private static void checkExpression(
     PsiExpression expression, PsiModifierListOwner owner, PsiType type, ProblemsHolder holder) {
   AllowedValues allowed = getAllowedValues(owner, type, null);
   if (allowed == null) return;
   PsiElement scope = PsiUtil.getTopLevelEnclosingCodeBlock(expression, null);
   if (scope == null) scope = expression;
   if (!isAllowed(scope, expression, allowed, expression.getManager())) {
     registerProblem(expression, allowed, holder);
   }
 }
  @Nullable
  public static HighlightInfo checkFinalVariableMightAlreadyHaveBeenAssignedTo(
      @NotNull PsiVariable variable,
      @NotNull PsiReferenceExpression expression,
      @NotNull Map<PsiElement, Collection<ControlFlowUtil.VariableInfo>> finalVarProblems) {
    if (!PsiUtil.isAccessedForWriting(expression)) return null;

    final PsiElement scope =
        variable instanceof PsiField
            ? variable.getParent()
            : variable.getParent() == null ? null : variable.getParent().getParent();
    PsiElement codeBlock = PsiUtil.getTopLevelEnclosingCodeBlock(expression, scope);
    if (codeBlock == null) return null;
    Collection<ControlFlowUtil.VariableInfo> codeBlockProblems =
        getFinalVariableProblemsInBlock(finalVarProblems, codeBlock);

    boolean alreadyAssigned = false;
    for (ControlFlowUtil.VariableInfo variableInfo : codeBlockProblems) {
      if (variableInfo.expression == expression) {
        alreadyAssigned = true;
        break;
      }
    }

    if (!alreadyAssigned) {
      if (!(variable instanceof PsiField)) return null;
      final PsiField field = (PsiField) variable;
      final PsiClass aClass = field.getContainingClass();
      if (aClass == null) return null;
      // field can get assigned in other field initializers
      final PsiField[] fields = aClass.getFields();
      boolean isFieldStatic = field.hasModifierProperty(PsiModifier.STATIC);
      for (PsiField psiField : fields) {
        PsiExpression initializer = psiField.getInitializer();
        if (psiField != field
            && psiField.hasModifierProperty(PsiModifier.STATIC) == isFieldStatic
            && initializer != null
            && initializer != codeBlock
            && !variableDefinitelyNotAssignedIn(field, initializer)) {
          alreadyAssigned = true;
          break;
        }
      }

      if (!alreadyAssigned) {
        // field can get assigned in class initializers
        final PsiMember enclosingConstructorOrInitializer =
            PsiUtil.findEnclosingConstructorOrInitializer(expression);
        if (enclosingConstructorOrInitializer == null
            || !aClass
                .getManager()
                .areElementsEquivalent(
                    enclosingConstructorOrInitializer.getContainingClass(), aClass)) {
          return null;
        }
        final PsiClassInitializer[] initializers = aClass.getInitializers();
        for (PsiClassInitializer initializer : initializers) {
          if (initializer.hasModifierProperty(PsiModifier.STATIC)
              == field.hasModifierProperty(PsiModifier.STATIC)) {
            final PsiCodeBlock body = initializer.getBody();
            if (body == codeBlock) return null;
            try {
              final ControlFlow controlFlow = getControlFlow(body);
              if (!ControlFlowUtil.isVariableDefinitelyNotAssigned(field, controlFlow)) {
                alreadyAssigned = true;
                break;
              }
            } catch (AnalysisCanceledException e) {
              // incomplete code
              return null;
            }
          }
        }
      }

      if (!alreadyAssigned && !field.hasModifierProperty(PsiModifier.STATIC)) {
        // then check if instance field already assigned in other constructor
        final PsiMethod ctr =
            codeBlock.getParent() instanceof PsiMethod ? (PsiMethod) codeBlock.getParent() : null;
        // assignment to final field in several constructors threatens us only if these are linked
        // (there is this() call in the beginning)
        final List<PsiMethod> redirectedConstructors =
            ctr != null && ctr.isConstructor()
                ? JavaHighlightUtil.getChainedConstructors(ctr)
                : null;
        for (int j = 0; redirectedConstructors != null && j < redirectedConstructors.size(); j++) {
          PsiMethod redirectedConstructor = redirectedConstructors.get(j);
          PsiCodeBlock body = redirectedConstructor.getBody();
          if (body != null && variableDefinitelyAssignedIn(variable, body)) {
            alreadyAssigned = true;
            break;
          }
        }
      }
    }

