{"ast_node_type":"variable","tokens":[{"end":79,"kind":"keyword","start":0,"text":"let"}]}
    let caller_mentioned_items = caller_body.mentioned_items.as_mut().unwrap();
    let callee_item = MentionedItem::Fn(func.ty(caller_body, tcx));
    if let Some(idx) = caller_mentioned_items.iter().position(|item| item.node == callee_item) {