Refactor and add note

byg/src/ComputationM.hs

@@ -8,7 +8,6 @@ module ComputationM
   ) where
 
 import Types
-import Sources
 
 import Control.Monad.State
 import Control.Monad.Writer

byg/src/Sources.hs

@@ -1,5 +1,7 @@
 module Sources where
 
+-- TODO: Figure out if any of this is useful.
+
 import Types
 
 data Source a where