Re-add FunTy (big patch)

With TypeInType Richard combined ForAllTy and FunTy, but that was often
awkward, and yielded little benefit becuase in practice the two were
always treated separately.  This patch re-introduces FunTy.  Specfically

* New type
    data TyVarBinder = TvBndr TyVar VisibilityFlag
  This /always/ has a TyVar it.  In many places that's just what
  what we want, so there are /lots/ of TyBinder -> TyVarBinder changes

* TyBinder still exists:
    data TyBinder = Named TyVarBinder | Anon Type

* data Type = ForAllTy TyVarBinder Type
            | FunTy Type Type
            |  ....

There are a LOT of knock-on changes, but they are all routine.

The Haddock submodule needs to be updated too

3 files changed, 153 insertions, 138 deletions

diff --git a/testsuite/tests/partial-sigs/should_compile/T10403.stderr b/testsuite/tests/partial-sigs/should_compile/T10403.stderr
index 753b983a15..3cebd8f92a 100644
--- a/testsuite/tests/partial-sigs/should_compile/T10403.stderr
+++ b/testsuite/tests/partial-sigs/should_compile/T10403.stderr
@@ -1,77 +1,82 @@
-

-T10403.hs:15:7: warning: [-Wpartial-type-signatures (in -Wdefault)]

-    • Found type wildcard ‘_’ standing for ‘Functor f’

-      Where: ‘f’ is a rigid type variable bound by

-               the inferred type of h1 :: Functor f => (a -> b) -> f a -> H f

-               at T10403.hs:17:1-41

-    • In the type signature: h1 :: _ => _

-

-T10403.hs:15:12: warning: [-Wpartial-type-signatures (in -Wdefault)]

-    • Found type wildcard ‘_’ standing for ‘(a -> b) -> f a -> H f’

-      Where: ‘f’ is a rigid type variable bound by

-               the inferred type of h1 :: Functor f => (a -> b) -> f a -> H f

-               at T10403.hs:17:1-41

-             ‘b’ is a rigid type variable bound by

-               the inferred type of h1 :: Functor f => (a -> b) -> f a -> H f

-               at T10403.hs:17:1-41

-             ‘a’ is a rigid type variable bound by

-               the inferred type of h1 :: Functor f => (a -> b) -> f a -> H f

-               at T10403.hs:17:1-41

-    • In the type signature: h1 :: _ => _

-

-T10403.hs:19:7: warning: [-Wpartial-type-signatures (in -Wdefault)]

-    • Found type wildcard ‘_’ standing for ‘(a -> b) -> f0 a -> H f0’

-      Where: ‘f0’ is an ambiguous type variable

-             ‘b’ is a rigid type variable bound by

-               the inferred type of h2 :: (a -> b) -> f0 a -> H f0

-               at T10403.hs:22:1-41

-             ‘a’ is a rigid type variable bound by

-               the inferred type of h2 :: (a -> b) -> f0 a -> H f0

-               at T10403.hs:22:1-41

-    • In the type signature: h2 :: _

-

-T10403.hs:22:15: warning: [-Wdeferred-type-errors (in -Wdefault)]

-    • Ambiguous type variable ‘f0’ arising from a use of ‘fmap’

-      prevents the constraint ‘(Functor f0)’ from being solved.

-      Relevant bindings include

-        b :: f0 a (bound at T10403.hs:22:6)

-        h2 :: (a -> b) -> f0 a -> H f0 (bound at T10403.hs:22:1)

-      Probable fix: use a type annotation to specify what ‘f0’ should be.

