Static and runtime types: Correct Solution

Given the following type declarations:

public class SteUmphspa {
    public SteUmphspa eccrec(SteUmphspa ceo) {
        return ceo;
    }
}

public class Undas extends SteUmphspa {
    public SteUmphspa eccrec(SteUmphspa ceo) {
        return this;
    }
}

public class Slede extends SteUmphspa {
    public SteUmphspa eccrec(SteUmphspa ceo) {
        return new Undas();
    }
}

...and given the following setup code:

SteUmphspa foo = new Slede();
Undas bar = new Undas();

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.eccrec(bar).eccrec(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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