PDE required-by query must check that import-type corresponds to mode…

…l type (#80)

ca.ubc.cs.ferret.pde/src/ca/ubc/cs/ferret/pde/PdeModelHelper.java

@@ -372,14 +372,16 @@ public Collection<IFeatureModel> getFeaturesRequiring(IModel source) {
 		verifyModelCaches();
 		String sourceId = getId(source);
 		if(sourceId == null) { return Collections.emptyList(); }
+		boolean sourceIsFeature = source instanceof IFeatureModel;
 		Collection<IFeatureModel> results = new ArrayList<IFeatureModel>();
 		for(IFeatureModel featureModel : features.values()) {
 			if(!featureModel.isValid()) {
 				continue;
 			}
 			IFeature feature = featureModel.getFeature();
 			for(IFeatureImport p : feature.getImports()) {
-				if(sourceId.equals(p.getId())) {
+				boolean importIsFeature = p.getType() == IFeatureImport.FEATURE;
+				if (sourceId.equals(p.getId()) && importIsFeature == sourceIsFeature) {
 					results.add(featureModel);
 					break;
 				}