ArrayStoreException: bug or expected behavior?

[Michael Hoffer]

Hi all,

I finally found the time to play with the newest Valhalla build. We have a lot of use cases for this in the scientific community. Thanks for working on it.

I prepared a small test program that throws an ArrayStoreException during the assignment of an "inline value" to an array. I wanted to test the behavior of casting between "inline" and the nullable "?" type and interfaces. 

My expectations are that such errors should be prevented by the type system and should be discovered at compile-time. Either Point2D shouldn’t be allowed to implement the Point2DI interface (hopefully, that’s not the case) or the assignment of the points-array with an array of "inline values“ should be prevented (which is better).

Is this a bug or the expected behavior of the preview build?

Regards,
Michael

--
Dr. Michael Hoffer

Web:    mihosoft.eu
Twitter: @mihosoft

Goethe-Zentrum für Wissenschaftliches Rechnen (G-CSC)
Goethe-Universität
Kettenhofweg 139
60325 Frankfurt am Main
phone: +49 69 798 25254
info at michaelhoffer.de


/**
 * <p>
 * <b>How to reproduce the behavior/potential bug:</b>  
 * 
 * Compile this code with <b>jdk-14-valhalla+1-8 (2019/7/4)</b>:
 * 
 * <pre>
 * javac Main.java && java Main
 * </pre>
 * 
 * </p>
 * <p>
 * <b>Actual behavior:</b> a java.lang.ArrayStoreException is thrown
 * unexpectedly in line 33. 
 * </p>
 * <p>
 * <b>Expected behavior:</b> compile-time error that prevents the problematic
 * assignment in line 30.
 * </p>
 * 
 * @author Michael Hoffer <info at michaelhoffer.de>
 */
public class Main {
    public static void main(String[] args) {

        int n = 100_000_000;

        System.out.println("> creating " + n + " points");

        Point2DI[] points = new Point2D[n];

        for(int i = 0; i < points.length;i++) {
            points[i] = new Point2DCls(i, i);
        }
    }

    static interface Point2DI {
        double getX();
        double getY();
    }
    
    static inline class Point2D implements Point2DI {
        public double x;
        public double y;

        Point2D(double x, double y) {
            this.x = x;
            this.y = y;
        }

        @Override
        public double getX() {
            return x;
        }

        @Override
        public double getY() {
            return y;
        }
    }

    static class Point2DCls implements Point2DI {
        public double x;
        public double y;

        Point2DCls(double x, double y) {
            this.x = x;
            this.y = y;
        }

        @Override
        public double getX() {
            return x;
        }

        @Override
        public double getY() {
            return y;
        }
    }
} // end class Main