syntax_data: {"ast_node_type":"variable","tokens":[{"end":83,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let impl_trait_header = self.tcx().impl_trait_header(impl_def_id).unwrap();
context_before:     ) -> Normalized<'tcx, GenericArgsRef<'tcx>> {
context_after:         match self.match_impl(impl_def_id, impl_trait_header, obligation) {