From 282302b59088c2f11fae37b2c3531ba3766264fc Mon Sep 17 00:00:00 2001
From: Alexey Kuleshevich <alexey.kuleshevich@iohk.io>
Date: Thu, 19 Dec 2024 15:30:44 -0700
Subject: [PATCH] Extract `indexProxy` from `HashAnnotated` type class and
 deprecate it

---
 libs/cardano-ledger-core/CHANGELOG.md                   | 1 +
 libs/cardano-ledger-core/src/Cardano/Ledger/Hashes.hs   | 4 ----
 libs/cardano-ledger-core/src/Cardano/Ledger/SafeHash.hs | 9 +++++++++
 3 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/libs/cardano-ledger-core/CHANGELOG.md b/libs/cardano-ledger-core/CHANGELOG.md
index a79861aee47..091ec6d4cc9 100644
--- a/libs/cardano-ledger-core/CHANGELOG.md
+++ b/libs/cardano-ledger-core/CHANGELOG.md
@@ -2,6 +2,7 @@
 
 ## 1.17.0.0
 
+* Extract `indexProxy` from `HashAnnotated` type class and deprecate it.
 * Extract `hashTxAuxData` from `EraTxAuxData` into a standalone function.
 * Add `TxAuxDataHash` and deprecate `AuxiliaryDayaHash` in its favor.
 * Deprecate `Cardano.Ledger.Crypto` module in favor of `cardano-protocol-tpraos:Cardano.Protocol.Crypto`
diff --git a/libs/cardano-ledger-core/src/Cardano/Ledger/Hashes.hs b/libs/cardano-ledger-core/src/Cardano/Ledger/Hashes.hs
index b78f55a2fb0..e51d833ad76 100644
--- a/libs/cardano-ledger-core/src/Cardano/Ledger/Hashes.hs
+++ b/libs/cardano-ledger-core/src/Cardano/Ledger/Hashes.hs
@@ -76,7 +76,6 @@ module Cardano.Ledger.Hashes (
   -- ** Other operations
   castSafeHash,
   extractHash,
-  indexProxy,
 )
 where
 
@@ -386,9 +385,6 @@ instance Hash.HashAlgorithm h => SafeToHash (Hash.Hash h i) where
 -- can be easily derived (because their methods have default methods when the type is a
 -- newtype around a type that is 'SafeToHash'). For example,
 class SafeToHash x => HashAnnotated x i | x -> i where
-  -- TODO: move outside of type class
-  indexProxy :: x -> Proxy i
-  indexProxy _ = Proxy @i
 
   -- | Create a @('SafeHash' i)@, given @(`HashAnnotated` x i)@ instance.
   hashAnnotated :: x -> SafeHash i
diff --git a/libs/cardano-ledger-core/src/Cardano/Ledger/SafeHash.hs b/libs/cardano-ledger-core/src/Cardano/Ledger/SafeHash.hs
index e3adb237cab..a465eda6c06 100644
--- a/libs/cardano-ledger-core/src/Cardano/Ledger/SafeHash.hs
+++ b/libs/cardano-ledger-core/src/Cardano/Ledger/SafeHash.hs
@@ -1,3 +1,7 @@
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TypeApplications #-}
+{-# OPTIONS_GHC -Wno-redundant-constraints #-}
+
 module Cardano.Ledger.SafeHash
   {-# DEPRECATED "Use `Cardano.Ledger.Hashes` instead" #-} (
   -- * SafeHash and SafeToHash
@@ -26,3 +30,8 @@ module Cardano.Ledger.SafeHash
 where
 
 import Cardano.Ledger.Hashes
+import Data.Proxy
+
+indexProxy :: forall x i. HashAnnotated x i => x -> Proxy i
+indexProxy _ = Proxy @i
+{-# DEPRECATED indexProxy "As useless and unused" #-}