From bc55e1c58fab8c62f91cf37eb10306219de3d8ec Mon Sep 17 00:00:00 2001
From: Simon Michael <simon@joyful.com>
Date: Tue, 2 Sep 2025 08:18:09 +0100
Subject: [PATCH] dev: fix liftA2, Foldable1 build errors with ghc <9.6 [#2395]

---
 hledger-lib/Hledger/Data/PeriodData.hs            | 6 ++++++
 hledger-lib/Hledger/Reports/MultiBalanceReport.hs | 4 ++++
 2 files changed, 10 insertions(+)

diff --git a/hledger-lib/Hledger/Data/PeriodData.hs b/hledger-lib/Hledger/Data/PeriodData.hs
index 13741163d..78032a2b9 100644
--- a/hledger-lib/Hledger/Data/PeriodData.hs
+++ b/hledger-lib/Hledger/Data/PeriodData.hs
@@ -19,7 +19,11 @@ module Hledger.Data.PeriodData
 , tests_PeriodData
 ) where
 
+#if MIN_VERSION_base(4,18,0)
 import Data.Foldable1 (Foldable1(..))
+#else
+import Control.Applicative (liftA2)
+#endif
 import qualified Data.IntMap.Strict as IM
 import qualified Data.IntSet as IS
 #if !MIN_VERSION_base(4,20,0)
@@ -48,10 +52,12 @@ instance Foldable PeriodData where
   foldl f z (PeriodData h as) = foldl f (f z h) as
   foldl' f z (PeriodData h as) = let fzh = f z h in fzh `seq` foldl' f fzh as
 
+#if MIN_VERSION_base(4,18,0)
 instance Foldable1 PeriodData where
   foldrMap1 f g (PeriodData h as) = foldr g (f h) as
   foldlMap1 f g (PeriodData h as) = foldl g (f h) as
   foldlMap1' f g (PeriodData h as) = let fh = f h in fh `seq` foldl' g fh as
+#endif
 
 instance Traversable PeriodData where
   traverse f (PeriodData h as) = liftA2 PeriodData (f h) $ traverse f as
diff --git a/hledger-lib/Hledger/Reports/MultiBalanceReport.hs b/hledger-lib/Hledger/Reports/MultiBalanceReport.hs
index 1e95b83aa..6f05cd061 100644
--- a/hledger-lib/Hledger/Reports/MultiBalanceReport.hs
+++ b/hledger-lib/Hledger/Reports/MultiBalanceReport.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP                 #-}
 {-# LANGUAGE FlexibleInstances   #-}
 {-# LANGUAGE OverloadedStrings   #-}
 {-# LANGUAGE NamedFieldPuns      #-}
@@ -33,6 +34,9 @@ module Hledger.Reports.MultiBalanceReport (
 )
 where
 
+#if !MIN_VERSION_base(4,18,0)
+import Control.Applicative (liftA2)
+#endif
 import Control.Monad (guard)
 import Data.Foldable (toList)
 import Data.List (sortOn)