Rocket.rs route by subdomain

hosts.rs

use rocket::{request::FromRequest, Outcome, Request};

pub struct WWWHost;
pub struct AAAHost;

impl<'a, 'r> FromRequest<'a, 'r> for WWWHost {
    type Error = ();

    fn from_request(request: &'a Request<'r>) -> rocket::request::Outcome<Self, Self::Error> {
        if let Some(hostname) = request.headers().get_one("host") {
            if hostname == "example.com" {
                Outcome::Success(WWWHost)
            } else if hostname == "www.example.com" {
                Outcome::Success(WWWHost)
            } else {
                Outcome::Forward(())
            }
        } else {
            // There was no host header (this shouldn't happen)
            Outcome::Forward(())
        }
    }
}

impl<'a, 'r> FromRequest<'a, 'r> for AAAHost {
    type Error = ();

    fn from_request(request: &'a Request<'r>) -> rocket::request::Outcome<Self, Self::Error> {
        if let Some(hostname) = request.headers().get_one("host") {
            if hostname == "aaa.example.com" {
                Outcome::Success(WWWHost)
            } else {
                Outcome::Forward(())
            }
        } else {
            // There was no host header (this shouldn't happen)
            Outcome::Forward(())
        }
    }
}

main.rs

#[macro_use]
extern crate rocket;

mod hosts;

#[get("/")]
fn root(host: WWWHost) -> String {
  String::from("Welcome to www.example.com!");
}

#[get("/")]
fn sub(host: AAAHost) -> String {
  String::from("Welcome to aaa.example.com!"); 
}

fn main() {
  rocket::ignite().mount("/", routes![root, sub]).launch();
}

Stumbled across this great gist and found that the trait structure has changed somewhat in 0.5-rc.
Modified version of hosts.rs, based on the docs example:

use rocket::http::Status;
use rocket::request::{FromRequest, Outcome, Request};

pub struct WWWHost;
pub struct AAAHost;

#[rocket::async_trait]
impl<'r> FromRequest<'r> for WWWHost {
    type Error = ();

    async fn from_request(req: &'r Request<'_>) -> Outcome<Self, Self::Error> {
        match req.headers().get_one("host") {
            None => Outcome::Failure((Status::BadRequest, ())),
            Some(host) if matches!(host, "example.com" | "www.example.com") => Outcome::Success(WWWHost),
            Some(_) => Outcome::Forward(()),
        }
    }
}

#[rocket::async_trait]
impl<'r> FromRequest<'r> for AAAHost {
    type Error = ();

    async fn from_request(req: &'r Request<'_>) -> Outcome<Self, Self::Error> {
        match req.headers().get_one("host") {
            None => Outcome::Failure((Status::BadRequest, ())),
            Some(host) if (host == "aaa.example.com") => Outcome::Success(AAAHost),
            Some(_) => Outcome::Forward(()),
        }
    }
}

Here's my version which uses the duplicate crate, the one for creating the structs is needless and adds extra lines, but it allows for only one allow macro. This includes a default struct which can be removed.

#[macro_use]
extern crate rocket;

use duplicate::duplicate_item;
use rocket::{
    http::Status,
    request::{FromRequest, Outcome},
    Request,
};

#[allow(clippy::upper_case_acronyms)]
#[duplicate_item(
    Name;
    [ API ];
    [ WEB ];
    [ DEF ];
)]
struct Name;

#[duplicate_item(
    Host    Name;
    [ API ] [ "api.shaybox.com" | "127.0.0.1:8000" ];
    [ WEB ] [ "www.shaybox.com" | "shaybox.com" ];
    [ DEF ] [ _ ];
)]
#[rocket::async_trait]
impl<'r> FromRequest<'r> for Host {
    type Error = ();

    async fn from_request(req: &'r Request<'_>) -> Outcome<Self, Self::Error> {
        match req.headers().get_one("host") {
            None => Outcome::Error((Status::BadRequest, ())),
            Some(Name) => Outcome::Success(Host),
            #[allow(unreachable_patterns)] // DEF
            Some(_) => Outcome::Forward(Status::Accepted),
            // Some(host) => { // Debug
            //     println!("{host}");
            //     Outcome::Forward(Status::Accepted)
            // }
        }
    }
}

#[get("/", rank = 2)]
fn def(_host: DEF) -> &'static str {
    "Hello, DEF!"
}

#[get("/", rank = 1)]
fn api(_host: API) -> &'static str {
    "Hello, API!"
}

#[get("/", rank = 0)]
fn web(_host: WEB) -> &'static str {
    "Hello, WEB!"
}

#[launch]
fn rocket() -> _ {
    rocket::build().mount("/", routes![api, web, def])
}