fn report_eii_mismatch<'tcx>(
infcx: &InferCtxt<'tcx>,
cause: ObligationCause<'tcx>,
param_env: ParamEnv<'tcx>,
terr: TypeError<'tcx>,
(declaration_did, declaration_sig): (DefId, FnSig<'tcx>),
(external_impl_did, external_impl_sig): (LocalDefId, FnSig<'tcx>),
eii_attr_span: Span,
eii_name: Symbol,
) -> ErrorGuaranteed