fn report_trait_method_mismatch<'tcx>(
    infcx: &InferCtxt<'tcx>,
    cause: ObligationCause<'tcx>,
    terr: TypeError<'tcx>,
    (trait_m, trait_sig): (AssocItem, FnSig<'tcx>),
    (impl_m, impl_sig): (AssocItem, FnSig<'tcx>),
    impl_trait_ref: TraitRef<'tcx>
) -> ErrorGuaranteed