error

    • Could not deduce (ToJSON a0)
      from the context: ToJSON a
        bound by the type of the constructor ‘Remove’:
                   forall a. ToJSON a => Operation
        at src/MixPanel/Types/EngageData.hs:20:5-35
      The type variable ‘a0’ is ambiguous
    • In the ambiguity check for ‘Remove’
      To defer the ambiguity check to use sites, enable AllowAmbiguousTypes
      In the definition of data constructor ‘Remove’
      In the data type declaration for ‘Operation’
   |
20 |     Remove :: ToJSON a => Operation
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

gadts.hs

data Operation where
    Set :: ToJSON a => Operation
    SetOnce :: ToJSON a => Operation
    Add :: ToJSON a => Operation
    Append :: ToJSON a => Operation
    Union :: ToJSON a => Operation
    Remove :: ToJSON a => Operation
    Unset :: ToJSON [a] => Operation
    Delete :: Operation