Replace usages of `-w` by `-fno-warn`s

And remove unused imports and language pragmas.

I checked that the minimum Happy and Alex version requirements, as
listed in aclocal.m4, don't have to change. Before building ghc, I ran:
  - cabal install happy==1.19.4 --with-ghc=ghc-7.8.4
  - cabal install alex==3.1.0 --with-ghc=ghc-7.6.3

Differential Revision: https://phabricator.haskell.org/D1032

2 files changed, 11 insertions, 20 deletions

diff --git a/compiler/parser/Lexer.x b/compiler/parser/Lexer.x
index 2e883fd102..1ee5c0315f 100644
--- a/compiler/parser/Lexer.x
+++ b/compiler/parser/Lexer.x
@@ -43,15 +43,17 @@
 {
 -- XXX The above flags turn off warnings in the generated code:
 {-# LANGUAGE BangPatterns #-}
-{-# LANGUAGE DeriveDataTypeable #-}
 {-# OPTIONS_GHC -fno-warn-unused-matches #-}
 {-# OPTIONS_GHC -fno-warn-unused-binds #-}
-{-# OPTIONS_GHC -fno-warn-unused-imports #-}
+{-# OPTIONS_GHC -fno-warn-tabs #-}
 {-# OPTIONS_GHC -fno-warn-missing-signatures #-}
--- But alex still generates some code that causes the "lazy unlifted bindings"
--- warning, and old compilers don't know about it so we can't easily turn
--- it off, so for now we use the sledge hammer:
-{-# OPTIONS_GHC -w #-}
+{-# OPTIONS_GHC -fno-warn-overlapping-patterns #-}
+{-# OPTIONS_GHC -fno-warn-incomplete-patterns #-}
+-- The above warning suppression flags are a temporary kludge.
+-- While working on this module you are encouraged to remove it and fix
+-- any warnings in the module. See
+--     http://ghc.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
+-- for details
 
 {-# OPTIONS_GHC -funbox-strict-fields #-}
 
@@ -77,13 +79,14 @@ module Lexer (
   ) where
 
 -- base
+#if __GLASGOW_HASKELL__ < 709
 import Control.Applicative
+#endif
 import Control.Monad
 import Data.Bits
-import Data.Char
+import Data.Char hiding (ord)
 import Data.List
 import Data.Maybe
-import Data.Ratio
 import Data.Word
 
 -- bytestring
@@ -93,10 +96,6 @@ import Data.ByteString (ByteString)
 import Data.Map (Map)
 import qualified Data.Map as Map
 
--- data/typeable
-import Data.Data
-import Data.Typeable
-
 -- compiler/utils
 import Bag
 import Outputable
diff --git a/compiler/parser/Parser.y b/compiler/parser/Parser.y
index b20b50c91b..a2d89b2498 100644
--- a/compiler/parser/Parser.y
+++ b/compiler/parser/Parser.y
@@ -8,14 +8,6 @@
 -- ---------------------------------------------------------------------------
 
 {
-{-# LANGUAGE BangPatterns #-} -- required for versions of Happy before 1.18.6
-{-# OPTIONS -Wwarn -w #-}
--- The above warning suppression flag is a temporary kludge.
--- While working on this module you are encouraged to remove it and fix
--- any warnings in the module. See
---     http://ghc.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
--- for details
-
 -- | This module provides the generated Happy parser for Haskell. It exports
 -- a number of parsers which may be used in any library that uses the GHC API.
 -- A common usage pattern is to initialize the parser state with a given string