E0010: Missing Return Statement

A function with a non-void return type doesn't return a value in all code paths.

Example

fn get_number() -> i64 {
    // Error: missing return of type `i64`
}

fn get_number(flag: bool) -> i64 {
    if flag {
        42
    }
    // Error: missing return when flag is false
}

How to fix

Ensure all code paths return a value:

fn get_number() -> i64 {
    42
}

fn get_number(flag: bool) -> i64 {
    if flag {
        42
    } else {
        0
    }
}