{"ast_node_type":"other","tokens":[{"end":99,"kind":"keyword","start":0,"text":"|this:"}]}
            |this: &Self, n| this.is_keyword_ahead(n, &[kw::Mut]) && is_isolated_self(this, n + 1);
        let is_isolated_mut_self =
        // Is `pin mut self` `n` tokens ahead?