Test case: GHCi uses UnicodeSyntax if the loaded file uses it.

Its marked as broken, as this does not work yet, but we are calling it a
day here soon, so I want this to be recorded (#8959).

testsuite/tests/ghci/scripts/T8959b.hs

+{-# LANGUAGE UnicodeSyntax, Arrows, RankNTypes #-}
+module T8959b where
+
+foo :: Int -> Int
+foo = ()
+
+bar :: ()
+bar = proc x -> do return -< x
+
+baz = () :: (forall a. a -> a) -> a
+

testsuite/tests/ghci/scripts/T8959b.script

+:l T8959b.hs

testsuite/tests/ghci/scripts/T8959b.stderr

+
+T8959b.hs:5:7:
+    Couldn't match expected type ‘Int → Int’ with actual type ‘()’
+    In the expression: ()
+    In an equation for ‘foo’: foo = ()
+
+T8959b.hs:8:7:
+    Couldn't match expected type ‘()’ with actual type ‘t0 → m0 t0’
+    In the expression: proc x -> do { return ↢ x }
+    In an equation for ‘bar’: bar = proc x -> do { return ↢ x }
+
+T8959b.hs:10:7:
+    Couldn't match expected type ‘(∀ a2. a2 → a2) → a1’
+                with actual type ‘()’
+    In the expression: () ∷ (∀ a. a -> a) -> a
+    In an equation for ‘baz’: baz = () ∷ (∀ a. a -> a) -> a

testsuite/tests/ghci/scripts/all.T

@@ -173,3 +173,4 @@ test('T8831', normal, ghci_script, ['T8831.script'])
 test('T8917', normal, ghci_script, ['T8917.script'])
 test('T8931', normal, ghci_script, ['T8931.script'])
 test('T8959', normal, ghci_script, ['T8959.script'])
+test('T8959b', expect_broken(8959), ghci_script, ['T8959b.script'])