/**
  * @param sideEffects if null, delete usages, otherwise collect side effects
  * @return true if there are at least one unrecoverable side effect found, false if no side
  *     effects, null if read usage found (may happen if interval between fix creation in invoke()
  *     call was long enough)
  * @throws com.intellij.util.IncorrectOperationException
  */
 static Boolean processUsage(
     PsiElement element, PsiVariable variable, List<PsiElement> sideEffects, int deleteMode)
     throws IncorrectOperationException {
   if (!element.isValid()) return null;
   PsiElementFactory factory =
       JavaPsiFacade.getInstance(variable.getProject()).getElementFactory();
   while (element != null) {
     if (element instanceof PsiAssignmentExpression) {
       PsiAssignmentExpression expression = (PsiAssignmentExpression) element;
       PsiExpression lExpression = expression.getLExpression();
       // there should not be read access to the variable, otherwise it is not unused
       if (!(lExpression instanceof PsiReferenceExpression)
           || variable != ((PsiReferenceExpression) lExpression).resolve()) {
         return null;
       }
       PsiExpression rExpression = expression.getRExpression();
       rExpression = PsiUtil.deparenthesizeExpression(rExpression);
       if (rExpression == null) return true;
       // replace assignment with expression and resimplify
       boolean sideEffectFound = checkSideEffects(rExpression, variable, sideEffects);
       if (!(element.getParent() instanceof PsiExpressionStatement)
           || PsiUtil.isStatement(rExpression)) {
         if (deleteMode == MAKE_STATEMENT
             || deleteMode == DELETE_ALL
                 && !(element.getParent() instanceof PsiExpressionStatement)) {
           element = replaceElementWithExpression(rExpression, factory, element);
           while (element.getParent() instanceof PsiParenthesizedExpression) {
             element = element.getParent().replace(element);
           }
           List<PsiElement> references = new ArrayList<PsiElement>();
           collectReferences(element, variable, references);
           deleteReferences(variable, references, deleteMode);
         } else if (deleteMode == DELETE_ALL) {
           deleteWholeStatement(element, factory);
         }
         return true;
       } else {
         if (deleteMode != CANCEL) {
           deleteWholeStatement(element, factory);
         }
         return !sideEffectFound;
       }
     } else if (element instanceof PsiExpressionStatement && deleteMode != CANCEL) {
       final PsiElement parent = element.getParent();
       if (parent instanceof PsiIfStatement
           || parent instanceof PsiLoopStatement
               && ((PsiLoopStatement) parent).getBody() == element) {
         element.replace(
             JavaPsiFacade.getElementFactory(element.getProject())
                 .createStatementFromText(";", element));
       } else {
         element.delete();
       }
       break;
     } else if (element instanceof PsiVariable && element == variable) {
       PsiExpression expression = variable.getInitializer();
       if (expression != null) {
         expression = PsiUtil.deparenthesizeExpression(expression);
       }
       boolean sideEffectsFound = checkSideEffects(expression, variable, sideEffects);
       if (expression != null
           && PsiUtil.isStatement(expression)
           && variable instanceof PsiLocalVariable
           && !(variable.getParent() instanceof PsiDeclarationStatement
               && ((PsiDeclarationStatement) variable.getParent()).getDeclaredElements().length
                   > 1)) {
         if (deleteMode == MAKE_STATEMENT) {
           element = element.replace(createStatementIfNeeded(expression, factory, element));
           List<PsiElement> references = new ArrayList<PsiElement>();
           collectReferences(element, variable, references);
           deleteReferences(variable, references, deleteMode);
         } else if (deleteMode == DELETE_ALL) {
           element.delete();
         }
         return true;
       } else {
         if (deleteMode != CANCEL) {
           if (element instanceof PsiField) {
             ((PsiField) element).normalizeDeclaration();
           }
           element.delete();
         }
         return !sideEffectsFound;
       }
     }
     element = element.getParent();
   }
   return true;
 }
  private void addTypesByVariable(
      HashSet<PsiType> typesSet,
      PsiVariable var,
      PsiFile scopeFile,
      HashSet<PsiVariable> checkedVariables,
      int flags,
      TextRange rangeToIgnore) {
    if (!checkedVariables.add(var)) return;
    // System.out.println("analyzing usages of " + var + " in file " + scopeFile);
    SearchScope searchScope = new LocalSearchScope(scopeFile);

    if (BitUtil.isSet(flags, CHECK_USAGE) || BitUtil.isSet(flags, CHECK_DOWN)) {
      for (PsiReference varRef : ReferencesSearch.search(var, searchScope, false)) {
        PsiElement ref = varRef.getElement();

        if (BitUtil.isSet(flags, CHECK_USAGE)) {
          PsiType type = guessElementTypeFromReference(myMethodPatternMap, ref, rangeToIgnore);
          if (type != null && !(type instanceof PsiPrimitiveType)) {
            typesSet.add(type);
          }
        }

        if (BitUtil.isSet(flags, CHECK_DOWN)) {
          if (ref.getParent() instanceof PsiExpressionList
              && ref.getParent().getParent() instanceof PsiMethodCallExpression) { // TODO : new
            PsiExpressionList list = (PsiExpressionList) ref.getParent();
            PsiExpression[] args = list.getExpressions();
            int argIndex = -1;
            for (int j = 0; j < args.length; j++) {
              PsiExpression arg = args[j];
              if (arg.equals(ref)) {
                argIndex = j;
                break;
              }
            }

            PsiMethodCallExpression methodCall = (PsiMethodCallExpression) list.getParent();
            PsiMethod method = (PsiMethod) methodCall.getMethodExpression().resolve();
            if (method != null) {
              PsiParameter[] parameters = method.getParameterList().getParameters();
              if (argIndex < parameters.length) {
                addTypesByVariable(
                    typesSet,
                    parameters[argIndex],
                    method.getContainingFile(),
                    checkedVariables,
                    flags | CHECK_USAGE,
                    rangeToIgnore);
              }
            }
          }
        }
      }
    }

    if (BitUtil.isSet(flags, CHECK_UP)) {
      if (var instanceof PsiParameter
          && var.getParent() instanceof PsiParameterList
          && var.getParent().getParent() instanceof PsiMethod) {
        PsiParameterList list = (PsiParameterList) var.getParent();
        PsiParameter[] parameters = list.getParameters();
        int argIndex = -1;
        for (int i = 0; i < parameters.length; i++) {
          PsiParameter parameter = parameters[i];
          if (parameter.equals(var)) {
            argIndex = i;
            break;
          }
        }

        PsiMethod method = (PsiMethod) var.getParent().getParent();
        // System.out.println("analyzing usages of " + method + " in file " + scopeFile);
        for (PsiReference methodRef : ReferencesSearch.search(method, searchScope, false)) {
          PsiElement ref = methodRef.getElement();
          if (ref.getParent() instanceof PsiMethodCallExpression) {
            PsiMethodCallExpression methodCall = (PsiMethodCallExpression) ref.getParent();
            PsiExpression[] args = methodCall.getArgumentList().getExpressions();
            if (args.length <= argIndex) continue;
            PsiExpression arg = args[argIndex];
            if (arg instanceof PsiReferenceExpression) {
              PsiElement refElement = ((PsiReferenceExpression) arg).resolve();
              if (refElement instanceof PsiVariable) {
                addTypesByVariable(
                    typesSet,
                    (PsiVariable) refElement,
                    scopeFile,
                    checkedVariables,
                    flags | CHECK_USAGE,
                    rangeToIgnore);
              }
            }
            // TODO : constructor
          }
        }
      }
    }
  }