Programming Languages

Quite close. The fields part is spot on. The shared methods should be provided as a default by the parent and overriden by the child with no super() possible.

Basically, inheritance should just be merging structs at compiler time to cause no runtime performance hit caused by looking up the parent.

struct Parent {
  something: bool
}

impl Parent {
  fn shared_parent_def() { println!("I'm shared and defined in parent"); }
  fn shared_overriden() { println!("I'm shared and defined in parent too"); }
}

impl

// inherits from Parent
struct Child {
  another_thing: bool
}

impl Child {
  fn shared_overriden() { println!("I'm specialized and overriden in child"); }
  fn child_only() { println!("I'm only in the child"); }
}

should compile to

struct Parent {
  something: bool
}

impl Parent {
  fn shared_parent_def() { println!("I'm shared and defined in parent"); }
  fn shared_overriden() { println!("I'm shared and defined in parent too"); }
}


struct Child {
  something: bool  #notice me
  another_thing: bool
}

impl Child {
  // notice copied shared_parent_def
  fn shared_parent_def() { println!("I'm shared and defined in parent"); }
  // notice override shared_overriden
  fn shared_overriden() { println!("I'm specialized and overriden in child"); }
  fn child_only() { println!("I'm only in the child"); }
}

This could all be written manually, but changing something in the Parent would require copy-pasting everything to the descendants. Not DRY at all. If Dada did the generation of the types in the compiler, it would be amazing.

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