Singletons/T78.hs:(0,0)-(0,0): Splicing declarations
    singletons
      [d| foo :: MaybeBool -> Bool
          foo (Just False) = False
          foo (Just True) = True
          foo Nothing = False |]
  ======>
    foo :: MaybeBool -> Bool
    foo (Just False) = False
    foo (Just True) = True
    foo Nothing = False
    type FooSym0 :: (~>) (Maybe Bool) Bool
    data FooSym0 :: (~>) (Maybe Bool) Bool
      where
        FooSym0KindInference :: SameKind (Apply FooSym0 arg) (FooSym1 arg) =>
                                FooSym0 a0123456789876543210
    type instance Apply FooSym0 a0123456789876543210 = Foo a0123456789876543210
    instance SuppressUnusedWarnings FooSym0 where
      suppressUnusedWarnings = snd ((,) FooSym0KindInference ())
    type FooSym1 :: Maybe Bool -> Bool
    type family FooSym1 (a0123456789876543210 :: Maybe Bool) :: Bool where
      FooSym1 a0123456789876543210 = Foo a0123456789876543210
    type Foo :: Maybe Bool -> Bool
    type family Foo (a :: Maybe Bool) :: Bool where
      Foo ('Just 'False) = FalseSym0
      Foo ('Just 'True) = TrueSym0
      Foo 'Nothing = FalseSym0
    sFoo ::
      (forall (t :: Maybe Bool).
       Sing t -> Sing (Apply FooSym0 t :: Bool) :: Type)
    sFoo (SJust SFalse) = SFalse
    sFoo (SJust STrue) = STrue
    sFoo SNothing = SFalse
    instance SingI (FooSym0 :: (~>) (Maybe Bool) Bool) where
      sing = singFun1 @FooSym0 sFoo