Rename () into Unit, (,,...,,) into Tuple<n> (#21294)

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

  - data () = ()
  - data (a,b) = (a,b)
  - data (a,b,c) = (a,b,c)
  ...
  + data Unit = ()
  + data Tuple2 a b = (a,b)
  + data Tuple3 a b c = (a,b,c)
  ...

And the rest of the patch makes sure that Unit and Tuple<n>
are pretty-printed as () and (,,...,,) in various contexts.

Updates the haddock submodule.

Co-authored-by: Vladislav Zavialov <vlad.z.4096@gmail.com>

16 files changed, 64 insertions, 39 deletions

diff --git a/testsuite/tests/ghc-api/T18522-dbg-ppr.stdout b/testsuite/tests/ghc-api/T18522-dbg-ppr.stdout
index c6e1d209e7..7daf9caf45 100644
--- a/testsuite/tests/ghc-api/T18522-dbg-ppr.stdout
+++ b/testsuite/tests/ghc-api/T18522-dbg-ppr.stdout
@@ -1,2 +1 @@
-forall k{tv}[tv] {j{tv}[tv]}.
-forall a{tv}[tv] b{tv}[tv] -> (){(w) tc}
+forall k{tv}[tv] {j{tv}[tv]}. forall a{tv}[tv] b{tv}[tv] -> ()
diff --git a/testsuite/tests/ghci/scripts/T12550.stdout b/testsuite/tests/ghci/scripts/T12550.stdout
index 5c2dccb767..6d76942568 100644
--- a/testsuite/tests/ghci/scripts/T12550.stdout
+++ b/testsuite/tests/ghci/scripts/T12550.stdout
@@ -23,6 +23,11 @@ class Functor f where
   (<$) ∷ ∀ a b. a → f b → f a
   {-# MINIMAL fmap #-}
   	-- 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 ∀ a. Functor ((,) a) -- Defined in ‘GHC.Base’
 instance ∀ a b. Functor ((,,) a b) -- Defined in ‘GHC.Base’
 instance ∀ a b c. Functor ((,,,) a b c) -- Defined in ‘GHC.Base’
@@ -32,11 +37,6 @@ instance ∀ a b c d e. Functor ((,,,,,) a b c d e)
   -- Defined in ‘GHC.Base’
 instance ∀ a b c d e f. Functor ((,,,,,,) a b c d e f)
   -- 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 ∀ a. Functor (Either a) -- Defined in ‘Data.Either’
 instance ∀ (f ∷ ★ → ★) (g ∷ ★ → ★).
          (Functor f, Functor g) ⇒
diff --git a/testsuite/tests/ghci/scripts/T4127.stdout b/testsuite/tests/ghci/scripts/T4127.stdout
index 3d2fad2539..d1cab7c0cc 100644
--- a/testsuite/tests/ghci/scripts/T4127.stdout
+++ b/testsuite/tests/ghci/scripts/T4127.stdout
@@ -1 +1 @@
-[InstanceD Nothing [] (AppT (ConT GHC.Base.Monad) (AppT (ConT GHC.Tuple.Prim.(,)) (VarT a_0))) [ValD (VarP GHC.Base.>>=) (NormalB (VarE GHC.Err.undefined)) []]]
+[InstanceD Nothing [] (AppT (ConT GHC.Base.Monad) (AppT (ConT GHC.Tuple.Prim.Tuple2) (VarT a_0))) [ValD (VarP GHC.Base.>>=) (NormalB (VarE GHC.Err.undefined)) []]]
diff --git a/testsuite/tests/ghci/scripts/T4175.stdout b/testsuite/tests/ghci/scripts/T4175.stdout
index 16b2ebc26a..c014d96b51 100644
--- a/testsuite/tests/ghci/scripts/T4175.stdout
+++ b/testsuite/tests/ghci/scripts/T4175.stdout
@@ -22,8 +22,8 @@ type family E a where
     E () = Bool
     E Int = String
   	-- Defined at T4175.hs:25:1
-type () :: *
-data () = ()
+type Unit :: *
+data Unit = ()
   	-- Defined in ‘GHC.Tuple.Prim’
 instance [safe] C () -- Defined at T4175.hs:22:10
 instance Monoid () -- Defined in ‘GHC.Base’
diff --git a/testsuite/tests/ghci/scripts/T7627.stdout b/testsuite/tests/ghci/scripts/T7627.stdout
index ba4640d01b..9deefb75a1 100644
--- a/testsuite/tests/ghci/scripts/T7627.stdout
+++ b/testsuite/tests/ghci/scripts/T7627.stdout
@@ -1,5 +1,5 @@
-type () :: *
-data () = ()
+type Unit :: *
+data Unit = ()
   	-- Defined in ‘GHC.Tuple.Prim’
 instance Monoid () -- Defined in ‘GHC.Base’
 instance Semigroup () -- Defined in ‘GHC.Base’
@@ -16,8 +16,8 @@ data (##) = (##)
 (##) :: (# #)
 (   ) :: ()
 (#   #) :: (# #)
-type (,) :: * -> * -> *
-data (,) a b = (,) a b
+type Tuple2 :: * -> * -> *
+data Tuple2 a b = (,) a b
   	-- Defined in ‘GHC.Tuple.Prim’
 instance Traversable ((,) a) -- Defined in ‘Data.Traversable’
 instance (Monoid a, Monoid b) => Monoid (a, b)
@@ -27,13 +27,13 @@ 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 (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’
