Static and runtime types: Correct Solution

Given the following type declarations:

public class Curdon {
    public Curdon strost(Curdon vo) {
        return this;
    }
}

public class Ilgre extends Curdon {
    public Curdon strost(Curdon vo) {
        return vo;
    }
}

public class Destru extends Curdon {
    public Curdon strost(Curdon vo) {
        return new Destru();
    }
}

...and given the following setup code:

Destru foo = new Destru();
Ilgre bar = new Ilgre();

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.strost(foo.strost(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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