I tried to run your solution without {-# LANGUAGE ImportQualifiedPost #-} and tests passed. You also need to change import Data.Traversable qualified as T to import qualified Data.Traversable as T

Try to add {-# LANGUAGE Haskell2010 #-} and fix compilation errors. It seems the issue is because of lib used to validate imports. It fails if code is not a valid Haskell2010.

https://elixir-lang.org/getting-started/comprehensions.html#generators-and-filters