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diff --git a/testsuite/tests/typecheck/should_run/T17104.hs b/testsuite/tests/typecheck/should_run/T17104.hs
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+++ b/testsuite/tests/typecheck/should_run/T17104.hs
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+{-# LANGUAGE ImplicitParams #-}
+{-# LANGUAGE GADTs #-}
+{-# LANGUAGE ConstraintKinds #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE TypeOperators #-}
+
+module Main where
+
+import GHC.Exts
+import Data.Type.Equality
+
+type family F x :: Constraint
+type instance F Int = (?x :: String)
+
+data Box where MkBox :: (?x :: String) => Box
+data Box2 a where MkBox2 :: F a => Box2 a
+
+f :: Box2 a -> Box -> a :~: Int -> String
+f MkBox2 MkBox Refl = ?x
+
+main :: IO ()
+main = do { let mb  = let ?x = "right"  in MkBox
+          ; let mb2 = let ?x = "wrong" in MkBox2
+          ; print (f mb2 mb Refl) }