Use GHC2021 as default language

52 files changed, 134 insertions, 105 deletions

diff --git a/testsuite/tests/deriving/should_compile/T12144_2.hs b/testsuite/tests/deriving/should_compile/T12144_2.hs
index dc9f64e90e..d3e5f771db 100644
--- a/testsuite/tests/deriving/should_compile/T12144_2.hs
+++ b/testsuite/tests/deriving/should_compile/T12144_2.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE Haskell2010 #-}
 {-# LANGUAGE DeriveAnyClass #-}
 module T12144_2 where
 
diff --git a/testsuite/tests/deriving/should_compile/T14578.hs b/testsuite/tests/deriving/should_compile/T14578.hs
index d0700ea9b0..231796cda9 100644
--- a/testsuite/tests/deriving/should_compile/T14578.hs
+++ b/testsuite/tests/deriving/should_compile/T14578.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE Haskell2010 #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 module T14578 where
 
diff --git a/testsuite/tests/deriving/should_compile/T14579.hs b/testsuite/tests/deriving/should_compile/T14579.hs
index 518dffe214..9addb5bc53 100644
--- a/testsuite/tests/deriving/should_compile/T14579.hs
+++ b/testsuite/tests/deriving/should_compile/T14579.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE Haskell2010 #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE DataKinds #-}
 {-# LANGUAGE PolyKinds #-}
diff --git a/testsuite/tests/deriving/should_compile/T14933.hs b/testsuite/tests/deriving/should_compile/T14933.hs
index de8562d189..5ab808365f 100644
--- a/testsuite/tests/deriving/should_compile/T14933.hs
+++ b/testsuite/tests/deriving/should_compile/T14933.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE Haskell2010 #-}
 {-# LANGUAGE DefaultSignatures #-}
 {-# LANGUAGE DeriveAnyClass    #-}
 {-# LANGUAGE TypeFamilies      #-}
diff --git a/testsuite/tests/deriving/should_compile/T17339.hs b/testsuite/tests/deriving/should_compile/T17339.hs
index 4312d2ffc4..a46e4c793d 100644
--- a/testsuite/tests/deriving/should_compile/T17339.hs
+++ b/testsuite/tests/deriving/should_compile/T17339.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE Haskell2010 #-}
 {-# LANGUAGE DeriveAnyClass #-}
 {-# LANGUAGE DerivingStrategies #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
diff --git a/testsuite/tests/deriving/should_compile/deriving-1935.hs b/testsuite/tests/deriving/should_compile/deriving-1935.hs
index d33b21af13..af62a747d4 100644
--- a/testsuite/tests/deriving/should_compile/deriving-1935.hs
+++ b/testsuite/tests/deriving/should_compile/deriving-1935.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE Haskell2010 #-}
 {-# OPTIONS_GHC -XDeriveDataTypeable #-}
 
 -- #1935
diff --git a/testsuite/tests/deriving/should_compile/deriving-1935.stderr b/testsuite/tests/deriving/should_compile/deriving-1935.stderr
index 091990bcd9..3864e8e2f0 100644
--- a/testsuite/tests/deriving/should_compile/deriving-1935.stderr
+++ b/testsuite/tests/deriving/should_compile/deriving-1935.stderr
@@ -1,15 +1,15 @@
 
-deriving-1935.hs:17:11: warning: [-Wmissing-methods (in -Wdefault)]
+deriving-1935.hs:18:11: warning: [-Wmissing-methods (in -Wdefault)]
     • No explicit implementation for
         either ‘==’ or ‘/=’
     • In the instance declaration for ‘Eq (T a)’
 
-deriving-1935.hs:20:11: warning: [-Wmissing-methods (in -Wdefault)]
+deriving-1935.hs:21:11: warning: [-Wmissing-methods (in -Wdefault)]
     • No explicit implementation for
         either ‘==’ or ‘/=’
     • In the instance declaration for ‘Eq (S a)’
 
-deriving-1935.hs:21:11: warning: [-Wmissing-methods (in -Wdefault)]
+deriving-1935.hs:22:11: warning: [-Wmissing-methods (in -Wdefault)]
     • No explicit implementation for
         either ‘compare’ or ‘<=’
     • In the instance declaration for ‘Ord (S a)’
diff --git a/testsuite/tests/deriving/should_compile/drv-empty-data.hs b/testsuite/tests/deriving/should_compile/drv-empty-data.hs
index 383ce8f9f7..0383b29dbb 100644
--- a/testsuite/tests/deriving/should_compile/drv-empty-data.hs
+++ b/testsuite/tests/deriving/should_compile/drv-empty-data.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE Haskell2010 #-}
 {-# LANGUAGE RoleAnnotations #-}
 {-# LANGUAGE DeriveTraversable, DeriveGeneric, EmptyCase,
     DeriveDataTypeable, StandaloneDeriving, DeriveLift #-}
diff --git a/testsuite/tests/deriving/should_compile/drv-foldable-traversable1.hs b/testsuite/tests/deriving/should_compile/drv-foldable-traversable1.hs
index 712f14a3b5..52e845798a 100644
--- a/testsuite/tests/deriving/should_compile/drv-foldable-traversable1.hs
+++ b/testsuite/tests/deriving/should_compile/drv-foldable-traversable1.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE Haskell2010 #-}
 {-# LANGUAGE DeriveFunctor, DeriveFoldable, DeriveTraversable #-}
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE FlexibleContexts, DatatypeContexts #-}
diff --git a/testsuite/tests/deriving/should_compile/drv-foldable-traversable1.stderr b/testsuite/tests/deriving/should_compile/drv-foldable-traversable1.stderr
index ceae10cabd..e8dc7162c2 100644
--- a/testsuite/tests/deriving/should_compile/drv-foldable-traversable1.stderr
+++ b/testsuite/tests/deriving/should_compile/drv-foldable-traversable1.stderr
@@ -1,3 +1,3 @@
 
