Compilation error: can't find crate for `core`

Question

I'm using Rust 1.35.0 to try out some Rust examples and I could not get it to compile, as I keep getting the following message:

error[E0463]: can't find crate for `core`

I ran rustc --explain E0463 and I see the following message:

You need to link your code to the relevant crate in order to be able to use it
(through Cargo or the `-L` option of rustc example). Plugins are crates as
well, and you link to them the same way.

Here is my Cargo.toml:

[package]
name = "sensor-node"
version = "0.1.0"
authors = ["joesan <[email protected]>"]
edition = "2018"

[dependencies]
dwm1001 = "0.1.0"
panic-halt = "0.2.0"
nb = "0.1.1"

Here is my main.rs:

fn main() {
    let s = String::from("hello");  // s comes into scope

    takes_ownership(s);             // s's value moves into the function...
                                    // ... and so is no longer valid here

    let x = 5;                      // x comes into scope

    makes_copy(x);                  // x would move into the function,
                                    // but i32 is Copy, so it’s okay to still
                                    // use x afterward

} // Here, x goes out of scope, then s. But because s's value was moved, nothing
  // special happens.

fn takes_ownership(some_string: String) { // some_string comes into scope
    println!("{}", some_string);
} // Here, some_string goes out of scope and `drop` is called. The backing
  // memory is freed.

fn makes_copy(some_integer: i32) { // some_integer comes into scope
    println!("{}", some_integer);
} // Here, some_integer goes out of scope. Nothing special happens.

Answer 1

Your code works fine on the Rust playground, so I recommend checking your Rust installation and environment settings.

---

You may want to use the preconfigured Rust Docker image to run your app. Have Docker installed, then:

docker pull rust

Go to your project folder and run:

docker run --rm --user "$(id -u)":"$(id -g)" -v "$PWD":/usr/src/myapp -w /usr/src/myapp rust cargo run

Output:

hello
5

---

For your simple example on a PC, you don't need any of these dependencies:

[dependencies]
dwm1001 = "0.1.0"
panic-halt = "0.2.0"
nb = "0.1.1"

Here are my steps to test your sample on Linux:

cargo new hello
cd hello
code .

Open main.rs and paste your sample main.rs and save:

fn main() {
    let s = String::from("hello"); // s comes into scope

    takes_ownership(s); // s's value moves into the function...
                        // ... and so is no longer valid here

    let x = 5; // x comes into scope

    makes_copy(x); // x would move into the function,
                   // but i32 is Copy, so it’s okay to still
                   // use x afterward
} // Here, x goes out of scope, then s. But because s's value was moved, nothing
  // special happens.

fn takes_ownership(some_string: String) {
    // some_string comes into scope
    println!("{}", some_string);
} // Here, some_string goes out of scope and `drop` is called. The backing
  // memory is freed.

fn makes_copy(some_integer: i32) {
    // some_integer comes into scope
    println!("{}", some_integer);
} // Here, some_integer goes out of scope. Nothing special happens.

In a terminal inside the hello folder, run:

cargo run

And the output is good:

hello
5

---

This may help:

1. Shell command

   rustup component list --installed
   

   Output:

   cargo-x86_64-unknown-linux-gnu
   clippy-x86_64-unknown-linux-gnu
   rls-x86_64-unknown-linux-gnu
   rust-analysis-x86_64-unknown-linux-gnu
   rust-docs-x86_64-unknown-linux-gnu
   rust-src
   rust-std-x86_64-unknown-linux-gnu
   rustc-x86_64-unknown-linux-gnu
   rustfmt-x86_64-unknown-linux-gnu
   

2. Shell command:

   rustup show
   

   Output:

   Default host: x86_64-unknown-linux-gnu
   
   installed toolchains
   --------------------
   
   stable-x86_64-unknown-linux-gnu (default)
   nightly-x86_64-unknown-linux-gnu
   
   active toolchain
   ----------------
   
   stable-x86_64-unknown-linux-gnu (default)
   rustc 1.35.0 (3c235d560 2019-05-20)