ExpandSynsFail3.hs:21:8: error:
    Couldn't match type ‘Int’ with ‘Bool’
    Expected type: T (T3, T5, Int)
      Actual type: T (T5, T3, Bool)
    Type synonyms expanded:
    Expected type: T (T3, T3, Int)
      Actual type: T (T3, T3, Bool)
    In the first argument of ‘f’, namely
      ‘(undefined :: T (T5, T3, Bool))’
    In the expression: f (undefined :: T (T5, T3, Bool))
    In an equation for ‘a’: a = f (undefined :: T (T5, T3, Bool))