Core Lint error with typed Template Haskell (The type variable ... is out of scope)

The parsley-0.1.0.1 Hackage library fails to compile with -dcore-lint. Here is a minimized version of the failing code:

{-# LANGUAGE TemplateHaskell #-}
module Bug where

import Control.Monad.ST
import Language.Haskell.TH

f :: Code Q Char
f = [|| runST $$([|| pure 'a' ||]) ||]

$ /opt/ghc/9.0.1/bin/ghc Bug.hs -dcore-lint
[1 of 1] Compiling Bug              ( Bug.hs, Bug.o, Bug.dyn_o )
*** Core Lint errors : in result of Desugar (before optimization) ***
<no location info>: warning:
    The type variable @s_a20Z[sk:1] is out of scope
    In the type of a binder: $dApplicative_a218
    In the type ‘Applicative (ST s_a20Z[sk:1])’
    Substitution: [TCvSubst
                     In scope: InScope {}
                     Type env: []
                     Co env: []]
*** Offending Program ***
Rec {
$dQuote_a211 :: Quote Q
[LclId]
$dQuote_a211 = $dQuote_a20R

$dQuote_a20R :: Quote Q
[LclId]
$dQuote_a20R = $fQuoteQ

$dApplicative_a218 :: Applicative (ST s_a20Z[sk:1])
[LclId]
$dApplicative_a218 = $fApplicativeST @s_a20Z[sk:1]

$trModule :: Module
[LclIdX]
$trModule = Module (TrNameS "main"#) (TrNameS "Bug"#)

f :: Code Q Char
[LclIdX]
f = unsafeCodeCoerce
      @'LiftedRep
      @Char
      @Q
      $dQuote_a20R
      (appE
         @Q
         $dQuote_a20R
         (varE
            @Q
            $dQuote_a20R
            (mkNameG_v
               (unpackCString# "base"#)
               (unpackCString# "GHC.ST"#)
               (unpackCString# "runST"#)))
         (unTypeCode
            @'LiftedRep
            @(ST s_a20Z[sk:1] Char)
            @Q
            $dQuote_a20R
            (unsafeCodeCoerce
               @'LiftedRep
               @(ST s_a20Z[sk:1] Char)
               @Q
               $dQuote_a211
               (appE
                  @Q
                  $dQuote_a211
                  (varE
                     @Q
                     $dQuote_a211
                     (mkNameG_v
                        (unpackCString# "base"#)
                        (unpackCString# "GHC.Base"#)
                        (unpackCString# "pure"#)))
                  (litE @Q $dQuote_a211 (charL (C# 'a'#)))))))
end Rec }

*** End of Offense ***


<no location info>: error: 
Compilation had errors