-drv-foldable-traversable1.hs:3:32:
-    Warning: -XDatatypeContexts is deprecated: It was widely considered a misfeature, and has been removed from the Haskell language.
+drv-foldable-traversable1.hs:4:32: warning:
+    -XDatatypeContexts is deprecated: It was widely considered a misfeature, and has been removed from the Haskell language.
diff --git a/testsuite/tests/deriving/should_compile/drv-functor1.hs b/testsuite/tests/deriving/should_compile/drv-functor1.hs
index 040d531341..2a09ab0b0e 100644
--- a/testsuite/tests/deriving/should_compile/drv-functor1.hs
+++ b/testsuite/tests/deriving/should_compile/drv-functor1.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE Haskell2010 #-}
 {-# LANGUAGE DeriveFunctor #-}
 {-# LANGUAGE ExistentialQuantification #-}
 {-# LANGUAGE RankNTypes #-}
diff --git a/testsuite/tests/deriving/should_compile/drv-functor1.stderr b/testsuite/tests/deriving/should_compile/drv-functor1.stderr
index a531dc56ef..5592b7d141 100644
--- a/testsuite/tests/deriving/should_compile/drv-functor1.stderr
+++ b/testsuite/tests/deriving/should_compile/drv-functor1.stderr
@@ -1,3 +1,3 @@
 
-drv-functor1.hs:5:14:
-    Warning: -XDatatypeContexts is deprecated: It was widely considered a misfeature, and has been removed from the Haskell language.
+drv-functor1.hs:6:14: warning:
+    -XDatatypeContexts is deprecated: It was widely considered a misfeature, and has been removed from the Haskell language.
diff --git a/testsuite/tests/deriving/should_fail/T10598_fail2.hs b/testsuite/tests/deriving/should_fail/T10598_fail2.hs
index ba77fe0fbf..7bffcf0c64 100644
--- a/testsuite/tests/deriving/should_fail/T10598_fail2.hs
+++ b/testsuite/tests/deriving/should_fail/T10598_fail2.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE Haskell2010 #-}
 {-# LANGUAGE DerivingStrategies #-}
 module T10598_fail2 where
 
diff --git a/testsuite/tests/deriving/should_fail/T10598_fail2.stderr b/testsuite/tests/deriving/should_fail/T10598_fail2.stderr
index 5ddd81dd1e..227be95c02 100644
--- a/testsuite/tests/deriving/should_fail/T10598_fail2.stderr
+++ b/testsuite/tests/deriving/should_fail/T10598_fail2.stderr
@@ -1,11 +1,11 @@
 
-T10598_fail2.hs:4:37: error:
+T10598_fail2.hs:5:37: error:
     • Can't make a derived instance of
         ‘Eq A’ with the anyclass strategy:
         Try enabling DeriveAnyClass
     • In the data declaration for ‘A’
 
-T10598_fail2.hs:5:37: error:
+T10598_fail2.hs:6:37: error:
     • Can't make a derived instance of
         ‘Eq B’ with the newtype strategy:
         Try GeneralizedNewtypeDeriving for GHC's newtype-deriving extension
diff --git a/testsuite/tests/deriving/should_fail/T10598_fail3.hs b/testsuite/tests/deriving/should_fail/T10598_fail3.hs
index 23f9ad987f..11e3e67e76 100644
--- a/testsuite/tests/deriving/should_fail/T10598_fail3.hs
+++ b/testsuite/tests/deriving/should_fail/T10598_fail3.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE Haskell2010 #-}
 {-# LANGUAGE DeriveAnyClass #-}
 {-# LANGUAGE DerivingStrategies #-}
 {-# LANGUAGE Safe #-}
diff --git a/testsuite/tests/deriving/should_fail/T10598_fail3.stderr b/testsuite/tests/deriving/should_fail/T10598_fail3.stderr
index c3f4e123b7..1ebc9c9c93 100644
--- a/testsuite/tests/deriving/should_fail/T10598_fail3.stderr
+++ b/testsuite/tests/deriving/should_fail/T10598_fail3.stderr
@@ -1,4 +1,4 @@
 
