syntax_data: {"ast_node_type":"variable","tokens":[{"end":54,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let arg = self.typing_env.as_query_input(arg);
context_before:     ) -> ty::GenericArg<'tcx> {
context_after:         self.tcx.try_normalize_generic_arg_after_erasing_regions(arg).unwrap_or_else(|_| {