Fix source spans hashcode implementation

Fix source spans hashcode implementation

R=justinfagnani@google.com

Committed: https://code.google.com/p/dart/source/detail?r=25514

[Siggi Cherem (dart-lang), 2013-07-26 00:22:31]

This addresses the warnings we saw with dart2js.

[justinfagnani, 2013-07-26 00:44:22]

lgtm

https://codereview.chromium.org/20600002/diff/2001/pkg/source_maps/lib/span.dart
File pkg/source_maps/lib/span.dart (right):

https://codereview.chromium.org/20600002/diff/2001/pkg/source_maps/lib/span.d...
pkg/source_maps/lib/span.dart:72: int get hashCode => sourceUrl.hashCode +
start.offset + (31 * length);
length includes information from start.offset already, why not just end.offset?

[Siggi Cherem (dart-lang), 2013-07-26 00:50:12]

thanks

https://codereview.chromium.org/20600002/diff/2001/pkg/source_maps/lib/span.dart
File pkg/source_maps/lib/span.dart (right):

https://codereview.chromium.org/20600002/diff/2001/pkg/source_maps/lib/span.d...
pkg/source_maps/lib/span.dart:72: int get hashCode => sourceUrl.hashCode +
start.offset + (31 * length);
On 2013/07/26 00:44:22, justinfagnani wrote:
> length includes information from start.offset already, why not just
end.offset?

I could argue the opposite: end.offset is always > start, so only length is a
relevant piece =)

I think it's ok either way, but I'm afraid of offsets*31 being too large, so
just encoding the length might be better.

[Siggi Cherem (dart-lang), 2013-07-26 00:50:37]

Committed patchset #2 manually as r25514 (presubmit successful).