-T10598_fail3.hs:8:36: error:
+T10598_fail3.hs:9:36: error:
     • Generic instances can only be derived in Safe Haskell using the stock strategy.
     • In the instance declaration for ‘Generic T’
diff --git a/testsuite/tests/deriving/should_fail/T10598_fail6.hs b/testsuite/tests/deriving/should_fail/T10598_fail6.hs
index 673bfcc971..8ed5cdd262 100644
--- a/testsuite/tests/deriving/should_fail/T10598_fail6.hs
+++ b/testsuite/tests/deriving/should_fail/T10598_fail6.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE Haskell2010 #-}
 {-# LANGUAGE DeriveAnyClass #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 module T10598_fail6 where
diff --git a/testsuite/tests/deriving/should_fail/T10598_fail6.stderr b/testsuite/tests/deriving/should_fail/T10598_fail6.stderr
index a80e5bab56..0de1fe50bf 100644
--- a/testsuite/tests/deriving/should_fail/T10598_fail6.stderr
+++ b/testsuite/tests/deriving/should_fail/T10598_fail6.stderr
@@ -1,5 +1,5 @@
 
-T10598_fail6.hs:5:41: error:
+T10598_fail6.hs:6:41: error:
     • Can't make a derived instance of ‘Functor F’
         (even with cunning GeneralizedNewtypeDeriving):
         You need DeriveFunctor to derive an instance for this class
diff --git a/testsuite/tests/deriving/should_fail/T10684.hs b/testsuite/tests/deriving/should_fail/T10684.hs
index fdda0c7e46..ae532a15bf 100644
--- a/testsuite/tests/deriving/should_fail/T10684.hs
+++ b/testsuite/tests/deriving/should_fail/T10684.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE Haskell2010 #-}
 module A where
 import GHC.Generics
 data A = A deriving (Show, Generic)
diff --git a/testsuite/tests/deriving/should_fail/T10684.stderr b/testsuite/tests/deriving/should_fail/T10684.stderr
index 6cdbac2301..0724f8ec84 100644
--- a/testsuite/tests/deriving/should_fail/T10684.stderr
+++ b/testsuite/tests/deriving/should_fail/T10684.stderr
@@ -1,5 +1,5 @@
 
-T10684.hs:3:28: error:
+T10684.hs:4:28: error:
     • Can't make a derived instance of ‘Generic A’:
         You need DeriveGeneric to derive an instance for this class
     • In the data declaration for ‘A’
diff --git a/testsuite/tests/deriving/should_fail/T1133A.hs b/testsuite/tests/deriving/should_fail/T1133A.hs
index 2c8421aaf1..743772dd14 100644
--- a/testsuite/tests/deriving/should_fail/T1133A.hs
+++ b/testsuite/tests/deriving/should_fail/T1133A.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE Haskell2010 #-}
 
 module T1133A where
 
diff --git a/testsuite/tests/deriving/should_fail/T1133A.stderr b/testsuite/tests/deriving/should_fail/T1133A.stderr
index 23b93409da..1c8f686f2a 100644
--- a/testsuite/tests/deriving/should_fail/T1133A.stderr
+++ b/testsuite/tests/deriving/should_fail/T1133A.stderr
@@ -1,7 +1,7 @@
 
-T1133A.hs:6:28:
-    Can't make a derived instance of ‘Enum X’:
-      ‘X’ must be an enumeration type
-      (an enumeration consists of one or more nullary, non-GADT constructors)
-      Try GeneralizedNewtypeDeriving for GHC's newtype-deriving extension
-    In the newtype declaration for ‘X’
+T1133A.hs:7:28: error:
+    • Can't make a derived instance of ‘Enum X’:
+        ‘X’ must be an enumeration type
+        (an enumeration consists of one or more nullary, non-GADT constructors)
+        Try GeneralizedNewtypeDeriving for GHC's newtype-deriving extension
+    • In the newtype declaration for ‘X’
diff --git a/testsuite/tests/deriving/should_fail/T12801.hs b/testsuite/tests/deriving/should_fail/T12801.hs
index 22bbdf0aae..6bb773a22d 100644
--- a/testsuite/tests/deriving/should_fail/T12801.hs
+++ b/testsuite/tests/deriving/should_fail/T12801.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE Haskell2010 #-}
 data Container
   = Container [Wibble Int]
   deriving (Eq, Show)
diff --git a/testsuite/tests/deriving/should_fail/T12801.stderr b/testsuite/tests/deriving/should_fail/T12801.stderr
index 7bc63df715..cd3193aabe 100644
--- a/testsuite/tests/deriving/should_fail/T12801.stderr
+++ b/testsuite/tests/deriving/should_fail/T12801.stderr
@@ -1,5 +1,5 @@
 
