Program with trivial polymorphism leads to out of scope dictionary

Almost certainly due to c2455e64

A trivial program now causes a core lint error due to an out-of-scope dictionary.

module A where

foo :: Code (IO ())
foo = [|| return () ||]

module B where

main :: IO ()
main = $$foo

*** Core Lint errors : in result of Desugar (before optimization) ***
<no location info>: warning:
    In the expression: return @ IO $dMonad_a4od @ () ()
    Out of scope: $dMonad_a4od :: Monad m_a4oc[tau:0]
                  [LclId]
*** Offending Program ***
Rec {
$trModule :: Module
[LclIdX]
$trModule = Module (TrNameS "main"#) (TrNameS "B"#)

main :: IO ()
[LclIdX]
main = return @ IO $dMonad_a4od @ () ()
end Rec }

*** End of Offense ***

Trac metadata

Trac field	Value
Version	8.7
Type	Bug
TypeOfFailure	OtherFailure
Priority	high
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture