Collection should have a default class (implementation)

[DartBot]

This issue was originally filed by @seaneagan

---

Collection represents a "multi set" or "bag", for which implementations do exist, thus it should have a default implementation just like almost every other core library interface. It should also have a copy constructor:

Collection.from(Iterable<E> other);

A no arg constructor does not make sense, so long as Collection does not contain any mutators. Java's Collection interface has optional mutators.

[dgrove]

Removed Type-Defect label.
Added Type-Enhancement, Area-Library, Triaged labels.

[lrhn]

The Collection class no longer exists.

An unordered multiset is an interesting idea, but not so often needed that we plan to add it to the core library.

---

Added NotPlanned label.

[lrhn]

The Collection class no longer exists.

An unordered multiset is an interesting idea, but not so often needed that we plan to add it to the core library.