asd.purs

newtype LuminaireState = LuminaireState
  { gateway :: GatewayId
  , lights :: Map LightId LightState
  }
derive instance newtypeLuminaireState :: Newtype LuminaireState _

...

setLight :: forall e. LuminaireId -> LightId -> LightColor -> Maybe Milliseconds -> AppState -> Eff (ref :: REF | e) Boolean
setLight luminaireId lightId color transitionTime appState = do
  curLuminaireState <- lookup luminaireId <$> readRef appState
  lights <- _.lights <$> (unwrap <$> curLuminaireState) -- boom
  pure true

-- error:
Error found:
in module State
at src/State.purs line 30, column 3 - line 30, column 56

  Could not match type

    Maybe

  with type

    Eff
      ( ref :: REF
      | t0
      )


while trying to match type Maybe t2
  with type Eff
              ( ref :: REF
              | t0
              )
              t1
while checking that expression (bind ((map (...)) ((...) curLuminaireState))) (\$1 ->
                                                                                 case $1 of
                                                                                   lights -> ...
                                                                              )
  has type Eff
             ( ref :: REF
             | t0
             )
             t1
in value declaration setLight

where t1 is an unknown type
      t0 is an unknown type
      t2 is an unknown type