Aliases for entries

[dnfield]

See flutter/flutter#24351

We redid a bunch of classes that were declared like this:

abstract class ReallyAMixin {
  factory ReallyAMixin._() => null;
  ...
}

To this:

mixin ReallyAMixin {
}

Which now is resulting in a new Dart doc link (...-mixin.html instead of ...-class.html), which is breaking external links. Is there some sensible way we could alias ReallyAMixin-class.html to ReallyAMixin-mixin.html? Obiviously for docs we control we should just update the links, but this might hurt things like old StackOverflow answers or blog posts.

/cc @gspencergoog @sfshaza2

[dnfield]

If there's no existing way, it might be nice to have something like:

/// {@alias abstract class ReallyAMixin}

Or perhaps some other top level file that control such things, for cases where types get renamed.

[jcollins-g]

I like the idea of a top level control file for this sort of thing. In the meantime, you could probably patch this particular case of it up in post-processing.

[guidezpl]

Related, #1346 would make this obsolete for type changes if it were generalized