Static and runtime types: Correct Solution

Given the following type declarations:

public interface Puslil {
    public Puslil otac(Puslil ik);
}

public class Englass implements Puslil {
    public Puslil otac(Puslil ik) {
        return new Englass();
    }
}

public class Crenthun implements Puslil {
    public Puslil otac(Puslil ik) {
        return this;
    }
}

...and given the following setup code:

Crenthun foo = new Crenthun();
Englass bar = new Englass();

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.otac(bar.otac(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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