-      These potential instances exist:

-        instance Functor IO -- Defined in ‘GHC.Base’

-        instance Functor (B t) -- Defined at T10403.hs:10:10

-        instance Functor I -- Defined at T10403.hs:6:10

-        ...plus four others

-        (use -fprint-potential-instances to see them all)

-    • In the second argument of ‘(.)’, namely ‘fmap (const ())’

-      In the expression: H . fmap (const ())

-      In the expression: (H . fmap (const ())) (fmap f b)

-

-T10403.hs:28:8: warning: [-Wdeferred-type-errors (in -Wdefault)]

-    • Couldn't match type ‘f0’ with ‘B t’

-        because type variable ‘t’ would escape its scope

-      This (rigid, skolem) type variable is bound by

-        the type signature for:

-          app2 :: H (B t)

-        at T10403.hs:27:1-15

-      Expected type: H (B t)

-        Actual type: H f0

-    • In the expression: h2 (H . I) (B ())

-      In an equation for ‘app2’: app2 = h2 (H . I) (B ())

-    • Relevant bindings include

-        app2 :: H (B t) (bound at T10403.hs:28:1)

-

-T10403.hs:28:20: warning: [-Wdeferred-type-errors (in -Wdefault)]

-    • Couldn't match type ‘f0’ with ‘B t’

-        because type variable ‘t’ would escape its scope

-      This (rigid, skolem) type variable is bound by

-        the type signature for:

-          app2 :: H (B t)

-        at T10403.hs:27:1-15

-      Expected type: f0 ()

-        Actual type: B t ()

-    • In the second argument of ‘h2’, namely ‘(B ())’

-      In the expression: h2 (H . I) (B ())

-      In an equation for ‘app2’: app2 = h2 (H . I) (B ())

-    • Relevant bindings include

-        app2 :: H (B t) (bound at T10403.hs:28:1)

+
+T10403.hs:15:7: warning: [-Wpartial-type-signatures (in -Wdefault)]
+    Found constraint wildcard ‘_’ standing for ‘Functor f’
+    In the type signature:
+      h1 :: _ => _
+
+T10403.hs:15:12: warning: [-Wpartial-type-signatures (in -Wdefault)]
+    • Found type wildcard ‘_’ standing for ‘(a -> b) -> f a -> H f’
+      Where: ‘b’ is a rigid type variable bound by
+               the inferred type of h1 :: Functor f => (a -> b) -> f a -> H f
+               at T10403.hs:17:1
+             ‘a’ is a rigid type variable bound by
+               the inferred type of h1 :: Functor f => (a -> b) -> f a -> H f
+               at T10403.hs:17:1
+             ‘f’ is a rigid type variable bound by
+               the inferred type of h1 :: Functor f => (a -> b) -> f a -> H f
+               at T10403.hs:17:1
+    • In the type signature:
+        h1 :: _ => _
+    • Relevant bindings include
+        h1 :: (a -> b) -> f a -> H f (bound at T10403.hs:17:1)
+
+T10403.hs:19:7: warning: [-Wpartial-type-signatures (in -Wdefault)]
+    • Found type wildcard ‘_’ standing for ‘(a -> b) -> f0 a -> H f0’
+      Where: ‘b’ is a rigid type variable bound by
+               the inferred type of h2 :: (a -> b) -> f0 a -> H f0
+               at T10403.hs:22:1
+             ‘a’ is a rigid type variable bound by
+               the inferred type of h2 :: (a -> b) -> f0 a -> H f0
+               at T10403.hs:22:1
+             ‘f0’ is an ambiguous type variable
+    • In the type signature:
+        h2 :: _
+    • Relevant bindings include
+        h2 :: (a -> b) -> f0 a -> H f0 (bound at T10403.hs:22:1)
+
+T10403.hs:22:15: warning: [-Wdeferred-type-errors (in -Wdefault)]
+    • Ambiguous type variable ‘f0’ arising from a use of ‘fmap’
+      prevents the constraint ‘(Functor f0)’ from being solved.
+      Relevant bindings include
+        b :: f0 a (bound at T10403.hs:22:6)
+        h2 :: (a -> b) -> f0 a -> H f0 (bound at T10403.hs:22:1)
+      Probable fix: use a type annotation to specify what ‘f0’ should be.
+      These potential instances exist:
+        instance Functor IO -- Defined in ‘GHC.Base’
+        instance Functor (B t) -- Defined at T10403.hs:10:10
+        instance Functor I -- Defined at T10403.hs:6:10
+        ...plus four others
+        (use -fprint-potential-instances to see them all)
+    • In the second argument of ‘(.)’, namely ‘fmap (const ())’
+      In the expression: H . fmap (const ())
+      In the expression: (H . fmap (const ())) (fmap f b)
+
+T10403.hs:28:8: warning: [-Wdeferred-type-errors (in -Wdefault)]
+    • Couldn't match type ‘f0’ with ‘B t’
+        because type variable ‘t’ would escape its scope
+      This (rigid, skolem) type variable is bound by
+        the type signature for:
+          app2 :: H (B t)
+        at T10403.hs:27:1-15
+      Expected type: H (B t)
+        Actual type: H f0
+    • In the expression: h2 (H . I) (B ())
+      In an equation for ‘app2’: app2 = h2 (H . I) (B ())
+    • Relevant bindings include
+        app2 :: H (B t) (bound at T10403.hs:28:1)
+
+T10403.hs:28:20: warning: [-Wdeferred-type-errors (in -Wdefault)]
+    • Couldn't match type ‘f0’ with ‘B t’
+        because type variable ‘t’ would escape its scope
+      This (rigid, skolem) type variable is bound by
+        the type signature for:
+          app2 :: H (B t)
+        at T10403.hs:27:1-15
+      Expected type: f0 ()
+        Actual type: B t ()
+    • In the second argument of ‘h2’, namely ‘(B ())’
+      In the expression: h2 (H . I) (B ())
+      In an equation for ‘app2’: app2 = h2 (H . I) (B ())
+    • Relevant bindings include
+        app2 :: H (B t) (bound at T10403.hs:28:1)
+
diff --git a/testsuite/tests/partial-sigs/should_compile/T11192.stderr b/testsuite/tests/partial-sigs/should_compile/T11192.stderr
index c2a9db5a96..c7420eb3d7 100644
--- a/testsuite/tests/partial-sigs/should_compile/T11192.stderr
+++ b/testsuite/tests/partial-sigs/should_compile/T11192.stderr
@@ -1,38 +1,45 @@
-

