LYR-SEM0017

a path of a function that returns no value

error · spec 07-statements

A function whose return type is not void has a path that reaches the end of its body without a return or a throw. A function returning never whose body can end, and a coroutine whose result is not returned on every path, are reported here too.

Explanation

A function that declares a result gives it on every path. The check follows the control flow: an if without an else, a loop that may end, or a break before the return all leave a path open.

Add the missing return (or a throw), usually at the end of the body.

Wrong

fn sign(n: int): int {
    if (n < 0) { return -1; }
    if (n > 0) { return 1; }
}

fn main(): void {
    let _ = sign(2);
}

Right

fn sign(n: int): int {
    if (n < 0) { return -1; }
    if (n > 0) { return 1; }
    return 0;
}

fn main(): void {
    let _ = sign(2);
}