Implement Extension Type Feature

[itsjustkevin]

Extension Type feature

Description

Implementation issue for https://github.com/dart-lang/language/issues/2727, extension type; a special kind of type that wraps an existing type into a new static type, without the overhead of a traditional class.

References

• Feature Spec
• Project
• Test Tracking Sheet

Work Items

• [x] https://github.com/dart-lang/language/issues/2420
• [ ] https://github.com/dart-lang/sdk/issues/49730
• [x] https://github.com/dart-lang/co19/issues/1400
• [x] https://github.com/dart-lang/sdk/issues/49731
• [ ] https://github.com/dart-lang/sdk/issues/49732
• [ ] https://github.com/dart-lang/sdk/issues/49733
• [ ] https://github.com/dart-lang/sdk/issues/49734
• [ ] https://github.com/dart-lang/sdk/issues/49735
• [ ] https://github.com/dart-lang/sdk/issues/49736
• [x] https://github.com/dart-lang/sdk/issues/49737
• [x] https://github.com/dart-lang/sdk/issues/49738
• [ ] https://github.com/dart-lang/sdk/issues/49739
• [ ] https://github.com/dart-lang/sdk/issues/49740
• [ ] https://github.com/dart-lang/sdk/issues/49741
• [ ] https://github.com/dart-lang/dart_style/issues/1129
• [x] https://github.com/dart-lang/dartdoc/issues/3123
• [ ] https://github.com/dart-lang/sdk/issues/49742
• [ ] https://github.com/dart-lang/sdk/issues/49743
• [ ] https://github.com/dart-lang/sdk/issues/49744
• [ ] https://github.com/dart-lang/sdk/issues/49745
• [x] https://github.com/dart-lang/site-www/issues/4177
• [x] https://github.com/dart-lang/sdk/issues/49746
• [x] https://github.com/dart-lang/sdk/issues/49747
• [ ] https://github.com/dart-lang/linter/issues/3625

[itsjustkevin]

CC: @leafpetersen @kevmoo @sigmundch

[eernstg]

Note that the mechanism is very likely being renamed to 'extension type', cf. https://github.com/dart-lang/language/pull/3182.

[mit-mit]

Updating; the construct has indeed been renamed.