DartDocs are missing from auto-import extension members

[DanTup]

Related to #4143, we're not finding the element to look up the docs.

[robertherber]

Need this badly! :) What do we need to do to enable this? Docs would be great but probably this should be default behaviour?

[DanTup]

@robertherber this title might have been a little ambiguous. This wasn't about documenting how to use this, the problem is that the DartDocs are missing from the auto-import extension members. Auto-imports of extension members is enabled by default, however they'll only show up in SDKs that include the fix at dart-lang/sdk@1c8bb85 (which is not the current stable releases, although it's likely in the current beta releases). I would expect the next major stable releases of Dart/Flutter include that, so they should show up automatically (although, without dartdocs in the details pane until I've fixed this issue).

[robertherber]

Aah, gotcha 👍 Being used to the smoothness of TypeScript I feel so handicapped without this. Thanks for your work on it!

[DanTup]

This was fixed along with #3787 in dart-lang/sdk@fc9581d:

Requires an SDK release to show up.