    if (alreadyAssigned) {
      String description =
          JavaErrorMessages.message("variable.already.assigned", variable.getName());
      final HighlightInfo highlightInfo =
          HighlightInfo.newHighlightInfo(HighlightInfoType.ERROR)
              .range(expression)
              .descriptionAndTooltip(description)
              .create();
      QuickFixAction.registerQuickFixAction(
          highlightInfo,
          QUICK_FIX_FACTORY.createModifierListFix(variable, PsiModifier.FINAL, false, false));
      QuickFixAction.registerQuickFixAction(
          highlightInfo, QUICK_FIX_FACTORY.createDeferFinalAssignmentFix(variable, expression));
      return highlightInfo;
    }

    return null;
  }
  @Nullable
  public static HighlightInfo checkVariableInitializedBeforeUsage(
      @NotNull PsiReferenceExpression expression,
      @NotNull PsiVariable variable,
      @NotNull Map<PsiElement, Collection<PsiReferenceExpression>> uninitializedVarProblems,
      @NotNull PsiFile containingFile) {
    if (variable instanceof ImplicitVariable) return null;
    if (!PsiUtil.isAccessedForReading(expression)) return null;
    int startOffset = expression.getTextRange().getStartOffset();
    final PsiElement topBlock;
    if (variable.hasInitializer()) {
      topBlock = PsiUtil.getVariableCodeBlock(variable, variable);
      if (topBlock == null) return null;
    } else {
      PsiElement scope =
          variable instanceof PsiField
              ? ((PsiField) variable).getContainingClass()
              : variable.getParent() != null ? variable.getParent().getParent() : null;
      if (scope instanceof PsiCodeBlock && scope.getParent() instanceof PsiSwitchStatement) {
        scope = PsiTreeUtil.getParentOfType(scope, PsiCodeBlock.class);
      }

      topBlock =
          FileTypeUtils.isInServerPageFile(scope) && scope instanceof PsiFile
              ? scope
              : PsiUtil.getTopLevelEnclosingCodeBlock(expression, scope);
      if (variable instanceof PsiField) {
        // non final field already initialized with default value
        if (!variable.hasModifierProperty(PsiModifier.FINAL)) return null;
        // final field may be initialized in ctor or class initializer only
        // if we're inside non-ctr method, skip it
        if (PsiUtil.findEnclosingConstructorOrInitializer(expression) == null
            && HighlightUtil.findEnclosingFieldInitializer(expression) == null) {
          return null;
        }
        if (topBlock == null) return null;
        final PsiElement parent = topBlock.getParent();
        // access to final fields from inner classes always allowed
        if (inInnerClass(expression, ((PsiField) variable).getContainingClass(), containingFile))
          return null;
        final PsiCodeBlock block;
        final PsiClass aClass;
        if (parent instanceof PsiMethod) {
          PsiMethod constructor = (PsiMethod) parent;
          if (!containingFile
              .getManager()
              .areElementsEquivalent(
                  constructor.getContainingClass(), ((PsiField) variable).getContainingClass()))
            return null;
          // static variables already initialized in class initializers
          if (variable.hasModifierProperty(PsiModifier.STATIC)) return null;
          // as a last chance, field may be initialized in this() call
          final List<PsiMethod> redirectedConstructors =
              JavaHighlightUtil.getChainedConstructors(constructor);
          for (int j = 0;
              redirectedConstructors != null && j < redirectedConstructors.size();
              j++) {
            PsiMethod redirectedConstructor = redirectedConstructors.get(j);
            // variable must be initialized before its usage
            // ???
            // if (startOffset < redirectedConstructor.getTextRange().getStartOffset()) continue;
            PsiCodeBlock body = redirectedConstructor.getBody();
            if (body != null && variableDefinitelyAssignedIn(variable, body)) {
              return null;
            }
          }
          block = constructor.getBody();
          aClass = constructor.getContainingClass();
        } else if (parent instanceof PsiClassInitializer) {
          final PsiClassInitializer classInitializer = (PsiClassInitializer) parent;
          if (!containingFile
              .getManager()
              .areElementsEquivalent(
                  classInitializer.getContainingClass(),
                  ((PsiField) variable).getContainingClass())) return null;
          block = classInitializer.getBody();
          aClass = classInitializer.getContainingClass();
        } else {
          // field reference outside code block
          // check variable initialized before its usage
          final PsiField field = (PsiField) variable;

