Incorrect dynamic proxy creation from map when there are default methods

package org.dimitrovchi.groovybugs;

import groovy.lang.GroovyShell;
import org.codehaus.groovy.control.CompilerConfiguration;
import org.codehaus.groovy.runtime.DefaultGroovyMethods;
import org.junit.Assert;
import org.junit.Test;

import java.util.Map;

/**
 * @author Dmitry Ovchinnikov
 */
public class MapToProxyTest {

    private final GroovyShell shell;

    public MapToProxyTest() {
        final CompilerConfiguration cc = new CompilerConfiguration();
        cc.setTargetBytecode(CompilerConfiguration.JDK8);
        shell = new GroovyShell(cc);
    }

    @Test
    public void testMapToProxy() {
        final Map map = (Map) shell.evaluate("[x: {10}, y: {20}]");
        final SomeInterface si = DefaultGroovyMethods.asType(map, SomeInterface.class);
        Assert.assertEquals(20, si.y());
        Assert.assertEquals(10, si.x()); // assertion error: si.x() == 1
    }

    public interface SomeInterface {

        default int x() {
            return 1;
        }

        int y();
    }
}