[Haskell-beginners] -fglasgow-exts in .cabal

[Imants Cekusins]

Cheers Sumit. it worked:

default-extensions:   FlexibleInstances
                      MultiParamTypeClasses
                      TypeSynonymInstances

needed to run cabal clean, then cabal build.

this needs to be specified in both library & test-suite spec section


hope this helps someone.