Example code does not compile.

[joboscribe]

Technical Bug Report

Your Environment

| Software | Version(s) |
| Rust | 1.30.1 |
| Form Factor | Desktop |
| Browser Type | Chrome |
| Browser Version | 70.0.3538.110 |

Is this an issue with Rust, CSS, or HTML (or a combination)?

I'm going to say HTML.

Expected Behavior

If i correctly followed (or copy/pasted) the code example under the heading "A Small Rust Application" then i should be able to compile and run the sample program.

Current Behavior

Compiling the sample code results in:

error[E0432]: unresolved import `ferris_says`
 --> src/main.rs:1:5
  |
1 | use ferris_says::say; // from the previous step
  |     ^^^^^^^^^^^ Maybe a missing `extern crate ferris_says;`?

error: aborting due to previous error

Step to Reproduce

Follow the instructions on the /learn/get-started page through the "A Small Rust Application" section.

[sojuhokari]

This is due to your version of Rust. Rust 1.31 introduced a new concept called “Editions,” explained in detail here. The basic gist of it is that Rust 2018 Edition introduces a number of breaking changes that are not available in the Rust 2015 Edition. As Rust 2018 is completely opt-in, and is a new feature as of Rust 1.31, any crate created with Rust 1.30.x and earlier will default to Rust 2015. In Rust 2015, an extern crate ferris_sys is needed in main.rs; in Rust 2018, it isn’t. Rust versions are specified in Cargo.toml by inserting edition = “year” under the [package] header.

TLDR: Two ways of solving the problem:

1. Update Rust to 1.31.x or higher, and insert edition = “2018” under the authors line of Cargo.toml
2. Insert extern crate ferris_sys at the top of main.rs

Something concisely explaining this might be useful at the bottom of the learn/get-started page.

[joboscribe]

My point was that a new user, following the instructions on the page, will be left with code that does not compile. That seems like a poor initial experience for potential rustaceans.

[sojuhokari]

That makes more sense. Sorry. And I completely agree.

[mbrubeck]

My point was that a new user, following the instructions on the page, will be left with code that does not compile. That seems like a poor initial experience for potential rustaceans.

It wlll work if they are using the current stable version of Rust.

[joboscribe]

I went through the example again and it does indeed now compile and run just fine. Thanks.

[xgqfrms]

1. Cargo.toml

Q:

Where is the path of Cargo.toml file?

A:

https://www.cnblogs.com/xgqfrms/p/16659275.html#5172235

https://github.com/xgqfrms/rust-in-action/blob/master/test/first_rust_package/Cargo.toml

You totally should update the example in the website. Just starting and stuff being broken when you're literally copy-pasting the example gave to you by the starting guide isn't cool at all

Okay, my bad, my bad completely sorry, I won't even edit the prior comment to show how dumb, we people can be, even with instructions crystal clear.

I was adding ferris-says = 0.2 at the bottom of [package], and not under [dependencies]

I'll leave these comments, so others know it's okay to be wrong, admit it, apologize, and then let your experience help others, even if you make yourself look very dumb.

[wangrm-oss]

cargo 1.71.0 (cfd3bbd8f 2023-06-08)
Cargo.toml --> edition = "2021"

仍然出错：
error[E0432]: unresolved import ferris_says
--> .\main.rs:1:5
|
1 |使用 ferris_says::say; // 从上一步开始
| ^^^^^^^^^^^^ 也许缺少一个箱子ferris_says？
|
=帮助：考虑添加extern crate ferris_says使用ferris_says板条箱

错误：由于先前的错误而中止

有关此错误的更多信息，请尝试rustc --explain E0432。

[senekor]

@wanghs-ctrl I can't read this, but "unresolved import" makes me guess you forgot to add the dependency in Cargo.toml:

[dependencies]
ferris-says = "0.2"

[wangrm-oss]

@senekor 不是这个原因，ferris-says = "0.2" 已经添加过了

[senekor]

I don't speak Chinese. I'd have to see the code to be able to help.