Remove redundant-constraints from -Wall (#10635)

Removes -Wredundant-constraints from -Wall, as per the
discussion in #10635.

Reviewers: austin, bgamari

Reviewed By: bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2498

GHC Trac Issues: #10635

8 files changed, 33 insertions, 9 deletions

diff --git a/compiler/main/DynFlags.hs b/compiler/main/DynFlags.hs
index 065a7329c6..fa471d38a1 100644
--- a/compiler/main/DynFlags.hs
+++ b/compiler/main/DynFlags.hs
@@ -3958,8 +3958,7 @@ minusWallOpts
         Opt_WarnUnusedDoBind,
         Opt_WarnTrustworthySafe,
         Opt_WarnUntickedPromotedConstructors,
-        Opt_WarnMissingPatternSynonymSignatures,
-        Opt_WarnRedundantConstraints
+        Opt_WarnMissingPatternSynonymSignatures
       ]
 
 -- | Things you get with -Weverything, i.e. *all* known warnings flags
diff --git a/testsuite/tests/typecheck/should_compile/T10632.hs b/testsuite/tests/typecheck/should_compile/T10632.hs
index 5c1a1778af..03478fc9d4 100644
--- a/testsuite/tests/typecheck/should_compile/T10632.hs
+++ b/testsuite/tests/typecheck/should_compile/T10632.hs
@@ -1,4 +1,5 @@
 {-# LANGUAGE ImplicitParams #-}
+{-# OPTIONS_GHC -Wredundant-constraints #-}
 
 f :: (?file1 :: String) => IO ()
 f = putStrLn $ "f2: "
diff --git a/testsuite/tests/typecheck/should_compile/T10632.stderr b/testsuite/tests/typecheck/should_compile/T10632.stderr
index c3d112f6bf..1733f0ae7a 100644
--- a/testsuite/tests/typecheck/should_compile/T10632.stderr
+++ b/testsuite/tests/typecheck/should_compile/T10632.stderr
@@ -1,5 +1,5 @@
 
-T10632.hs:3:1: warning: [-Wredundant-constraints (in -Wall)]
+T10632.hs:4:1: warning: [-Wredundant-constraints]
     • Redundant constraint: ?file1::String
     • In the type signature for:
            f :: (?file1::String) => IO ()
diff --git a/testsuite/tests/typecheck/should_compile/T10635.hs b/testsuite/tests/typecheck/should_compile/T10635.hs
new file mode 100644
index 0000000000..1382466f2a
--- /dev/null
+++ b/testsuite/tests/typecheck/should_compile/T10635.hs
@@ -0,0 +1,22 @@
+{-# LANGUAGE GADTs #-}
+
+module T9939 where
+
+f1 :: (Eq a, Ord a) => a -> a -> Bool
+-- Eq a redundant
+f1 x y = (x == y) && (x > y)
+
+f2 :: (Eq a, Ord a) => a -> a -> Bool
+-- Ord a redundant, but Eq a is reported
+f2 x y = (x == y)
+
+f3 :: (Eq a, a ~ b, Eq b) => a -> b -> Bool
+-- Eq b redundant
+f3 x y = x==y
+
+data Equal a b where
+  EQUAL :: Equal a a
+
+f4 :: (Eq a, Eq b) => a -> b -> Equal a b -> Bool
+-- Eq b redundant
+f4 x y EQUAL = y==y
diff --git a/testsuite/tests/typecheck/should_compile/T9939.hs b/testsuite/tests/typecheck/should_compile/T9939.hs
index 4ae370b147..3ceab5167a 100644
--- a/testsuite/tests/typecheck/should_compile/T9939.hs
+++ b/testsuite/tests/typecheck/should_compile/T9939.hs
@@ -1,4 +1,5 @@
 {-# LANGUAGE GADTs #-}
+{-# OPTIONS_GHC -Wredundant-constraints #-}
 
 module T9939 where
 
diff --git a/testsuite/tests/typecheck/should_compile/T9939.stderr b/testsuite/tests/typecheck/should_compile/T9939.stderr
index d10c51016d..c4866790c8 100644
--- a/testsuite/tests/typecheck/should_compile/T9939.stderr
+++ b/testsuite/tests/typecheck/should_compile/T9939.stderr
@@ -1,20 +1,20 @@
 
-T9939.hs:5:1: warning: [-Wredundant-constraints (in -Wall)]
+T9939.hs:6:1: warning: [-Wredundant-constraints]
     • Redundant constraint: Eq a
     • In the type signature for:
            f1 :: (Eq a, Ord a) => a -> a -> Bool
 
-T9939.hs:9:1: warning: [-Wredundant-constraints (in -Wall)]
+T9939.hs:10:1: warning: [-Wredundant-constraints]
     • Redundant constraint: Eq a
     • In the type signature for:
            f2 :: (Eq a, Ord a) => a -> a -> Bool
 
-T9939.hs:13:1: warning: [-Wredundant-constraints (in -Wall)]
+T9939.hs:14:1: warning: [-Wredundant-constraints]
     • Redundant constraint: Eq b
     • In the type signature for:
            f3 :: (Eq a, a ~ b, Eq b) => a -> b -> Bool
 
-T9939.hs:20:1: warning: [-Wredundant-constraints (in -Wall)]
+T9939.hs:21:1: warning: [-Wredundant-constraints]
     • Redundant constraint: Eq a
     • In the type signature for:
            f4 :: (Eq a, Eq b) => a -> b -> Equal a b -> Bool
diff --git a/testsuite/tests/typecheck/should_compile/all.T b/testsuite/tests/typecheck/should_compile/all.T
index 4bebf97038..b9f452d15c 100644
--- a/testsuite/tests/typecheck/should_compile/all.T
+++ b/testsuite/tests/typecheck/should_compile/all.T
@@ -537,4 +537,5 @@ test('T12185', normal, compile, [''])
 test('T12133', normal, compile, [''])
 test('T12381', normal, compile, [''])
 test('T12082', normal, compile, [''])
+test('T10635', normal, compile, [''])
 test('T12170b', normal, compile, [''])
diff --git a/testsuite/tests/warnings/should_compile/PluralS.stderr b/testsuite/tests/warnings/should_compile/PluralS.stderr
index b1ceab6762..416ebb815b 100644
--- a/testsuite/tests/warnings/should_compile/PluralS.stderr
+++ b/testsuite/tests/warnings/should_compile/PluralS.stderr
@@ -14,12 +14,12 @@ PluralS.hs:17:24: warning: [-Wtype-defaults (in -Wall)]
       In an equation for ‘defaultingNumAndShow’:
           defaultingNumAndShow = show 123
 
-PluralS.hs:23:1: warning: [-Wredundant-constraints (in -Wall)]
+PluralS.hs:23:1: warning: [-Wredundant-constraints]
     • Redundant constraint: Num a
     • In the type signature for:
            redundantNum :: (Num a, Num a) => a
 
-PluralS.hs:26:1: warning: [-Wredundant-constraints (in -Wall)]
+PluralS.hs:26:1: warning: [-Wredundant-constraints]
     • Redundant constraints: (Show a, Num a, Eq a, Eq a)
     • In the type signature for:
            redundantMultiple :: (Num a, Show a, Num a, Eq a, Eq a) => a