---
page-title: "Scope and Shadowing - Rust By Example"
url: https://doc.rust-lang.org/rust-by-example/variable_bindings/scope.html
date: "2023-03-23 13:59:16"
---
## [Scope and Shadowing](https://doc.rust-lang.org/rust-by-example/variable_bindings/scope.html#scope-and-shadowing)

Variable bindings have a scope, and are constrained to live in a *block*. A block is a collection of statements enclosed by braces `{}`.

``` rust
fn main() {
    // This binding lives in the main function
    let long_lived_binding = 1;

    // This is a block, and has a smaller scope than the main function
    {
        // This binding only exists in this block
        let short_lived_binding = 2;

        println!("inner short: {}", short_lived_binding);
    }
    // End of the block

    // Error! `short_lived_binding` doesn't exist in this scope
    println!("outer short: {}", short_lived_binding);
    // FIXME ^ Comment out this line

    println!("outer long: {}", long_lived_binding);
}
```

Also, [variable shadowing](https://en.wikipedia.org/wiki/Variable_shadowing) is allowed.

``` rust
fn main() {
    let shadowed_binding = 1;

    {
        println!("before being shadowed: {}", shadowed_binding);

        // This binding *shadows* the outer one
        let shadowed_binding = "abc";

        println!("shadowed in inner block: {}", shadowed_binding);
    }
    println!("outside inner block: {}", shadowed_binding);

    // This binding *shadows* the previous binding
    let shadowed_binding = 2;
    println!("shadowed in outer block: {}", shadowed_binding);
}

```