Pattern synonyms: swap provided/required

This patch swaps the order of provided and required constraints in
a pattern signature, so it now goes

      pattern P :: req => prov => t1 -> ... tn -> res_ty

See the long discussion in Trac #10928.

I think I have found all the places, but I could have missed something
particularly in comments.

There is a Haddock changes; so a submodule update.

7 files changed, 32 insertions, 4 deletions

diff --git a/testsuite/tests/ghci/scripts/T8776.stdout b/testsuite/tests/ghci/scripts/T8776.stdout
index 7f8d57e7ee..937a270963 100644
--- a/testsuite/tests/ghci/scripts/T8776.stdout
+++ b/testsuite/tests/ghci/scripts/T8776.stdout
@@ -1 +1,2 @@
-pattern P :: (Num t, Eq t1) => A t t1 	-- Defined at T8776.hs:6:1
+pattern P :: () => (Num t, Eq t1) => A t t1
+  	-- Defined at T8776.hs:6:1
diff --git a/testsuite/tests/patsyn/should_compile/T10997_1a.hs b/testsuite/tests/patsyn/should_compile/T10997_1a.hs
index af98f495f7..f6a292aa54 100644
--- a/testsuite/tests/patsyn/should_compile/T10997_1a.hs
+++ b/testsuite/tests/patsyn/should_compile/T10997_1a.hs
@@ -11,7 +11,7 @@ extractJust :: Maybe a -> (Bool, a)
 extractJust (Just a) = (True, a)
 extractJust _        = (False, undefined)
 
-pattern Just' :: () => (Showable a) => a -> (Maybe a)
+pattern Just' :: Showable a => a -> (Maybe a)
 pattern Just' a <- (extractJust -> (True, a)) where
   Just' a = Just a
 
diff --git a/testsuite/tests/patsyn/should_compile/T10997a.hs b/testsuite/tests/patsyn/should_compile/T10997a.hs
index bed19f74e9..ec3c54238d 100644
--- a/testsuite/tests/patsyn/should_compile/T10997a.hs
+++ b/testsuite/tests/patsyn/should_compile/T10997a.hs
@@ -5,7 +5,7 @@ module T10997a where
 data Exp ty where
   LitB :: Bool -> Exp Bool
 
-pattern Tru :: b ~ Bool => Exp b
+pattern Tru :: () => b ~ Bool => Exp b
 pattern Tru = LitB True
 
 
diff --git a/testsuite/tests/patsyn/should_compile/T8584-2.hs b/testsuite/tests/patsyn/should_compile/T8584-2.hs
index 24147a258d..379a8c872e 100644
--- a/testsuite/tests/patsyn/should_compile/T8584-2.hs
+++ b/testsuite/tests/patsyn/should_compile/T8584-2.hs
@@ -3,7 +3,7 @@
 
 module ShouldCompile where
 
-pattern Single :: () => (Show a) => a -> [a]
+pattern Single :: Show a => a -> [a]
 pattern Single x = [x]
 
 f :: (Show a) => [a] -> a
diff --git a/testsuite/tests/patsyn/should_fail/T11010.hs b/testsuite/tests/patsyn/should_fail/T11010.hs
new file mode 100644
index 0000000000..c0bdb6e0d4
--- /dev/null
+++ b/testsuite/tests/patsyn/should_fail/T11010.hs
@@ -0,0 +1,18 @@
+{-# LANGUAGE PatternSynonyms, ExistentialQuantification, GADTSyntax #-}
+
+module T11010 where
+
+data Expr a where
+  Fun :: String -> (a -> b) -> (Expr a -> Expr b)
+
+pattern IntFun :: (a ~ Int) => String -> (a -> b) -> (Expr a -> Expr b)
+pattern IntFun str f x = Fun str f x
+
+-- Alternative syntax for pattern synonyms:
+--   pattern
+--     Suc :: () => (a ~ Int) => Expr a -> Expr Int
+--     Suc n <- IntFun _     _     n where
+--     Suc n =  IntFun "suc" (+ 1) n
+pattern Suc :: (a ~ Int) => Expr a -> Expr Int
+pattern Suc n <- IntFun _     _     n where
+         Suc n =  IntFun "suc" (+ 1) n
diff --git a/testsuite/tests/patsyn/should_fail/T11010.stderr b/testsuite/tests/patsyn/should_fail/T11010.stderr
new file mode 100644
index 0000000000..5f62b1357e
--- /dev/null
+++ b/testsuite/tests/patsyn/should_fail/T11010.stderr
@@ -0,0 +1,8 @@
+
+T11010.hs:8:1: error:
+    The 'required' context ‘a ~ Int’
+      mentions existential type variable ‘a’
+
+T11010.hs:16:1: error:
+    The 'required' context ‘a ~ Int’
+      mentions existential type variable ‘a’
diff --git a/testsuite/tests/patsyn/should_fail/all.T b/testsuite/tests/patsyn/should_fail/all.T
index de5d6db3b4..846d2d37d9 100644
--- a/testsuite/tests/patsyn/should_fail/all.T
+++ b/testsuite/tests/patsyn/should_fail/all.T
@@ -8,3 +8,4 @@ test('T9705-1', normal, compile_fail, [''])
 test('T9705-2', normal, compile_fail, [''])
 test('unboxed-bind', normal, compile_fail, [''])
 test('unboxed-wrapper-naked', normal, compile_fail, [''])
+test('T11010', normal, compile_fail, [''])
\ No newline at end of file