[ADP-3350] Fix Cardano.Wallet.Read.Block.SlotNo (#4535)

This pull request fixes the `Cardano.Wallet.Read.Block.SlotNo` module
which encountered some difficulties with type class resolution and
orphan instances, to the point where I suspected a compiler bug.

I have also added `NoThunks` and `Generic` instances for the
`Cardano.Wallet.Read.SlotNo` type in preparation for future pull
requests.

### Issue Number

Discovered during ADP-3350

lib/read/cardano-wallet-read.cabal

@@ -122,6 +122,7 @@ library
     , generics-sop
     , lens
     , memory
+    , nothunks
     , operational
     , ouroboros-consensus
     , ouroboros-consensus-cardano

lib/read/lib/Cardano/Wallet/Read/Block/Block.hs

@@ -56,6 +56,8 @@ import qualified Ouroboros.Consensus.Shelley.Ledger as O
 type ConsensusBlock = O.CardanoBlock O.StandardCrypto
 
 -- Family of era-specific block types
+-- TODO: ADP-3351 The results of this type family should be ledger types,
+-- not ouroboros-consensus types.
 type family BlockT era where
     BlockT Byron =
         O.ByronBlock

lib/read/lib/Cardano/Wallet/Read/Block/SlotNo.hs

@@ -1,3 +1,4 @@
+{-# LANGUAGE DeriveGeneric #-}
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE GADTs #-}
 {-# LANGUAGE ScopedTypeVariables #-}
@@ -10,26 +11,25 @@ module Cardano.Wallet.Read.Block.SlotNo
 
 import Prelude
 
-import Cardano.Ledger.Binary.Group
-    ( EncCBORGroup
+import Cardano.Ledger.Block
+    ( bheader
     )
 import Cardano.Ledger.Crypto
-    ( Crypto
-    )
-import Cardano.Ledger.Era
-    ( EraSegWits (..)
+    ( StandardCrypto
     )
 import Cardano.Wallet.Read.Block.Block
     ( Block (..)
     )
-import Cardano.Wallet.Read.Block.BlockNo
-    ()
-    -- ?! GHC 9.6.4: This import looks redundant, but the compilation
-    -- of getSlotNoShelley will fail if we don't that. No idea why.
 import Cardano.Wallet.Read.Eras.KnownEras
     ( Era (..)
     , IsEra (..)
     )
+import GHC.Generics
+    ( Generic
+    )
+import NoThunks.Class
+    ( NoThunks (..)
+    )
 import Numeric.Natural
     ( Natural
     )
@@ -39,11 +39,14 @@ import Ouroboros.Consensus.Protocol.Praos
 import Ouroboros.Consensus.Protocol.TPraos
     ( TPraos
     )
+import Ouroboros.Consensus.Shelley.Protocol.Abstract
+    ( pHeaderSlot
+    )
+import Ouroboros.Consensus.Shelley.Protocol.Praos
+    ()
+import Ouroboros.Consensus.Shelley.Protocol.TPraos
+    ()
 
-import qualified Cardano.Ledger.Api as L
-import qualified Cardano.Ledger.Shelley.API as Shelley
-import qualified Cardano.Protocol.TPraos.BHeader as Shelley
-import qualified Ouroboros.Consensus.Protocol.Praos.Header as O
 import qualified Ouroboros.Consensus.Shelley.Ledger.Block as O
 import qualified Ouroboros.Network.Block as O
 
@@ -62,20 +65,18 @@ getEraSlotNo = case theEra @era of
     k = SlotNo . fromIntegral . O.unSlotNo
 
 newtype SlotNo = SlotNo {unSlotNo :: Natural}
-    deriving (Eq, Show)
+    deriving (Eq, Ord, Show, Generic)
+
+instance NoThunks SlotNo
 
 getSlotNoShelley
-    :: (L.Era era, EncCBORGroup (TxSeq era), Crypto c)
-    => O.ShelleyBlock (TPraos c) era
+    :: O.ShelleyBlock (TPraos StandardCrypto) era
     -> O.SlotNo
-getSlotNoShelley
-    (O.ShelleyBlock (Shelley.Block (Shelley.BHeader header _) _) _) =
-        Shelley.bheaderSlotNo header
+getSlotNoShelley (O.ShelleyBlock block _) =
+    pHeaderSlot $ bheader block
 
 getSlotNoBabbage
-    :: (L.Era era, EncCBORGroup (TxSeq era), Crypto crypto)
-    => O.ShelleyBlock (Praos crypto) era
+    :: O.ShelleyBlock (Praos StandardCrypto) era
     -> O.SlotNo
-getSlotNoBabbage
-    (O.ShelleyBlock (Shelley.Block (O.Header header _) _) _) =
-        O.hbSlotNo header
+getSlotNoBabbage (O.ShelleyBlock block _) =
+    pHeaderSlot $ bheader block