inheritance.rs

#![feature(core)]

macro_rules! inherit {
    {
        $(#[$flag_struct:meta])* struct $child:ident : $parent:ty {
            $($(#[$flag_field:meta])* $field:ident: $ty:ty),*
        }
    } => {
        extern crate core;

        $(#[$flag_struct])* struct $child {
            super_: $parent,
            $($(#[$flag_field])* $field: $ty),*
        }

        impl core::ops::Deref for $child {
            type Target = $parent;

            fn deref(&self) -> &$parent { &self.super_ }
        }

        impl core::ops::DerefMut for $child {
            fn deref_mut(&mut self) -> &mut $parent { &mut self.super_ }
        }
    }
}

struct Parent { parent_member: &'static str }

trait SomeTrait {
    fn overriden_method(&self);
}

impl Parent {
    fn super_method(&self) {
        println!("I am in the parent: {} and will not be overriden in the child.", self.parent_member);
    }
}

impl SomeTrait for Parent {
    fn overriden_method(&self) {
        println!("I am in the parent: {} but will be overriden in the child.", self.parent_member);
    }
}

inherit! {
    struct Child : Parent { child_member: &'static str }
}

impl SomeTrait for Child {
    fn overriden_method(&self) {
        println!("I am in the child: {} and will call explicit super on my parent.", self.child_member);
        self.super_.overriden_method();
    }
}

fn main() {
    let child = Child { super_: Parent { parent_member: "Parent" }, child_member: "Child" };
    
    child.super_method();
    child.overriden_method();
}