LYR-SEM0004

a condition that is not a bool

error · spec 07-statements

The condition of an if, while, do … while or a guard has a type other than bool.

Explanation

A condition is a bool; nothing converts to one. A number is not true when it is non-zero, and an optional is not true when it holds a value.

Write the test out: n != 0, x != null, !s.isEmpty().

Wrong

fn main(): void {
    let n = 3;
    if (n) { let _ = n; }
}

Right

fn main(): void {
    let n = 3;
    if (n != 0) { let _ = n; }
}