From 6ebaa916ff8266f208bf750595f68eaa2ddf7909 Mon Sep 17 00:00:00 2001
From: Oleg Grenrus <oleg.grenrus@iki.fi>
Date: Wed, 13 May 2026 21:17:20 +0300
Subject: [PATCH] Fix build against semialign-1.3

---
 .github/workflows/haskell-ci.yml |  6 ++++++
 ChangeLog.md                     |  4 ++++
 cabal.haskell-ci                 |  3 +++
 src/Data/TreeDiff/OMap.hs        | 11 +++++++++--
 tree-diff.cabal                  |  2 +-
 5 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/.github/workflows/haskell-ci.yml b/.github/workflows/haskell-ci.yml
index 6749a57..8330f81 100644
--- a/.github/workflows/haskell-ci.yml
+++ b/.github/workflows/haskell-ci.yml
@@ -267,6 +267,12 @@ jobs:
       - name: prepare for constraint sets
         run: |
           rm -f cabal.project.local
+      - name: constraint set semialign-1.3
+        run: |
+          $CABAL v2-build $ARG_COMPILER --disable-tests --disable-benchmarks --constraint='semialign >=1.3 && <1.4' all --dry-run
+          cabal-plan topo | sort
+          $CABAL v2-build $ARG_COMPILER --disable-tests --disable-benchmarks --constraint='semialign >=1.3 && <1.4' --dependencies-only -j2 all
+          $CABAL v2-build $ARG_COMPILER --disable-tests --disable-benchmarks --constraint='semialign >=1.3 && <1.4' all
       - name: constraint set random-hashable
         run: |
           if [ $((HCNUMVER >= 90400 && HCNUMVER < 90600)) -ne 0 ] ; then $CABAL v2-build $ARG_COMPILER --enable-tests --disable-benchmarks --constraint='hashable >=1.3.2.0' --constraint='hashable +random-initial-seed' all --dry-run ; fi
diff --git a/ChangeLog.md b/ChangeLog.md
index 6067903..6c23bd9 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,3 +1,7 @@
+## 0.4.1
+
+- Fix build with semialign-1.3
+
 ## 0.4
 
 - Drop `ansi-wl-pprint` dependency, use `prettyprinter` directly.
diff --git a/cabal.haskell-ci b/cabal.haskell-ci
index 4f3666d..2d95f1a 100644
--- a/cabal.haskell-ci
+++ b/cabal.haskell-ci
@@ -13,3 +13,6 @@ constraint-set random-hashable
   constraints: hashable >=1.3.2.0, hashable +random-initial-seed
   tests: True
   run-tests: True
+
+constraint-set semialign-1.3
+  constraints: semialign >=1.3 && <1.4
diff --git a/src/Data/TreeDiff/OMap.hs b/src/Data/TreeDiff/OMap.hs
index 3ce21ae..4a8a3e0 100644
--- a/src/Data/TreeDiff/OMap.hs
+++ b/src/Data/TreeDiff/OMap.hs
@@ -14,10 +14,12 @@ module Data.TreeDiff.OMap (
     elems,
 ) where
 
+import Prelude hiding (zipWith)
+
 import Control.DeepSeq (NFData (..))
 import Data.List       (sortBy)
 import Data.Ord        (comparing)
-import Data.Semialign  (Semialign(..), Unzip (..), unzipDefault)
+import Data.Semialign  (Semialign(..), Unzip (..), Zip (..), unzipDefault)
 import Data.These      (These (..))
 
 import qualified Data.Map.Strict as Map
@@ -149,5 +151,10 @@ instance Ord k => Semialign (OMap k) where
         g (That (Val j y))            = Val j (f (That y))
         g (These (Val i x) (Val j y)) = Val (min i j) (f (These x y))
 
-instance Unzip (OMap k) where
+instance Ord k => Zip (OMap k) where
+    zipWith f (OMap xs) (OMap ys) = OMap (zipWith g xs ys) where
+        g (Val i x) (Val j y) = Val (min i j) (f x y)
+
+-- Ord k is required for semialign <1.4
+instance Ord k => Unzip (OMap k) where
     unzip = unzipDefault
diff --git a/tree-diff.cabal b/tree-diff.cabal
index 9608c39..7fb4a1f 100644
--- a/tree-diff.cabal
+++ b/tree-diff.cabal
@@ -1,6 +1,6 @@
 cabal-version:      2.2
 name:               tree-diff
-version:            0.4
+version:            0.4.1
 synopsis:           Diffing of (expression) trees.
 category:           Data, Testing
 description: