Consider this layout:

lib/
  a.dart (which exports b.dart)
  b.dart

We would like the names from b.dart, which appear as part of a.dart, to linked to from b.dart (instead of appearing as they come from a.dart).

Today, the names from b.dart appear (in the URL) as if they are part of a.dart. Which is mostly true, because a.dart exports b.dart. But this is confusing to developers when a.dart's export of b.dart is simply a convenience for developers.