          aClass = field.getContainingClass();
          if (aClass == null
              || isFieldInitializedInOtherFieldInitializer(
                  aClass, field, field.hasModifierProperty(PsiModifier.STATIC))) {
            return null;
          }
          final PsiField anotherField =
              PsiTreeUtil.getTopmostParentOfType(expression, PsiField.class);
          int offset = startOffset;
          if (anotherField != null
              && anotherField.getContainingClass() == aClass
              && !field.hasModifierProperty(PsiModifier.STATIC)) {
            offset = 0;
          }
          block = null;
          // initializers will be checked later
          final PsiMethod[] constructors = aClass.getConstructors();
          for (PsiMethod constructor : constructors) {
            // variable must be initialized before its usage
            if (offset < constructor.getTextRange().getStartOffset()) continue;
            PsiCodeBlock body = constructor.getBody();
            if (body != null && variableDefinitelyAssignedIn(variable, body)) {
              return null;
            }
            // as a last chance, field may be initialized in this() call
            final List<PsiMethod> redirectedConstructors =
                JavaHighlightUtil.getChainedConstructors(constructor);
            for (int j = 0;
                redirectedConstructors != null && j < redirectedConstructors.size();
                j++) {
              PsiMethod redirectedConstructor = redirectedConstructors.get(j);
              // variable must be initialized before its usage
              if (offset < redirectedConstructor.getTextRange().getStartOffset()) continue;
              PsiCodeBlock redirectedBody = redirectedConstructor.getBody();
              if (redirectedBody != null
                  && variableDefinitelyAssignedIn(variable, redirectedBody)) {
                return null;
              }
            }
          }
        }

        if (aClass != null) {
          // field may be initialized in class initializer
          final PsiClassInitializer[] initializers = aClass.getInitializers();
          for (PsiClassInitializer initializer : initializers) {
            PsiCodeBlock body = initializer.getBody();
            if (body == block) break;
            // variable referenced in initializer must be initialized in initializer preceding
            // assignment
            // variable referenced in field initializer or in class initializer
            boolean shouldCheckInitializerOrder =
                block == null || block.getParent() instanceof PsiClassInitializer;
            if (shouldCheckInitializerOrder
                && startOffset < initializer.getTextRange().getStartOffset()) continue;
            if (initializer.hasModifierProperty(PsiModifier.STATIC)
                == variable.hasModifierProperty(PsiModifier.STATIC)) {
              if (variableDefinitelyAssignedIn(variable, body)) return null;
            }
          }
        }
      }
    }
    if (topBlock == null) return null;
    Collection<PsiReferenceExpression> codeBlockProblems = uninitializedVarProblems.get(topBlock);
    if (codeBlockProblems == null) {
      try {
        final ControlFlow controlFlow = getControlFlow(topBlock);
        codeBlockProblems = ControlFlowUtil.getReadBeforeWriteLocals(controlFlow);
      } catch (AnalysisCanceledException | IndexNotReadyException e) {
        codeBlockProblems = Collections.emptyList();
      }
      uninitializedVarProblems.put(topBlock, codeBlockProblems);
    }
    if (codeBlockProblems.contains(expression)) {
      final String name = expression.getElement().getText();
      String description = JavaErrorMessages.message("variable.not.initialized", name);
      HighlightInfo highlightInfo =
          HighlightInfo.newHighlightInfo(HighlightInfoType.ERROR)
              .range(expression)
              .descriptionAndTooltip(description)
              .create();
      QuickFixAction.registerQuickFixAction(
          highlightInfo, QUICK_FIX_FACTORY.createAddVariableInitializerFix(variable));
      if (variable instanceof PsiField) {
        QuickFixAction.registerQuickFixAction(
            highlightInfo,
            QUICK_FIX_FACTORY.createModifierListFix(variable, PsiModifier.FINAL, false, false));
      }
      return highlightInfo;
    }

    return null;
  }