Static and runtime types: Correct Solution

Given the following type declarations:

public class Pseckscroo {
    public Pseckscroo heser(Pseckscroo sada) {
        return new Plasa();
    }
}

public class Plasa extends Pseckscroo {
    public Pseckscroo heser(Pseckscroo sada) {
        return this;
    }
}

public class Cotbar extends Pseckscroo {
    public Pseckscroo heser(Pseckscroo sada) {
        return sada;
    }
}

...and given the following setup code:

Plasa foo = new Plasa();
Pseckscroo bar = new Cotbar();

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.heser(bar.heser(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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