private static void checkCodeBlock(
     final PsiCodeBlock body, final Set<PsiField> candidates, Set<PsiField> usedFields) {
   try {
     final ControlFlow controlFlow =
         ControlFlowFactory.getInstance(body.getProject())
             .getControlFlow(body, AllVariablesControlFlowPolicy.getInstance());
     final List<PsiVariable> usedVars =
         ControlFlowUtil.getUsedVariables(controlFlow, 0, controlFlow.getSize());
     for (PsiVariable usedVariable : usedVars) {
       if (usedVariable instanceof PsiField) {
         final PsiField usedField = (PsiField) usedVariable;
         if (!usedFields.add(usedField)) {
           candidates.remove(usedField); // used in more than one code block
         }
       }
     }
     final List<PsiReferenceExpression> readBeforeWrites =
         ControlFlowUtil.getReadBeforeWrite(controlFlow);
     for (final PsiReferenceExpression readBeforeWrite : readBeforeWrites) {
       final PsiElement resolved = readBeforeWrite.resolve();
       if (resolved instanceof PsiField) {
         final PsiField field = (PsiField) resolved;
         PsiElement parent = body.getParent();
         if (!(parent instanceof PsiMethod)
             || !((PsiMethod) parent).isConstructor()
             || field.getInitializer() == null
             || field.hasModifierProperty(PsiModifier.STATIC)) {
           candidates.remove(field);
         }
       }
     }
   } catch (AnalysisCanceledException e) {
     candidates.clear();
   }
 }
 static HighlightInfo checkUnreachableStatement(@Nullable PsiCodeBlock codeBlock) {
   if (codeBlock == null) return null;
   // do not compute constant expressions for if() statement condition
   // see JLS 14.20 Unreachable Statements
   try {
     AllVariablesControlFlowPolicy policy = AllVariablesControlFlowPolicy.getInstance();
     final ControlFlow controlFlow =
         ControlFlowFactory.getInstance(codeBlock.getProject())
             .getControlFlow(codeBlock, policy, false, false);
     final PsiElement unreachableStatement = ControlFlowUtil.getUnreachableStatement(controlFlow);
     if (unreachableStatement != null) {
       String description = JavaErrorMessages.message("unreachable.statement");
       return HighlightInfo.newHighlightInfo(HighlightInfoType.ERROR)
           .range(unreachableStatement)
           .descriptionAndTooltip(description)
           .create();
     }
   } catch (AnalysisCanceledException | IndexNotReadyException e) {
     // incomplete code
   }
   return null;
 }