From f8b2091aed6ca42a0cf1fa7b6a920f6c3a5227a9 Mon Sep 17 00:00:00 2001
From: Tom Smeding <tom@tomsmeding.com>
Date: Thu, 27 Mar 2025 19:04:28 +0100
Subject: Fix refcount bug with indexing for nested arrays

---
 src/Compile.hs | 1 +
 test/Main.hs   | 3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/Compile.hs b/src/Compile.hs
index 2652ed4..6e46f74 100644
--- a/src/Compile.hs
+++ b/src/Compile.hs
@@ -831,6 +831,7 @@ compile' env = \case
 
     resname <- genName' "ixres"
     emit $ SVarDecl True (repSTy t) resname (CEIndex (CELit (arrname ++ ".buf->xs")) (toLinearIdx n arrname idxname))
+    incrementVarAlways "idxelt" Increment t resname
     incrementVarAlways "idx" Decrement (STArr n t) arrname
     return (CELit resname)
 
diff --git a/test/Main.hs b/test/Main.hs
index be15e65..20b4ef0 100644
--- a/test/Main.hs
+++ b/test/Main.hs
@@ -471,7 +471,8 @@ tests_AD = testGroup "AD"
   -- Regression test for a simplifier bug (89b78d4)
   ,adTestTp "regression-simpl1" (C "" 1) term_regression_simpl1
 
-  ,adTestTp "regression-accum1" (C "" 1 :$ C "" 1) $
+  -- Regression test for refcounts when indexing in nested arrays
+  ,adTestTp "regression-idx1" (C "" 1 :$ C "" 1) $
     fromNamed $ lambda @(TArr N2 R) #L $ body $
       if_ (const_ @TI64 1 Language..> 0)
         (idx0 $ sum1i (build1 1 $ #_ :->
-- 
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