From 48e4977f3e0a88ff24410987b80bf6003c45dfb7 Mon Sep 17 00:00:00 2001
From: Tom Smeding <tom@tomsmeding.com>
Date: Wed, 18 Jun 2025 13:56:42 +0200
Subject: Don't destroy effects in UnMonoid

---
 src/AST/UnMonoid.hs | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/AST/UnMonoid.hs b/src/AST/UnMonoid.hs
index d498aaa..ef01bf8 100644
--- a/src/AST/UnMonoid.hs
+++ b/src/AST/UnMonoid.hs
@@ -60,7 +60,7 @@ unMonoid = \case
   EError _ t s -> EError ext t s
 
 zero :: SMTy t -> Ex env (ZeroInfo t) -> Ex env t
-zero SMTNil _ = ENil ext
+zero SMTNil e = elet e $ ENil ext
 zero (SMTPair t1 t2) e =
   ELet ext e $ EPair ext (zero t1 (EFst ext (EVar ext (typeOf e) IZ)))
                          (zero t2 (ESnd ext (EVar ext (typeOf e) IZ)))
@@ -74,7 +74,7 @@ zero (SMTScal t) _ = case t of
   STF64 -> EConst ext STF64 0.0
 
 deepZero :: SMTy t -> Ex env (DeepZeroInfo t) -> Ex env t
-deepZero SMTNil _ = ENil ext
+deepZero SMTNil e = elet e $ ENil ext
 deepZero (SMTPair t1 t2) e =
   ELet ext e $ EPair ext (deepZero t1 (EFst ext (EVar ext (typeOf e) IZ)))
                          (deepZero t2 (ESnd ext (EVar ext (typeOf e) IZ)))
@@ -95,7 +95,8 @@ deepZero (SMTScal t) _ = case t of
   STF64 -> EConst ext STF64 0.0
 
 plus :: SMTy t -> Ex env t -> Ex env t -> Ex env t
-plus SMTNil _ _ = ENil ext
+-- don't destroy the effects!
+plus SMTNil a b = elet a $ elet (weakenExpr WSink b) $ ENil ext
 plus (SMTPair t1 t2) a b =
   let t = STPair (fromSMTy t1) (fromSMTy t2)
   in ELet ext a $
-- 
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