FromRequest guard for arbritrary headers

[infogulch]

I wrote a simple request guard that parses headers from a request and provides them as params to any handler. It relies on #![feature(adt_const_params)] to compile header selection statically.

#![feature(adt_const_params)]
mod header {
    use rocket::{
        request::{FromRequest, Outcome},
        Request,
    };

    pub struct Header<'a, const NAME: &'static str> {
        pub value: &'a str,
    }

    #[rocket::async_trait]
    impl<'r, const NAME: &'static str> FromRequest<'r> for Header<'r, NAME> {
        type Error = std::convert::Infallible;

        async fn from_request(request: &'r Request<'_>) -> Outcome<Self, Self::Error> {
            match request.headers().get_one(NAME) {
                Some(r) => Outcome::Success(Header { value: r }),
                None => Outcome::Forward(()),
            }
        }
    }

    pub type IfMatch<'a> = Header<'a, "If-Match">;
    // etc
}

Example usage:

#[get("/")]
fn index(ifmatch: IfMatch) -> String {
    ifmatch.value.to_string()
}

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Thoughts?