Not recognizing overload of abstract method

In GPars is the test file groovyx/gpars/memoize/MemoizeTest.groovy it comprises:

package groovyx.gpars.memoize
        
/**
 * @author Vaclav Pech
 * Date: Jun 21, 2010
 */
        
public class MemoizeTest extends AbstractMemoizeTest {
    Closure buildMemoizeClosure(Closure cl) {
        cl.memoize()
    }
}

GrEclipse redlines the MemoizeTest with the console error:

/GPars/src/test/groovy/groovyx/gpars/memoize/MemoizeTest.groovy: 24 Groovy:Can't have an abstract method in a non-abstract class. The class 'groovyx.gpars.memoize.MemoizeTest' must be declared abstract or the method 'Closure buildMemoizeClosure(Closure)' must be implemented.

which seems a bit unfair. This doesn't stop the code compiling and executing so the problem must only be in the part of GrEclipse to do with highlighting things.

Hovering gives the error message:

Multiple markers at this line

• The hierarchy of the type MemoizeTest is inconsistent
• Groovy:Can't have an abstract method in a non-abstract class. The class 'groovyx.gpars.memoize.MemoizeTest' must be declared abstract or the method 'Closure buildMemoizeClosure
  (Closure)' must be implemented.