syntax_data: {"ast_node_type":"variable","tokens":[{"end":79,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let variance_info = if variance == ty::Invariant && fetch_ty_for_diag {
context_before:         let variance = variances.get(i).unwrap();
context_after:             let ty = *cached_ty.get_or_insert_with(|| cx.type_of(ty_def_id).instantiate(cx, a_arg));