[commit: ghc] ghc-8.2: Update docs to reflect changes to DeriveDataTypeable (46d350d)

[git at git.haskell.org]

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

On branch  : ghc-8.2
Link       : http://ghc.haskell.org/trac/ghc/changeset/46d350d2d60791af77d1f0763b61b0f710d9b664/ghc

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

commit 46d350d2d60791af77d1f0763b61b0f710d9b664
Author: Chris Martin <ch.martin at gmail.com>
Date:   Mon Jun 26 14:55:15 2017 -0400

    Update docs to reflect changes to DeriveDataTypeable
    
    (cherry picked from commit 914962ca23e407efdd3429dc89adcca7bee15f28)


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

46d350d2d60791af77d1f0763b61b0f710d9b664
 docs/users_guide/extending_ghc.rst |  2 +-
 docs/users_guide/glasgow_exts.rst  | 21 ++++++++++++---------
 docs/users_guide/safe_haskell.rst  |  5 -----
 3 files changed, 13 insertions(+), 15 deletions(-)

diff --git a/docs/users_guide/extending_ghc.rst b/docs/users_guide/extending_ghc.rst
index 10c1b3d..a7fb538 100644
--- a/docs/users_guide/extending_ghc.rst
+++ b/docs/users_guide/extending_ghc.rst
@@ -425,7 +425,7 @@ will print out the name of any top-level non-recursive binding with the
     import Control.Monad (unless)
     import Data.Data
 
-    data SomeAnn = SomeAnn deriving (Data, Typeable)
+    data SomeAnn = SomeAnn deriving Data
 
     plugin :: Plugin
     plugin = defaultPlugin {
diff --git a/docs/users_guide/glasgow_exts.rst b/docs/users_guide/glasgow_exts.rst
index c738862..c116a5e 100644
--- a/docs/users_guide/glasgow_exts.rst
+++ b/docs/users_guide/glasgow_exts.rst
@@ -3590,8 +3590,7 @@ automatically derived:
    ``Functor``, defined in ``GHC.Base``. See :ref:`deriving-functor`.
 
 -  With :ghc-flag:`-XDeriveDataTypeable`, you can derive instances of the class
-   ``Data``, defined in ``Data.Data``. See :ref:`deriving-typeable` for
-   deriving ``Typeable``.
+   ``Data``, defined in ``Data.Data``. See :ref:`deriving-data`.
 
 -  With :ghc-flag:`-XDeriveFoldable`, you can derive instances of the class
    ``Foldable``, defined in ``Data.Foldable``. See
@@ -3906,14 +3905,19 @@ For a full specification of the algorithms used in :ghc-flag:`-XDeriveFunctor`,
 :ghc-flag:`-XDeriveFoldable`, and :ghc-flag:`-XDeriveTraversable`, see
 :ghc-wiki:`this wiki page <Commentary/Compiler/DeriveFunctor>`.
 
-.. _deriving-typeable:
+.. _deriving-data:
 
-Deriving ``Typeable`` instances
+Deriving ``Data`` instances
 -------------------------------
 
 .. ghc-flag:: -XDeriveDataTypeable
 
-    Enable automatic deriving of instances for the ``Typeable`` typeclass
+    Enable automatic deriving of instances for the ``Data`` typeclass
+
+.. _deriving-typeable:
+
+Deriving ``Typeable`` instances
+-------------------------------
 
 The class ``Typeable`` is very special:
 
@@ -3924,8 +3928,9 @@ The class ``Typeable`` is very special:
    ensures that the programmer cannot subvert the type system by writing
    bogus instances.
 
--  Derived instances of ``Typeable`` are ignored, and may be reported as
-   an error in a later version of the compiler.
+-  Derived instances of ``Typeable`` may be declared if the
+   :ghc-flag:`-XDeriveDataTypeable` extension is enabled, but they are ignored,
+   and they may be reported as an error in a later version of the compiler.
 
 -  The rules for solving \`Typeable\` constraints are as follows:
 
@@ -12355,7 +12360,6 @@ That being said, with the appropriate use of wrapper datatypes, the
 above limitations induce no loss of generality: ::
 
     {-# LANGUAGE ConstraintKinds           #-}
-    {-# LANGUAGE DeriveDataTypeable        #-}
     {-# LANGUAGE ExistentialQuantification #-}
     {-# LANGUAGE Rank2Types                #-}
     {-# LANGUAGE StandaloneDeriving        #-}
@@ -12366,7 +12370,6 @@ above limitations induce no loss of generality: ::
     import GHC.StaticPtr
 
     data Dict c = c => Dict
-      deriving Typeable
 
     g1 :: Typeable a => StaticPtr (Dict (Show a) -> a -> String)
     g1 = static (\Dict -> show)
diff --git a/docs/users_guide/safe_haskell.rst b/docs/users_guide/safe_haskell.rst
index 5193f06..cdd5228 100644
--- a/docs/users_guide/safe_haskell.rst
+++ b/docs/users_guide/safe_haskell.rst
@@ -273,11 +273,6 @@ Furthermore, we restrict the following features:
   this reason, the ``Data.Coerce`` module is also considered unsafe. We are
   hoping to find a better solution here in the future.
 
-- ``Data.Typeable`` — Hand crafted instances of the Typeable type class are not allowed
-  in Safe Haskell as this can easily be abused to unsafely coerce
-  between types. Derived instances (through the :ghc-flag:`-XDeriveDataTypeable`
-  extension) are still allowed.
-
 - ``GHC.Generics`` — Hand crafted instances of the ``Generic`` type class are
   not allowed in Safe Haskell. Such instances aren't strictly unsafe, but
   there is an important invariant that a ``Generic`` instance should adhere to