{"ast_node_type":"other","tokens":[{"end":94,"kind":"keyword","start":0,"text":"//"}]}
    // Here `idx` refers to the order of which the discriminant appears, and its index in `vs`
    // Helper closure to reduce duplicate code. This gets called everytime we detect a duplicate.
    let report = |dis: Discr<'tcx>, idx, err: &mut Diag<'_>| {