[Git][ghc/ghc][wip/jeltsch/system-io-uncovering] 2 commits: Move some `IsString` instance declarations to `base`

23 Feb 2026

Wolfgang Jeltsch pushed to branch wip/jeltsch/system-io-uncovering at Glasgow Haskell Compiler / GHC


Commits:
8241360d by Wolfgang Jeltsch at 2026-02-23T20:33:33+02:00
Move some `IsString` instance declarations to `base`

- - - - -
04369afe by Wolfgang Jeltsch at 2026-02-23T20:33:56+02:00
Move `* -> *` `Heap.Closure` instances into `ghc-heap`

- - - - -


11 changed files:

- libraries/base/src/Data/String.hs
- libraries/ghc-heap/GHC/Exts/Heap/Closures.hs
- libraries/ghc-internal/src/GHC/Internal/Data/String.hs
- libraries/ghc-internal/src/GHC/Internal/Heap/Closures.hs
- testsuite/tests/interface-stability/base-exports.stdout
- testsuite/tests/interface-stability/base-exports.stdout-javascript-unknown-ghcjs
- testsuite/tests/interface-stability/base-exports.stdout-mingw32
- testsuite/tests/interface-stability/base-exports.stdout-ws-32
- testsuite/tests/interface-stability/ghc-experimental-exports.stdout
- testsuite/tests/interface-stability/ghc-experimental-exports.stdout-mingw32
- testsuite/tests/typecheck/should_fail/T12921.stderr


Changes:

=====================================
libraries/base/src/Data/String.hs
=====================================
@@ -1,4 +1,8 @@
-{-# LANGUAGE Safe #-}
+{-# LANGUAGE Trustworthy #-}
+
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+{-# LANGUAGE PolyKinds #-}
+{-# LANGUAGE StandaloneDeriving #-}
 
 -- |
 --
@@ -23,4 +27,13 @@ module Data.String
      unwords
      ) where
 
-import GHC.Internal.Data.String
\ No newline at end of file
+import GHC.Internal.Data.String
+
+import GHC.Internal.Data.Functor.Const (Const (Const))
+import GHC.Internal.Data.Functor.Identity (Identity (Identity))
+
+-- | @since base-4.9.0.0
+deriving instance IsString a => IsString (Const a (b :: k))
+
+-- | @since base-4.9.0.0
+deriving instance IsString a => IsString (Identity a)


=====================================
libraries/ghc-heap/GHC/Exts/Heap/Closures.hs
=====================================
@@ -1,10 +1,5 @@
 {-# LANGUAGE CPP #-}
-{-# LANGUAGE ForeignFunctionInterface #-}
-{-# LANGUAGE GHCForeignImportPrim #-}
-{-# LANGUAGE MagicHash #-}
-{-# LANGUAGE RecordWildCards #-}
-{-# LANGUAGE UnliftedFFITypes #-}
-{-# LANGUAGE DeriveGeneric #-}
+{-# LANGUAGE StandaloneDeriving #-}
 {-# LANGUAGE DeriveTraversable #-}
 -- Late cost centres introduce a thunk in the asBox function, which leads to
 -- an additional wrapper being added to any value placed inside a box.
@@ -42,3 +37,23 @@ module GHC.Exts.Heap.Closures (
     ) where
 
 import GHC.Internal.Heap.Closures
+
+import GHC.Internal.Data.Functor
+import GHC.Internal.Data.Foldable
+import GHC.Internal.Data.Traversable
+
+deriving instance Functor GenClosure
+deriving instance Foldable GenClosure
+deriving instance Traversable GenClosure
+
+deriving instance Functor GenStgStackClosure
+deriving instance Foldable GenStgStackClosure
+deriving instance Traversable GenStgStackClosure
+
+deriving instance Functor GenStackField
+deriving instance Foldable GenStackField
+deriving instance Traversable GenStackField
+
+deriving instance Functor GenStackFrame
+deriving instance Foldable GenStackFrame
+deriving instance Traversable GenStackFrame


=====================================
libraries/ghc-internal/src/GHC/Internal/Data/String.hs
=====================================
@@ -1,8 +1,5 @@
 {-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE NoImplicitPrelude #-}
-{-# LANGUAGE PolyKinds #-}
-{-# LANGUAGE StandaloneDeriving #-}
 {-# LANGUAGE Trustworthy #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE TypeOperators #-}
@@ -33,8 +30,6 @@ module GHC.Internal.Data.String (
  ) where
 
 import GHC.Internal.Base
-import GHC.Internal.Data.Functor.Const (Const (Const))
-import GHC.Internal.Data.Functor.Identity (Identity (Identity))
 import GHC.Internal.Data.List (lines, words, unlines, unwords)
 
