syntax_data: {"ast_node_type":"variable","tokens":[{"end":47,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let self_ty = tcx.type_of(impl_def_id);
context_before:         let tcx = self.tcx();
context_after:         let impl_trait_ref = tcx.impl_trait_ref(impl_def_id);