static PsiElement[] getOccurrences(GrIntroduceParameterSettings settings) {
    final GrParametersOwner scope = settings.getToReplaceIn();

    final GrExpression expression = settings.getExpression();
    if (expression != null) {
      final PsiElement expr = PsiUtil.skipParentheses(expression, false);
      if (expr == null) return PsiElement.EMPTY_ARRAY;

      final PsiElement[] occurrences = GroovyRefactoringUtil.getExpressionOccurrences(expr, scope);
      if (occurrences == null || occurrences.length == 0) {
        throw new GrRefactoringError(GroovyRefactoringBundle.message("no.occurrences.found"));
      }
      return occurrences;
    } else {
      final GrVariable var = settings.getVar();
      LOG.assertTrue(var != null);
      final List<PsiElement> list = Collections.synchronizedList(new ArrayList<PsiElement>());
      ReferencesSearch.search(var, new LocalSearchScope(scope))
          .forEach(
              new Processor<PsiReference>() {
                @Override
                public boolean process(PsiReference psiReference) {
                  final PsiElement element = psiReference.getElement();
                  if (element != null) {
                    list.add(element);
                  }
                  return true;
                }
              });
      return list.toArray(new PsiElement[list.size()]);
    }
  }
  @Override
  protected void performRefactoring(UsageInfo[] usages) {
    GroovyPsiElementFactory factory = GroovyPsiElementFactory.getInstance(myProject);

    PsiType initializerType = mySettings.getSelectedType();

    // Changing external occurrences (the tricky part)

    IntroduceParameterUtil.processUsages(usages, this);

    final GrMethod toReplaceIn = (GrMethod) mySettings.getToReplaceIn();
    final PsiMethod toSearchFor = (PsiMethod) mySettings.getToSearchFor();

    final boolean methodsToProcessAreDifferent = toReplaceIn != toSearchFor;
    if (mySettings.generateDelegate()) {
      GroovyIntroduceParameterUtil.generateDelegate(toReplaceIn, myParameterInitializer, myProject);
      if (methodsToProcessAreDifferent) {
        final GrMethod method =
            GroovyIntroduceParameterUtil.generateDelegate(
                toSearchFor, myParameterInitializer, myProject);
        final PsiClass containingClass = method.getContainingClass();
        if (containingClass != null && containingClass.isInterface()) {
          final GrOpenBlock block = method.getBlock();
          if (block != null) {
            block.delete();
          }
        }
      }
    }

    // Changing signature of initial method
    // (signature of myMethodToReplaceIn will be either changed now or have already been changed)
    LOG.assertTrue(initializerType == null || initializerType.isValid());

    final FieldConflictsResolver fieldConflictsResolver =
        new FieldConflictsResolver(mySettings.getName(), toReplaceIn.getBlock());
    IntroduceParameterUtil.changeMethodSignatureAndResolveFieldConflicts(
        new UsageInfo(toReplaceIn), usages, this);
    if (methodsToProcessAreDifferent) {
      IntroduceParameterUtil.changeMethodSignatureAndResolveFieldConflicts(
          new UsageInfo(toSearchFor), usages, this);
    }

    // Replacing expression occurrences
    for (UsageInfo usage : usages) {
      if (usage instanceof ChangedMethodCallInfo) {
        PsiElement element = usage.getElement();

        GroovyIntroduceParameterUtil.processChangedMethodCall(element, mySettings, myProject);
      } else if (usage instanceof InternalUsageInfo) {
        PsiElement element = usage.getElement();
        if (element == null) continue;
        GrExpression newExpr = factory.createExpressionFromText(mySettings.getName());
        if (element instanceof GrExpression) {
          ((GrExpression) element).replaceWithExpression(newExpr, true);
        } else {
          element.replace(newExpr);
        }
      }
    }

    final StringPartInfo stringPartInfo = mySettings.getStringPartInfo();
    if (stringPartInfo != null) {
      final GrExpression expr =
          GrIntroduceHandlerBase.processLiteral(
              mySettings.getName(), mySettings.getStringPartInfo(), mySettings.getProject());
      final Editor editor = PsiUtilBase.findEditor(expr);
      if (editor != null) {
        editor.getSelectionModel().removeSelection();
        editor.getCaretModel().moveToOffset(expr.getTextRange().getEndOffset());
      }
    }

    final GrVariable var = mySettings.getVar();
    if (var != null && mySettings.removeLocalVariable()) {
      var.delete();
    }
    fieldConflictsResolver.fix();
  }