Do not imply NoStarIsType by TypeOperators/TypeInType

Implementation of the "Embrace TypeInType" proposal was done according
to the spec, which specified that TypeOperators must imply NoStarIsType.
This implication was meant to prevent breakage and to be removed in 2
releases.  However, compiling head.hackage has shown that this
implication only magnified the breakage, so there is no reason to have
it in the first place.

To remain in compliance with the three-release policy, we add a
workaround to define the (*) type operator even when -XStarIsType is on.

Test Plan: ./validate

Reviewers: bgamari, RyanGlScott, goldfire, phadej, hvr

Reviewed By: bgamari, RyanGlScott

Subscribers: harpocrates, rwbarton, thomie, carter

Differential Revision: https://phabricator.haskell.org/D4865

13 files changed, 66 insertions, 57 deletions

diff --git a/testsuite/tests/dependent/ghci/T14238.stdout b/testsuite/tests/dependent/ghci/T14238.stdout
index 729f821af7..fddbc0de54 100644
--- a/testsuite/tests/dependent/ghci/T14238.stdout
+++ b/testsuite/tests/dependent/ghci/T14238.stdout
@@ -1 +1 @@
-Foo :: forall k -> k -> Type
+Foo :: forall k -> k -> *
diff --git a/testsuite/tests/partial-sigs/should_compile/T15039b.stderr b/testsuite/tests/partial-sigs/should_compile/T15039b.stderr
index 020c253516..5726c7fa65 100644
--- a/testsuite/tests/partial-sigs/should_compile/T15039b.stderr
+++ b/testsuite/tests/partial-sigs/should_compile/T15039b.stderr
@@ -1,62 +1,57 @@
 
 T15039b.hs:19:14: warning: [-Wpartial-type-signatures (in -Wdefault)]
-    • Found type wildcard ‘_’
-        standing for ‘Dict ((a :: Type) ~ (b :: Type))’
+    • Found type wildcard ‘_’ standing for ‘Dict ((a :: *) ~ (b :: *))’
       Where: ‘a’, ‘b’ are rigid type variables bound by
                the type signature for:
-                 ex1 :: forall a b. Dict ((a :: Type) ~ (b :: Type)) -> ()
+                 ex1 :: forall a b. Dict ((a :: *) ~ (b :: *)) -> ()
                at T15039b.hs:18:1-45
     • In a pattern type signature: _
       In the pattern: Dict :: _
       In an equation for ‘ex1’: ex1 (Dict :: _) = ()
     • Relevant bindings include
-        ex1 :: Dict ((a :: Type) ~ (b :: Type)) -> ()
-          (bound at T15039b.hs:19:1)
+        ex1 :: Dict ((a :: *) ~ (b :: *)) -> () (bound at T15039b.hs:19:1)
 
 T15039b.hs:22:14: warning: [-Wpartial-type-signatures (in -Wdefault)]
-    • Found type wildcard ‘_’
-        standing for ‘Dict ((a :: Type) ~ (b :: Type))’
+    • Found type wildcard ‘_’ standing for ‘Dict ((a :: *) ~ (b :: *))’
       Where: ‘a’, ‘b’ are rigid type variables bound by
                the type signature for:
-                 ex2 :: forall a b. Dict ((a :: Type) ~ (b :: Type)) -> ()
+                 ex2 :: forall a b. Dict ((a :: *) ~ (b :: *)) -> ()
                at T15039b.hs:21:1-46
     • In a pattern type signature: _
       In the pattern: Dict :: _
       In an equation for ‘ex2’: ex2 (Dict :: _) = ()
     • Relevant bindings include
-        ex2 :: Dict ((a :: Type) ~ (b :: Type)) -> ()
-          (bound at T15039b.hs:22:1)
+        ex2 :: Dict ((a :: *) ~ (b :: *)) -> () (bound at T15039b.hs:22:1)
 
 T15039b.hs:25:14: warning: [-Wpartial-type-signatures (in -Wdefault)]
     • Found type wildcard ‘_’
-        standing for ‘Dict ((a :: Type) ~~ (b :: k))’
+        standing for ‘Dict ((a :: *) ~~ (b :: k))’
       Where: ‘a’, ‘b’, ‘k’ are rigid type variables bound by
                the type signature for:
-                 ex3 :: forall k a (b :: k). Dict ((a :: Type) ~~ (b :: k)) -> ()
+                 ex3 :: forall k a (b :: k). Dict ((a :: *) ~~ (b :: k)) -> ()
                at T15039b.hs:24:1-43
     • In a pattern type signature: _
       In the pattern: Dict :: _
       In an equation for ‘ex3’: ex3 (Dict :: _) = ()
     • Relevant bindings include
-        ex3 :: Dict ((a :: Type) ~~ (b :: k)) -> ()
-          (bound at T15039b.hs:25:1)
+        ex3 :: Dict ((a :: *) ~~ (b :: k)) -> () (bound at T15039b.hs:25:1)
 
