syntax_data: {"ast_node_type":"other","tokens":[{"end":62,"kind":"keyword","start":0,"text":"if"}]}
source_snippet:         if !self.seen.insert(alias_ty.def_id.expect_local()) {
context_before:     fn visit_opaque_ty(&mut self, alias_ty: ty::AliasTy<'tcx>) {
context_after:             return;