@Nullable
 private PsiType extractContentTypeFromType(PsiType collectionType) {
   if (!(collectionType instanceof PsiClassType)) {
     return null;
   }
   final PsiClassType classType = (PsiClassType) collectionType;
   final PsiType[] parameterTypes = classType.getParameters();
   if (parameterTypes.length == 0) {
     return null;
   }
   final PsiType parameterType = parameterTypes[0];
   if (parameterType == null) {
     return null;
   }
   if (parameterType instanceof PsiWildcardType) {
     final PsiWildcardType wildcardType = (PsiWildcardType) parameterType;
     return wildcardType.getExtendsBound();
   } else if (parameterType instanceof PsiCapturedWildcardType) {
     final PsiCapturedWildcardType capturedWildcardType =
         (PsiCapturedWildcardType) parameterType;
     final PsiWildcardType wildcardType = capturedWildcardType.getWildcard();
     return wildcardType.getExtendsBound();
   }
   return parameterType;
 }
 private static boolean isIndexedListLoopStatement(PsiForStatement forStatement, boolean ignoreUntypedCollections) {
   final PsiStatement initialization = forStatement.getInitialization();
   if (!(initialization instanceof PsiDeclarationStatement)) {
     return false;
   }
   final PsiDeclarationStatement declaration = (PsiDeclarationStatement)initialization;
   final PsiElement[] declaredElements = declaration.getDeclaredElements();
   final PsiElement secondDeclaredElement;
   if (declaredElements.length == 1) {
     secondDeclaredElement = null;
   }
   else if (declaredElements.length == 2) {
     secondDeclaredElement = declaredElements[1];
   }
   else {
     return false;
   }
   final PsiElement declaredElement = declaredElements[0];
   if (!(declaredElement instanceof PsiVariable)) {
     return false;
   }
   final PsiVariable indexVariable = (PsiVariable)declaredElement;
   final PsiExpression initialValue = indexVariable.getInitializer();
   if (initialValue == null) {
     return false;
   }
   final Object constant = ExpressionUtils.computeConstantExpression(initialValue);
   if (!(constant instanceof Number)) {
     return false;
   }
   final Number number = (Number)constant;
   if (number.intValue() != 0) {
     return false;
   }
   final PsiExpression condition = forStatement.getCondition();
   final Holder collectionHolder = getCollectionFromSizeComparison(condition, indexVariable, secondDeclaredElement);
   if (collectionHolder == null) {
     return false;
   }
   final PsiStatement update = forStatement.getUpdate();
   if (!VariableAccessUtils.variableIsIncremented(indexVariable, update)) {
     return false;
   }
   final PsiStatement body = forStatement.getBody();
   if (!isIndexVariableOnlyUsedAsListIndex(collectionHolder, indexVariable, body)) {
     return false;
   }
   if (collectionHolder != Holder.DUMMY) {
     final PsiVariable collection = collectionHolder.getVariable();
     final PsiClassType collectionType = (PsiClassType)collection.getType();
     final PsiType[] parameters = collectionType.getParameters();
     if (ignoreUntypedCollections && parameters.length == 0) {
       return false;
     }
     return !VariableAccessUtils.variableIsAssigned(collection, body);
   }
   return true;
 }