private void reportNullableReturns(
      DataFlowInstructionVisitor visitor,
      ProblemsHolder holder,
      Set<PsiElement> reportedAnchors,
      @NotNull PsiElement block) {
    final PsiMethod method = getScopeMethod(block);
    if (method == null || NullableStuffInspectionBase.isNullableNotInferred(method, true)) return;

    boolean notNullRequired = NullableNotNullManager.isNotNull(method);
    if (!notNullRequired && !SUGGEST_NULLABLE_ANNOTATIONS) return;

    PsiType returnType = method.getReturnType();
    // no warnings in void lambdas, where the expression is not returned anyway
    if (block instanceof PsiExpression
        && block.getParent() instanceof PsiLambdaExpression
        && returnType == PsiType.VOID) return;

    // no warnings for Void methods, where only null can be possibly returned
    if (returnType == null || returnType.equalsToText(CommonClassNames.JAVA_LANG_VOID)) return;

    for (PsiElement statement : visitor.getProblems(NullabilityProblem.nullableReturn)) {
      assert statement instanceof PsiExpression;
      final PsiExpression expr = (PsiExpression) statement;
      if (!reportedAnchors.add(expr)) continue;

      if (notNullRequired) {
        final String text =
            isNullLiteralExpression(expr)
                ? InspectionsBundle.message("dataflow.message.return.null.from.notnull")
                : InspectionsBundle.message("dataflow.message.return.nullable.from.notnull");
        holder.registerProblem(expr, text);
      } else if (AnnotationUtil.isAnnotatingApplicable(statement)) {
        final NullableNotNullManager manager =
            NullableNotNullManager.getInstance(expr.getProject());
        final String defaultNullable = manager.getDefaultNullable();
        final String presentableNullable = StringUtil.getShortName(defaultNullable);
        final String text =
            isNullLiteralExpression(expr)
                ? InspectionsBundle.message(
                    "dataflow.message.return.null.from.notnullable", presentableNullable)
                : InspectionsBundle.message(
                    "dataflow.message.return.nullable.from.notnullable", presentableNullable);
        final LocalQuickFix[] fixes =
            PsiTreeUtil.getParentOfType(expr, PsiMethod.class, PsiLambdaExpression.class)
                    instanceof PsiLambdaExpression
                ? LocalQuickFix.EMPTY_ARRAY
                : new LocalQuickFix[] {
                  new AnnotateMethodFix(
                      defaultNullable, ArrayUtil.toStringArray(manager.getNotNulls())) {
                    @Override
                    public int shouldAnnotateBaseMethod(
                        PsiMethod method, PsiMethod superMethod, Project project) {
                      return 1;
                    }
                  }
                };
        holder.registerProblem(expr, text, fixes);
      }
    }
  }
  @Override
  protected String validateAndCommitData() {
    PsiManager manager = PsiManager.getInstance(myProject);
    PsiElementFactory factory = JavaPsiFacade.getInstance(manager.getProject()).getElementFactory();

    String name = getMethodName();
    if (!JavaPsiFacade.getInstance(manager.getProject()).getNameHelper().isIdentifier(name)) {
      return RefactoringMessageUtil.getIncorrectIdentifierMessage(name);
    }

    if (myMethod.canChangeReturnType() == MethodDescriptor.ReadWriteOption.ReadWrite) {
      try {
        ((PsiTypeCodeFragment) myReturnTypeCodeFragment).getType();
      } catch (PsiTypeCodeFragment.TypeSyntaxException e) {
        myReturnTypeField.requestFocus();
        return RefactoringBundle.message(
            "changeSignature.wrong.return.type", myReturnTypeCodeFragment.getText());
      } catch (PsiTypeCodeFragment.NoTypeException e) {
        myReturnTypeField.requestFocus();
        return RefactoringBundle.message("changeSignature.no.return.type");
      }
    }

