use of undeclared type or module `HttpResponse`: not found in this scope

Question

I must admit, I am having a hard time making sense of the Rust compiler error messages.

I have this module:

src/adapters.js

use actix_web::{Responder, HttpResponse};

pub mod Basic {

    pub fn api_index() -> &'static str {
        "API"
    }

    pub fn admin_index() -> impl Responder {
        HttpResponse::Ok().body("hello world!")
    }

}

The Rust compiler keeps telling me when I use

use crate::actix_web::{Responder, HttpResponse};

that:

E0432: unresolved import `crate::actix_web`  maybe a missing crate `actix_web`?

Rest assured, crate::actix_web is not missing, because I can run simple requests from main.rs. The problem starts when I want to use the actix_web modules within my own modules.

If I have

use actix_web::{Responder, HttpResponse};

Rust keeps teeling me:

error[E0433]: failed to resolve: use of undeclared type or module `HttpResponse`

HttpResponse::Ok().body("hello world!")
^^^^^^^^^^^^ not found in this scope



help: consider importing one of these items
use actix_web::HttpResponse;
use crate::adapters::HttpResponse;


E0432: unresolved import `crate::actix_web`  maybe a missing crate `actix_web`?

I my main.rs, as the first line, I've also declared:

extern crate actix_web;

For the sake of making sure, I've also added "extern crate actix_web;" to the adapters.rs module right at the start. That didn't change anything either.

I am running out of options, I don't know what else I could possibly do.

Jarvis42 Jarvis42 · Accepted Answer · 2020-10-11T17:39:49

Basically You have created one another module Basic inside adapters module.So Basic is submodule of adapters module. So two ways you can access the external crate in this case.

Import external crate modules inside your Basic Module.

pub mod Basic {
    use actix_web::{Responder, HttpResponse};

    pub fn api_index() -> &'static str {
        "API"
    }

    pub fn admin_index() -> impl Responder {
        HttpResponse::Ok().body("hello world!")
    }
}

Or import an external module in outer module module and access those module using use super keyword in inner module.

use actix_web::{Responder, HttpResponse};

pub mod Basic {

    pub fn api_index() -> &'static str {
        "API"
    }

    pub fn admin_index() -> impl super::Responder {
        super::HttpResponse::Ok().body("hello world!")
    }
}

use of undeclared type or module `HttpResponse`: not found in this scope

1 Answers