Have eqTypeM fall back to eqType pre-GHC 9.4

plugin/src/ConCat/NormaliseType.hs

@@ -1,7 +1,10 @@
+{-# LANGUAGE CPP #-}
+
 -- | Utility functions for normalising, comparing types modulo type families.
-module ConCat.NormaliseType(runDsM, normaliseTypeM, eqTypeM, runTcForSolver) where
+module ConCat.NormaliseType (eqTypeM) where
 
 import GHC.Plugins
+#if MIN_VERSION_GLASGOW_HASKELL(9,4,0,0)
 import GHC.HsToCore.Monad
 import Data.Maybe (maybe)
 import GHC.HsToCore.Monad
@@ -10,6 +13,20 @@ import GHC.Tc.Instance.Family (tcGetFamInstEnvs)
 import GHC.Core.FamInstEnv (normaliseType)
 import GHC.Core.Reduction (reductionReducedType)
 import GHC.Tc.Types (TcM)
+#endif
+
+-- | compare two types after first normalising out type families
+eqTypeM :: HscEnv -> DynFlags -> ModGuts -> Type -> Type -> IO Bool
+#if MIN_VERSION_GLASGOW_HASKELL(9,4,0,0)
+eqTypeM env dflags guts ty1 ty2 =
+  if ty1 `eqType` ty2
+  then return True
+  else
+  runTcForSolver env dflags guts $ do
+    famInstEnvs <- tcGetFamInstEnvs
+    let reduction1 = normaliseType famInstEnvs Nominal ty1
+    let reduction2 = normaliseType famInstEnvs Nominal ty2
+    return (reductionReducedType reduction1 `eqType` reductionReducedType reduction2)
 
 -- | run a DsM program inside IO
 runDsM :: HscEnv -> DynFlags -> ModGuts -> DsM a -> IO a
@@ -31,16 +48,6 @@ normaliseTypeM env dflags guts ty =
     famInstEnvs <- tcGetFamInstEnvs
     let reduction = normaliseType famInstEnvs Nominal ty
     return (reductionReducedType reduction)
-
--- | compare two types after first normalising out type families
-eqTypeM :: HscEnv -> DynFlags -> ModGuts -> Type -> Type -> IO Bool
-eqTypeM env dflags guts ty1 ty2 =
-  if ty1 `eqType` ty2
-  then return True
-  else
-  runTcForSolver env dflags guts $ do
-    famInstEnvs <- tcGetFamInstEnvs
-    let reduction1 = normaliseType famInstEnvs Nominal ty1
-    let reduction2 = normaliseType famInstEnvs Nominal ty2
-    return (reductionReducedType reduction1 `eqType` reductionReducedType reduction2)
-
+#else
+eqTypeM _ _ _ ty1 ty2 = pure $ ty1 `eqType` ty2
+#endif