 -- | `IsString` is used in combination with the @-XOverloadedStrings@
@@ -105,9 +100,3 @@ ensure the good behavior of the above example remains in the future.
 instance (a ~ Char) => IsString [a] where
          -- See Note [IsString String]
     fromString xs = xs
-

--- | @since base-4.9.0.0
-deriving instance IsString a => IsString (Const a (b :: k))
-
--- | @since base-4.9.0.0
-deriving instance IsString a => IsString (Identity a)


=====================================
libraries/ghc-internal/src/GHC/Internal/Heap/Closures.hs
=====================================
@@ -5,7 +5,6 @@
 {-# LANGUAGE RecordWildCards #-}
 {-# LANGUAGE UnliftedFFITypes #-}
 {-# LANGUAGE DeriveGeneric #-}
-{-# LANGUAGE DeriveTraversable #-}
 -- Late cost centres introduce a thunk in the asBox function, which leads to
 -- an additional wrapper being added to any value placed inside a box.
 -- This can be removed once our boot compiler is no longer affected by #25212
@@ -69,8 +68,7 @@ in the profiling way. (#15197)
 import GHC.Internal.Heap.ProfInfo.Types
 
 import GHC.Internal.Data.Bits
-import GHC.Internal.Data.Foldable (Foldable, toList)
-import GHC.Internal.Data.Traversable (Traversable)
+import GHC.Internal.Data.Foldable (toList)
 import GHC.Internal.Int
 import GHC.Internal.Num
 import GHC.Internal.Real
@@ -383,7 +381,7 @@ data GenClosure b
     -- or an Int#).
   |  UnknownTypeWordSizedPrimitive
         { wordVal :: !Word }
-  deriving (Show, Generic, Functor, Foldable, Traversable)
+  deriving (Show, Generic)
 
 -- | Get the info table for a heap closure, or Nothing for a prim value
 --
@@ -500,7 +498,7 @@ data GenStgStackClosure b = GenStgStackClosure
       , ssc_stack_size      :: !Word32 -- ^ stack size in *words*
       , ssc_stack           :: ![GenStackFrame b]
       }
-  deriving (Foldable, Functor, Generic, Show, Traversable)
+  deriving (Generic, Show)
 
 type StackField = GenStackField Box
 
@@ -510,7 +508,7 @@ data GenStackField b
     = StackWord !Word
     -- | A pointer field
     | StackBox  !b
-  deriving (Foldable, Functor, Generic, Show, Traversable)
+  deriving (Generic, Show)
 
 type StackFrame = GenStackFrame Box
 
@@ -579,7 +577,7 @@ data GenStackFrame b =
       { info_tbl            :: !StgInfoTable
       , annotation          :: !b
       }
-  deriving (Foldable, Functor, Generic, Show, Traversable)
+  deriving (Generic, Show)
 
 data PrimType
   = PInt


=====================================
testsuite/tests/interface-stability/base-exports.stdout
=====================================
@@ -1673,7 +1673,7 @@ module Data.Semigroup where
   stimesMonoid :: forall b a. (GHC.Internal.Real.Integral b, GHC.Internal.Base.Monoid a) => b -> a -> a
 
 module Data.String where
-  -- Safety: Safe
+  -- Safety: Trustworthy
   type IsString :: * -> Constraint
   class IsString a where
     fromString :: String -> a
@@ -11778,8 +11778,8 @@ instance GHC.Internal.Data.Foldable.Foldable Data.Semigroup.First -- Defined in
 instance GHC.Internal.Data.Foldable.Foldable Data.Semigroup.Last -- Defined in ‘Data.Semigroup’
 instance GHC.Internal.Data.Foldable.Foldable Data.Semigroup.Max -- Defined in ‘Data.Semigroup’
 instance GHC.Internal.Data.Foldable.Foldable Data.Semigroup.Min -- Defined in ‘Data.Semigroup’
-instance forall a k (b :: k). GHC.Internal.Data.String.IsString a => GHC.Internal.Data.String.IsString (GHC.Internal.Data.Functor.Const.Const a b) -- Defined in ‘GHC.Internal.Data.String’
-instance forall a. GHC.Internal.Data.String.IsString a => GHC.Internal.Data.String.IsString (GHC.Internal.Data.Functor.Identity.Identity a) -- Defined in ‘GHC.Internal.Data.String’
+instance forall a k (b :: k). GHC.Internal.Data.String.IsString a => GHC.Internal.Data.String.IsString (GHC.Internal.Data.Functor.Const.Const a b) -- Defined in ‘Data.String’
+instance forall a. GHC.Internal.Data.String.IsString a => GHC.Internal.Data.String.IsString (GHC.Internal.Data.Functor.Identity.Identity a) -- Defined in ‘Data.String’
 instance forall a. (a ~ GHC.Internal.Types.Char) => GHC.Internal.Data.String.IsString [a] -- Defined in ‘GHC.Internal.Data.String’
 instance GHC.Internal.Data.Traversable.Traversable GHC.Internal.Functor.ZipList.ZipList -- Defined in ‘GHC.Internal.Functor.ZipList’
 instance forall (f :: * -> *) (g :: * -> *). (GHC.Internal.Data.Traversable.Traversable f, GHC.Internal.Data.Traversable.Traversable g) => GHC.Internal.Data.Traversable.Traversable (f GHC.Internal.Generics.:*: g) -- Defined in ‘GHC.Internal.Data.Traversable’


