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--Testing GADTs, type families as well as a ton of crazy type stuff
:set -XGADTs
:set -XTypeFamilies
:set -XOverlappingInstances
:set -XFunctionalDependencies
:set -XFlexibleContexts
:set -XFlexibleInstances
:set -XUndecidableInstances
data A
data B
data C
:{
data ABorC t where
Foo :: Int -> ABorC A
Bar :: Bool -> ABorC A
Baz :: Char -> ABorC B
Quz :: ABorC B
Yud :: String -> ABorC C
Myp :: Double -> ABorC C
:}
data HTrue
data HFalse
class TypeEq x y b | x y -> b
instance (HTrue ~ b) => TypeEq x x b
instance (HFalse ~ b) => TypeEq x y b
type family Or a b
type instance Or HTrue HTrue = HTrue
type instance Or HTrue HFalse = HTrue
type instance Or HFalse HTrue = HTrue
type instance Or HFalse HFalse = HFalse
let f :: (Or a c ~ HTrue, TypeEq t A a, TypeEq t C c) => ABorC t -> Int ; f x = 1
f $ Foo 1
f $ Bar True
f $ Baz 'a'
f $ Quz
f $ Yud "a"
f $ Myp 4.3
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