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diff --git a/testsuite/tests/simplCore/should_compile/T22715_2a.hs b/testsuite/tests/simplCore/should_compile/T22715_2a.hs
new file mode 100644
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+++ b/testsuite/tests/simplCore/should_compile/T22715_2a.hs
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+{-# OPTIONS_GHC -Wno-missing-methods #-}
+
+module T22715_2a where
+
+newtype IdentityT m a = IdentityT (m a) deriving Functor
+newtype IdT m a = IdT {runIdT :: m a} deriving Functor
+
+class Functor m => SillyA m where
+  unused :: m a -> m a
+
+class SillyA m => SillyB m where
+  unused2 :: m a -> m a
+
+instance SillyA m => SillyA (IdentityT m) where
+instance SillyB m => SillyB (IdentityT m) where
+
+instance SillyA m => SillyA (IdT m) where
+instance SillyB m => SillyB (IdT m) where
+
+instance SillyA IO where
+instance SillyB IO where
+
+class Functor m => Special m
+instance Functor m => Special (IdT m)
+
+type Input m = IdentityT (IdentityT m)
+
+class (Special m, SillyB m) => CommandMonad m
+instance SillyB m => CommandMonad (IdT (Input m))