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Understanding Rust Error E0584

Rust Error E0584 Overview

Rust Error E0584 occurs when a doc comment is not attached to anything. Doc comments must be placed directly before the item they're supposed to document, such as a function, trait, or struct.

Incorrectly Placed Doc Comments

Here's an example of erroneous code that produces Rust Error E0584:

```rust
#![allow(unused)]
fn main() {
trait Island {
    fn lost();

    /// I'm lost!
}
}
```

Correctly Placed Doc Comments

To fix Rust Error E0584, place the doc comment before the trait or function you're trying to document. Here's the corrected code:

```rust
#![allow(unused)]
fn main() {
/// I'm THE island!
trait Island {
    /// I'm lost!
    fn lost();
}
}
```

Using Doc Comments with Other Items

Doc comments can also be used to document other items, such as structs and enums. The same rule applies: place the doc comment directly before the item you're documenting.

Example: Documenting a Struct

```rust
/// A student with a name and age.
struct Student {
    name: String,
    age: u8,
}
```

Example: Documenting an Enum

```rust
/// Different shapes with dimensions.
enum Shape {
    /// A rectangle with width and height.
    Rectangle(f64, f64),
    /// A circle with radius.
    Circle(f64),
}
```

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