-T11192.hs:7:14: warning: [-Wpartial-type-signatures (in -Wdefault)]

-    • Found type wildcard ‘_’ standing for ‘Int -> t -> t’

-      Where: ‘t’ is a rigid type variable bound by

-               the inferred type of go :: Int -> t -> t at T11192.hs:8:8-17

-    • In the type signature: go :: _

-      In the expression:

-        let

-          go :: _

-          go 0 a = a

-        in go (0 :: Int) undefined

-      In an equation for ‘fails’:

-          fails

-            = let

-                go :: _

-                go 0 a = a

-              in go (0 :: Int) undefined

-    • Relevant bindings include fails :: a (bound at T11192.hs:6:1)

-

-T11192.hs:13:14: warning: [-Wpartial-type-signatures (in -Wdefault)]

-    • Found type wildcard ‘_’ standing for ‘t1 -> t -> t’

-      Where: ‘t’ is a rigid type variable bound by

-               the inferred type of go :: t1 -> t -> t at T11192.hs:14:8-17

-             ‘t1’ is a rigid type variable bound by

-               the inferred type of go :: t1 -> t -> t at T11192.hs:14:8-17

-    • In the type signature: go :: _

-      In the expression:

-        let

-          go :: _

-          go _ a = a

-        in go (0 :: Int) undefined

-      In an equation for ‘succeeds’:

-          succeeds

-            = let

-                go :: _

-                go _ a = a

-              in go (0 :: Int) undefined

-    • Relevant bindings include succeeds :: a (bound at T11192.hs:12:1)

