clippy too_many_arguments in #[tarpc_service]

After some recent changes in my code I am seeing errors like this:

```
warning: this function has too many arguments (8/7)
--> src/rpc_server.rs:158:1
|
158 | #[tarpc::service]
| ^^^^^^^^^^^^^^^^^
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#too_many_arguments
= note: `#[warn(clippy::too_many_arguments)]` on by default
= note: this warning originates in the attribute macro `tarpc::service` (in Nightly builds, run with -Z macro-backtrace for more info)``
```

If I place a `#[allow(clippy::too_many_arguments)]` above the `#[tarpc::service]` the warning still occurs. The only way I've found to silence it is to decorate the entire rpc_server module that contains the tarpc::service, which is not ideal..

I'm not certain but I'm guessing the problem now occurs because I added an additional argument to all RPC methods. Unfortunately removing args is not an option.