=====================================
testsuite/tests/interface-stability/base-exports.stdout-javascript-unknown-ghcjs
=====================================
@@ -1673,7 +1673,7 @@ module Data.Semigroup where
   stimesMonoid :: forall b a. (GHC.Internal.Real.Integral b, GHC.Internal.Base.Monoid a) => b -> a -> a
 
 module Data.String where
-  -- Safety: Safe
+  -- Safety: Trustworthy
   type IsString :: * -> Constraint
   class IsString a where
     fromString :: String -> a
@@ -11805,8 +11805,8 @@ instance GHC.Internal.Data.Foldable.Foldable Data.Semigroup.First -- Defined in
 instance GHC.Internal.Data.Foldable.Foldable Data.Semigroup.Last -- Defined in ‘Data.Semigroup’
 instance GHC.Internal.Data.Foldable.Foldable Data.Semigroup.Max -- Defined in ‘Data.Semigroup’
 instance GHC.Internal.Data.Foldable.Foldable Data.Semigroup.Min -- Defined in ‘Data.Semigroup’
-instance forall a k (b :: k). GHC.Internal.Data.String.IsString a => GHC.Internal.Data.String.IsString (GHC.Internal.Data.Functor.Const.Const a b) -- Defined in ‘GHC.Internal.Data.String’
-instance forall a. GHC.Internal.Data.String.IsString a => GHC.Internal.Data.String.IsString (GHC.Internal.Data.Functor.Identity.Identity a) -- Defined in ‘GHC.Internal.Data.String’
+instance forall a k (b :: k). GHC.Internal.Data.String.IsString a => GHC.Internal.Data.String.IsString (GHC.Internal.Data.Functor.Const.Const a b) -- Defined in ‘Data.String’
+instance forall a. GHC.Internal.Data.String.IsString a => GHC.Internal.Data.String.IsString (GHC.Internal.Data.Functor.Identity.Identity a) -- Defined in ‘Data.String’
 instance forall a. (a ~ GHC.Internal.Types.Char) => GHC.Internal.Data.String.IsString [a] -- Defined in ‘GHC.Internal.Data.String’
 instance GHC.Internal.Data.Traversable.Traversable GHC.Internal.Functor.ZipList.ZipList -- Defined in ‘GHC.Internal.Functor.ZipList’
 instance forall (f :: * -> *) (g :: * -> *). (GHC.Internal.Data.Traversable.Traversable f, GHC.Internal.Data.Traversable.Traversable g) => GHC.Internal.Data.Traversable.Traversable (f GHC.Internal.Generics.:*: g) -- Defined in ‘GHC.Internal.Data.Traversable’


=====================================
testsuite/tests/interface-stability/base-exports.stdout-mingw32
=====================================
@@ -1673,7 +1673,7 @@ module Data.Semigroup where
   stimesMonoid :: forall b a. (GHC.Internal.Real.Integral b, GHC.Internal.Base.Monoid a) => b -> a -> a
 
