syntax_data: {"ast_node_type":"variable","tokens":[{"end":94,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:             let args = if let Some(variances) = cx.opt_alias_variances(a.kind(cx), a.def_id) {
context_before:             let cx = relation.cx();
context_after:                 relate_args_with_variances(