:
> I thought in resolution we were treating each of these methods as returning
any
> js class. Perhaps we should fix the bug in that direction instead of here? 

Good question - we have been debating about this too. 

I like that it would make things safer, but we also were worried that if we do
that we will include everything that extends from JavaScriptObject pretty
quickly.

I just realized though that by including JavaScriptObject, you still don't bring
anything from the DOM (since those are extending directly from Interceptor) -
Stephen, if that's the case, does that lessen your worry?

[Siggi Cherem (dart-lang), 2015-11-20 01:56:15]

https://codereview.chromium.org/1458313002/diff/40001/pkg/compiler/lib/src/ss...
File pkg/compiler/lib/src/ssa/builder.dart (right):

https://codereview.chromium.org/1458313002/diff/40001/pkg/compiler/lib/src/ss...
pkg/compiler/lib/src/ssa/builder.dart:5947: // we want.
On 2015/11/20 01:06:17, Siggi Cherem (dart-lang) wrote:
> On 2015/11/20 00:50:34, Jacob wrote:
> > I thought in resolution we were treating each of these methods as returning
> any
> > js class. Perhaps we should fix the bug in that direction instead of here? 
> 
> Good question - we have been debating about this too. 
> 
> I like that it would make things safer, but we also were worried that if we do
> that we will include everything that extends from JavaScriptObject pretty
> quickly.
> 
> I just realized though that by including JavaScriptObject, you still don't
bring
> anything from the DOM (since those are extending directly from Interceptor) -
> Stephen, if that's the case, does that lessen your worry? 

I made a CL with the alternative approach, I'm still not convinced though. Here
is the link https://codereview.chromium.org/1457383003/.

If we really want tree-shaking, we could expose an interop identify function
that enables side-casts without the tree-shaking cost.

[sra1, 2015-11-20 19:01:56]

lgtm