-T12801.hs:8:17: error:
+T12801.hs:9:17: error:
     • Can't make a derived instance of ‘Functor Wibble’:
         You need DeriveFunctor to derive an instance for this class
     • In the data declaration for ‘Wibble’
diff --git a/testsuite/tests/deriving/should_fail/T16181.hs b/testsuite/tests/deriving/should_fail/T16181.hs
index 29692dd1a1..b54991c153 100644
--- a/testsuite/tests/deriving/should_fail/T16181.hs
+++ b/testsuite/tests/deriving/should_fail/T16181.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE Haskell2010 #-}
 {-# LANGUAGE DerivingVia #-}
 {-# LANGUAGE KindSignatures #-}
 module T16181 where
diff --git a/testsuite/tests/deriving/should_fail/T16181.stderr b/testsuite/tests/deriving/should_fail/T16181.stderr
index cbac319a2c..ed08f53bb2 100644
--- a/testsuite/tests/deriving/should_fail/T16181.stderr
+++ b/testsuite/tests/deriving/should_fail/T16181.stderr
@@ -1,19 +1,19 @@
 
-T16181.hs:13:13: error:
+T16181.hs:14:13: error:
     • Cannot eta-reduce to an instance of form
         instance (...) => Show1 (FlipConst a)
     • In the newtype declaration for ‘FlipConst’
 
-T16181.hs:13:20: error:
+T16181.hs:14:20: error:
     • Cannot eta-reduce to an instance of form
         instance (...) => Eq1 (FlipConst a)
     • In the newtype declaration for ‘FlipConst’
 
-T16181.hs:18:14: error:
+T16181.hs:19:14: error:
     • Cannot eta-reduce to an instance of form
         instance (...) => MonadTrans (Q x)
     • In the newtype declaration for ‘Q’
 
-T16181.hs:25:12: error:
+T16181.hs:26:12: error:
     • Cannot eta-reduce to an instance of form instance (...) => C T
     • In the data declaration for ‘T’
diff --git a/testsuite/tests/deriving/should_fail/T1830_1.hs b/testsuite/tests/deriving/should_fail/T1830_1.hs
index e3c2889c1c..a3ddece390 100644
--- a/testsuite/tests/deriving/should_fail/T1830_1.hs
+++ b/testsuite/tests/deriving/should_fail/T1830_1.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE Haskell2010 #-}
 module T1830_1 where
 
 import Language.Haskell.TH.Syntax (Lift)
diff --git a/testsuite/tests/deriving/should_fail/T1830_1.stderr b/testsuite/tests/deriving/should_fail/T1830_1.stderr
index c869b0cd16..f4e5417710 100644
--- a/testsuite/tests/deriving/should_fail/T1830_1.stderr
+++ b/testsuite/tests/deriving/should_fail/T1830_1.stderr
@@ -1,5 +1,5 @@
 
-T1830_1.hs:5:29: error:
-    Can't make a derived instance of ‘Lift (Foo a)’:
-      You need DeriveLift to derive an instance for this class
-    In the data declaration for ‘Foo’
+T1830_1.hs:6:29: error:
+    • Can't make a derived instance of ‘Lift (Foo a)’:
+        You need DeriveLift to derive an instance for this class
+    • In the data declaration for ‘Foo’
diff --git a/testsuite/tests/deriving/should_fail/T3833.hs b/testsuite/tests/deriving/should_fail/T3833.hs
index d1196c4112..eecb9e789e 100644
--- a/testsuite/tests/deriving/should_fail/T3833.hs
+++ b/testsuite/tests/deriving/should_fail/T3833.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE Haskell2010 #-}
 
 {-# LANGUAGE StandaloneDeriving #-}
 -- {-# LANGUAGE GeneralizedNewtypeDeriving #-}
diff --git a/testsuite/tests/deriving/should_fail/T3833.stderr b/testsuite/tests/deriving/should_fail/T3833.stderr
index bf9a59cb8a..001fdc4c64 100644
--- a/testsuite/tests/deriving/should_fail/T3833.stderr
+++ b/testsuite/tests/deriving/should_fail/T3833.stderr
@@ -1,6 +1,6 @@
 
-T3833.hs:9:1: error:
-    Can't make a derived instance of ‘Monoid (DecodeMap e)’:
-      ‘Monoid’ is not a stock derivable class (Eq, Show, etc.)
-      Try GeneralizedNewtypeDeriving for GHC's newtype-deriving extension
-    In the stand-alone deriving instance for ‘Monoid (DecodeMap e)’
+T3833.hs:10:1: error:
+    • Can't make a derived instance of ‘Monoid (DecodeMap e)’:
+        ‘Monoid’ is not a stock derivable class (Eq, Show, etc.)
+        Try GeneralizedNewtypeDeriving for GHC's newtype-deriving extension
+    • In the stand-alone deriving instance for ‘Monoid (DecodeMap e)’
diff --git a/testsuite/tests/deriving/should_fail/T3834.hs b/testsuite/tests/deriving/should_fail/T3834.hs
index 614170198e..fa6df580e8 100644
--- a/testsuite/tests/deriving/should_fail/T3834.hs
+++ b/testsuite/tests/deriving/should_fail/T3834.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE Haskell2010 #-}
 
