Cannot print error message from bmp::open

I'm trying to print out the error it throws when bmp::open failed

let image_result = bmp::open(argument);
        let image = match image_result {
            Ok(i) => i,
            Err(error) => {
                println!("Error! {error:?}");
            },
        };

However, I've been getting the below error message

Thanks in advance!

This is because in Rust, the match statement has to return the same type from its match arms. So your first match arm

Ok(i) => i

returns a type of Image where as second match arm

Err(error) => {
     println!("Error! {error:?}");
}

does not return anything hence the compiler infer the return type as ()(unit) type.

There are multiple ways you could solve this, but it's really depends upon how you want to handle with the error case. If your intention is to handle only Ok case, you could destructure the Result.

if let Ok(i) = bmp::open(argument) {
   print("Do something with {i}")
}

Alternatively you can panic if the file is failed to open.

let image_result = bmp::open(argument);
let image = match image_result {
    Ok(i) => i,
    Err(error) => {
        panic!("Error! {error:?}");
    }
};

OR with unwrap_or_else,

let img = bmp::open("test/rgbw.bmp").unwrap_or_else(|e| {
   panic!("Failed to open: {}", e);
});