+-- | Gets the index of the given datacon in the given typed thing.
+-- Errors out if it does not occur or if the type is not an ADT.
+datacon_index :: TypedThing t => t -> DataCon.DataCon -> Int
+datacon_index tt dc = case List.elemIndex dc dcs of
+ Nothing -> error $ "Datacon " ++ pprString dc ++ " does not occur in typed thing: " ++ pprString tt
+ Just i -> i
+ where
+ dcs = datacons_for tt
+
+-- | Gets all datacons for the given typed thing. Errors out if the
+-- typed thing is not ADT typed.
+datacons_for :: TypedThing t => t -> [DataCon.DataCon]
+datacons_for tt =
+ case getType tt of
+ Nothing -> error $ "Getting datacon index of untyped thing? " ++ pprString tt
+ Just ty -> case Type.splitTyConApp_maybe ty of
+ Nothing -> error $ "Trying to find datacon in a type without a tycon?" ++ pprString ty
+ Just (tycon, _) -> case TyCon.tyConDataCons_maybe tycon of
+ Nothing -> error $ "Trying to find datacon in a type without datacons?" ++ pprString ty
+ Just dcs -> dcs
+