 T15039b.hs:33:14: warning: [-Wpartial-type-signatures (in -Wdefault)]
-    • Found type wildcard ‘_’ standing for ‘Dict (Coercible Type a b)’
+    • Found type wildcard ‘_’ standing for ‘Dict (Coercible * a b)’
       Where: ‘a’, ‘b’ are rigid type variables bound by
                the type signature for:
-                 ex6 :: forall a b. Dict (Coercible Type a b) -> ()
+                 ex6 :: forall a b. Dict (Coercible * a b) -> ()
                at T15039b.hs:32:1-53
     • In a pattern type signature: _
       In the pattern: Dict :: _
       In an equation for ‘ex6’: ex6 (Dict :: _) = ()
     • Relevant bindings include
-        ex6 :: Dict (Coercible Type a b) -> () (bound at T15039b.hs:33:1)
+        ex6 :: Dict (Coercible * a b) -> () (bound at T15039b.hs:33:1)
 
 T15039b.hs:35:8: warning: [-Wpartial-type-signatures (in -Wdefault)]
-    • Found type wildcard ‘_’ standing for ‘Coercible Type a b’
+    • Found type wildcard ‘_’ standing for ‘Coercible * a b’
       Where: ‘a’, ‘b’ are rigid type variables bound by
-               the inferred type of ex7 :: Coercible Type a b => Coercion Type a b
+               the inferred type of ex7 :: Coercible * a b => Coercion * a b
                at T15039b.hs:36:1-14
     • In the type signature:
         ex7 :: _ => Coercion (a :: Type) (b :: Type)
diff --git a/testsuite/tests/partial-sigs/should_compile/T15039d.stderr b/testsuite/tests/partial-sigs/should_compile/T15039d.stderr
index 6c6e1a0c24..7a0f4acf26 100644
--- a/testsuite/tests/partial-sigs/should_compile/T15039d.stderr
+++ b/testsuite/tests/partial-sigs/should_compile/T15039d.stderr
@@ -1,64 +1,59 @@
 
 T15039d.hs:19:14: warning: [-Wpartial-type-signatures (in -Wdefault)]
-    • Found type wildcard ‘_’
-        standing for ‘Dict ((a :: Type) ~ (b :: Type))’
+    • Found type wildcard ‘_’ standing for ‘Dict ((a :: *) ~ (b :: *))’
       Where: ‘a’, ‘b’ are rigid type variables bound by
                the type signature for:
-                 ex1 :: forall a b. Dict ((a :: Type) ~ (b :: Type)) -> ()
+                 ex1 :: forall a b. Dict ((a :: *) ~ (b :: *)) -> ()
                at T15039d.hs:18:1-45
     • In a pattern type signature: _
       In the pattern: Dict :: _
       In an equation for ‘ex1’: ex1 (Dict :: _) = ()
     • Relevant bindings include
-        ex1 :: Dict ((a :: Type) ~ (b :: Type)) -> ()
-          (bound at T15039d.hs:19:1)
+        ex1 :: Dict ((a :: *) ~ (b :: *)) -> () (bound at T15039d.hs:19:1)
 
 T15039d.hs:22:14: warning: [-Wpartial-type-signatures (in -Wdefault)]
     • Found type wildcard ‘_’
-        standing for ‘Dict ((a :: Type) ~~ (b :: Type))’
+        standing for ‘Dict ((a :: *) ~~ (b :: *))’
       Where: ‘a’, ‘b’ are rigid type variables bound by
                the type signature for:
-                 ex2 :: forall a b. Dict ((a :: Type) ~~ (b :: Type)) -> ()
+                 ex2 :: forall a b. Dict ((a :: *) ~~ (b :: *)) -> ()
                at T15039d.hs:21:1-46
     • In a pattern type signature: _
       In the pattern: Dict :: _
       In an equation for ‘ex2’: ex2 (Dict :: _) = ()
     • Relevant bindings include
-        ex2 :: Dict ((a :: Type) ~~ (b :: Type)) -> ()
-          (bound at T15039d.hs:22:1)
+        ex2 :: Dict ((a :: *) ~~ (b :: *)) -> () (bound at T15039d.hs:22:1)
 