 instance Monoid a => Monad ((,) a) -- Defined in ‘GHC.Base’
+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 (Show a, Show b) => Show (a, b) -- Defined in ‘GHC.Show’
 type (#,#) :: *
               -> *
               -> TYPE
diff --git a/testsuite/tests/ghci/scripts/ghci011.stdout b/testsuite/tests/ghci/scripts/ghci011.stdout
index 32190117fd..e0fbe20927 100644
--- a/testsuite/tests/ghci/scripts/ghci011.stdout
+++ b/testsuite/tests/ghci/scripts/ghci011.stdout
@@ -13,8 +13,8 @@ instance MonadFail [] -- Defined in ‘Control.Monad.Fail’
 instance Monad [] -- Defined in ‘GHC.Base’
 instance Eq a => Eq [a] -- Defined in ‘GHC.Classes’
 instance Ord a => Ord [a] -- Defined in ‘GHC.Classes’
-type () :: *
-data () = ()
+type Unit :: *
+data Unit = ()
   	-- Defined in ‘GHC.Tuple.Prim’
 instance Monoid () -- Defined in ‘GHC.Base’
 instance Semigroup () -- Defined in ‘GHC.Base’
@@ -24,8 +24,8 @@ instance Enum () -- Defined in ‘GHC.Enum’
 instance Ord () -- Defined in ‘GHC.Classes’
 instance Show () -- Defined in ‘GHC.Show’
 instance Eq () -- Defined in ‘GHC.Classes’
-type (,) :: * -> * -> *
-data (,) a b = (,) a b
+type Tuple2 :: * -> * -> *
+data Tuple2 a b = (,) a b
   	-- Defined in ‘GHC.Tuple.Prim’
 instance Traversable ((,) a) -- Defined in ‘Data.Traversable’
 instance (Monoid a, Monoid b) => Monoid (a, b)
@@ -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’
diff --git a/testsuite/tests/hiefile/should_run/HieQueries.stdout b/testsuite/tests/hiefile/should_run/HieQueries.stdout
index 11fc74a84f..42492acb0c 100644
--- a/testsuite/tests/hiefile/should_run/HieQueries.stdout
+++ b/testsuite/tests/hiefile/should_run/HieQueries.stdout
@@ -46,7 +46,7 @@ At point (23,9), we found:
 |
 `- ┌
    │ $dShow at HieQueries.hs:23:1-22, of type: Show (Integer, x, A)
-   │     is an evidence variable bound by a let, depending on: [$fShow(,,),
+   │     is an evidence variable bound by a let, depending on: [$fShowTuple3,
    │                                                            $dShow, $dShow, $dShow]
    │           with scope: LocalScope HieQueries.hs:23:1-22
    │           bound at: HieQueries.hs:23:1-22
@@ -54,7 +54,7 @@ At point (23,9), we found:
    └
    |
    +- ┌
-   |  │ $fShow(,,) at HieQueries.hs:23:1-22, of type: forall a b c. (Show a, Show b, Show c) => Show (a, b, c)
+   |  │ $fShowTuple3 at HieQueries.hs:23:1-22, of type: forall a b c. (Show a, Show b, Show c) => Show (a, b, c)
    |  │     is a usage of an external evidence variable
    |  │     Defined in `GHC.Show'
    |  └
diff --git a/testsuite/tests/module/TupleTyConUserSyntax.hs b/testsuite/tests/module/TupleTyConUserSyntax.hs
new file mode 100644
index 0000000000..12501795bd
--- /dev/null
+++ b/testsuite/tests/module/TupleTyConUserSyntax.hs
@@ -0,0 +1,13 @@
+module TupleTyConUserSyntax where
+
+import TupleTyConUserSyntaxA
+
+type T1 = Tuple1
+
+type T2 = Tuple2
+
+type T23 = Tuple23
+
+type T46 = Tuple46
+
+type T64 = Tuple64
\ No newline at end of file
diff --git a/testsuite/tests/module/TupleTyConUserSyntaxA.hs b/testsuite/tests/module/TupleTyConUserSyntaxA.hs
new file mode 100644
index 0000000000..086e9a905d
--- /dev/null
+++ b/testsuite/tests/module/TupleTyConUserSyntaxA.hs
@@ -0,0 +1,11 @@
+module TupleTyConUserSyntaxA (module GHC.Tuple) where
+
+import GHC.Tuple
+
+type T1 = Tuple1
+
+type T2 = Tuple2
+
+type T23 = Tuple23
+
+type T64 = Tuple64
\ No newline at end of file
diff --git a/testsuite/tests/module/all.T b/testsuite/tests/module/all.T
index 415f40717e..516a252b8c 100644
--- a/testsuite/tests/module/all.T
+++ b/testsuite/tests/module/all.T
@@ -295,3 +295,5 @@ test('T13704b', [], multimod_compile, ['T13704b1.hs T13704b2.hs', '-main-is T137
 test('T20562', normal, compile, [''])
 
