Drop deprecated `OverlappingInstances` from base

With #9242 the `OverlappingInstances` extension got deprecated, this
commit adapts the only two remaining places in `base` where it was still
used.

Starting with this commit, the `Typeable (s t)` instance (which seemingly
was the motivation for using `OverlappingInstances` in the first place
when `Typeable` was neither polykinded nor auto-derived-only, see also
commit ce3fd0e02826367e6134a3362d8d37aa114236f5 which introduced
overlapping instances) does no longer allow overlapping instances, and
there doesn't seem to be any good reason to keep allowing overlapping
instance now.

This also removes redundant `LANGUAGE`/`OPTIONS_GHC` pragmas from
`Data.Typeable` and refactors the language pragmas into more uniform
single-line pragmas.

Reviewed By: austin

Differential Revision: https://phabricator.haskell.org/D377

diff --git a/libraries/base/Data/Typeable.hs b/libraries/base/Data/Typeable.hs
index f658a9e..ddb9582 100644 (file)
--- a/libraries/base/Data/Typeable.hs
+++ b/libraries/base/Data/Typeable.hs
@@ -1,20 +1,9 @@
+{-# LANGUAGE GADTs #-}
+{-# LANGUAGE NoImplicitPrelude #-}
+{-# LANGUAGE PolyKinds #-}
+{-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE Trustworthy #-}
-{-# LANGUAGE NoImplicitPrelude
-           , OverlappingInstances
-           , ScopedTypeVariables
-           , FlexibleInstances
-           , TypeOperators
-           , PolyKinds
-           , GADTs
-           , MagicHash
-  #-}
-{-# OPTIONS_GHC -funbox-strict-fields #-}
-
--- The -XOverlappingInstances flag allows the user to over-ride
--- the instances for Typeable given here.  In particular, we provide an instance
---      instance ... => Typeable (s a) 
--- But a user might want to say
---      instance ... => Typeable (MyType a b)
+{-# LANGUAGE TypeOperators #-}
 
 -----------------------------------------------------------------------------
 -- |

diff --git a/libraries/base/Data/Typeable/Internal.hs b/libraries/base/Data/Typeable/Internal.hs
index 140b895..475f083 100644 (file)
--- a/libraries/base/Data/Typeable/Internal.hs
+++ b/libraries/base/Data/Typeable/Internal.hs
@@ -1,5 +1,16 @@
-{-# LANGUAGE Unsafe             #-}
 {-# LANGUAGE BangPatterns #-}
+{-# LANGUAGE CPP #-}
+{-# LANGUAGE ConstraintKinds #-}
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE DeriveDataTypeable #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE MagicHash #-}
+{-# LANGUAGE NoImplicitPrelude #-}
+{-# LANGUAGE PolyKinds #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE StandaloneDeriving #-}
+{-# LANGUAGE UndecidableInstances #-}
+{-# LANGUAGE Unsafe #-}
 
 -----------------------------------------------------------------------------
 -- |
@@ -13,20 +24,6 @@
 --
 -----------------------------------------------------------------------------
 
-{-# LANGUAGE CPP
-           , NoImplicitPrelude
-           , OverlappingInstances
-           , ScopedTypeVariables
-           , FlexibleInstances
-           , MagicHash
-           , KindSignatures
-           , PolyKinds
-           , ConstraintKinds
-           , DeriveDataTypeable
-           , DataKinds
-           , UndecidableInstances
-           , StandaloneDeriving #-}
-
 module Data.Typeable.Internal (
     Proxy (..),
     TypeRep(..),

diff --git a/libraries/base/base.cabal b/libraries/base/base.cabal
index 957053d..6277d89 100644 (file)
--- a/libraries/base/base.cabal
+++ b/libraries/base/base.cabal
@@ -69,7 +69,6 @@ Library
         NegativeLiterals
         NoImplicitPrelude
         NondecreasingIndentation
-        OverlappingInstances
         OverloadedStrings
         ParallelArrays
         PolyKinds