I've been using Rust for around 3 years now, and I'm running into a problem with an Axum handler. If you could offer some guidance, it would be much appreciated.

use axum::{Router, extract::State, response::IntoResponse, routing::get};
use std::sync::Arc;

use crate::web::WebAppState;

pub fn debug_router(state: Arc<WebAppState>) -> Router<Arc<WebAppState>> {
    Router::new()
        .route("/seed_db", get(seed_db_handler))
        .with_state(state)
}

#[axum::debug_handler]
pub async fn seed_db_handler(State(state): State<Arc<WebAppState>>) -> impl IntoResponse {
    let res = db::seed_database(&state.repo.clone_inner()).await;
    match res {
        Ok(_) => "Database Seeded Successfully!".into_response(),
        Err(e) => format!("Error Seeding Database: {:?}", e).into_response(),
    }
}

When I try to compile this code I get this error:

error[E0277]: the trait bound `fn(axum::extract::State<Arc<WebAppState>>) -> impl futures_util::Future<Output = impl IntoResponse> {web::debug::seed_db_handler}: Handler<_, _>` is not satisfied
   --> web\src\web\debug.rs:8:32
    |
8   |         .route("/seed_db", get(seed_db_handler))
    |                            --- ^^^^^^^^^^^^^^^ the trait `Handler<_, _>` is not implemented for fn item `fn(axum::extract::State<Arc<WebAppState>>) -> impl futures_util::Future<Output = impl IntoResponse> {web::debug::seed_db_handler}`
    |                            |
    |                            required by a bound introduced by this call
    |
    = note: Consider using `#[axum::debug_handler]` to improve the error message
    = help: the following other types implement trait `Handler<T, S>`:
              `MethodRouter<S>` implements `Handler<(), S>`
              `axum::handler::Layered<L, H, T, S>` implements `Handler<T, S>`
note: required by a bound in `axum::routing::get`
   --> C:\Users\User\.cargo\registry\src\index.crates.io-1949cf8c6b5b557f\axum-0.8.4\src\routing\method_routing.rs:441:1
    |
441 | 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)

I've gone through the Handler trait requirements on docs.rs and I believe I'm using it correctly, but it still is not compiling. Also, the #[debug_handler] macro is does not give any helpful guidance, the compiler output is the same with and without it.

This router is gated behind a #[cfg(debug_assertions)] in my main axum setup, like this:

let router = Router::new().route( ... ).with_state(state);
#[cfg(debug_assertions)]
let router = router.nest("/debug", debug::debug_router(self.clone()));

Removing the #[cfg(debug_assertions)] does not solve the problem.

rust-analyzer also gives an error for one of my other handlers with the same error. The thing is I don't believe I have even changed that handler since the code compiled last. This may just be a problem with r-a.

If you could offer some guidance, it would be much appreciated.

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