    List<ParameterTableModelItemBase<ParameterInfoImpl>> parameterInfos =
        myParametersTableModel.getItems();
    final int newParametersNumber = parameterInfos.size();

    for (int i = 0; i < newParametersNumber; i++) {
      final ParameterTableModelItemBase<ParameterInfoImpl> item = parameterInfos.get(i);

      if (!JavaPsiFacade.getInstance(manager.getProject())
          .getNameHelper()
          .isIdentifier(item.parameter.getName())) {
        return RefactoringMessageUtil.getIncorrectIdentifierMessage(item.parameter.getName());
      }

      final PsiType type;
      try {
        type = ((PsiTypeCodeFragment) parameterInfos.get(i).typeCodeFragment).getType();
      } catch (PsiTypeCodeFragment.TypeSyntaxException e) {
        return RefactoringBundle.message(
            "changeSignature.wrong.type.for.parameter",
            item.typeCodeFragment.getText(),
            item.parameter.getName());
      } catch (PsiTypeCodeFragment.NoTypeException e) {
        return RefactoringBundle.message(
            "changeSignature.no.type.for.parameter", item.parameter.getName());
      }

      item.parameter.setType(type);

      if (type instanceof PsiEllipsisType && i != newParametersNumber - 1) {
        return RefactoringBundle.message("changeSignature.vararg.not.last");
      }

      if (item.parameter.oldParameterIndex < 0) {
        item.parameter.defaultValue =
            ApplicationManager.getApplication()
                .runWriteAction(
                    new Computable<String>() {
                      @Override
                      public String compute() {
                        return JavaCodeStyleManager.getInstance(myProject)
                            .qualifyClassReferences(item.defaultValueCodeFragment)
                            .getText();
                      }
                    });
        String def = item.parameter.defaultValue;
        def = def.trim();
        if (!(type instanceof PsiEllipsisType)) {
          try {
            if (!StringUtil.isEmpty(def)) {
              factory.createExpressionFromText(def, null);
            }
          } catch (IncorrectOperationException e) {
            return e.getMessage();
          }
        }
      }
    }

    ThrownExceptionInfo[] exceptionInfos = myExceptionsModel.getThrownExceptions();
    PsiTypeCodeFragment[] typeCodeFragments = myExceptionsModel.getTypeCodeFragments();
    for (int i = 0; i < exceptionInfos.length; i++) {
      ThrownExceptionInfo exceptionInfo = exceptionInfos[i];
      PsiTypeCodeFragment typeCodeFragment = typeCodeFragments[i];
      try {
        PsiType type = typeCodeFragment.getType();
        if (!(type instanceof PsiClassType)) {
          return RefactoringBundle.message(
              "changeSignature.wrong.type.for.exception", typeCodeFragment.getText());
        }

        PsiClassType throwable =
            JavaPsiFacade.getInstance(myProject)
                .getElementFactory()
                .createTypeByFQClassName("java.lang.Throwable", type.getResolveScope());
        if (!throwable.isAssignableFrom(type)) {
          return RefactoringBundle.message(
              "changeSignature.not.throwable.type", typeCodeFragment.getText());
        }
        exceptionInfo.setType((PsiClassType) type);
      } catch (PsiTypeCodeFragment.TypeSyntaxException e) {
        return RefactoringBundle.message(
            "changeSignature.wrong.type.for.exception", typeCodeFragment.getText());
      } catch (PsiTypeCodeFragment.NoTypeException e) {
        return RefactoringBundle.message("changeSignature.no.type.for.exception");
      }
    }

    // warnings
    try {
      if (myMethod.canChangeReturnType() == MethodDescriptor.ReadWriteOption.ReadWrite) {
        if (!RefactoringUtil.isResolvableType(
            ((PsiTypeCodeFragment) myReturnTypeCodeFragment).getType())) {
          if (Messages.showOkCancelDialog(
                  myProject,
                  RefactoringBundle.message(
                      "changeSignature.cannot.resolve.return.type",
                      myReturnTypeCodeFragment.getText()),
                  RefactoringBundle.message("changeSignature.refactoring.name"),
                  Messages.getWarningIcon())
              != 0) {
            return EXIT_SILENTLY;
          }
        }
      }
      for (ParameterTableModelItemBase<ParameterInfoImpl> item : parameterInfos) {

