Static and runtime types: Correct Solution

Given the following type declarations:

public class Trusm {
    public Trusm meru(Trusm plic) {
        return new Edtes();
    }
}

public class Edtes extends Trusm {
    public Trusm meru(Trusm plic) {
        return this;
    }
}

public class Arher extends Trusm {
    public Trusm meru(Trusm plic) {
        return plic;
    }
}

...and given the following setup code:

Arher foo = new Arher();
Trusm bar = new Edtes();

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.meru(foo).meru(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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