{"ast_node_type":"variable","tokens":[{"end":89,"kind":"keyword","start":0,"text":"let"}]}
                    let a_fields = a_def.variants().iter().flat_map(|v| v.fields.iter());
                    // Grab a flattened representation of all fields.
                    let b_fields = b_def.variants().iter().flat_map(|v| v.fields.iter());