tree c23259cfe84dfba7cbd3cc95623eedf9e55d87de
parent 265ecc7488d14699febdafc01445227c0d1098c7
author Paul Berry <paulberry@google.com> 1603215904 +0000
committer commit-bot@chromium.org <commit-bot@chromium.org> 1603215904 +0000

Add special case migration logic for iterator methods.

This logic allows us to migrate code like this:

    int firstEven(Iterable<int> values)
        => values.firstWhere((i) => i.isEven, orElse: () => null);

Into:

    import 'package:collection/collection.dart' show IterableExtension;

    int? firstEven(Iterable<int> values)
        => values.firstWhereOrNull((i) => i.isEven);

Rather than the default behavior, which would migrate it to:

    int? firsteven(Iterable<int?> values)
        => values.firstWhere((i) => i!.isEven, orElse: () => null);

(The new migration is far superior because it doesn't require the
input iterable to accept null).

This functionality is disabled at the moment, because:
- The changes it makes don't show up properly in the web preview.
- The pubspec is not yet properly updated.

I will address these issues in follow-up CLs and then enable the
feature.

Change-Id: I96f3b12d682c586631920b38406bad6aa3f4789e
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/168500
Reviewed-by: Samuel Rawlins <srawlins@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>