Add `ClassBody.members` and `EnumBody.constants`/`members` so callers
can access class and enum contents through the common body interfaces
instead of pattern matching on `BlockClassBody` and `BlockEnumBody`.
Implement empty node lists for empty class and enum bodies, update the
public API, and migrate analyzer, analysis_server, analyzer_plugin, and
linter code to use the new accessors directly. This removes the ad hoc
`members2` helper extensions and a large amount of repeated `tryCast`
and `switch` logic, making body traversal more uniform.
Change-Id: I51d75f2253c7e6f75efecae84bf0443ff5eb6788
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/488263
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Reviewed-by: Paul Berry <paulberry@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>
Konstantin Shcheglov
e655e9fd6c