 T15039d.hs:25:14: warning: [-Wpartial-type-signatures (in -Wdefault)]
     • Found type wildcard ‘_’
-        standing for ‘Dict ((a :: Type) ~~ (b :: k))’
+        standing for ‘Dict ((a :: *) ~~ (b :: k))’
       Where: ‘a’, ‘b’, ‘k’ are rigid type variables bound by
                the type signature for:
-                 ex3 :: forall k a (b :: k). Dict ((a :: Type) ~~ (b :: k)) -> ()
+                 ex3 :: forall k a (b :: k). Dict ((a :: *) ~~ (b :: k)) -> ()
                at T15039d.hs:24:1-43
     • In a pattern type signature: _
       In the pattern: Dict :: _
       In an equation for ‘ex3’: ex3 (Dict :: _) = ()
     • Relevant bindings include
-        ex3 :: Dict ((a :: Type) ~~ (b :: k)) -> ()
-          (bound at T15039d.hs:25:1)
+        ex3 :: Dict ((a :: *) ~~ (b :: k)) -> () (bound at T15039d.hs:25:1)
 
 T15039d.hs:33:14: warning: [-Wpartial-type-signatures (in -Wdefault)]
-    • Found type wildcard ‘_’ standing for ‘Dict (Coercible Type a b)’
+    • Found type wildcard ‘_’ standing for ‘Dict (Coercible * a b)’
       Where: ‘a’, ‘b’ are rigid type variables bound by
                the type signature for:
-                 ex6 :: forall a b. Dict (Coercible Type a b) -> ()
+                 ex6 :: forall a b. Dict (Coercible * a b) -> ()
                at T15039d.hs:32:1-53
     • In a pattern type signature: _
       In the pattern: Dict :: _
       In an equation for ‘ex6’: ex6 (Dict :: _) = ()
     • Relevant bindings include
-        ex6 :: Dict (Coercible Type a b) -> () (bound at T15039d.hs:33:1)
+        ex6 :: Dict (Coercible * a b) -> () (bound at T15039d.hs:33:1)
 
 T15039d.hs:35:8: warning: [-Wpartial-type-signatures (in -Wdefault)]
-    • Found type wildcard ‘_’
-        standing for ‘(a :: Type) ~R# (b :: Type)’
+    • Found type wildcard ‘_’ standing for ‘(a :: *) ~R# (b :: *)’
       Where: ‘a’, ‘b’ are rigid type variables bound by
                the inferred type of
-                 ex7 :: ((a :: Type) ~R# (b :: Type)) => Coercion Type a b
+                 ex7 :: ((a :: *) ~R# (b :: *)) => Coercion * a b
                at T15039d.hs:36:1-14
     • In the type signature:
         ex7 :: _ => Coercion (a :: Type) (b :: Type)
diff --git a/testsuite/tests/partial-sigs/should_fail/T14584.stderr b/testsuite/tests/partial-sigs/should_fail/T14584.stderr
index f4f1887f4d..f22178774e 100644
--- a/testsuite/tests/partial-sigs/should_fail/T14584.stderr
+++ b/testsuite/tests/partial-sigs/should_fail/T14584.stderr
@@ -1,13 +1,13 @@
 
 T14584.hs:56:41: warning: [-Wdeferred-type-errors (in -Wdefault)]
-    • Could not deduce: m1 ~ Type
+    • Could not deduce: m1 ~ *
       from the context: (Action act, Monoid a, Good m1)
         bound by the instance declaration at T14584.hs:54:10-89
       ‘m1’ is a rigid type variable bound by
         the instance declaration
         at T14584.hs:54:10-89
       When matching types
-        a :: Type
+        a :: *
         a0 :: m
       Expected type: Sing a0
         Actual type: Sing a
diff --git a/testsuite/tests/polykinds/T10134.hs b/testsuite/tests/polykinds/T10134.hs
index 0b64625f28..746758ce2f 100644
--- a/testsuite/tests/polykinds/T10134.hs
+++ b/testsuite/tests/polykinds/T10134.hs
@@ -3,7 +3,7 @@
 
 module T10134 where
 
-import GHC.TypeLits
+import GHC.TypeLits as L
 import T10134a
 import Prelude
 
@@ -11,9 +11,9 @@ type Positive n = ((n-1)+1)~n
 
 data Dummy n d = Dummy { vec :: Vec n (Vec d Bool) }
 
-nextDummy :: Positive (2*(n+d)) => Dummy n d -> Dummy n d
+nextDummy :: Positive (2 L.* (n+d)) => Dummy n d -> Dummy n d
 nextDummy d = Dummy { vec = vec dFst }
    where (dFst,dSnd) = nextDummy' d
 
