How to prevent automatic folding symbols？

[lao-boli]

when I write haskell code in idea, it automatic folding some symbol ,which makes my code indentation messy. Is there any way to prevent him, or can you tell me the reason for him to fold automatically like this?

quicksort :: (Ord a) => [a] -> [a]
quicksort [] = []
quicksort (x : xs) =
  let smallerSorted = quicksort [a | a <- xs, a <= x]
      bigggerSorted = quicksort [b | b <- xs, b > x]
   in smallerSorted ++ (x : bigggerSorted)

fold symbol 'let' to '├'

[lao-boli]

I'm sorry for posting the issue before uploading the image. This should be uploaded together with the image.