Set.add returns true if item has been added, otherwise false

Set.add returns true if item has been added, otherwise false

BUG= https://code.google.com/p/dart/issues/detail?id=3546
R=floitsch@google.com

Committed: https://code.google.com/p/dart/source/detail?r=28863

[Lasse Reichstein Nielsen, 2013-10-08 12:35:03]

I want another pair of eyes on this before accepting it (it is a breaking change
of the Set interface for anyone already implementing Set), so comments are
tentative on the change being accepted - i.e., don't start fixing it if we
decide not to do the change anyway.

With that in mind: There are at least two more implementations of Set:
CssClassSet in dart:html and UnmodifiableSetView in pkg/unmodifiable_collection,
which should also be changed to have return type "bool".

https://codereview.chromium.org/26280002/diff/6001/sdk/lib/core/set.dart
File sdk/lib/core/set.dart (right):

https://codereview.chromium.org/26280002/diff/6001/sdk/lib/core/set.dart#newc...
sdk/lib/core/set.dart:56: * Adds [value] into the set. Returns `true` if [value]
was added to the set.
Put "Returns ..." sentence at the end of the dartdoc as a separate paragraph.

The structure we aim for (more or less, it's more of a guideline than a hard
rule) is:

/**
 * Single sentence description.
 *
 * More elaborate description, if necessary.
 *
 * Meaning of, and restrictions on, parameters. May be intermixed
 * with description above.
 *
 * Result description, starting with "Returns ..".
 *
 * If necessary, exception description starting with "Throws"
 */

[kevmoo-old, 2013-10-09 18:14:54]

Friendly ping for "another pair of eyes".

Runtime cost is trivial -- quite useful in a number of context.

[floitsch, 2013-10-10 09:35:25]

LGTM once Lasse's comments are addressed.

[kevmoo-old, 2013-10-18 17:24:41]

Committed patchset #7 manually as r28863 (presubmit successful).