Program: 11757
Project: 11757
Buggy source:
@Override protected boolean prepare(){
  boolean result=false;
  if (owner != null) {
    if (domain.isReadOnly(owner.eResource())) {
      return false;
    }
    EClass eMetaObject=owner.eClass();
    EList<EStructuralFeature> eAllStructuralFeatures=eMetaObject.getEAllStructuralFeatures();
    if (eAllStructuralFeatures.contains(feature) || eAllStructuralFeatures.contains(ExtendedMetaData.INSTANCE.getAffiliation(eMetaObject,feature))) {
      EClassifier eType=feature.getEType();
      if (ownerList != null) {
        if (index >= 0 && index < ownerList.size() && eType.isInstance(value) && (!feature.isUnique() || !ownerList.contains(value))) {
          oldValue=ownerList.get(index);
          result=true;
        }
      }
 else       if (feature.isMany()) {
        if (owner.eIsSet(feature)) {
          oldValue=new BasicEList<Object>((EList<?>)owner.eGet(feature));
        }
 else {
          oldValue=UNSET_VALUE;
        }
        if (value == UNSET_VALUE) {
          result=true;
        }
 else         if (value instanceof Collection<?>) {
          Collection<?> collection=(Collection<?>)value;
          result=true;
          for (          Object object : collection) {
            if (!eType.isInstance(object)) {
              result=false;
              break;
            }
          }
        }
      }
 else {
        if (owner.eIsSet(feature)) {
          oldValue=owner.eGet(feature);
        }
 else {
          oldValue=UNSET_VALUE;
        }
        result=value == null || value == UNSET_VALUE || eType.isInstance(value);
      }
      if (result && feature instanceof EReference && ((EReference)feature).isContainment()) {
        for (EObject container=owner; container != null; container=container.eContainer()) {
          if (value == container) {
            result=false;
            break;
          }
        }
      }
    }
  }
  return result;
}

Fixed version (ground truth):
@Override protected boolean prepare(){
  boolean result=false;
  if (owner != null) {
    if (domain.isReadOnly(owner.eResource())) {
      return false;
    }
    EClass eMetaObject=owner.eClass();
    EList<EStructuralFeature> eAllStructuralFeatures=eMetaObject.getEAllStructuralFeatures();
    if (eAllStructuralFeatures.contains(feature) || feature != null && eAllStructuralFeatures.contains(ExtendedMetaData.INSTANCE.getAffiliation(eMetaObject,feature))) {
      EClassifier eType=feature.getEType();
      if (ownerList != null) {
        if (index >= 0 && index < ownerList.size() && eType.isInstance(value) && (!feature.isUnique() || !ownerList.contains(value))) {
          oldValue=ownerList.get(index);
          result=true;
        }
      }
 else       if (feature.isMany()) {
        if (owner.eIsSet(feature)) {
          oldValue=new BasicEList<Object>((EList<?>)owner.eGet(feature));
        }
 else {
          oldValue=UNSET_VALUE;
        }
        if (value == UNSET_VALUE) {
          result=true;
        }
 else         if (value instanceof Collection<?>) {
          Collection<?> collection=(Collection<?>)value;
          result=true;
          for (          Object object : collection) {
            if (!eType.isInstance(object)) {
              result=false;
              break;
            }
          }
        }
      }
 else {
        if (owner.eIsSet(feature)) {
          oldValue=owner.eGet(feature);
        }
 else {
          oldValue=UNSET_VALUE;
        }
        result=value == null || value == UNSET_VALUE || eType.isInstance(value);
      }
      if (result && feature instanceof EReference && ((EReference)feature).isContainment()) {
        for (EObject container=owner; container != null; container=container.eContainer()) {
          if (value == container) {
            result=false;
            break;
          }
        }
      }
    }
  }
  return result;
}