Merge pull request #6015 from quasicomputational/extension-empty-data…

…-deriving Add EmptyDataDeriving as an Extension constructor.
haskell · Apr 26, 2019 · 6316102 · 6316102
2 parents 8de49e6 + 3f0a07f
commit 6316102
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diff --git a/Cabal/ChangeLog.md b/Cabal/ChangeLog.md
@@ -4,7 +4,8 @@
     ([#5906](https://github.com/haskell/cabal/pull/5906)).
   * 'check' reports warnings for various ghc-\*-options fields separately
     ([#5342](https://github.com/haskell/cabal/issues/5432)).
-  * `KnownExtension`: added new extension `DerivingVia`.
+  * `KnownExtension`: added new extensions `DerivingVia` and
+    `EmptyDataDeriving`.
   * Add `extra-dynamic-library-flavours`, to specify extra dynamic library
     flavours to build and install from a .cabal file.
   * `autoconfUserHooks` now passes `--host=$HOST` when cross-compiling

diff --git a/Cabal/Language/Haskell/Extension.hs b/Cabal/Language/Haskell/Extension.hs
@@ -818,6 +818,11 @@ data KnownExtension =
   -- | Have @*@ refer to @Type@.
   | StarIsType
 
+  -- | Liberalises deriving to provide instances for empty data types.
+  --
+  -- * <https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/glasgow_exts.html#deriving-instances-for-empty-data-types>
+  | EmptyDataDeriving
+
   deriving (Generic, Show, Read, Eq, Ord, Enum, Bounded, Typeable, Data)
 
 instance Binary KnownExtension