+
+T11192.hs:7:14: warning: [-Wpartial-type-signatures (in -Wdefault)]
+    • Found type wildcard ‘_’ standing for ‘Int -> t -> t’
+      Where: ‘t’ is a rigid type variable bound by
+               the inferred type of go :: Int -> t -> t at T11192.hs:8:8
+    • In the type signature:
+        go :: _
+      In the expression:
+        let
+          go :: _
+          go 0 a = a
+        in go (0 :: Int) undefined
+      In an equation for ‘fails’:
+          fails
+            = let
+                go :: _
+                go 0 a = a
+              in go (0 :: Int) undefined
+    • Relevant bindings include
+        go :: Int -> t -> t (bound at T11192.hs:8:8)
+        fails :: a (bound at T11192.hs:6:1)
+
+T11192.hs:13:14: warning: [-Wpartial-type-signatures (in -Wdefault)]
+    • Found type wildcard ‘_’ standing for ‘t -> t1 -> t1’
+      Where: ‘t’ is a rigid type variable bound by
+               the inferred type of go :: t -> t1 -> t1 at T11192.hs:14:8
+             ‘t1’ is a rigid type variable bound by
+               the inferred type of go :: t -> t1 -> t1 at T11192.hs:14:8
+    • In the type signature:
+        go :: _
+      In the expression:
+        let
+          go :: _
+          go _ a = a
+        in go (0 :: Int) undefined
+      In an equation for ‘succeeds’:
+          succeeds
+            = let
+                go :: _
+                go _ a = a
+              in go (0 :: Int) undefined
+    • Relevant bindings include
+        go :: t -> t1 -> t1 (bound at T11192.hs:14:8)
+        succeeds :: a (bound at T11192.hs:12:1)
+
diff --git a/testsuite/tests/partial-sigs/should_fail/T10045.stderr b/testsuite/tests/partial-sigs/should_fail/T10045.stderr
index 74bfaae357..e9cac55e9e 100644
--- a/testsuite/tests/partial-sigs/should_fail/T10045.stderr
+++ b/testsuite/tests/partial-sigs/should_fail/T10045.stderr
@@ -1,23 +1,26 @@
-

-T10045.hs:6:18: error:

-    • Found type wildcard ‘_’ standing for ‘t2 -> Bool -> t1’

-      Where: ‘t1’ is a rigid type variable bound by

-               the inferred type of copy :: t2 -> Bool -> t1 at T10045.hs:7:10-34

-             ‘t2’ is a rigid type variable bound by

-               the inferred type of copy :: t2 -> Bool -> t1 at T10045.hs:7:10-34

-      To use the inferred type, enable PartialTypeSignatures

-    • In the type signature: copy :: _

-      In the expression:

-        let

-          copy :: _

-          copy w from = copy w True

-        in copy ws1 False

-      In an equation for ‘foo’:

-          foo (Meta ws1)

-            = let

-                copy :: _

-                copy w from = copy w True

-              in copy ws1 False

-    • Relevant bindings include

-        ws1 :: () (bound at T10045.hs:5:11)

-        foo :: Meta -> t (bound at T10045.hs:5:1)

+
+T10045.hs:6:18: error:
+    • Found type wildcard ‘_’ standing for ‘t1 -> Bool -> t2’
+      Where: ‘t1’ is a rigid type variable bound by
+               the inferred type of copy :: t1 -> Bool -> t2 at T10045.hs:7:10
+             ‘t2’ is a rigid type variable bound by
+               the inferred type of copy :: t1 -> Bool -> t2 at T10045.hs:7:10
+      To use the inferred type, enable PartialTypeSignatures
+    • In the type signature:
+        copy :: _
+      In the expression:
+        let
+          copy :: _
+          copy w from = copy w True
+        in copy ws1 False
+      In an equation for ‘foo’:
+          foo (Meta ws1)
+            = let
+                copy :: _
+                copy w from = copy w True
+              in copy ws1 False
+    • Relevant bindings include
+        copy :: t1 -> Bool -> t2 (bound at T10045.hs:7:10)
+        ws1 :: () (bound at T10045.hs:5:11)
+        foo :: Meta -> t (bound at T10045.hs:5:1)
+