asdf.purs

-- types
newtype LightId = LightId String
instance showLightId :: Show LightId where
  show (LightId id) = show id

derive instance eqLightId :: Eq LightId
derive instance ordLightId :: Ord LightId
derive instance newtypeLightId :: Newtype LightId _

newtype Light = Light
  { color :: LightColor
  , prevColor :: LightColor
  , transitionStart :: Instant
  , transitionTime :: Milliseconds
  }

newtype Luminaire = Luminaire
  { gateway :: GatewayId
  , lights :: Map LightId Light
  }
derive instance newtypeLuminaire :: Newtype Luminaire _

type Luminaires = Ref (Map LuminaireId Luminaire)

-- this one works (or at least compiles)
getLuminaire
  :: forall e
   . LuminaireId
  -> Luminaires
  -> Eff (ref :: REF) (Maybe Luminaire)
getLuminaire id luminaires = do
  lookup id <$> readRef luminaires

-- this one doesn't
getLuminaireLight
  :: forall e
   . LuminaireId
  -> LightId
  -> Luminaires
  -> Eff (ref :: REF) (Maybe Light)
getLuminaireLight id lid luminaires = do
  luminaire <- getLuminaire id luminaires
  let lights = _.lights <<< unwrap <$> luminaire
  let light = lookup lid <$> lights -- boom
  pure light
  
------------------------------

Error found:
in module Luminaire
at src/Luminaire.purs line 57, column 3 - line 57, column 42

  Could not match type

    Maybe t0

  with type

    Light


while trying to match type Maybe (Maybe t0)
  with type Maybe Light
while checking that expression (bind ((getLuminaire id) luminaires)) (\$1 ->
                                                                        case $1 of
                                                                          luminaire -> ...
                                                                     )
  has type Eff
             ( ref :: REF
             )
             (Maybe Light)
in value declaration getLuminaireLight

where t0 is an unknown type