Added bool.hashCode patch.

Added bool.hashCode patch.

BUG: 7244
Committed: https://code.google.com/p/dart/source/detail?r=16011

[cshapiro, 2012-12-12 00:35:13]

lgtm

https://codereview.chromium.org/11557002/diff/1/runtime/lib/bool_patch.dart
File runtime/lib/bool_patch.dart (right):

https://codereview.chromium.org/11557002/diff/1/runtime/lib/bool_patch.dart#n...
runtime/lib/bool_patch.dart:12: // Object.equals is fine, since true and false
are singletons.
Presumably, this is defaulting to some sort of is-same-object equals method?  Is
there any harm in putting in an equals method?

[srdjan, 2012-12-12 00:55:25]

https://codereview.chromium.org/11557002/diff/1/runtime/lib/bool_patch.dart
File runtime/lib/bool_patch.dart (right):

https://codereview.chromium.org/11557002/diff/1/runtime/lib/bool_patch.dart#n...
runtime/lib/bool_patch.dart:12: // Object.equals is fine, since true and false
are singletons.
On 2012/12/12 00:35:13, cshapiro wrote:
> Presumably, this is defaulting to some sort of is-same-object equals method? 
Is
> there any harm in putting in an equals method?

Object's equal calls identical.

AFAIK, compiler has optimizations where it recognizes that equal was not
overriden, therefore I would not replicate code here.

[cshapiro, 2012-12-12 00:59:07]

Sounds like a good enough reason for me!

[sra1, 2012-12-12 01:23:22]

https://codereview.chromium.org/11557002/diff/6001/runtime/lib/bool_patch.dart
File runtime/lib/bool_patch.dart (right):

https://codereview.chromium.org/11557002/diff/6001/runtime/lib/bool_patch.dar...
runtime/lib/bool_patch.dart:10: return this ? 1231 : 1237;
These values are not different mod 2.  A small hash table with two slots will
have a collision for true and false.

[cshapiro, 2012-12-12 01:26:30]

That is only true if the hash code does not subsequently pass through a mixing
function.  Otherwise, the same will be true of hash tables with small fixnum
values.

[sra1, 2012-12-12 02:09:05]

On 2012/12/12 01:26:30, cshapiro wrote:
> That is only true if the hash code does not subsequently pass through a mixing
> function.  Otherwise, the same will be true of hash tables with small fixnum
> values.

Sure.  On the other hand, there is no mixing function in lib/core/map.dart.
But since _INITIAL_CAPACITY = 8 (huge IMO), the point is moot.