Resolving dependencies...
Downloading data-category-0.0.1...
Configuring data-category-0.0.1...
Building data-category-0.0.1...
Preprocessing library data-category-0.0.1...
[1 of 9] Compiling Data.Category    ( Data/Category.hs, dist/build/Data/Category.o )

Data/Category.hs:8:17:
    Unexpected type ‘(~>)’
    In the class declaration for ‘CategoryO’
    A class declaration should have form
      class CategoryO a b where ...
Failed to install data-category-0.0.1
cabal: Error: some packages failed to install:
data-category-0.0.1 failed during the building phase. The exception was:
ExitFailure 1