signature conflicts

IntSet used in ConstantIntSet

package com.gs.fw.common.mithra;

public interface IntSet extends com.gs.collections.api.set.primitive.IntSet, org.eclipse.collections.api.set.primitive.IntSet
{
    // COMPILE ERROR:
    // 'asLazy()' in 'org.eclipse.collections.api.IntIterable' clashes with
    // 'asLazy()' in 'com.gs.collections.api.IntIterable'; methods have unrelated return types
}

UnifiedSet used in ConstantStringSet

package com.gs.fw.common.mithra;

import com.gs.collections.api.set.MutableSet;

public class UnifiedSet<T> extends org.eclipse.collections.impl.set.mutable.UnifiedSet<T> implements MutableSet<T>
{
    // COMPILE ERROR:
    //'zip(Iterable<S>, R)' in 'com.gs.collections.api.RichIterable' clashes with
    // 'zip(Iterable<S>, R)' in 'org.eclipse.collections.api.RichIterable'; both methods have same erasure,
    // yet neither overrides the other

    // 'zipWithIndex(R)' in 'com.gs.collections.api.RichIterable' clashes with
    // 'zipWithIndex(R)' in 'org.eclipse.collections.api.RichIterable'; both methods have same erasure,
    // yet neither overrides the other
    
    // Class 'UnifiedSet' must either be declared abstract or implement abstract method 'zipWithIndex(R)' in 'RichIterable'
}