{"ast_node_type":"variable","tokens":[{"end":88,"kind":"keyword","start":0,"text":"let"}]}
        let begin_ptr = self.bytes.as_mut_ptr().wrapping_add(range.start.bytes_usize());
        // Crucially, we go via `AllocBytes::as_mut_ptr`, not `AllocBytes::deref_mut`.
        let len = range.end().bytes_usize() - range.start.bytes_usize();