syntax_data: {"ast_node_type":"variable","tokens":[{"end":49,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let variance = variances.get(i).unwrap();
context_before:     let params = iter::zip(a_arg.iter(), b_arg.iter()).enumerate().map(|(i, (a, b))| {
context_after:         let variance_info = if variance == ty::Invariant && fetch_ty_for_diag {