 test('T21752', [extra_files(['T21752A.hs', 'T21752.hs'])], multimod_compile, ['T21752', '-v0'])
+
+test('TupleTyConUserSyntax', [extra_files(['TupleTyConUserSyntaxA.hs', 'TupleTyConUserSyntax.hs'])], multimod_compile, ['TupleTyConUserSyntax', '-v0'])
diff --git a/testsuite/tests/partial-sigs/should_fail/NamedWildcardsNotInMonotype.stderr b/testsuite/tests/partial-sigs/should_fail/NamedWildcardsNotInMonotype.stderr
index 388ba5a0a1..806bda59fb 100644
--- a/testsuite/tests/partial-sigs/should_fail/NamedWildcardsNotInMonotype.stderr
+++ b/testsuite/tests/partial-sigs/should_fail/NamedWildcardsNotInMonotype.stderr
@@ -8,7 +8,7 @@ NamedWildcardsNotInMonotype.hs:5:1: error: [GHC-39999]
       The type variable ‘w0’ is ambiguous
       Potentially matching instances:
         instance Eq Ordering -- Defined in ‘GHC.Classes’
-        instance Eq () -- Defined in ‘GHC.Classes’
+        instance Eq a => Eq (Solo a) -- Defined in ‘GHC.Classes’
         ...plus 22 others
         ...plus four instances involving out-of-scope types
         (use -fprint-potential-instances to see them all)
diff --git a/testsuite/tests/roles/should_compile/T8958.stderr b/testsuite/tests/roles/should_compile/T8958.stderr
index ec5ede1aa1..9a8e781e67 100644
--- a/testsuite/tests/roles/should_compile/T8958.stderr
+++ b/testsuite/tests/roles/should_compile/T8958.stderr
@@ -18,7 +18,7 @@ CLASS INSTANCES
     -- Defined at T8958.hs:11:10
   instance [incoherent] Nominal a -- Defined at T8958.hs:8:10
 Dependent modules: []
-Dependent packages: [base-4.17.0.0]
+Dependent packages: [base-4.18.0.0]
 