        if (!RefactoringUtil.isResolvableType(
            ((PsiTypeCodeFragment) item.typeCodeFragment).getType())) {
          if (Messages.showOkCancelDialog(
                  myProject,
                  RefactoringBundle.message(
                      "changeSignature.cannot.resolve.parameter.type",
                      item.typeCodeFragment.getText(),
                      item.parameter.getName()),
                  RefactoringBundle.message("changeSignature.refactoring.name"),
                  Messages.getWarningIcon())
              != 0) {
            return EXIT_SILENTLY;
          }
        }
      }
    } catch (PsiTypeCodeFragment.IncorrectTypeException ignored) {
    }
    return null;
  }
  @NotNull
  private static LookupElement castQualifier(
      @NotNull LookupElement item,
      @Nullable final PsiTypeLookupItem castTypeItem,
      @Nullable PsiType plainQualifier,
      JavaCompletionProcessor processor) {
    if (castTypeItem == null) {
      return item;
    }
    if (plainQualifier != null) {
      Object o = item.getObject();
      if (o instanceof PsiMethod) {
        PsiType castType = castTypeItem.getType();
        if (plainQualifier instanceof PsiClassType && castType instanceof PsiClassType) {
          PsiMethod method = (PsiMethod) o;
          PsiClassType.ClassResolveResult plainResult =
              ((PsiClassType) plainQualifier).resolveGenerics();
          PsiClass plainClass = plainResult.getElement();
          if (plainClass != null && plainClass.findMethodBySignature(method, true) != null) {
            PsiClass castClass = ((PsiClassType) castType).resolveGenerics().getElement();

            if (castClass == null || !castClass.isInheritor(plainClass, true)) {
              return item;
            }

            PsiSubstitutor plainSub = plainResult.getSubstitutor();
            PsiSubstitutor castSub =
                TypeConversionUtil.getSuperClassSubstitutor(plainClass, (PsiClassType) castType);
            PsiType returnType = method.getReturnType();
            if (method.getSignature(plainSub).equals(method.getSignature(castSub))) {
              PsiType typeAfterCast = toRaw(castSub.substitute(returnType));
              PsiType typeDeclared = toRaw(plainSub.substitute(returnType));
              if (typeAfterCast != null
                  && typeDeclared != null
                  && typeAfterCast.isAssignableFrom(typeDeclared)
                  && processor.isAccessible(plainClass.findMethodBySignature(method, true))) {
                return item;
              }
            }
          }
        }
      } else if (containsMember(plainQualifier, o)) {
        return item;
      }
    }

    return LookupElementDecorator.withInsertHandler(
        item,
        new InsertHandlerDecorator<LookupElement>() {
          @Override
          public void handleInsert(
              InsertionContext context, LookupElementDecorator<LookupElement> item) {
            final Document document = context.getEditor().getDocument();
            context.commitDocument();
            final PsiFile file = context.getFile();
            final PsiJavaCodeReferenceElement ref =
                PsiTreeUtil.findElementOfClassAtOffset(
                    file, context.getStartOffset(), PsiJavaCodeReferenceElement.class, false);
            if (ref != null) {
              final PsiElement qualifier = ref.getQualifier();
              if (qualifier != null) {
                final CommonCodeStyleSettings settings = context.getCodeStyleSettings();

                final String parenSpace = settings.SPACE_WITHIN_PARENTHESES ? " " : "";
                document.insertString(qualifier.getTextRange().getEndOffset(), parenSpace + ")");

                final String spaceWithin = settings.SPACE_WITHIN_CAST_PARENTHESES ? " " : "";
                final String prefix = "(" + parenSpace + "(" + spaceWithin;
                final String spaceAfter = settings.SPACE_AFTER_TYPE_CAST ? " " : "";
                final int exprStart = qualifier.getTextRange().getStartOffset();
                document.insertString(exprStart, prefix + spaceWithin + ")" + spaceAfter);

                CompletionUtil.emulateInsertion(context, exprStart + prefix.length(), castTypeItem);
                PsiDocumentManager.getInstance(file.getProject())
                    .doPostponedOperationsAndUnblockDocument(document);
                context.getEditor().getCaretModel().moveToOffset(context.getTailOffset());
              }
            }

            item.getDelegate().handleInsert(context);
          }
        });
  }