From 27aa7351340045b2aaf7d7447cbf711c793cf654 Mon Sep 17 00:00:00 2001
From: Richard Marko <srk@48.io>
Date: Tue, 28 Apr 2020 12:56:50 +0200
Subject: [PATCH] add GEq instnaces for IORef and STRef

---
 some.cabal                 |  1 +
 src/Data/GADT/Instances.hs | 21 +++++++++++++++++++++
 2 files changed, 22 insertions(+)
 create mode 100644 src/Data/GADT/Instances.hs

diff --git a/some.cabal b/some.cabal
index 8dc21de..d46079f 100644
--- a/some.cabal
+++ b/some.cabal
@@ -63,6 +63,7 @@ library
   exposed-modules:
     Data.GADT.Compare
     Data.GADT.DeepSeq
+    Data.GADT.Instances
     Data.GADT.Show
     Data.Some
     Data.Some.Church
diff --git a/src/Data/GADT/Instances.hs b/src/Data/GADT/Instances.hs
new file mode 100644
index 0000000..1fa358e
--- /dev/null
+++ b/src/Data/GADT/Instances.hs
@@ -0,0 +1,21 @@
+{-# LANGUAGE CPP                 #-}
+{-# OPTIONS_GHC -fno-warn-orphans #-}
+
+module Data.GADT.Instances where
+
+import Data.IORef          (IORef)
+import Data.STRef          (STRef)
+import Unsafe.Coerce       (unsafeCoerce)
+
+import Data.GADT.Compare   (GEq(..))
+
+#if __GLASGOW_HASKELL__ >=708
+import Data.Typeable ((:~:)( Refl ))
+#endif
+
+instance GEq IORef where
+  a `geq` b = if a == unsafeCoerce b then Just $ unsafeCoerce Refl else Nothing
+
+instance GEq (STRef s) where
+  a `geq` b = if a == unsafeCoerce b then Just $ unsafeCoerce Refl else Nothing
+