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diff --git a/testsuite/tests/typecheck/should_run/T14218.hs b/testsuite/tests/typecheck/should_run/T14218.hs
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+++ b/testsuite/tests/typecheck/should_run/T14218.hs
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+{-# LANGUAGE ConstraintKinds #-}       -- For 'C'
+{-# LANGUAGE MultiParamTypeClasses #-} -- For nullary 'Trivial' class
+{-# LANGUAGE ImplicitParams #-}
+{-# OPTIONS_GHC -Wno-simplifiable-class-constraints #-}
+module Main where
+
+import qualified GHC.Stack as Ghc
+
+class Trivial where
+instance Trivial where
+
+type C = (Ghc.HasCallStack, Trivial)
+
+-- | Print the functions on the call stack.
+callStack :: C => IO ()
+callStack = print $ map fst (Ghc.getCallStack Ghc.callStack)
+
+f :: C => a -> IO ()
+f x = callStack
+
+type C2 =  (?x::Int, ?y::Int)
+
+h1 :: C2 => Int -> IO ()
+h1 v = print (?x+v)
+
+h2 :: C2 => Int -> IO ()
+h2 v = let ?x = 0 in h1 v
+
+main = do { let { ?x = 3; ?y = 4 }  in h2 4
+            -- Should print 4+0 = 4
+
+          ; f "ugh"
+            -- Should print @["callStack", "f"]@.
+          }