 ==================== Typechecker ====================
 T8958.$tcMap
@@ -53,7 +53,7 @@ $krep [InlPrag=[~]]
   = GHC.Types.KindRepFun GHC.Types.krep$* GHC.Types.krep$Constraint
 $krep [InlPrag=[~]]
   = GHC.Types.KindRepTyConApp
-      GHC.Tuple.Prim.$tc(,)
+      GHC.Tuple.Prim.$tcTuple2
       ((:) @GHC.Types.KindRep
          $krep ((:) @GHC.Types.KindRep $krep [] @GHC.Types.KindRep))
 $krep [InlPrag=[~]]
diff --git a/testsuite/tests/stranal/sigs/T21119.stderr b/testsuite/tests/stranal/sigs/T21119.stderr
index 1c27b4c9a4..a0549af229 100644
--- a/testsuite/tests/stranal/sigs/T21119.stderr
+++ b/testsuite/tests/stranal/sigs/T21119.stderr
@@ -1,7 +1,7 @@
 
 ==================== Strictness signatures ====================
-T21119.$fMyShow(,): <1!A>
 T21119.$fMyShowInt: <1!A>
+T21119.$fMyShowTuple2: <1!A>
 T21119.get: <1!P(1!P(L),1!P(L))><1!P(L)><1L>
 T21119.getIO: <1P(1L,ML)><1L><ML><L>
 T21119.indexError: <1C(1,L)><1!B><S!S><S>b
@@ -10,8 +10,8 @@ T21119.throwIndexError: <MC(1,L)><MA><L><L><L>x
 
 
 ==================== Cpr signatures ====================
-T21119.$fMyShow(,):
 T21119.$fMyShowInt:
+T21119.$fMyShowTuple2:
 T21119.get:
 T21119.getIO: 1
 T21119.indexError: b
@@ -20,8 +20,8 @@ T21119.throwIndexError: b
 
 
 ==================== Strictness signatures ====================
-T21119.$fMyShow(,): <1!A>
 T21119.$fMyShowInt: <1!A>
+T21119.$fMyShowTuple2: <1!A>
 T21119.get: <1!P(1!P(L),1!P(L))><1!P(L)><1L>
 T21119.getIO: <1P(1L,ML)><1L><ML><L>
 T21119.indexError: <1C(1,L)><1!B><S!S><S>b
diff --git a/testsuite/tests/stranal/sigs/T21888.stderr b/testsuite/tests/stranal/sigs/T21888.stderr
index d52d0c7d78..ff046ca2cf 100644
--- a/testsuite/tests/stranal/sigs/T21888.stderr
+++ b/testsuite/tests/stranal/sigs/T21888.stderr
@@ -1,30 +1,30 @@
 
 ==================== Strictness signatures ====================
-Data.MemoTrie.$fHasTrie(): <L>
-Data.MemoTrie.$fHasTrie(,): <1C(1,L)><LC(S,L)><L>
 Data.MemoTrie.$fHasTrieBool: <1!P(L,L)>
 Data.MemoTrie.$fHasTrieEither: <1C(1,L)><1C(1,L)><1!P(L,L)>
 Data.MemoTrie.$fHasTrieInteger: <1!P(1!P(S,1!P(1!P(S,1L),1!P(S,1L))),1!P(S,1!P(1!P(S,1L),1!P(S,1L))))>b
 Data.MemoTrie.$fHasTrieList: <SC(S,L)><1!P(L,L)>
+Data.MemoTrie.$fHasTrieTuple2: <1C(1,L)><LC(S,L)><L>
+Data.MemoTrie.$fHasTrieUnit: <L>
 
