[1mMain.hs:6.7-14:[1;31m error:[0m[1m
   • Data type contexts are not supported; put constraints on individual
     constructors instead
  [1;34m|[0m
[1;34m6[0m [1;34m| [0mdata ([1;31mC a, D a[0m) => T a = MkT a
  [1;34m|[0m       [1;31m^^^^^^^^[0m

