tree 80c5c41b9dca605f162f815fc439962460006b9b
parent fd590c54c2c858c519ae2c98cf810935d985f7f3
author Lasse R.H. Nielsen <lrn@google.com> 1656080489 +0000
committer Commit Bot <commit-bot@chromium.org> 1656080489 +0000

Deprecate `BidirectionalIterator`.

There is only one use of it in the SDK, `RuneIterator`,
one use of it outside, `TreeSet` from `package:quiver`,
and one known use in Google internal code.

There are other bi-directional iteration interfaces,
like `CharacterRange` from `package:characters`,
which can move a cursor in two directions,
but which didn't loke the `movePrevious` name and therefore
are not `BidirectionalIterator`s.
(There is also a Google internal class which mentions explicitly
why they're not `BidirectionalIterator`.)

There is no real need for this "shared" interface.
It doesn't carry its own weight.
We have no abstractions which work on the *interface*,
only code that works on one specific concrete implementation.

I'd recommend:
* `quiver` introduce a `TreeSetIterator` for their use-case
  (the actual class has more public members than `BidirectionalIterator`,
  which cannot be accessed through the declared type.)
* the Google internal code introduces its own interface
  (which is just `Iterable` + `movePrevious`.
* The SDK will just make `RuneIterator` not implement
  `BidirectionalIterator` at some (breaking) point.
  Maybe just when we remove the type.


FLUTTER: Needs to land https://github.com/flutter/flutter/pull/106471 before merging this CL into Flutter.

Change-Id: Iaaa6b0c428d30eb3b68898c077d265ac0a622805
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/249486
Reviewed-by: Nate Bosch <nbosch@google.com>
Commit-Queue: Lasse Nielsen <lrn@google.com>