syntax_data: {"ast_node_type":"other","tokens":[{"end":31,"kind":"keyword","start":0,"text":"target_trait_def_id:"}]}
source_snippet:     target_trait_def_id: DefId,
context_before:     source_trait_ref: ty::PolyTraitRef<'tcx>,
context_after: ) -> Vec<ty::PolyTraitRef<'tcx>> {