syntax_data: {"ast_node_type":"other","tokens":[{"end":67,"kind":"keyword","start":0,"text":"(specializing_impl_def_id,"}]}
source_snippet:     (specializing_impl_def_id, parent_impl_def_id): (DefId, DefId),
context_before:     tcx: TyCtxt<'_>,
context_after: ) -> bool {