 {-# LANGUAGE StandaloneDeriving #-}
 
diff --git a/testsuite/tests/deriving/should_fail/T3834.stderr b/testsuite/tests/deriving/should_fail/T3834.stderr
index 9d2223e1f8..23a605f614 100644
--- a/testsuite/tests/deriving/should_fail/T3834.stderr
+++ b/testsuite/tests/deriving/should_fail/T3834.stderr
@@ -1,6 +1,6 @@
 
-T3834.hs:8:1: error:
-    Can't make a derived instance of ‘C T’:
-      ‘C’ is not a stock derivable class (Eq, Show, etc.)
-      Try GeneralizedNewtypeDeriving for GHC's newtype-deriving extension
-    In the stand-alone deriving instance for ‘C T’
+T3834.hs:9:1: error:
+    • Can't make a derived instance of ‘C T’:
+        ‘C’ is not a stock derivable class (Eq, Show, etc.)
+        Try GeneralizedNewtypeDeriving for GHC's newtype-deriving extension
+    • In the stand-alone deriving instance for ‘C T’
diff --git a/testsuite/tests/deriving/should_fail/T5287.hs b/testsuite/tests/deriving/should_fail/T5287.hs
index 6495b62be9..3af467c2cf 100644
--- a/testsuite/tests/deriving/should_fail/T5287.hs
+++ b/testsuite/tests/deriving/should_fail/T5287.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE Haskell2010 #-}
 {-# LANGUAGE MultiParamTypeClasses, UndecidableInstances #-}
 module Bug where
 class A a oops
diff --git a/testsuite/tests/deriving/should_fail/T5287.stderr b/testsuite/tests/deriving/should_fail/T5287.stderr
index 20ad31dec3..479f1f84b5 100644
--- a/testsuite/tests/deriving/should_fail/T5287.stderr
+++ b/testsuite/tests/deriving/should_fail/T5287.stderr
@@ -1,10 +1,10 @@
 
-T5287.hs:6:10: error:
+T5287.hs:7:10: error:
     • Could not deduce (A a oops0)
       from the context: A a oops
         bound by an instance declaration:
                    forall a oops. A a oops => Read (D a)
-        at T5287.hs:6:10-31
+        at T5287.hs:7:10-31
       The type variable ‘oops0’ is ambiguous
     • In the ambiguity check for an instance declaration
       To defer the ambiguity check to use sites, enable AllowAmbiguousTypes
diff --git a/testsuite/tests/deriving/should_fail/T7401_fail.hs b/testsuite/tests/deriving/should_fail/T7401_fail.hs
index 730223f179..29ae0ae6db 100644
--- a/testsuite/tests/deriving/should_fail/T7401_fail.hs
+++ b/testsuite/tests/deriving/should_fail/T7401_fail.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE Haskell2010 #-}
 module T7401_fail where
 
 data D deriving Eq
diff --git a/testsuite/tests/deriving/should_fail/T7401_fail.stderr b/testsuite/tests/deriving/should_fail/T7401_fail.stderr
index feb841f962..7f26d3b9e4 100644
--- a/testsuite/tests/deriving/should_fail/T7401_fail.stderr
+++ b/testsuite/tests/deriving/should_fail/T7401_fail.stderr
@@ -1,5 +1,5 @@
 
-T7401_fail.hs:3:17: error:
+T7401_fail.hs:4:17: error:
     • Can't make a derived instance of ‘Eq D’:
         ‘D’ must have at least one data constructor
         Use EmptyDataDeriving to enable deriving for empty data types
diff --git a/testsuite/tests/deriving/should_fail/T8851.hs b/testsuite/tests/deriving/should_fail/T8851.hs
index 8b5c0e579d..9015d2be35 100644
--- a/testsuite/tests/deriving/should_fail/T8851.hs
+++ b/testsuite/tests/deriving/should_fail/T8851.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE Haskell2010 #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving, ConstrainedClassMethods #-}
 
 module T8851 where
diff --git a/testsuite/tests/deriving/should_fail/T8851.stderr b/testsuite/tests/deriving/should_fail/T8851.stderr
index dd4a614785..c4bfff3559 100644
--- a/testsuite/tests/deriving/should_fail/T8851.stderr
+++ b/testsuite/tests/deriving/should_fail/T8851.stderr
@@ -1,11 +1,11 @@
 
