{"ast_node_type":"other","tokens":[{"end":57,"kind":"keyword","start":0,"text":"//"}]}
                    // the call to `all` will fail below.
                    // so just map to `None` here if there are bound vars, ensuring that
                    approx_env_bounds.iter().map(|b| b.map_bound(|b| b.1).no_bound_vars()),