I am learning Sized Trait and Trait Object, and there is a rule that if I want to create a trait object,
Sized must not be a supertrait. In other words, it must not require Self: Sized.

many resources have tell me that a trait method that returns Self needs the Trait to be Sized. What's more? Is there a rule that can determine a method or a trait should be `Sized?

here is a example that cannot be compiled:

trait SizedTrait {
    fn get_self(self) -> Self;
}

struct MyStruct {}

impl SizedTrait for MyStruct {
    fn get_self(self) -> Self {
        MyStruct {}
    }
}

struct OtherStruct {}

impl SizedTrait for OtherStruct {
    fn get_self(self) -> Self {
        OtherStruct {}
    }
}

fn main() {
    let x = MyStruct {};
    let y = OtherStruct {};
    let v = vec![&x as &dyn SizedTrait, &y as &dyn SizedTrait];
    for i in v {
        i.print_self();
    }
}

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