The `main` function was incorrectly declared.
Erroneous code example:
```compile_fail,E0580
fn main(x: i32) { // error: main function has wrong type
println!("{}", x);
}
```
The `main` function prototype should never take arguments.
Example:
```
fn main() {
// your code
}
```
If you want to get command-line arguments, use `std::env::args`. To exit with a
specified exit code, use `std::process::exit`.