 module Data.String where
-  -- Safety: Safe
+  -- Safety: Trustworthy
   type IsString :: * -> Constraint
   class IsString a where
     fromString :: String -> a
@@ -12036,8 +12036,8 @@ instance GHC.Internal.Data.Foldable.Foldable Data.Semigroup.First -- Defined in
 instance GHC.Internal.Data.Foldable.Foldable Data.Semigroup.Last -- Defined in ‘Data.Semigroup’
 instance GHC.Internal.Data.Foldable.Foldable Data.Semigroup.Max -- Defined in ‘Data.Semigroup’
 instance GHC.Internal.Data.Foldable.Foldable Data.Semigroup.Min -- Defined in ‘Data.Semigroup’
-instance forall a k (b :: k). GHC.Internal.Data.String.IsString a => GHC.Internal.Data.String.IsString (GHC.Internal.Data.Functor.Const.Const a b) -- Defined in ‘GHC.Internal.Data.String’
-instance forall a. GHC.Internal.Data.String.IsString a => GHC.Internal.Data.String.IsString (GHC.Internal.Data.Functor.Identity.Identity a) -- Defined in ‘GHC.Internal.Data.String’
+instance forall a k (b :: k). GHC.Internal.Data.String.IsString a => GHC.Internal.Data.String.IsString (GHC.Internal.Data.Functor.Const.Const a b) -- Defined in ‘Data.String’
+instance forall a. GHC.Internal.Data.String.IsString a => GHC.Internal.Data.String.IsString (GHC.Internal.Data.Functor.Identity.Identity a) -- Defined in ‘Data.String’
 instance forall a. (a ~ GHC.Internal.Types.Char) => GHC.Internal.Data.String.IsString [a] -- Defined in ‘GHC.Internal.Data.String’
 instance GHC.Internal.Data.Traversable.Traversable GHC.Internal.Functor.ZipList.ZipList -- Defined in ‘GHC.Internal.Functor.ZipList’
 instance forall (f :: * -> *) (g :: * -> *). (GHC.Internal.Data.Traversable.Traversable f, GHC.Internal.Data.Traversable.Traversable g) => GHC.Internal.Data.Traversable.Traversable (f GHC.Internal.Generics.:*: g) -- Defined in ‘GHC.Internal.Data.Traversable’


=====================================
testsuite/tests/interface-stability/base-exports.stdout-ws-32
=====================================
@@ -1673,7 +1673,7 @@ module Data.Semigroup where
   stimesMonoid :: forall b a. (GHC.Internal.Real.Integral b, GHC.Internal.Base.Monoid a) => b -> a -> a
 
 module Data.String where
-  -- Safety: Safe
+  -- Safety: Trustworthy
   type IsString :: * -> Constraint
   class IsString a where
     fromString :: String -> a
@@ -11778,8 +11778,8 @@ instance GHC.Internal.Data.Foldable.Foldable Data.Semigroup.First -- Defined in
 instance GHC.Internal.Data.Foldable.Foldable Data.Semigroup.Last -- Defined in ‘Data.Semigroup’
 instance GHC.Internal.Data.Foldable.Foldable Data.Semigroup.Max -- Defined in ‘Data.Semigroup’
 instance GHC.Internal.Data.Foldable.Foldable Data.Semigroup.Min -- Defined in ‘Data.Semigroup’
-instance forall a k (b :: k). GHC.Internal.Data.String.IsString a => GHC.Internal.Data.String.IsString (GHC.Internal.Data.Functor.Const.Const a b) -- Defined in ‘GHC.Internal.Data.String’
-instance forall a. GHC.Internal.Data.String.IsString a => GHC.Internal.Data.String.IsString (GHC.Internal.Data.Functor.Identity.Identity a) -- Defined in ‘GHC.Internal.Data.String’
+instance forall a k (b :: k). GHC.Internal.Data.String.IsString a => GHC.Internal.Data.String.IsString (GHC.Internal.Data.Functor.Const.Const a b) -- Defined in ‘Data.String’
+instance forall a. GHC.Internal.Data.String.IsString a => GHC.Internal.Data.String.IsString (GHC.Internal.Data.Functor.Identity.Identity a) -- Defined in ‘Data.String’
 instance forall a. (a ~ GHC.Internal.Types.Char) => GHC.Internal.Data.String.IsString [a] -- Defined in ‘GHC.Internal.Data.String’
 instance GHC.Internal.Data.Traversable.Traversable GHC.Internal.Functor.ZipList.ZipList -- Defined in ‘GHC.Internal.Functor.ZipList’
 instance forall (f :: * -> *) (g :: * -> *). (GHC.Internal.Data.Traversable.Traversable f, GHC.Internal.Data.Traversable.Traversable g) => GHC.Internal.Data.Traversable.Traversable (f GHC.Internal.Generics.:*: g) -- Defined in ‘GHC.Internal.Data.Traversable’


