Static and runtime types: Correct Solution

Given the following type declarations:

public class PseJeng {
    public PseJeng conast(PseJeng oss) {
        return oss;
    }
}

public class Siangu extends PseJeng {
    public PseJeng conast(PseJeng oss) {
        return this;
    }
}

public class Ellian extends PseJeng {
    public PseJeng conast(PseJeng oss) {
        return new Ellian();
    }
}

...and given the following setup code:

Ellian foo = new Ellian();
PseJeng bar = new Siangu();

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.conast(bar.conast(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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