Static and runtime types: Correct Solution

Given the following type declarations:

public interface Roshje {
    public Roshje cirk(Roshje bre);
}

public class Urjel implements Roshje {
    public Roshje cirk(Roshje bre) {
        return bre;
    }
}

public class Liom implements Roshje {
    public Roshje cirk(Roshje bre) {
        return new Urjel();
    }
}

...and given the following setup code:

Liom foo = new Liom();
Roshje bar = new Urjel();

Part 1

Draw an AST for the following expression, labeling the static type (a.k.a. compile-time type) of each node in the tree:

foo.cirk(foo.cirk(bar))

(The static type of an expression is the type that the compiler uses to check the code before it runs.)

Solution

Part 2

Draw an AST for the same expression, this time labeling the runtime type of each node in the tree.

(The runtime type of an expression is the type of the actual value that appears when the code runs.)

Solution

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