-nextDummy' :: Positive (2*(n+d)) => Dummy n d -> ( Dummy n d, Bool )
+nextDummy' :: Positive (2 L.* (n+d)) => Dummy n d -> ( Dummy n d, Bool )
 nextDummy' _ = undefined
diff --git a/testsuite/tests/th/TH_unresolvedInfix.hs b/testsuite/tests/th/TH_unresolvedInfix.hs
index 49f283bcd8..aa684f7f23 100644
--- a/testsuite/tests/th/TH_unresolvedInfix.hs
+++ b/testsuite/tests/th/TH_unresolvedInfix.hs
@@ -1,4 +1,5 @@
 {-# LANGUAGE TypeOperators #-}
+{-# LANGUAGE NoStarIsType #-}
 {-# LANGUAGE QuasiQuotes #-}
 
 module Main where
diff --git a/testsuite/tests/th/TH_unresolvedInfix_Lib.hs b/testsuite/tests/th/TH_unresolvedInfix_Lib.hs
index e6ad9f027b..a88b93fc8a 100644
--- a/testsuite/tests/th/TH_unresolvedInfix_Lib.hs
+++ b/testsuite/tests/th/TH_unresolvedInfix_Lib.hs
@@ -1,4 +1,5 @@
 {-# LANGUAGE TypeOperators #-}
+{-# LANGUAGE NoStarIsType #-}
 
 module TH_unresolvedInfix_Lib where
 
diff --git a/testsuite/tests/typecheck/should_compile/TcTypeNatSimple.hs b/testsuite/tests/typecheck/should_compile/TcTypeNatSimple.hs
index 911a43e507..d0077edbdb 100644
--- a/testsuite/tests/typecheck/should_compile/TcTypeNatSimple.hs
+++ b/testsuite/tests/typecheck/should_compile/TcTypeNatSimple.hs
@@ -1,6 +1,6 @@
 {-# LANGUAGE DataKinds, TypeOperators, TypeFamilies #-}
 module TcTypeNatSimple where
-import GHC.TypeLits
+import GHC.TypeLits as L
 import Data.Proxy
 
 --------------------------------------------------------------------------------
@@ -8,7 +8,7 @@ import Data.Proxy
 e1 :: Proxy (2 + 3) -> Proxy 5
 e1 = id
 
-e2 :: Proxy (2 * 3) -> Proxy 6
+e2 :: Proxy (2 L.* 3) -> Proxy 6
 e2 = id
 
 e3 :: Proxy (2 ^ 3) -> Proxy 8
@@ -20,16 +20,16 @@ e4 = id
 e5 :: Proxy (x + 0) -> Proxy x
 e5 = id
 
-e6 :: Proxy (x * 0) -> Proxy 0
+e6 :: Proxy (x L.* 0) -> Proxy 0
 e6 = id
 
-e7 :: Proxy (0 * x) -> Proxy 0
+e7 :: Proxy (0 L.* x) -> Proxy 0
 e7 = id
 
-e8 :: Proxy (x * 1) -> Proxy x
+e8 :: Proxy (x L.* 1) -> Proxy x
 e8 = id
 
-e9 :: Proxy (1 * x) -> Proxy x
+e9 :: Proxy (1 L.* x) -> Proxy x
 e9 = id
 
 e10 :: Proxy (x ^ 1) -> Proxy x
@@ -83,10 +83,10 @@ e23 = id
 ti2 :: Proxy (y + x) -> Proxy x -> ()
 ti2 _ _ = ()
 
-ti3 :: Proxy (2 * y) -> ()
+ti3 :: Proxy (2 L.* y) -> ()
 ti3 _ = ()
 
-ti4 :: Proxy (y * 2) -> ()
+ti4 :: Proxy (y L.* 2) -> ()
 ti4 _ = ()
 
 ti5 :: Proxy (2 ^ y) -> ()
diff --git a/testsuite/tests/typecheck/should_compile/type_in_type_hole_fits.hs b/testsuite/tests/typecheck/should_compile/type_in_type_hole_fits.hs
index 92d20daa56..566f8aa102 100644
--- a/testsuite/tests/typecheck/should_compile/type_in_type_hole_fits.hs
+++ b/testsuite/tests/typecheck/should_compile/type_in_type_hole_fits.hs
@@ -2,7 +2,7 @@
              UndecidableInstances, ConstraintKinds #-}
 module TypeInTypeSubstitutions where
 
