Implementation issue for the generalized type alias feature

[eernstg]

[Edit Feb 2021: The implementation issue needs to be in the SDK repo, so we will use https://github.com/dart-lang/sdk/issues/44951 as the implementation issue for non-function type aliases. Deleted the check boxes below to avoid duplication and confusion.]

This issue is for tracking implementation of the generalized type alias feature:

Request issue: #66
Feature issue: #65
Main SDK tracking issue: dart-lang/sdk#44951

Feature specification:
https://github.com/dart-lang/language/blob/master/accepted/future-releases/generalized-typedef-2018/feature-specification.md

Implementation plan:
https://github.com/dart-lang/language/blob/master/accepted/future-releases/generalized-typedef-2018/implementation-plan.md

[List of tasks and check boxes deleted: See https://github.com/dart-lang/sdk/issues/44951]

[srawlins]

I think this needs another step, "Implementation in DartDoc".

[leafpetersen]

Added some missing things.

[srawlins]

I think there are some important missing items from the check list. Considering grok (now Kythe), Cider, and Angular are in Phase 0, these should probably be Phase 0:

• analysis_server core features (Go To Definition, Find References, Sort Declarations)
• analysis_server auto-complete (name, constructors)
• analyzer: include generalized type alias test cases in existing diagnostic tests (invalid assignment, type alias application in places like catch, extends, constructor redirection, unnecessary cast with as, unused type aliases, invalid access to a @protected constructor, member, etc)
• linter: consider existing lints; add test cases and application to generalized type alias

[eernstg]

Thanks, added those items to the list.

[eernstg]

Closing this issue, the new implementation issue for this feature is dart-lang/sdk#44951.