-T8851.hs:24:12: error:
-    Couldn't match type ‘Parser’ with ‘MyParser’
-      arising from the coercion of the method ‘notFollowedBy’
-        from type ‘forall a.
-                   (Monad Parser, Show a) =>
-                   Parser a -> Parser ()’
-          to type ‘forall a.
-                   (Monad MyParser, Show a) =>
-                   MyParser a -> MyParser ()’
-    When deriving the instance for (Parsing MyParser)
+T8851.hs:25:12: error:
+    • Couldn't match type ‘Parser’ with ‘MyParser’
+        arising from the coercion of the method ‘notFollowedBy’
+          from type ‘forall a.
+                     (Monad Parser, Show a) =>
+                     Parser a -> Parser ()’
+            to type ‘forall a.
+                     (Monad MyParser, Show a) =>
+                     MyParser a -> MyParser ()’
+    • When deriving the instance for (Parsing MyParser)
diff --git a/testsuite/tests/deriving/should_fail/T9600.hs b/testsuite/tests/deriving/should_fail/T9600.hs
index a6663ce8c8..0547e9dbee 100644
--- a/testsuite/tests/deriving/should_fail/T9600.hs
+++ b/testsuite/tests/deriving/should_fail/T9600.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE Haskell2010 #-}
 import Control.Applicative
 
 newtype Foo a = Foo (a -> a) deriving Applicative
diff --git a/testsuite/tests/deriving/should_fail/T9600.stderr b/testsuite/tests/deriving/should_fail/T9600.stderr
index 5c03f2efc2..734e3af997 100644
--- a/testsuite/tests/deriving/should_fail/T9600.stderr
+++ b/testsuite/tests/deriving/should_fail/T9600.stderr
@@ -1,6 +1,6 @@
 
-T9600.hs:3:39: error:
-    Can't make a derived instance of ‘Applicative Foo’:
-      ‘Applicative’ is not a stock derivable class (Eq, Show, etc.)
-      Try GeneralizedNewtypeDeriving for GHC's newtype-deriving extension
-    In the newtype declaration for ‘Foo’
+T9600.hs:4:39: error:
+    • Can't make a derived instance of ‘Applicative Foo’:
+        ‘Applicative’ is not a stock derivable class (Eq, Show, etc.)
+        Try GeneralizedNewtypeDeriving for GHC's newtype-deriving extension
+    • In the newtype declaration for ‘Foo’
diff --git a/testsuite/tests/deriving/should_fail/deriving-via-fail.hs b/testsuite/tests/deriving/should_fail/deriving-via-fail.hs
index 0cb521de78..95c462a6ea 100644
--- a/testsuite/tests/deriving/should_fail/deriving-via-fail.hs
+++ b/testsuite/tests/deriving/should_fail/deriving-via-fail.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE Haskell2010 #-}
 {-# LANGUAGE DerivingVia #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE StandaloneDeriving #-}
diff --git a/testsuite/tests/deriving/should_fail/deriving-via-fail.stderr b/testsuite/tests/deriving/should_fail/deriving-via-fail.stderr
index 5179f53c03..ea07442a82 100644
--- a/testsuite/tests/deriving/should_fail/deriving-via-fail.stderr
+++ b/testsuite/tests/deriving/should_fail/deriving-via-fail.stderr
@@ -1,28 +1,28 @@
 
-deriving-via-fail.hs:9:34: error:
+deriving-via-fail.hs:10:34: error:
     • Couldn't match representation of type ‘a’ with that of ‘b’
         arising from the coercion of the method ‘showsPrec’
           from type ‘Int -> Identity b -> ShowS’
             to type ‘Int -> Foo1 a -> ShowS’
       ‘a’ is a rigid type variable bound by
         the deriving clause for ‘Show (Foo1 a)’
-        at deriving-via-fail.hs:9:34-37
+        at deriving-via-fail.hs:10:34-37
       ‘b’ is a rigid type variable bound by
         the deriving clause for ‘Show (Foo1 a)’
-        at deriving-via-fail.hs:9:34-37
+        at deriving-via-fail.hs:10:34-37
     • When deriving the instance for (Show (Foo1 a))
 
-deriving-via-fail.hs:12:12: error:
+deriving-via-fail.hs:13:12: error:
     • Cannot derive instance via ‘fooo’
         Class ‘Category’ expects an argument of kind ‘* -> * -> *’,
         but ‘fooo’ has kind ‘*’
     • In the newtype declaration for ‘Foo2’
 
-deriving-via-fail.hs:15:20: error:
+deriving-via-fail.hs:16:20: error:
     • Couldn't match representation of type ‘a’ with that of ‘Foo3’
         arising from the coercion of the method ‘==’
           from type ‘a -> a -> Bool’ to type ‘Foo3 -> Foo3 -> Bool’
       ‘a’ is a rigid type variable bound by
         the deriving clause for ‘Eq Foo3’
-        at deriving-via-fail.hs:15:20-21
+        at deriving-via-fail.hs:16:20-21
     • When deriving the instance for (Eq Foo3)
diff --git a/testsuite/tests/deriving/should_fail/deriving-via-fail4.hs b/testsuite/tests/deriving/should_fail/deriving-via-fail4.hs
index 2e16abfa20..e58ffca658 100644
--- a/testsuite/tests/deriving/should_fail/deriving-via-fail4.hs
+++ b/testsuite/tests/deriving/should_fail/deriving-via-fail4.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE Haskell2010 #-}
 {-# LANGUAGE DerivingVia #-}
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
diff --git a/testsuite/tests/deriving/should_fail/deriving-via-fail4.stderr b/testsuite/tests/deriving/should_fail/deriving-via-fail4.stderr
index 9c4ee15209..9c1b305fbf 100644
--- a/testsuite/tests/deriving/should_fail/deriving-via-fail4.stderr
+++ b/testsuite/tests/deriving/should_fail/deriving-via-fail4.stderr
@@ -1,18 +1,18 @@
 
