{"ast_node_type":"other","tokens":[{"end":77,"kind":"keyword","start":0,"text":"err.span_label(call_span,"}]}
                err.span_label(call_span, "expects `Fn` instead of `FnMut`");
                err.span_label(span, "change this to accept `FnMut` instead of `Fn`");
                err.span_label(closure_span, "in this closure");