Where is accepted in LambdaCase

Summary

This example should not compile in my opinion:

{-# LANGUAGE LambdaCase #-}
import Data.Function ((&))

main = () & (\case () -> x where x = pure ())

But the following code does produce a parse error:

{-# LANGUAGE LambdaCase #-}
import Data.Function ((&))

main = () & (\case () -> x
  where x = pure ())

And this also produces an error:

{-# LANGUAGE LambdaCase #-}
import Data.Function ((&))

main = () & (\case () -> x where
  x = pure ())

I think all of those should be rejected, because I want the following to be accepted:

{-# LANGUAGE LambdaCase, BlockArguments #-}
import Data.Function ((&))

main = () & \case () -> x where
  x = pure ()

Here the where block should be on the whole right hand side of the main function, but currently I think it parses it as being on the lambda case. I expected it would be parsed the same as:

{-# LANGUAGE LambdaCase, BlockArguments #-}
import Data.Function ((&))

main = (() & \case () -> x) where
  x = pure ()

Which does work properly, but it has ugly seemingly redundant parentheses.

Environment

• GHC version used: 9.0.1

Optional:

• Operating System: NixOS 21.05
• System Architecture: x86_64