E0005: Unary Operator Type Mismatch

You used a unary operator with the wrong type.

Example

fn main() {
    let x = -true;  // Error: unary `-` expects type `i64` but found `bool`
}

fn main() {
    let x = !42;  // Error: unary `!` expects type `bool` but found `i64`
}

How to fix

Use the correct type for the operator:

fn main() {
    let x = -42;    // OK: negating an integer
    let y = !true;  // OK: logical not on a boolean
}