Formatted print doesn't work as expected with debug + enum

[macabeus]

If you use the debug print and a formatter such as {: <3?} with a enum to print the case name, the code does not work as expected.

#[derive(Debug)]
enum MyEnum {
    AB,
}

fn main() {
    let value = MyEnum::AB;
    println!("[{: <3?}]", value); // The result is `[AB]`
                                  // while I expected that the result is `[AB ]`.
}

It's only work if the enum has a value:

#[derive(Debug)]
enum MyEnum {
    AB(i32),
}

fn main() {
    let value = MyEnum::AB(42);
    println!("[{:<3?}]", value); // The result is `[42 ]`
}

Maybe we should fix this behaviour?

Also, I've open a question at Stackoverflow about this behaviour.

[hellow554]

As already said on Stackoverflow, this might be related to #55584

[estebank]

Closing as duplicate of #55584.