This is in preparation for a CL the removes @fields/@=fields canonical
names in favor of @getters/@setters and therefore needs stricter handling
of how duplicates and conflicts are emitted in the AST.
Change-Id: I87220a41c9777c94f9e9bce51ff5223fafdc738f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/180342
Commit-Queue: Johnni Winther <johnniwinther@google.com>
Reviewed-by: Dmitry Stefantsov <dmitryas@google.com>
Johnni Winther