Groovy compiler chokes on MBCS in the script

package project1;

import groovy.lang.Binding;
import groovy.lang.GroovyShell;

import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.Charset;

import org.codehaus.groovy.control.CompilationUnit;
import org.codehaus.groovy.control.CompilerConfiguration;
import org.codehaus.groovy.control.ErrorCollector;
import org.codehaus.groovy.control.MultipleCompilationErrorsException;
import org.codehaus.groovy.control.SourceUnit;

public class TestMBCSWithGroovy {
    public TestMBCSWithGroovy() {
        super();
    }

    public static void main(String[] args) {
        try {
            byte[] b = { '' };
            String encodingName = "UTF-8";
            Charset cs = Charset.forName(encodingName);
            ByteBuffer bb = ByteBuffer.wrap(b);
            CharBuffer cb = cs.decode(bb);
            String s = cb.toString();
            //        s = new String(someBytes, encodingName);
            //        s = "æ¥æ";
            CompilerConfiguration debugConfiguration =
                new CompilerConfiguration(CompilerConfiguration.DEFAULT);
            debugConfiguration.setSourceEncoding(encodingName);
            GroovyShell mGS =
                new GroovyShell(Thread.currentThread().getContextClassLoader(),
                                new Binding(), debugConfiguration);
            CompilerConfiguration conf =
                new CompilerConfiguration(CompilerConfiguration.DEFAULT);
            ErrorCollector err = new ErrorCollector(conf);
            SourceUnit src =
                new SourceUnit("test", s, conf, mGS.getClassLoader(), err);
            CompilationUnit compilationUnit = new CompilationUnit(conf);
            compilationUnit.addSource(src);
            compilationUnit.compile();

        } catch (MultipleCompilationErrorsException me) {
            me.printStackTrace();
        }

    }
}