private static boolean isSafeStringBufferUsage(PsiExpression expression) {
      if (expression == null) {
        return false;
      }
      if (ExpressionUtils.isVoidContext(expression)) {
        return true;
      }
      final PsiElement parent = expression.getParent();
      if (parent instanceof PsiReferenceExpression) {
        final PsiElement grandParent = parent.getParent();
        if (grandParent instanceof PsiMethodCallExpression) {
          final String methodName = ((PsiReferenceExpression)parent).getReferenceName();
          if ("toString".equals(methodName)) {
            return true;
          }
          else if ("append".equals(methodName) || "appendCodePoint".equals(methodName) || "insert".equals(methodName)) {
            return isSafeStringBufferUsage((PsiExpression)grandParent);
          }
        }
      }
      return false;
    }
private static boolean isSafeStringBufferUsage(PsiExpression expression)