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 FooSym1 (a0123456789876543210 :: Maybe Bool) =
        Foo a0123456789876543210
    instance SuppressUnusedWarnings FooSym0 where
      suppressUnusedWarnings = snd (((,) FooSym0KindInference) ())
    data FooSym0 :: (~>) (Maybe Bool) Bool
      where
        FooSym0KindInference :: forall a0123456789876543210
                                       arg. SameKind (Apply FooSym0 arg) (FooSym1 arg) =>
                                FooSym0 a0123456789876543210
    type instance Apply FooSym0 a0123456789876543210 = Foo a0123456789876543210
    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)
    sFoo (SJust SFalse) = SFalse
    sFoo (SJust STrue) = STrue
    sFoo SNothing = SFalse
    instance SingI (FooSym0 :: (~>) (Maybe Bool) Bool) where
      sing = (singFun1 @FooSym0) sFoo