Generic State Handler<_, _> is not satified

[djkato]

Summary

Hello, trying to write an app that uses generics inside the State, but unfortunately there are some trait issues I cannot resolve with the Handler. The minimal reproduction repo is here: https://github.com/djkato/axum-generics-issues

The tl;dr
Error:

error[E0277]: the trait bound `fn(HeaderMap, Json<AuthToken>, State<AppState<_>>) -> impl Future<Output = Result<StatusCode, AppError>> {manifest::<_>}: Handler<_, _>` is not satisfied
   --> src/routes/mod.rs:9:37
    |
9   |         .route("/api/manifest", get(manifest))
    |                                 --- ^^^^^^^^ the trait `Handler<_, _>` is not implemented for fn item `fn(HeaderMap, Json<AuthToken>, State<AppState<_>>) -> impl Future<Output = Result
<StatusCode, AppError>> {manifest::<_>}`
    |                                 |
    |                                 required by a bound introduced by this call
    |
    = help: the following other types implement trait `Handler<T, S>`:
              <Layered<L, H, T, S> as Handler<T, S>>
              <MethodRouter<S> as Handler<(), S>>
note: required by a bound in `axum::routing::get`
   --> /home/djkato/.cargo/registry/src/index.crates.io-6f17d22bba15001f/axum-0.7.4/src/routing/method_routing.rs:385:1
    |
385 | top_level_handler_fn!(get, GET);
    | ^^^^^^^^^^^^^^^^^^^^^^---^^^^^^
    | |                     |
    | |                     required by a bound in this function
    | required by this bound in `get`
    = note: this error originates in the macro `top_level_handler_fn` (in Nightly builds, run with -Z macro-backtrace for more info)

For more information about this error, try `rustc --explain E0277`.

main.rs

fn main() {
    let manifest = AppManifest {
        name: "saleor app".to_owned(),
    };

    let app_state = AppState {
        manifest,
        saleor_app: Arc::new(Mutex::new(SaleorApp {
            apl: RedisApl {
                client: "Client".to_owned(),
            },
        })),
    };

    let router = create_routes(app_state); 
    /* Rest of the program */
}

#[derive(Clone, Debug)]
pub struct AppManifest { name: String }

#[derive(Clone, Debug)]
pub struct AppState<A: APL> {
    pub saleor_app: Arc<Mutex<SaleorApp<A>>>,
    pub manifest: AppManifest,
}

#[derive(Clone, Debug)]
pub struct SaleorApp<A: APL> { apl: A }

pub trait APL: Sized + Send + Sync + Clone + std::fmt::Debug {
    async fn get(&self) -> u32;
}

#[derive(Debug, Clone)]
pub struct RedisApl { client: String }

impl APL for RedisApl {
    async fn get(&self) -> u32 { 32 }
}

/routes/mod.rs

pub fn create_routes<T: APL>(state: AppState<T>) -> Router<AppState<T>> {
    Router::new()
        .route("/api/manifest", get(manifest))
        .with_state(state)
}

/routes/manifest.rs

struct AuthToken { auth_token: String }

pub async fn manifest<A: APL>(
    _headers: HeaderMap,
    Json(_auth_token): Json<AuthToken>,
    State(_state): State<AppState<A>>,
) -> Result<StatusCode, AppError> {
    Ok(StatusCode::OK)
}

axum version

0.7.4

[djkato]

https://docs.rs/axum/latest/axum/extract/index.html#the-order-of-extractors states that the json extractor has to be last, because of how axum does things... Weel that was a headache