Implement the Q1 2021 small features release in external syntax highlighting tools.

[leafpetersen]

Implementation issue for syntax highlighting associated with this set of features.

• Issue for implementation in Github syntax highlighting:
• Issue for copying Github grammar for use with VS Code:
• Issue for highlight.js support (api.dart.dev, api.pub.dev, Dartdoc):
• Issue for codemirror support (Cider, dartpad):

cc @devoncarew @franklinyow

[lrhn]

The Github syntax highlighting appears to be trivially satisfied:

@Annot<T Function<T>(T)>()
void main() {
  var c = Annot<T Function<T>(T)>();
  c >> 2;
  c >>> 3;
  c >>>> 4;
}
class Annot<T extends T Function<T>(T)> {
  const Annot();
  int operator >>>>(int x) => x;
  int operator >>>(int x) => x;
  int operator >>(int x) => x;
}

It's not complicated enough to recognize that type arguments belong to an annotation, or that they can't be generic function types, so those already worked like any other type argument.
The >>> operator is already recognized, likely because it just recognizes any sequence of operator characters.

[devoncarew]

I believe we're good from the POV of codemirror as well; this is from dartpad:

[devoncarew]

@srawlins - do you mind confirming that highlight.js is good as is (doesn't need any changes)?

[srawlins]

Agree.