Duplicated object in Set

[DartBot]

This issue was originally filed by [email protected]

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What steps will reproduce the problem?

Set mapSet = new Set();
mapSet.add({'map item': 'First Item'});
mapSet.add({'map item': 'Second Item'});
mapSet.add({'map item': 'Third Item'});
mapSet.add({'map item': 'Third Item'});

What is the expected output? What do you see instead?

Expected mapSet to be {{map item: First Item}, {map item: Second Item}, {map item: Third Item}}
mapSet is instead {{map item: First Item}, {map item: Second Item}, {map item: Third Item}, {map item: Third Item}}

What version of the product are you using? On what operating system?
Dart VM version: 0.8.5.1_r28990 (Tue Oct 22 05:03:51 2013) on "macos_x64"

Additional:
Summary line from http://api.dartlang.org/docs/releases/latest/dart_core/Set.html
"A collection of objects in which each object can occur only once."

[dgrove]

Added Area-Library, Triaged labels.

[floitschG]

Two different map literals are not the same object. That is:
identical({'map item': 'foo'}, {'map item': 'foo'}); // returns false.
Furthermore sets use identical for their "==operator". This means that:
({'map item': 'foo'}) == ({'map item': 'foo'}); // returns false.

The default implementation of Set uses ==operator for determining if two elements are equal.

If you prefer a different equality you have to provide the equality and hashcode methods:
http://api.dartlang.org/docs/releases/latest/dart_collection/LinkedHashSet.html#

You can also use the collection_helpers package which provides some helpers for deep equality. I'm not sure it is already publicly available, but here is the review: https://codereview.chromium.org/23567044/

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Added Duplicate label.
Marked as being merged into #10391.