Topic on Talk:Stable interface policy

Class aliases are basically deprecated names for classes. I think that the deprecation process should apply for them, so it is clear when we can remove them. But there is no good way to emit deprecation warnings...

For things that can't be warned about, we generally do a 'best efforts' approach, looking through codebase through Code Search and determining how likely it is that people will be disrupted (and writing patches to migrate where the codebases are current enough to pass CI). Not sure that this needs formalisation?