Map interface should implement iterator() getter for compat with ES Map

[DartBot]

This issue was originally filed by caitpot...@gmail.com

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ES includes a default iterator for Map classes, https://people.mozilla.org/~jorendorff/es6-draft.html#sec-map.prototype-@@iterator --- making them useful in for...of loops.

For code which transpiles to dart (such as https://github.com/angular/angular), it would be useful if we could trust that classes which are iterable in ES are also iterable in Dart.

This would mean exposing an entries() method on Map, and returning the value of entries() as the default iterator for the object.

Is there some reason why this was not done to begin with? The method should still be overridable in subclasses, if needed.

[iposva-google]

Added Area-Library, Library-Core, Triaged labels.

[lrhn]

Removed Type-Defect label.
Added Type-Enhancement label.

[lrhn]

We are unlikely to change the Map interface at this point.

[DartBot]

This comment was originally written by @seaneagan

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This is another duplicate (at least the 4th one) of issue #7088. Issue #16117 as well. Clearly this is a much-desired feature. There has been no comment yet from the dart team on issue #7088.

[DartBot]

This comment was originally written by caitpotter8...@gmail.com

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Ah, my duplicate-finding skills on code.google.com are even worse than they are on github =)

We can work around this in angular if it's not provided by the standard library --- but it would be so much better (not just for Angular, but for everyone) if the Map interface were extended to include this.

However, lrn@ indicates that Map is likely to be crippled forever, so it may not come to pass. That would be a pity.

[lrhn]

Added Duplicate label.
Marked as being merged into #7088.