Fixed top-level factoring

parsley-core/src/ghc/Parsley/Internal/Backend/CodeGenerator.hs

@@ -53,11 +53,11 @@ codeGen :: (Trace, ?flags :: Opt.Flags)
 codeGen letBound p rs μ0 = trace ("GENERATING " ++ name ++ ": " ++ show p ++ "\nMACHINE: " ++ show (elems rs) ++ " => " ++ show m) $ makeLetBinding m rs newMeta
   where
     name = maybe "TOP LEVEL" show letBound
+    addCoinsTop = maybe addCoinsNeeded (const id) letBound
     m = finalise (histo alg p)
     alg :: Combinator (Cofree Combinator (CodeGen o a)) x -> CodeGen o a x
     alg = deep |> (\x -> CodeGen (shallow (imap extract x)))
-    -- it is now safe to add coins to the top-level of a binding, because it is always assumed to not cut
-    finalise cg = addCoinsNeeded (runCodeGenStack (runCodeGen cg (In4 Ret)) μ0 0)
+    finalise cg = addCoinsTop (runCodeGenStack (runCodeGen cg (In4 Ret)) μ0 0)
 
 pattern (:<$>:) :: Core.Defunc (a -> b) -> Cofree Combinator k a -> Combinator (Cofree Combinator k) b
 pattern f :<$>: p <- (_ :< Pure f) :<*>: p

parsley-core/src/ghc/Parsley/Internal/Frontend/Analysis/Cut.hs

@@ -33,6 +33,8 @@ newtype CutAnalysis a = CutAnalysis { doCut :: Bool -> (Fix Combinator a, Bool)
 -- TODO: UnguardedEffects should track a set of registers
 data Guardedness (a :: Type) = Guarded | UnguardedEffect | NoEffect deriving stock Eq
 
+-- FIXME: the top-level binding needs a `cut unit *>` at the top-level
+
 guardednessAlg :: Combinator Guardedness a -> Guardedness a
 guardednessAlg Pure{} = NoEffect
 guardednessAlg Satisfy{} = Guarded