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-rw-r--r--testsuite/tests/typecheck/should_compile/free_monad_hole_fits.hs25
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diff --git a/testsuite/tests/typecheck/should_compile/free_monad_hole_fits.hs b/testsuite/tests/typecheck/should_compile/free_monad_hole_fits.hs
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+++ b/testsuite/tests/typecheck/should_compile/free_monad_hole_fits.hs
@@ -0,0 +1,25 @@
+{-# OPTIONS_GHC -frefinement-level-hole-fits=2 #-}
+{-# LANGUAGE MonoLocalBinds #-}
+module TG where
+import Prelude ( Monad, Applicative, Functor
+ , fmap, (<*>), pure, (>>=)
+ , (=<<), ($), (<$>) )
+
+data Free f a = Pure a | Free (f (Free f a))
+
+instance Functor f => Functor (Free f) where
+ fmap f = go where
+ go (Pure a) = Pure (f a)
+ -- Should suggest (fmap)
+ go (Free fa) = Free (_a go fa)
+
+instance Functor f => Applicative (Free f) where
+ pure = Pure
+ Pure a <*> Pure b = Pure (a b)
+ Pure a <*> Free mb = Free (fmap a <$> mb)
+ Free ma <*> b = Free ((<*> b) <$> ma)
+
+instance Applicative f => Monad (Free f) where
+ Pure a >>= f = f a
+ -- Should suggest ((=<< (_ :: a -> Free f b))
+ Free f >>= g = Free (fmap _a f)