Type parameter when returning Scope with middleware from fn

[Tipnos]

Context

Route configuration of a service Scope changes regards to a clap argument when starting an actix server.

The route configuration is implemented in a function which takes the clap argument as param and return the corresponding Scope. Everything works fine as long as no middleware is wrapped inside the function.

The simple example below trigger the error.

Example

use actix_web::{http::Method, middleware, web, App, HttpResponse, HttpServer};

#[actix_web::main]
async fn main() -> std::io::Result<()> {
    HttpServer::new(|| {
        App::new()
            .service(web::resource("/health-check").route(web::get().to(HttpResponse::Ok)))
            .service(api_service(12))
    })
    .bind(("127.0.0.1", 8080))?
    .run()
    .await
}

fn api_service(arg_from_clap: i64) -> actix_web::Scope {
    actix_web::Scope::new("/api")
        .wrap(middleware::DefaultHeaders::new().add(("X-Version", "0.2"))) // Example compile if this line is removed
        .service(
            web::resource("/test")
                .route(web::get().to(HttpResponse::Ok))
                .route(web::method(Method::HEAD).to(HttpResponse::MethodNotAllowed)),
        )
} 

Compiler error

expected struct 'actix_web::Scope<actix_web::scope::ScopeEndpoint>' found struct 'actix_web::Scope<impl ServiceFactory<ServiceRequest, Config = (), Response = ServiceResponse, Error = actix_web::Error, InitError = ()>>'

Version

actix-web = 4
rustc = 1.69.0

[robjtede]

To change the default type parameter for Scopes:

fn api_service(arg_from_clap: i64) -> actix_web::Scope<
    impl ServiceFactory<
        ServiceRequest,
        Response = ServiceResponse<impl MessageBody>,
        Config = (),
        InitError = (),
        Error = actix_web::Error,
    >,
> {
    // ...
}