-import GHC.TypeLits
+import GHC.TypeLits as L
 import Data.Type.Bool
 import Data.Type.Equality
 import Data.List (sort)
@@ -21,7 +21,7 @@ type One   = NLogN 0 0
 type O (a :: AsympPoly) = a
 
 type family (^.) (n :: AsympPoly) (m :: Nat) :: AsympPoly where
-  (NLogN a b) ^. n = (NLogN (a * n) (b * n))
+  (NLogN a b) ^. n = (NLogN (a L.* n) (b L.* n))
 
 type family (*.) (n :: AsympPoly) (m :: AsympPoly) :: AsympPoly where
   (NLogN a b) *. (NLogN c d) = NLogN (a+c) (b+d)
diff --git a/testsuite/tests/typecheck/should_run/TcTypeNatSimpleRun.hs b/testsuite/tests/typecheck/should_run/TcTypeNatSimpleRun.hs
index fb1463cc86..c12d53cde6 100644
--- a/testsuite/tests/typecheck/should_run/TcTypeNatSimpleRun.hs
+++ b/testsuite/tests/typecheck/should_run/TcTypeNatSimpleRun.hs
@@ -1,6 +1,6 @@
 {-# LANGUAGE DataKinds, TypeOperators, TypeFamilies #-}
 module Main(main) where
-import GHC.TypeLits
+import GHC.TypeLits as L
 import Data.Proxy
 
 --------------------------------------------------------------------------------
@@ -12,10 +12,10 @@ tsub _ _ = Proxy
 tsub2 :: Proxy (x + y) -> (Proxy x, Proxy y)
 tsub2 _ = (Proxy, Proxy)
 
-tdiv :: Proxy (x * y) -> Proxy y -> Proxy x
+tdiv :: Proxy (x L.* y) -> Proxy y -> Proxy x
 tdiv _ _ = Proxy
 
-tdiv2 :: Proxy (x * y) -> (Proxy x, Proxy y)
+tdiv2 :: Proxy (x L.* y) -> (Proxy x, Proxy y)
 tdiv2 _ = (Proxy, Proxy)
 
 troot :: Proxy (x ^ y) -> Proxy y -> Proxy x
diff --git a/testsuite/tests/warnings/should_compile/StarBinder.hs b/testsuite/tests/warnings/should_compile/StarBinder.hs
new file mode 100644
index 0000000000..09f51684ac
--- /dev/null
+++ b/testsuite/tests/warnings/should_compile/StarBinder.hs
@@ -0,0 +1,5 @@
+{-# LANGUAGE TypeOperators, TypeFamilies #-}
+
+module X (type (X.*)) where
+
+type family (*) a b where { (*) a b = Either b a }
diff --git a/testsuite/tests/warnings/should_compile/StarBinder.stderr b/testsuite/tests/warnings/should_compile/StarBinder.stderr
new file mode 100644
index 0000000000..2dbcf0e800
--- /dev/null
+++ b/testsuite/tests/warnings/should_compile/StarBinder.stderr
@@ -0,0 +1,10 @@
+
+StarBinder.hs:5:14: warning: [-Wstar-binder (in -Wdefault)]
+    Found binding occurrence of ‘*’ yet StarIsType is enabled.
+    NB. To use (or export) this operator in modules with StarIsType,
+        including the definition module, you must qualify it.
+
+StarBinder.hs:5:30: warning: [-Wstar-binder (in -Wdefault)]
+    Found binding occurrence of ‘*’ yet StarIsType is enabled.
+    NB. To use (or export) this operator in modules with StarIsType,
+        including the definition module, you must qualify it.
diff --git a/testsuite/tests/warnings/should_compile/all.T b/testsuite/tests/warnings/should_compile/all.T
index 6740990853..fd2ba85035 100644
--- a/testsuite/tests/warnings/should_compile/all.T
+++ b/testsuite/tests/warnings/should_compile/all.T
@@ -20,3 +20,5 @@ test('Werror01', normal, compile, [''])
 test('Werror02', normal, compile, [''])
 
 test('MissingMod', normal, multimod_compile, ['MissingMod', '-Wmissing-home-modules'])
+
+test('StarBinder', normal, compile, [''])
\ No newline at end of file