{"ast_node_type":"other","tokens":[{"end":87,"kind":"keyword","start":0,"text":"//"}]}
                // We canonicalize placeholder regions as existentials in query inputs.
            ty::RePlaceholder(placeholder) => match self.canonicalize_mode {
                CanonicalizeMode::Input(_) => CanonicalVarKind::Region(ty::UniverseIndex::ROOT),