Static and runtime types: Correct Solution

Given the following type declarations:

public class Nopxal {
    public Nopxal eilt(Nopxal umda) {
        return this;
    }
}

public class Psiu extends Nopxal {
    public Nopxal eilt(Nopxal umda) {
        return new Sidir();
    }
}

public class Sidir extends Nopxal {
    public Nopxal eilt(Nopxal umda) {
        return umda;
    }
}

...and given the following setup code:

Nopxal foo = new Sidir();
Psiu bar = new Psiu();

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.eilt(foo).eilt(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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