-deriving-via-fail4.hs:14:12: error:
+deriving-via-fail4.hs:15:12: error:
     • Couldn't match representation of type ‘Int’ with that of ‘Char’
         arising from the coercion of the method ‘==’
           from type ‘Char -> Char -> Bool’ to type ‘F1 -> F1 -> Bool’
     • When deriving the instance for (Eq F1)
 
-deriving-via-fail4.hs:17:13: error:
+deriving-via-fail4.hs:18:13: error:
     • Couldn't match representation of type ‘a’ with that of ‘a1’
         arising from the coercion of the method ‘c’
           from type ‘a -> a -> Bool’ to type ‘a -> F2 a1 -> Bool’
       ‘a’ is a rigid type variable bound by
         the deriving clause for ‘C a (F2 a1)’
-        at deriving-via-fail4.hs:17:13-15
+        at deriving-via-fail4.hs:18:13-15
       ‘a1’ is a rigid type variable bound by
         the deriving clause for ‘C a (F2 a1)’
-        at deriving-via-fail4.hs:17:13-15
+        at deriving-via-fail4.hs:18:13-15
     • When deriving the instance for (C a (F2 a1))
diff --git a/testsuite/tests/deriving/should_fail/drvfail-functor1.hs b/testsuite/tests/deriving/should_fail/drvfail-functor1.hs
index 94ebd925b8..aef52421e0 100644
--- a/testsuite/tests/deriving/should_fail/drvfail-functor1.hs
+++ b/testsuite/tests/deriving/should_fail/drvfail-functor1.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE Haskell2010 #-}
 module ShouldFail where
 
 -- Derive Functor without a DeriveFunctor language pragma
diff --git a/testsuite/tests/deriving/should_fail/drvfail-functor1.stderr b/testsuite/tests/deriving/should_fail/drvfail-functor1.stderr
index bff4d27a49..07ce81f4ab 100644
--- a/testsuite/tests/deriving/should_fail/drvfail-functor1.stderr
+++ b/testsuite/tests/deriving/should_fail/drvfail-functor1.stderr
@@ -1,5 +1,5 @@
 
-drvfail-functor1.hs:6:14:
-    Can't make a derived instance of ‘Functor List’:
-      You need DeriveFunctor to derive an instance for this class
-    In the data declaration for ‘List’
+drvfail-functor1.hs:7:14: error:
+    • Can't make a derived instance of ‘Functor List’:
+        You need DeriveFunctor to derive an instance for this class
+    • In the data declaration for ‘List’
diff --git a/testsuite/tests/deriving/should_fail/drvfail-functor2.hs b/testsuite/tests/deriving/should_fail/drvfail-functor2.hs
index 77e17cf381..be5413f773 100644
--- a/testsuite/tests/deriving/should_fail/drvfail-functor2.hs
+++ b/testsuite/tests/deriving/should_fail/drvfail-functor2.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE Haskell2010 #-}
 {-# LANGUAGE DeriveFunctor, DatatypeContexts #-}
 module ShouldFail where
 
diff --git a/testsuite/tests/deriving/should_fail/drvfail-functor2.stderr b/testsuite/tests/deriving/should_fail/drvfail-functor2.stderr
index e0aa34656c..1c3a0238a4 100644
--- a/testsuite/tests/deriving/should_fail/drvfail-functor2.stderr
+++ b/testsuite/tests/deriving/should_fail/drvfail-functor2.stderr
@@ -1,31 +1,31 @@
 
-drvfail-functor2.hs:1:29: Warning:
+drvfail-functor2.hs:2:29: warning:
     -XDatatypeContexts is deprecated: It was widely considered a misfeature, and has been removed from the Haskell language.
 
-drvfail-functor2.hs:7:14:
-    Can't make a derived instance of ‘Functor InFunctionArgument’:
-      Constructor ‘InFunctionArgument’ must not use the type variable in a function argument
-    In the newtype declaration for ‘InFunctionArgument’
+drvfail-functor2.hs:8:14: error:
+    • Can't make a derived instance of ‘Functor InFunctionArgument’:
+        Constructor ‘InFunctionArgument’ must not use the type variable in a function argument
+    • In the newtype declaration for ‘InFunctionArgument’
 
-drvfail-functor2.hs:10:14:
-    Can't make a derived instance of ‘Functor OnSecondArg’:
-      Constructor ‘OnSecondArg’ must use the type variable only as the last argument of a data type
-    In the newtype declaration for ‘OnSecondArg’
+drvfail-functor2.hs:11:14: error:
+    • Can't make a derived instance of ‘Functor OnSecondArg’:
+        Constructor ‘OnSecondArg’ must use the type variable only as the last argument of a data type
+    • In the newtype declaration for ‘OnSecondArg’
 
