Implementation tracking/meta Issue for Super Mixins

[JekCharlsonYu]

This issue is for tracking implementation of Super Mixins:

• Request issue: Mixins with super-calls. #6
• Feature issue: Mixin declaration allowing super-invocations. #7
• Feature specification:
  https://github.com/dart-lang/language/blob/master/accepted/2.1/super-mixins/feature-specification.md
• Implementation plan: https://github.com/dart-lang/language/blob/master/accepted/2.1/super-mixins/implementation-plan.md

TODO/Dependencies

• Discussion and feedback
  • General discussion: Mixin declaration allowing super-invocations. #7
  • Breaking change: Discussion of cost of super mixin breaking change #10
  • Syntax: Finalize on vs requires for super mixins #9
• Implementation team sign off (this issue):

P0 Blockers

• Issue for language tests
• Issue for implementation in Analyzer
  • Mixin inference
• Issue for implementation in CFE/Kernel
• Issue for implementation in VM
• Issue for implementation in Intellij
• Issue for implementation in Grok
• Issue for implementation in Dartfmt
• Issue for implementation in Documentation/Website
• Issue for linter
• Issue for migration to flutter (@yjbanov)
• Issue for updating documentation (TODO)
• Issue for implementation in Dartdoc flutter

P1 Blockers

• Issue for co19 tests
• Issue for implementation in dart2js
• Issue for implementation in DDC

Non-Blockers

• Issue for CodeMirror
• Issue for implementation in Dartpad
• Misc syntax:
  • Dart-atom: https://github.com/dart-atom/dart/tree/master/grammars
  • github markdown

**Based on meta issue template

[leafpetersen]

I have added an initial cut on an implementation plan here. If you are an assignee of this bug, please review the implementation plan and the proposal itself (if needed), and provide any feedback and comments. If you see no technical issues with the proposal, and believe that the implementation plan is reasonable, please LGTM the plan here in the issue tracker.

@a-siva for VM
@kmillikin for CFE
@munificent for dartfmt
@jwren for grok, intellij
@jcollins-g for dartdoc
@bwilkerson for analyzer
@devoncarew for dartpad
@kwalrath for documentation
@vsmenon for DDC
@johnniwinther for dart2js
@Hixie for flutter migration

cc @JekCharlsonYu @dgrove @lrhn @rakudrama @sigmundch

[leafpetersen]

cc @mit-mit @timsneath @kevmoo @sethladd @filiph

[leafpetersen]

Hmm. I don't seem to be able to assign this issue to most of you, but if you're listed above, please take a look and sign off.

[kevmoo]

I guess you could have made a "sign-off" PR and have us all approve.

LGTM

[bwilkerson]

lgtm

[Hixie]

I believe @yjbanov has volunteered to do the Flutter migration.

[Hixie]

For Flutter our usual policy is to only allow one syntax at a time, and to require lints to force us onto the new syntax if we change the allowed syntax. I would feel more comfortable if Flutter was moved to the new syntax in phase 3 after the lint has been made available in phase 2. LGTM assuming that we do the migration on Flutter's side after we've got a lint to enforce it.

[leafpetersen]

@Hixie I'm happy to handle the migration however works best for you. My worry was/is this: I can't give you a lint to change a definition of a super mixin to the new syntax, because I have no way of knowing what things are super mixins until they are used. So the lint will fire on uses, not definitions.

So I think it would be bad to land the analyzer hint that tells you are using an old style super mixin before we fix flutter. Otherwise users will see hints telling them to fix flutter... :)

But we should be able to land them (essentially) simultaneously: migrate flutter to the new syntax and roll in a new analyzer with the hint. Or maybe we can roll in the new analyzer, but initially only turn on the hint inside of flutter?

Does this seem reasonable?

[Hixie]

What we normally do is implement the lint, roll that, then turn on the lint and fix the bugs it finds at the same time (in a separate later PR).

[devoncarew]

Based on the above discussion, we should also call out above the necessary work in the linter.