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Ticket extracted from #17801 (closed).

To reproduce, use two files:

-- Foo.hs
module Foo where

import Control.Monad.Except

class Monad m => ReadTCState m where
  locallyTCState :: m ()
  liftReduce :: m ()

instance ReadTCState m => ReadTCState (ExceptT err m) where
  locallyTCState = undefined
  liftReduce = lift liftReduce

instance MonadIO m => ReadTCState (TCMT m) where
  locallyTCState = (undefined <$> liftReduce) <* TCM (\_ -> return ())
  liftReduce = undefined

newtype TCMT m a = TCM { unTCM :: () -> m a }

instance MonadIO m => Functor (TCMT m) where
  fmap f (TCM m) = TCM $ \r -> liftM f (m r )

instance MonadIO m => Applicative (TCMT m) where
  pure x = TCM (\_ -> return x)
  (<*>) (TCM mf) (TCM m) = TCM $ \r -> ap (mf r) (m r)

instance MonadIO m => Monad (TCMT m) where
  (>>=) (TCM m) k = TCM $ \r -> m r >>= \x -> unTCM (k x) r 

-- Bar.hs
module Bar where

import Control.Monad.Except
import Foo

f :: ExceptT e (TCMT IO) ()
f = liftReduce

and compile with

ghc -fforce-recomp Bar.hs -dcore-lint -O -fspecialise-aggressively

[1 of 2] Compiling Foo              ( Foo.hs, Foo.o )
[2 of 2] Compiling Bar              ( Bar.hs, Bar.o )
*** Core Lint errors : in result of Specialise ***
<no location info>: warning:
    Recursive or top-level binder has strict demand info: $dMonad_s2iO
    Binder's demand info: <S(LLC(C(S))L),U(1*U(1*U(1*C1(C1(U)),A),A,A,A,A,A),C(C1(U)),C(C1(U)),C(U))>
    In the RHS of $dMonad_s2iO :: Monad IO
    Substitution: [TCvSubst
                     In scope: InScope {f $trModule $dReadTCState_s2im $dMonad_s2in
                                        f_s2ip $trModule_s2iq $trModule_s2ir $trModule_s2is
                                        $trModule_s2it ww_s2iy ww1_s2iz ww3_s2iA ww4_s2iB ww8_s2iC
                                        ww9_s2iD $dMonad_s2iO $s$fFunctorTCMT2_s2iQ
                                        $s$fFunctorTCMT1_s2iR $s$fFunctorTCMT_s2iS
                                        $s$fApplicativeTCMT_s2iT $s$fMonadTCMT_$c>>_s2iU
                                        $s$fMonadTCMT_s2iV $s$w$cliftReduce_s2iW
                                        $s$fReadTCStateExceptT1_s2iX $sap'_s2iZ
                                        $s$fReadTCStateTCMT_$clocallyTCState_s2j0
                                        $s$fReadTCStateTCMT_s2j1}
                     Type env: []
                     Co env: []]

@awson says that reverting b911c532 cures this issue. I could not confirm.