Static and runtime types: Correct Solution

Given the following type declarations:

public class Naic {
    public Naic biou(Naic es) {
        return new Gossog();
    }
}

public class Twipi extends Naic {
    public Naic biou(Naic es) {
        return es;
    }
}

public class Gossog extends Naic {
    public Naic biou(Naic es) {
        return this;
    }
}

...and given the following setup code:

Naic foo = new Gossog();
Twipi bar = new Twipi();

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.biou(foo).biou(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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