{"ast_node_type":"variable","tokens":[{"end":86,"kind":"keyword","start":0,"text":"let"}]}
    let err = if let Some(closure_region_requirements) = closure_region_requirements {
    let def_span = tcx.def_span(body.source.def_id());
        let mut err = infcx.dcx().struct_span_note(def_span, "external requirements");