-drvfail-functor2.hs:15:14:
-    Cannot derive well-kinded instance of form ‘Functor (NoArguments ...)’
-      Class ‘Functor’ expects an argument of kind ‘* -> *’
-    In the newtype declaration for ‘NoArguments’
+drvfail-functor2.hs:16:14: error:
+    • Cannot derive well-kinded instance of form ‘Functor (NoArguments ...)’
+        Class ‘Functor’ expects an argument of kind ‘* -> *’
+    • In the newtype declaration for ‘NoArguments’
 
-drvfail-functor2.hs:20:14:
-    Can't make a derived instance of ‘Functor StupidConstraint’:
-      Data type ‘StupidConstraint’ must not have a class context: Eq a
-    In the data declaration for ‘StupidConstraint’
+drvfail-functor2.hs:21:14: error:
+    • Can't make a derived instance of ‘Functor StupidConstraint’:
+        Data type ‘StupidConstraint’ must not have a class context: Eq a
+    • In the data declaration for ‘StupidConstraint’
 
-drvfail-functor2.hs:26:14:
-    No instance for (Functor NoFunctor)
-      arising from the first field of ‘UseNoFunctor’ (type ‘NoFunctor a’)
-    Possible fix:
-      use a standalone 'deriving instance' declaration,
-        so you can specify the instance context yourself
-    When deriving the instance for (Functor UseNoFunctor)
+drvfail-functor2.hs:27:14: error:
+    • No instance for (Functor NoFunctor)
+        arising from the first field of ‘UseNoFunctor’ (type ‘NoFunctor a’)
+      Possible fix:
+        use a standalone 'deriving instance' declaration,
+          so you can specify the instance context yourself
+    • When deriving the instance for (Functor UseNoFunctor)
diff --git a/testsuite/tests/deriving/should_fail/drvfail008.hs b/testsuite/tests/deriving/should_fail/drvfail008.hs
index af8628b4d5..1636bd1353 100644
--- a/testsuite/tests/deriving/should_fail/drvfail008.hs
+++ b/testsuite/tests/deriving/should_fail/drvfail008.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE Haskell2010 #-}
 -- Should fail without GeneralizedNewtypeDeriving
 -- Succeeds with GeneralizedNewtypeDeriving
 
diff --git a/testsuite/tests/deriving/should_fail/drvfail008.stderr b/testsuite/tests/deriving/should_fail/drvfail008.stderr
index dcd43eca62..e942f087e7 100644
--- a/testsuite/tests/deriving/should_fail/drvfail008.stderr
+++ b/testsuite/tests/deriving/should_fail/drvfail008.stderr
@@ -1,5 +1,5 @@
 
-drvfail008.hs:10:43: error:
+drvfail008.hs:11:43: error:
     • Can't make a derived instance of ‘Monad M’:
         ‘Monad’ is not a stock derivable class (Eq, Show, etc.)
         Try GeneralizedNewtypeDeriving for GHC's newtype-deriving extension
diff --git a/testsuite/tests/deriving/should_fail/drvfail015.hs b/testsuite/tests/deriving/should_fail/drvfail015.hs
index 32d6134d34..8f1235c0b8 100644
--- a/testsuite/tests/deriving/should_fail/drvfail015.hs
+++ b/testsuite/tests/deriving/should_fail/drvfail015.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE Haskell2010 #-}
 {-# OPTIONS_GHC -XStandaloneDeriving #-}
 
 module ShouldFail where
diff --git a/testsuite/tests/deriving/should_fail/drvfail015.stderr b/testsuite/tests/deriving/should_fail/drvfail015.stderr
index c38ff00456..b731032fc3 100644
--- a/testsuite/tests/deriving/should_fail/drvfail015.stderr
+++ b/testsuite/tests/deriving/should_fail/drvfail015.stderr
@@ -1,13 +1,13 @@
 
-drvfail015.hs:10:19:
-    Illegal instance declaration for ‘Eq T’
-      (All instance types must be of the form (T t1 ... tn)
-       where T is not a synonym.
-       Use TypeSynonymInstances if you want to disable this.)
-    In the stand-alone deriving instance for ‘Eq T’
+drvfail015.hs:11:19: error:
+    • Illegal instance declaration for ‘Eq T’
+        (All instance types must be of the form (T t1 ... tn)
+         where T is not a synonym.
+         Use TypeSynonymInstances if you want to disable this.)
+    • In the stand-alone deriving instance for ‘Eq T’
 
-drvfail015.hs:13:1:
-    Can't make a derived instance of ‘Eq Handle’:
-      The data constructors of ‘Handle’ are not all in scope
-        so you cannot derive an instance for it
-    In the stand-alone deriving instance for ‘Eq Handle’
+drvfail015.hs:14:1: error:
+    • Can't make a derived instance of ‘Eq Handle’:
+        The data constructors of ‘Handle’ are not all in scope
+          so you cannot derive an instance for it
+    • In the stand-alone deriving instance for ‘Eq Handle’