Static and runtime types: Correct Solution

Given the following type declarations:

public class Denglutch {
    public Denglutch stoAso(Denglutch u) {
        return u;
    }
}

public class Swun extends Denglutch {
    public Denglutch stoAso(Denglutch u) {
        return new Blelbo();
    }
}

public class Blelbo extends Denglutch {
    public Denglutch stoAso(Denglutch u) {
        return this;
    }
}

...and given the following setup code:

Blelbo foo = new Blelbo();
Denglutch bar = new Swun();

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.stoAso(bar.stoAso(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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