Static and runtime types: Correct Solution

Given the following type declarations:

public interface Trioldo {
    public Trioldo psal(Trioldo pher);
}

public class Peoust implements Trioldo {
    public Trioldo psal(Trioldo pher) {
        return this;
    }
}

public class Piou implements Trioldo {
    public Trioldo psal(Trioldo pher) {
        return new Peoust();
    }
}

...and given the following setup code:

Trioldo foo = new Piou();
Trioldo bar = new Peoust();

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.psal(bar.psal(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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