Can't compile the http server example

[dotSlashLu]

Version

rustc 1.39.0 (4560ea788 2019-11-04)

└── tokio v0.2.0-alpha.6
    ├── tokio-codec v0.2.0-alpha.6
    │   └── tokio-io v0.2.0-alpha.6
    ├── tokio-executor v0.2.0-alpha.6
    │   ├── tokio-sync v0.2.0-alpha.6
    ├── tokio-fs v0.2.0-alpha.6
    │   ├── tokio-executor v0.2.0-alpha.6 (*)
    │   ├── tokio-io v0.2.0-alpha.6 (*)
    │   └── tokio-sync v0.2.0-alpha.6 (*)
    ├── tokio-io v0.2.0-alpha.6 (*)
    ├── tokio-macros v0.2.0-alpha.6
    ├── tokio-net v0.2.0-alpha.6
    │   ├── tokio-codec v0.2.0-alpha.6 (*)
    │   ├── tokio-executor v0.2.0-alpha.6 (*)
    │   ├── tokio-io v0.2.0-alpha.6 (*)
    │   ├── tokio-sync v0.2.0-alpha.6 (*)
    ├── tokio-sync v0.2.0-alpha.6 (*)
    ├── tokio-timer v0.3.0-alpha.6
    │   ├── tokio-executor v0.2.0-alpha.6 (*)
    │   └── tokio-sync v0.2.0-alpha.6 (*)

Platform

Linux jarvis.local 3.10.0-862.el7.x86_64 #1 SMP Fri Apr 20 16:44:24 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

Description

I tried to compile the http server example on the documentation index, but I can't get it compiled with type annotation error and mainly this no method named unwrap found for type impl std::future::Future in the current scope error I don't know how to solve since this is my first try to update to tokio-0.2.x and std future.

error[E0599]: no method named `unwrap` found for type `impl std::future::Future` in the current scope
  --> src/main.rs:13:49
   |
13 |     let mut listener = TcpListener::bind(&addr).unwrap();
   |                                                 ^^^^^^ method not found in `impl std::future::Future`

error[E0698]: type inside `async` object must be known in this context
  --> src/main.rs:25:17
   |
25 |             let mut buf = [0; 1024];
   |                 ^^^^^^^ cannot infer type for `{integer}`
   |
note: the type is part of the `async` object because of this `await`
  --> src/main.rs:55:33
   |
55 |                 if let Err(e) = socket.write_all(&buf[0..n]).await {
   |                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0698]: type inside `async` object must be known in this context
  --> src/main.rs:33:48
   |
33 |                 let n = match socket.read(&mut buf).await {
   |                                                ^^^ cannot infer type for `{integer}`
   |
note: the type is part of the `async` object because of this `await`
  --> src/main.rs:33:31
   |
33 |                 let n = match socket.read(&mut buf).await {
   |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0698]: type inside `async` object must be known in this context
  --> src/main.rs:33:43
   |
33 |                 let n = match socket.read(&mut buf).await {
   |                                           ^^^^^^^^ cannot infer type for `{integer}`
   |
note: the type is part of the `async` object because of this `await`
  --> src/main.rs:33:31
   |
33 |                 let n = match socket.read(&mut buf).await {
   |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0698]: type inside `async` object must be known in this context
  --> src/main.rs:55:51
   |
55 |                 if let Err(e) = socket.write_all(&buf[0..n]).await {
   |                                                   ^^^ cannot infer type for `{integer}`
   |
note: the type is part of the `async` object because of this `await`
  --> src/main.rs:55:33
   |
55 |                 if let Err(e) = socket.write_all(&buf[0..n]).await {
   |                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0698]: type inside `async` object must be known in this context
  --> src/main.rs:55:51
   |
55 |                 if let Err(e) = socket.write_all(&buf[0..n]).await {
   |                                                   ^^^^^^^^^ cannot infer type for `{integer}`
   |
note: the type is part of the `async` object because of this `await`
  --> src/main.rs:55:33
   |
55 |                 if let Err(e) = socket.write_all(&buf[0..n]).await {
   |                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0698]: type inside `async` object must be known in this context
  --> src/main.rs:55:50
   |
55 |                 if let Err(e) = socket.write_all(&buf[0..n]).await {
   |                                                  ^^^^^^^^^^ cannot infer type for `{integer}`
   |
note: the type is part of the `async` object because of this `await`
  --> src/main.rs:55:33
   |
55 |                 if let Err(e) = socket.write_all(&buf[0..n]).await {
   |                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 7 previous errors

[ghost]

Hi @dotSlashLu example is working for me after couple of changes mentioned as a comment in the following code:

use tokio::net::TcpListener;
use tokio::prelude::*;
use std::net::SocketAddr; // Added `SocketAddr` in scope

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let addr: SocketAddr  = "127.0.0.1:8080".parse()?; // explicitly specified `SocketAddr`
    let mut listener = TcpListener::bind(&addr).await.unwrap(); // unwrap after await

    loop {
        let (mut socket, _) = listener.accept().await?;

        tokio::spawn(async move {
            let mut buf = [0u8; 1024]; // explicitly specified type `u8`

            // In a loop, read data from the socket and write the data back.
            loop {
                let n = match socket.read(&mut buf).await {
                    // socket closed
                    Ok(n) if n == 0 => return,
                    Ok(n) => n,
                    Err(e) => {
                        println!("failed to read from socket; err = {:?}", e);
                        return;
                    }
                };

                // Write the data back
                if let Err(e) = socket.write_all(&buf[0..n]).await {
                    println!("failed to write to socket; err = {:?}", e);
                    return;
                }
            }
        });
    }
}

[dotSlashLu]

Thanks @abdul-rehman0 , the unwrap error makes sense to me now. Seems the example needs to be corrected then.

[ghost]

@dotSlashLu if you check out the main page of this repository, you will find the correct working example. The documentation on the crate seems to be outdated.

[carllerche]

The docs found on docs.rs will be fixed as soon as the crate is published 👍