=====================================
testsuite/tests/interface-stability/ghc-experimental-exports.stdout
=====================================
@@ -11188,8 +11188,6 @@ instance forall a. GHC.Internal.Classes.Ord (GHC.Internal.Ptr.FunPtr a) -- Defin
 instance forall a. GHC.Internal.Classes.Ord (GHC.Internal.Ptr.Ptr a) -- Defined in ‘GHC.Internal.Ptr’
 instance forall a. GHC.Internal.Classes.Ord a => GHC.Internal.Classes.Ord (GHC.Internal.Base.NonEmpty a) -- Defined in ‘GHC.Internal.Base’
 instance GHC.Internal.Classes.Ord GHC.Internal.Base.Void -- Defined in ‘GHC.Internal.Base’
-instance forall a k (b :: k). GHC.Internal.Data.String.IsString a => GHC.Internal.Data.String.IsString (GHC.Internal.Data.Functor.Const.Const a b) -- Defined in ‘GHC.Internal.Data.String’
-instance forall a. GHC.Internal.Data.String.IsString a => GHC.Internal.Data.String.IsString (GHC.Internal.Data.Functor.Identity.Identity a) -- Defined in ‘GHC.Internal.Data.String’
 instance forall a. (a ~ GHC.Internal.Types.Char) => GHC.Internal.Data.String.IsString [a] -- Defined in ‘GHC.Internal.Data.String’
 instance forall a. GHC.Internal.Enum.Bounded a => GHC.Internal.Enum.Bounded (GHC.Internal.Data.Ord.Down a) -- Defined in ‘GHC.Internal.Data.Ord’
 instance forall a. (GHC.Internal.Enum.Enum a, GHC.Internal.Enum.Bounded a, GHC.Internal.Classes.Eq a) => GHC.Internal.Enum.Enum (GHC.Internal.Data.Ord.Down a) -- Defined in ‘GHC.Internal.Data.Ord’


=====================================
testsuite/tests/interface-stability/ghc-experimental-exports.stdout-mingw32
=====================================
@@ -11191,8 +11191,6 @@ instance forall a. GHC.Internal.Classes.Ord (GHC.Internal.Ptr.FunPtr a) -- Defin
 instance forall a. GHC.Internal.Classes.Ord (GHC.Internal.Ptr.Ptr a) -- Defined in ‘GHC.Internal.Ptr’
 instance forall a. GHC.Internal.Classes.Ord a => GHC.Internal.Classes.Ord (GHC.Internal.Base.NonEmpty a) -- Defined in ‘GHC.Internal.Base’
 instance GHC.Internal.Classes.Ord GHC.Internal.Base.Void -- Defined in ‘GHC.Internal.Base’
-instance forall a k (b :: k). GHC.Internal.Data.String.IsString a => GHC.Internal.Data.String.IsString (GHC.Internal.Data.Functor.Const.Const a b) -- Defined in ‘GHC.Internal.Data.String’
-instance forall a. GHC.Internal.Data.String.IsString a => GHC.Internal.Data.String.IsString (GHC.Internal.Data.Functor.Identity.Identity a) -- Defined in ‘GHC.Internal.Data.String’
 instance forall a. (a ~ GHC.Internal.Types.Char) => GHC.Internal.Data.String.IsString [a] -- Defined in ‘GHC.Internal.Data.String’
 instance forall a. GHC.Internal.Enum.Bounded a => GHC.Internal.Enum.Bounded (GHC.Internal.Data.Ord.Down a) -- Defined in ‘GHC.Internal.Data.Ord’
 instance forall a. (GHC.Internal.Enum.Enum a, GHC.Internal.Enum.Bounded a, GHC.Internal.Classes.Eq a) => GHC.Internal.Enum.Enum (GHC.Internal.Data.Ord.Down a) -- Defined in ‘GHC.Internal.Data.Ord’


=====================================
testsuite/tests/typecheck/should_fail/T12921.stderr
=====================================
@@ -24,8 +24,6 @@ T12921.hs:4:16: error: [GHC-39999]
       Potentially matching instance:
         instance (a ~ Char) => GHC.Internal.Data.String.IsString [a]
           -- Defined in ‘GHC.Internal.Data.String’
-        ...plus two instances involving out-of-scope types
-        (use -fprint-potential-instances to see them all)
     • In the annotation:
         {-# ANN module "HLint: ignore Reduce duplication" #-}
 



View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/1d6cba74fad4f7d154768b3b360b518...

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[Git][ghc/ghc][wip/jeltsch/system-io-uncovering] 2 commits: Move some `IsString` instance declarations to `base`

Wolfgang Jeltsch (＠jeltsch)