[commit: ghc] ghc-8.6: Expose the StableName constructor (768cc53)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : ghc-8.6
Link       : http://ghc.haskell.org/trac/ghc/changeset/768cc53d73e46954b01df69c6b215a41b3533f56/ghc

>---------------------------------------------------------------

commit 768cc53d73e46954b01df69c6b215a41b3533f56
Author: David Feuer <david.feuer at gmail.com>
Date:   Mon Aug 20 20:08:14 2018 -0400

    Expose the StableName constructor
    
    * Move the definition of `StableName` from `System.Mem.StableName`
      to a new `GHC.StableName` module.
    
    * Expose the `StableName` data constructor from `GHC.StableName`.
      Once we have `UnliftedArray#`, this will enable `StableName`s to
      be stored in `UnliftedArray`s (from `primitive`) without unsafe
      coercions.
    
    Reviewers: hvr, bgamari, andrewthad, osa1
    
    Reviewed By: osa1
    
    Subscribers: osa1, rwbarton, carter
    
    GHC Trac Issues: #15535
    
    Differential Revision: https://phabricator.haskell.org/D5078
    
    (cherry picked from commit 9c4e6c6b1affd410604f8f76ecf56abfcc5cccb6)


>---------------------------------------------------------------

768cc53d73e46954b01df69c6b215a41b3533f56
 libraries/base/{System/Mem => GHC}/StableName.hs |  4 +-
 libraries/base/System/Mem/StableName.hs          | 75 +-----------------------
 libraries/base/base.cabal                        |  1 +
 3 files changed, 5 insertions(+), 75 deletions(-)

diff --git a/libraries/base/System/Mem/StableName.hs b/libraries/base/GHC/StableName.hs
similarity index 98%
copy from libraries/base/System/Mem/StableName.hs
copy to libraries/base/GHC/StableName.hs
index dcd5273..7369f41 100644
--- a/libraries/base/System/Mem/StableName.hs
+++ b/libraries/base/GHC/StableName.hs
@@ -27,9 +27,9 @@
 --
 -------------------------------------------------------------------------------
 
-module System.Mem.StableName (
+module GHC.StableName (
   -- * Stable Names
-  StableName,
+  StableName (..),
   makeStableName,
   hashStableName,
   eqStableName
diff --git a/libraries/base/System/Mem/StableName.hs b/libraries/base/System/Mem/StableName.hs
index dcd5273..064d928 100644
--- a/libraries/base/System/Mem/StableName.hs
+++ b/libraries/base/System/Mem/StableName.hs
@@ -1,7 +1,4 @@
-{-# LANGUAGE Trustworthy #-}
-{-# LANGUAGE StandaloneDeriving #-}
-{-# LANGUAGE MagicHash #-}
-{-# LANGUAGE UnboxedTuples #-}
+{-# LANGUAGE Safe #-}
 
 -----------------------------------------------------------------------------
 -- |
@@ -35,72 +32,4 @@ module System.Mem.StableName (
   eqStableName
   ) where
 
-import GHC.IO           ( IO(..) )
-import GHC.Base         ( Int(..), StableName#, makeStableName#
-                        , eqStableName#, stableNameToInt# )
-
------------------------------------------------------------------------------
--- Stable Names
-
-{-|
-  An abstract name for an object, that supports equality and hashing.
-
-  Stable names have the following property:
-
-  * If @sn1 :: StableName@ and @sn2 :: StableName@ and @sn1 == sn2@
-   then @sn1@ and @sn2@ were created by calls to @makeStableName@ on
-   the same object.
-
-  The reverse is not necessarily true: if two stable names are not
-  equal, then the objects they name may still be equal.  Note in particular
-  that `makeStableName` may return a different `StableName` after an
-  object is evaluated.
-
-  Stable Names are similar to Stable Pointers ("Foreign.StablePtr"),
-  but differ in the following ways:
-
-  * There is no @freeStableName@ operation, unlike "Foreign.StablePtr"s.
-    Stable names are reclaimed by the runtime system when they are no
-    longer needed.
-
-  * There is no @deRefStableName@ operation.  You can\'t get back from
-    a stable name to the original Haskell object.  The reason for
-    this is that the existence of a stable name for an object does not
-    guarantee the existence of the object itself; it can still be garbage
-    collected.
--}
-
-data StableName a = StableName (StableName# a)
-
--- | Makes a 'StableName' for an arbitrary object.  The object passed as
--- the first argument is not evaluated by 'makeStableName'.
-makeStableName  :: a -> IO (StableName a)
-makeStableName a = IO $ \ s ->
-    case makeStableName# a s of (# s', sn #) -> (# s', StableName sn #)
-
--- | Convert a 'StableName' to an 'Int'.  The 'Int' returned is not
--- necessarily unique; several 'StableName's may map to the same 'Int'
--- (in practice however, the chances of this are small, so the result
--- of 'hashStableName' makes a good hash key).
-hashStableName :: StableName a -> Int
-hashStableName (StableName sn) = I# (stableNameToInt# sn)
-
--- | @since 2.01
-instance Eq (StableName a) where
-    (StableName sn1) == (StableName sn2) =
-       case eqStableName# sn1 sn2 of
-         0# -> False
-         _  -> True
-
--- | Equality on 'StableName' that does not require that the types of
--- the arguments match.
---
--- @since 4.7.0.0
-eqStableName :: StableName a -> StableName b -> Bool
-eqStableName (StableName sn1) (StableName sn2) =
-       case eqStableName# sn1 sn2 of
-         0# -> False
-         _  -> True
-  -- Requested by Emil Axelsson on glasgow-haskell-users, who wants to
-  -- use it for implementing observable sharing.
-
+import GHC.StableName
diff --git a/libraries/base/base.cabal b/libraries/base/base.cabal
index dbeec33..f02ff08 100644
--- a/libraries/base/base.cabal
+++ b/libraries/base/base.cabal
@@ -278,6 +278,7 @@ Library
         GHC.STRef
         GHC.Show
         GHC.Stable
+        GHC.StableName
         GHC.Stack
         GHC.Stack.CCS
         GHC.Stack.Types