Work towards #60635
In this change, we rework the AnalysisErrorListener deprecation to
better support users who have their own class that implements
AnalysisErrorListener. This change introduces a sealed supertype,
DiagnosticOrErrorListener, with the old implementation,
AnalysisErrorListener, and the new implementation, DiagnosticListener,
as its sole direct subclasses. Users who have implemented
AnalysisErrorListener should be able to instead implement
DiagnosticListener, and their class is an acceptable instance of
DiagnosticOrErrorListener, wherever that is needed.
In a breaking change we can drop AnalysisErrorListener and deprecate
DiagnosticOrErrorListener, and in the next breaking change, we can drop
DiagnosticOrErrorListener.
For reference, see the first API difference when deprecating AnalysisErrorListener and introducing DiagnosticListener: https://github.com/dart-lang/sdk/commit/903d77cc8229972a424941dcb7b7b79741e833eb#diff-dec15868961d7eadcd009f49d129bebcdb747aaa8dbfde5f5a08884e0cf11e32
Change-Id: I3ccf11d54b41fbca98d020d89978d250c16b4c04
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/436480
Reviewed-by: Paul Berry <paulberry@google.com>
Commit-Queue: Samuel Rawlins <srawlins@google.com>
Sam Rawlins
ee69f45a1f