How to add a finalizer for an effect action?

[MuhammedZakir]

I have two effects:

data E1 :: Effect where
  GetStuff :: E1 m Stuff
  DiscardStuff :: Stuff -> E1 m ()

-- 'E1' effect is necessary for 'E2'
data E2 :: Effect where
  FuncThatUseStuff :: E2 m ()

There are two ways E1 can be used:

1. user discards the Stuff they got:

use1 = do
  s <- getStuff
  ...
  discardStuff s

2. if user doesn't discard any Stuff they got, then I will have to handle it:

use2 = do
  s1 <- getStuff
  s2 <- getStuff
  ...
  discardStuff s1
  -- user didn't discard `s2`, so I'll have to handle it

The problem is, I don't know how attach a finalizer without using continuation / passing function:

handler stuffs = reinterpret (runState stuffs) $ \_ -> \case
  GetStuff  -> do
    s <- pop
    save s
    pure s
    -- HERE: after `s` is used, I want to handle it if user doesn't call `discardStuff`.

  DiscardStuff s -> do
    when (inSavedStuff s) $ delete s

---

I am using free monad interpreter atm. In it, I did something like:

run = \case
  ...
  GetStuff nextFn -> do
    s <- pop
    save s
    res <- run (nextFn s)
      `finally` (handleIfNotDiscarded s)
    deleteSaved s
    pure res
  ...

[mmhat]

It seems like resourcet-effectful would work for. Just reinterpret E1 in terms of the Resource effect.

[MuhammedZakir]

Thanks!