 
 
 ==================== Cpr signatures ====================
-Data.MemoTrie.$fHasTrie():
-Data.MemoTrie.$fHasTrie(,):
 Data.MemoTrie.$fHasTrieBool:
 Data.MemoTrie.$fHasTrieEither:
 Data.MemoTrie.$fHasTrieInteger:
 Data.MemoTrie.$fHasTrieList:
+Data.MemoTrie.$fHasTrieTuple2:
+Data.MemoTrie.$fHasTrieUnit:
 
 
 
 ==================== Strictness signatures ====================
-Data.MemoTrie.$fHasTrie(): <L>
-Data.MemoTrie.$fHasTrie(,): <1C(1,L)><LC(S,L)><L>
 Data.MemoTrie.$fHasTrieBool: <1!P(L,L)>
 Data.MemoTrie.$fHasTrieEither: <1C(1,L)><1C(1,L)><1!P(L,L)>
 Data.MemoTrie.$fHasTrieInteger: <1!P(1!P(B,1!P(1!P(B,1!P(L,L)),1!P(B,1!P(L,L)))),1!P(B,1!P(1!B,1!B)))>b
 Data.MemoTrie.$fHasTrieList: <SC(S,L)><1!P(L,L)>
+Data.MemoTrie.$fHasTrieTuple2: <1C(1,L)><LC(S,L)><L>
+Data.MemoTrie.$fHasTrieUnit: <L>
 
 
diff --git a/testsuite/tests/th/T12478_4.stderr b/testsuite/tests/th/T12478_4.stderr
index 2f1b3f4e50..852b104cd5 100644
--- a/testsuite/tests/th/T12478_4.stderr
+++ b/testsuite/tests/th/T12478_4.stderr
@@ -2,5 +2,5 @@
 T12478_4.hs:7:7: error: [GHC-97721]
     • Illegal sum arity: 1
         Sums must have an arity of at least 2
-      When splicing a TH type: (#  #) GHC.Tuple.Prim.()
+      When splicing a TH type: (#  #) GHC.Tuple.Prim.Unit
     • In the untyped splice: $(unboxedSumT 1 `appT` conT ''())
diff --git a/testsuite/tests/typecheck/should_compile/T18529.stderr b/testsuite/tests/typecheck/should_compile/T18529.stderr
index 71542931fc..21b41159d4 100644
--- a/testsuite/tests/typecheck/should_compile/T18529.stderr
+++ b/testsuite/tests/typecheck/should_compile/T18529.stderr
@@ -6,7 +6,7 @@ TYPE CONSTRUCTORS
 COERCION AXIOMS
   axiom Bug.N:C :: forall a b. C a b = a -> b -> ()
 Dependent modules: []
-Dependent packages: [base-4.17.0.0]
+Dependent packages: [base-4.18.0.0]
 
 ==================== Typechecker ====================
 Bug.$tcC
@@ -32,7 +32,7 @@ $krep [InlPrag=[~]]
   = GHC.Types.KindRepFun GHC.Types.krep$* GHC.Types.krep$Constraint
 $krep [InlPrag=[~]]
   = GHC.Types.KindRepTyConApp
-      GHC.Tuple.Prim.$tc() [] @GHC.Types.KindRep
+      GHC.Tuple.Prim.$tcUnit [] @GHC.Types.KindRep
 Bug.$trModule
   = GHC.Types.Module
       (GHC.Types.TrNameS "main"#) (GHC.Types.TrNameS "Bug"#)