private static void checkMethodCall(RefElement refWhat, final PsiElement element) {
    if (!(refWhat instanceof RefMethod)) return;
    final RefMethod refMethod = (RefMethod) refWhat;
    final PsiElement psiElement = refMethod.getElement();
    if (!(psiElement instanceof PsiMethod)) return;
    final PsiMethod psiMethod = (PsiMethod) psiElement;
    if (!PsiType.BOOLEAN.equals(psiMethod.getReturnType())) return;
    element.accept(
        new JavaRecursiveElementWalkingVisitor() {
          @Override
          public void visitMethodCallExpression(PsiMethodCallExpression call) {
            super.visitMethodCallExpression(call);
            final PsiReferenceExpression methodExpression = call.getMethodExpression();
            if (methodExpression.isReferenceTo(psiMethod)) {
              if (isInvertedMethodCall(methodExpression)) return;
              refMethod.putUserData(ALWAYS_INVERTED, Boolean.FALSE);
            }
          }

          @Override
          public void visitMethodReferenceExpression(PsiMethodReferenceExpression expression) {
            super.visitMethodReferenceExpression(expression);
            if (expression.isReferenceTo(psiElement)) {
              refMethod.putUserData(ALWAYS_INVERTED, Boolean.FALSE);
            }
          }
        });
  }
 @Override
 public void onInitialize(RefElement refElement) {
   if (refElement instanceof RefMethod) {
     final PsiElement element = refElement.getElement();
     if (!(element instanceof PsiMethod)) return;
     if (!PsiType.BOOLEAN.equals(((PsiMethod) element).getReturnType())) return;
     refElement.putUserData(ALWAYS_INVERTED, Boolean.TRUE); // initial mark boolean methods
   }
 }
 private static boolean isCompileTimeFlagReference(PsiElement element) {
   PsiElement resolved =
       element instanceof PsiReferenceExpression
           ? ((PsiReferenceExpression) element).resolve()
           : null;
   if (!(resolved instanceof PsiField)) return false;
   PsiField field = (PsiField) resolved;
   return field.hasModifierProperty(PsiModifier.FINAL)
       && field.hasModifierProperty(PsiModifier.STATIC)
       && PsiType.BOOLEAN.equals(field.getType());
 }