At least on recent trunk, FieldDecl::getParent() does
and I noticed some plugin calling it crashing with a failed assertion
(isa<X>(Val) && "cast<Ty>() argument of incompatible type!")
when getDeclContext() happened to be an ObjCInterfaceDecl.
Is FieldDecl::getParent() known to only be callable under certain circumstances (i.e., the plugin broken), or is something else broken?