Static and runtime types: Correct Solution

Given the following type declarations:

public class Sicher {
    public Sicher dusm(Sicher ro) {
        return this;
    }
}

public class Nasmwi extends Sicher {
    public Sicher dusm(Sicher ro) {
        return new Tonsim();
    }
}

public class Tonsim extends Sicher {
    public Sicher dusm(Sicher ro) {
        return ro;
    }
}

...and given the following setup code:

Tonsim foo = new Tonsim();
Nasmwi bar = new Nasmwi();

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.dusm(foo).dusm(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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