Understanding Rust Error E0432: Unresolved Import

Rust Error E0432 Overview

Rust Error E0432 occurs when an import statement cannot be resolved. This can happen due to mistakes in the import path, missing module declarations, or incorrect handling of importing external crates.

Erroneous Code Example

Consider this erroneous code example which results in Rust Error E0432:
fn main() {
  use something::Foo; // error: unresolved import `something::Foo`.

In Rust 2015, the `use` statement paths are relative to the crate root. For referencing items from the current or parent module, use the `self::` and `super::` prefixes, respectively. In Rust 2018 and later, the paths in `use` statements are relative to the current module, except when starting with the name of a crate or the literal `crate::`, which refers to the crate root.

Possible solutions

Following are some possible solutions for Rust Error E0432:

1. Fix the import path

Ensure that the import path is correct. In the erroneous code example, using `self::something::Foo` instead of `something::Foo` will fix the error:

use self::something::Foo;

mod something {
    pub struct Foo;
fn main() {}

2. Add missing external crate declaration (Rust 2015)

For Rust 2015, if the unresolved import refers to an external crate, make sure you've added the `extern crate` declaration in the crate root:

extern crate core; // Required for Rust 2015
use core::any;
fn main() {}

3. Import the external crate directly (Rust 2018)

In Rust 2018, the `extern crate` declaration is not required. Instead, import the external crate directly:

use core::any; // No 'extern crate' required for Rust 2018
fn main() {}

4. Verify module and item existence

Ensure that the imported item exists in the specified module. Check for any typos or naming mistakes in both the import path and the module declaration.