`Unresolved import` error highlighting when nothing is wrong

[tuvtran]

I was following chapter 12.3 of the Rust book [0]. Particularly this snippet from Listing 12-14:

use std::env;
use std::process;

use minigrep;
use minigrep::Config;

fn main() {
    // --snip--
    if let Err(e) = minigrep::run(config) {
        // --snip--
    }
}

However, the VS Code extension threw me some errors:

Upon digging this issue, I found out that prior to the 2018 Edition, the Rust compiler would have caught these issues [1]. After updating Rust to 1.32.0 and adding edition = "2018" to Cargo.toml, my code ran just fine in the terminal. Yet, these errors still persist inside VS Code via the Rust extension. Is it just me or the extension never fixes this error?

[0] https://doc.rust-lang.org/book/ch12-03-improving-error-handling-and-modularity.html
[1] rust-lang/book#1676 (comment)

[tiagoamaro]

@tuvtran, I had this same issue with Rust 1.32.0. Upgraded to version 1.33.0 and RLS stopped reporting these false-negatives.

[colezlaw]

I'm running Rust 1.33.0 and RLS, and am still getting these issues - everything builds and runs fine, but an libraries pulled in from crates can't be resolved in the editor.

Adding extern crate foo fixes the problem in VS Code, so maybe the tooling just hasn't quite caught up? The edition is set to 2018.

[Xanewok]

Could you post your rust.* VSCode configs and the contents of Cargo.toml? Most recent stable RLS should work, assuming the edition = "2018" is in the Cargo.toml.

[Jayz33]

@tuvtran, changing the edition = "2018" to another (random) year and then back to 2018 solved the issue for me in VS Code.

[tqwewe]

@tuvtran I think you need to just change your VSCode theme, when you change everything should be much better.

[TobiasWehrum]

I had the problem described in the opening post running rustc 1.33.0. Most of my tools, including Rust itself and the Rust VSCode plugins, have been installed not a week ago. The project is freshly created with cargo new and had edition = "2018".

changing the edition = "2018" to another (random) year and then back to 2018 solved the issue for me in VS Code.

That "fixed" it for me too.

edit:
Correction - it only removed the errors, but it wouldn't autocomplete for minigrep:: and anything inside. I added extern crate minigrep; and now everything works as I'd expect it: No errors and autocomplete.

@Xanewok
Cargo.toml:

[package]
name = "minigrep"
version = "0.1.0"
authors = ["Tobias Wehrum <Tobias.Wehrum@dragonlab.de>"]
edition = "2018"

[dependencies]

Where can I find the "rust.* VSCode configs" you wanted? (I'm on Windows 7.)

[Xanewok]

@TobiasWehrum Hit Ctrl+, and click the "{}" button to the right to open the settings.json, you should have some options changed there.

[TobiasWehrum]

@Xanewok These is my whole settings.json:

{
    "[markdown]": {
        
    },
    "editor.formatOnType": true,
    "editor.formatOnSave": true,
    "terminal.integrated.shell.windows": "C:\\Windows\\System32\\cmd.exe",
    "explorer.openEditors.visible": 0,
    "editor.suggestSelection": "first",
    "vsintellicode.modify.editor.suggestSelection": "automaticallyOverrodeDefaultValue"
}

[Xanewok]

So I had a simple cargo new t pre-created already with a bare src/lib.rs and src/main.rs and when I added

use t;
use t::MyStruct; // pub struct MyStruct { ... } inside the src/lib.rs

this works as expected.

Could you possibly provide a very detailed, step-by-step reproduction? Do you start with a cargo new --bin project, add a lib.rs separately and then add the import directives?

[TobiasWehrum]

cargo new t doesn't create a src/lib.rs for me, only a src/main.rs.

1. cargo new t
2. Open project folder in VS Studio Code.
3. Create and open src/lib.rs.
4. Add pub struct MyStruct {} to lib.rs.
5. Open src/main.rs.
6. At the beginning of the file, type use t::, don't get offered MyStruct by intellisense, remove the line again.
7. Add extern crate t;.
8. Type "use t::" below and this time get an intellisense offering to complete with MyStruct.

[Chris-Andrews]

I have this same problem on Windows 10. I see the same behavior with deleting the line and re-typing the use line. I also had the above behavior with changing the year in Cargo.toml and changing it back.

[fzxu]

exit vscode and re-open, fixed the issue.

[karipov]

I'm having the exact same issue while running rustc 1.36.0 (a53f9df32 2019-07-03). Adding extern crate doesn't seem to fix anything for me as RLS can't find the crate at all.

These are the errors and warnings I am getting, although none of these show up as I compile and run the program:

I had to follow @fzxu and restart vscode (and by extension RLS)