A very long Haskell type

For GUI programming I've migrated from the gtk2hs library to the gi-gtk library. This uses overloaded labels to access the properties of GTK3 objects.

I wanted a function which would set the background and foreground colours of a widget. Rather than simply have it modify the object I decided to have it return a list of property setters. It looks like this (the function "contrastText" just returns either white or black):

setColour c = do
      bg <- colourToRGBA c
      fg <- colourToRGBA $ contrastText c
      return [#backgroundRgba := bg, #foregroundRgba := fg]

However when I couldn't get it to type-check I asked ghci what the type should be. Here is the reply!

> :type setColour
setColour
  :: (Data.GI.Base.Attributes.AttrOpIsAllowed
        tag
        (Data.GI.Base.Attributes.AttrAllowedOps
           (Data.GI.Base.Overloading.FindElement
              "foregroundRgba"
              (Data.GI.Base.Overloading.AttributeList obj)
              (((('GHC.TypeLits.Text "Unknown attribute \8216"
                  'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "foregroundRgba")
                 'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "\8217 for object \8216")
                'GHC.TypeLits.:<>: 'GHC.TypeLits.ShowType obj)
               'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "\8217.")))
        (Data.GI.Base.Attributes.AttrLabel
           (Data.GI.Base.Overloading.FindElement
              "foregroundRgba"
              (Data.GI.Base.Overloading.AttributeList obj)
              (((('GHC.TypeLits.Text "Unknown attribute \8216"
                  'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "foregroundRgba")
                 'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "\8217 for object \8216")
                'GHC.TypeLits.:<>: 'GHC.TypeLits.ShowType obj)
               'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "\8217.")))
        (Data.GI.Base.Attributes.AttrOrigin
           (Data.GI.Base.Overloading.FindElement
              "foregroundRgba"
              (Data.GI.Base.Overloading.AttributeList obj)
              (((('GHC.TypeLits.Text "Unknown attribute \8216"
                  'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "foregroundRgba")
                 'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "\8217 for object \8216")
                'GHC.TypeLits.:<>: 'GHC.TypeLits.ShowType obj)
               'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "\8217.")))
        obj
      ~
      'Data.GI.Base.Attributes.OpIsAllowed,
      Data.GI.Base.Attributes.AttrOpIsAllowed
        tag
        (Data.GI.Base.Attributes.AttrAllowedOps
           (Data.GI.Base.Overloading.FindElement
              "backgroundRgba"
              (Data.GI.Base.Overloading.AttributeList obj)
              (((('GHC.TypeLits.Text "Unknown attribute \8216"
                  'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "backgroundRgba")
                 'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "\8217 for object \8216")
                'GHC.TypeLits.:<>: 'GHC.TypeLits.ShowType obj)
               'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "\8217.")))
        (Data.GI.Base.Attributes.AttrLabel
           (Data.GI.Base.Overloading.FindElement
              "backgroundRgba"
              (Data.GI.Base.Overloading.AttributeList obj)
              (((('GHC.TypeLits.Text "Unknown attribute \8216"
                  'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "backgroundRgba")
                 'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "\8217 for object \8216")
                'GHC.TypeLits.:<>: 'GHC.TypeLits.ShowType obj)
               'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "\8217.")))
        (Data.GI.Base.Attributes.AttrOrigin
           (Data.GI.Base.Overloading.FindElement
              "backgroundRgba"
              (Data.GI.Base.Overloading.AttributeList obj)
              (((('GHC.TypeLits.Text "Unknown attribute \8216"
                  'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "backgroundRgba")
                 'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "\8217 for object \8216")
                'GHC.TypeLits.:<>: 'GHC.TypeLits.ShowType obj)
               'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "\8217.")))
        obj
      ~
      'Data.GI.Base.Attributes.OpIsAllowed,
      Data.GI.Base.Attributes.AttrInfo
        (Data.GI.Base.Overloading.FindElement
           "foregroundRgba"
           (Data.GI.Base.Overloading.AttributeList obj)
           (((('GHC.TypeLits.Text "Unknown attribute \8216"
               'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "foregroundRgba")
              'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "\8217 for object \8216")
             'GHC.TypeLits.:<>: 'GHC.TypeLits.ShowType obj)
            'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "\8217.")),
      Data.GI.Base.Attributes.AttrInfo
        (Data.GI.Base.Overloading.FindElement
           "backgroundRgba"
           (Data.GI.Base.Overloading.AttributeList obj)
           (((('GHC.TypeLits.Text "Unknown attribute \8216"
               'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "backgroundRgba")
              'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "\8217 for object \8216")
             'GHC.TypeLits.:<>: 'GHC.TypeLits.ShowType obj)
            'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "\8217.")),
      Control.Monad.IO.Class.MonadIO m,
      Data.GI.Base.Overloading.HasAttributeList obj,
      Data.GI.Base.Attributes.AttrBaseTypeConstraint
        (Data.GI.Base.Overloading.FindElement
           "backgroundRgba"
           (Data.GI.Base.Overloading.AttributeList obj)
           (((('GHC.TypeLits.Text "Unknown attribute \8216"
               'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "backgroundRgba")
              'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "\8217 for object \8216")
             'GHC.TypeLits.:<>: 'GHC.TypeLits.ShowType obj)
            'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "\8217."))
        obj,
      Data.GI.Base.Attributes.AttrSetTypeConstraint
        (Data.GI.Base.Overloading.FindElement
           "backgroundRgba"
           (Data.GI.Base.Overloading.AttributeList obj)
           (((('GHC.TypeLits.Text "Unknown attribute \8216"
               'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "backgroundRgba")
              'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "\8217 for object \8216")
             'GHC.TypeLits.:<>: 'GHC.TypeLits.ShowType obj)
            'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "\8217."))
        GI.Gdk.Structs.RGBA.RGBA,
      Data.GI.Base.Attributes.AttrBaseTypeConstraint
        (Data.GI.Base.Overloading.FindElement
           "foregroundRgba"
           (Data.GI.Base.Overloading.AttributeList obj)
           (((('GHC.TypeLits.Text "Unknown attribute \8216"
               'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "foregroundRgba")
              'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "\8217 for object \8216")
             'GHC.TypeLits.:<>: 'GHC.TypeLits.ShowType obj)
            'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "\8217."))
        obj,
      Data.GI.Base.Attributes.AttrSetTypeConstraint
        (Data.GI.Base.Overloading.FindElement
           "foregroundRgba"
           (Data.GI.Base.Overloading.AttributeList obj)
           (((('GHC.TypeLits.Text "Unknown attribute \8216"
               'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "foregroundRgba")
              'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "\8217 for object \8216")
             'GHC.TypeLits.:<>: 'GHC.TypeLits.ShowType obj)
            'GHC.TypeLits.:<>: 'GHC.TypeLits.Text "\8217."))
        GI.Gdk.Structs.RGBA.RGBA) =>
     Reactive.Banana.Common.Colour
     -> m [Data.GI.Base.Attributes.AttrOp obj tag]