Function fn_abi_of_instance 

fn fn_abi_of_instance<'tcx>(
    tcx: TyCtxt<'tcx>,
    query: PseudoCanonicalInput<'tcx, (Instance<'tcx>, &'tcx List<Ty<'tcx>>)>,
) -> Result<&'tcx FnAbi<'tcx, Ty<'tcx>>, &'tcx FnAbiError<'tcx>>