E0007: Condition is Not a Boolean

The condition in an if or while statement must be a boolean, but you provided a different type.

Example

fn main() {
    if 42 {  // Error: the if condition must have type `bool`, found `i64`
        // ...
    }
}

fn main() {
    while 1 {  // Error: the while condition must have type `bool`, found `i64`
        // ...
    }
}

Use a boolean expression as the condition:

fn main() {
    if true {
        // ...
    }
}

Or use a comparison to produce a boolean:

fn main() {
    let x = 42;
    if x > 0 {
        // ...
    }
}