syntax_data: {"ast_node_type":"variable","tokens":[{"end":60,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:             let alias_ty = relation.relate(a_data, b_data)?;
context_before:         (ty::Alias(a_kind, a_data), ty::Alias(b_kind, b_data)) => {
context_after:             assert_eq!(a_kind, b_kind);