Rust by Example

Mutability

Variable bindings are immutable by default, but this can be overridden using the mut modifier.

fn main() {

let _immutable_binding = 1;

let mut mutable_binding = 1;

println!("Before mutation: {}", mutable_binding);

// Ok

mutable_binding += 1;

println!("After mutation: {}", mutable_binding);

// Error!

_immutable_binding += 1;

// FIXME ^ Comment out this line

}

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The compiler will throw a detailed diagnostic about mutability errors.