codegen for a `bool` return type when Hubpack is involved is invalid

[Aaron-Hartwig]

I have the following idol function:

        "rail_good": (
            args: {
                "name": "RailName",
            },
            reply: Simple("bool"),
            idempotent: true,
            encoding: Hubpack,
        ),

Which yields the following codegen:

pub fn rail_good(&self, name: RailName) -> bool {
        let (arg_name) = (name);
        #[allow(non_camel_case_types)]
        #[derive(serde::Serialize, hubpack::SerializedSize)]
        struct Sequencer_rail_good_ARGS {
            name: RailName,
        }
        const REPLY_SIZE: usize = { <bool as hubpack::SerializedSize>::MAX_SIZE };
        let mut reply = [0u8; REPLY_SIZE];
        let args = Sequencer_rail_good_ARGS {
            name: arg_name,
        };
        let mut argsbuf = [0; <Sequencer_rail_good_ARGS as hubpack::SerializedSize>::MAX_SIZE];
        let arglen = hubpack::serialize(&mut argsbuf, &args).unwrap_lite();
        loop {
            let task = self.current_id.get();
            let (rc, len) = sys_send(
                task,
                SequencerOperation::rail_good as u16,
                &argsbuf[..arglen],
                &mut reply,
                &[],
            );
            if let Some(g) = userlib::extract_new_generation(rc) {
                let _len = len;
                self.current_id.set(userlib::TaskId::for_index_and_gen(task.index(), g));
                continue;
            }
            let (v, _): (bool, _) = hubpack::deserialize(&reply[..len]).unwrap_lite();
            counters::count!(__SEQUENCER_CLIENT_COUNTERS, SequencerEvent::rail_good);
            return v != 0;
        }
    }

The code that is generated does not compile:

error[E0308]: mismatched types
   --> /hubris/target/thumbv7em-none-eabihf/release/build/drv-medusa-seq-api-d7233a5df42ce3bf/out/client_stub.rs:216:25
    |
216 |             return v != 0;
    |                    -    ^ expected `bool`, found integer
    |                    |
    |                    expected because this is `bool`

For more information about this error, try `rustc --explain E0308`.