Rename [] to List (#21294)

This patch implements a small part of GHC Proposal #475.
The key change is in GHC.Types:

	- data [] a = [] | a : [a]
	+ data List a = [] | a : List a

And the rest of the patch makes sure that List is pretty-printed as []
in various contexts.

Updates the haddock submodule.

5 files changed, 16 insertions, 4 deletions

diff --git a/testsuite/tests/ghci/scripts/T12550.stdout b/testsuite/tests/ghci/scripts/T12550.stdout
index d753d4f666..0a30edf362 100644
--- a/testsuite/tests/ghci/scripts/T12550.stdout
+++ b/testsuite/tests/ghci/scripts/T12550.stdout
@@ -28,9 +28,9 @@ instance ∀ a b. Functor ((,,) a b) -- Defined in ‘GHC.Base’
 instance ∀ a b c. Functor ((,,,) a b c) -- Defined in ‘GHC.Base’
 instance ∀ r. Functor ((->) r) -- Defined in ‘GHC.Base’
 instance Functor IO -- Defined in ‘GHC.Base’
+instance Functor [] -- Defined in ‘GHC.Base’
 instance Functor Maybe -- Defined in ‘GHC.Base’
 instance Functor Solo -- Defined in ‘GHC.Base’
-instance Functor [] -- Defined in ‘GHC.Base’
 instance ∀ a. Functor (Either a) -- Defined in ‘Data.Either’
 instance ∀ (f ∷ ★ → ★) (g ∷ ★ → ★).
          (Functor f, Functor g) ⇒
diff --git a/testsuite/tests/ghci/scripts/T21294a.script b/testsuite/tests/ghci/scripts/T21294a.script
new file mode 100644
index 0000000000..e4a91a5d83
--- /dev/null
+++ b/testsuite/tests/ghci/scripts/T21294a.script
@@ -0,0 +1,5 @@
+type L0 = []
+:i L0
+
+type L1 a = [a]
+:i L1
diff --git a/testsuite/tests/ghci/scripts/T21294a.stdout b/testsuite/tests/ghci/scripts/T21294a.stdout
new file mode 100644
index 0000000000..58fb4e6c27
--- /dev/null
+++ b/testsuite/tests/ghci/scripts/T21294a.stdout
@@ -0,0 +1,6 @@
+type L0 :: * -> *
+type L0 = [] :: * -> *
+  	-- Defined at <interactive>:1:1
+type L1 :: * -> *
+type L1 a = [a]
+  	-- Defined at <interactive>:4:1
diff --git a/testsuite/tests/ghci/scripts/all.T b/testsuite/tests/ghci/scripts/all.T
index f2d03bd8cf..9e7ca144a6 100755
--- a/testsuite/tests/ghci/scripts/all.T
+++ b/testsuite/tests/ghci/scripts/all.T
@@ -367,3 +367,4 @@ test('T21088', normal, ghci_script, ['T21088.script'])
 test('T21110', [extra_files(['T21110A.hs'])], ghci_script,
                 ['T21110.script'])
 test('T17830', [filter_stdout_lines(r'======.*')], ghci_script, ['T17830.script'])
+test('T21294a', normal, ghci_script, ['T21294a.script'])
diff --git a/testsuite/tests/ghci/scripts/ghci011.stdout b/testsuite/tests/ghci/scripts/ghci011.stdout
index d03977e3b5..edb6158456 100644
--- a/testsuite/tests/ghci/scripts/ghci011.stdout
+++ b/testsuite/tests/ghci/scripts/ghci011.stdout
@@ -1,5 +1,5 @@
-type [] :: * -> *
-data [] a = [] | a : [a]
+type List :: * -> *
+data List a = [] | a : [a]
   	-- Defined in ‘GHC.Types’
 instance Monoid [a] -- Defined in ‘GHC.Base’
 instance Semigroup [a] -- Defined in ‘GHC.Base’
@@ -35,9 +35,9 @@ instance (Semigroup a, Semigroup b) => Semigroup (a, b)
 instance Foldable ((,) a) -- Defined in ‘Data.Foldable’
 instance (Bounded a, Bounded b) => Bounded (a, b)
   -- Defined in ‘GHC.Enum’
-instance (Read a, Read b) => Read (a, b) -- Defined in ‘GHC.Read’
 instance (Eq a, Eq b) => Eq (a, b) -- Defined in ‘GHC.Classes’
 instance (Ord a, Ord b) => Ord (a, b) -- Defined in ‘GHC.Classes’
+instance (Read a, Read b) => Read (a, b) -- Defined in ‘GHC.Read’
 instance (Show a, Show b) => Show (a, b) -- Defined in ‘GHC.Show’
 instance Monoid a => Applicative ((,) a) -- Defined in ‘GHC.Base’
 instance Functor ((,) a) -- Defined in ‘GHC.Base’