It has been living in RootDatabase::apply_change almost a year by now.
AnalysisChange
Change
(The type was renamed/moved in 8716c4cec3a05ba891b20b5f28df69d925b913ad)
This seems like a better factoring logically; ideally, clients shouldn't touch `set_` methods of the database directly. Additionally, I think this should remove the unfortunate duplication in fixture code.