Remove warnings-silencing flags for code generated by Alex

Current versions of Alex don't seem to produce as many warnings any
more.

In order to silence a warning and to avoid overlong lines, I've taken
the liberty of refactoring 'tok_num'.

Test Plan: ./validate

Reviewers: bgamari, simonmar

Reviewed By: simonmar

Subscribers: erikd, rwbarton, carter

Differential Revision: https://phabricator.haskell.org/D5319

1 files changed, 9 insertions, 45 deletions

diff --git a/compiler/parser/Lexer.x b/compiler/parser/Lexer.x
index f99a344d31..9597f10b0a 100644
--- a/compiler/parser/Lexer.x
+++ b/compiler/parser/Lexer.x
@@ -42,13 +42,7 @@
 
 {
 {-# LANGUAGE BangPatterns #-}
-
--- See Note [Warnings in code generated by Alex] in compiler/parser/Lexer.x
-{-# 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 #-}
+{-# LANGUAGE LambdaCase #-}
 
 {-# OPTIONS_GHC -funbox-strict-fields #-}
 
@@ -1388,13 +1382,15 @@ tok_integral itint transint transbuf translen (radix,char_to_int) span buf len =
        (offsetBytes transbuf buf) (subtract translen len) radix char_to_int
 
 tok_num :: (Integer -> Integer)
-                        -> Int -> Int
-                        -> (Integer, (Char->Int)) -> Action
-tok_num = tok_integral itint
+        -> Int -> Int
+        -> (Integer, (Char->Int)) -> Action
+tok_num = tok_integral $ \case
+    st@(SourceText ('-':_)) -> itint st (const True)
+    st@(SourceText _)       -> itint st (const False)
+    st@NoSourceText         -> itint st (< 0)
   where
-    itint st@(SourceText ('-':str)) val = ITinteger (((IL $! st) $! True)      $! val)
-    itint st@(SourceText      str ) val = ITinteger (((IL $! st) $! False)     $! val)
-    itint st@(NoSourceText        ) val = ITinteger (((IL $! st) $! (val < 0)) $! val)
+    itint :: SourceText -> (Integer -> Bool) -> Integer -> Token
+    itint !st is_negative !val = ITinteger ((IL st $! is_negative val) val)
 
 tok_primint :: (Integer -> Integer)
             -> Int -> Int
@@ -3114,36 +3110,4 @@ isDocComment (ITdocCommentNamed _)   = True
 isDocComment (ITdocSection      _ _) = True
 isDocComment (ITdocOptions      _)   = True
 isDocComment _ = False
-
-{- Note [Warnings in code generated by Alex]
-
-We add the following warning suppression flags to all code generated by Alex:
-
-{-# 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 #-}
-
-Without these flags, current versions of Alex will generate code that is not
-warning free. Note that this is the result of Alex' internals, not of the way
-we have written our (Lexer).x files.
-
-As always, we need code to be warning free when validating with -Werror.
-
-The list of flags is as short as possible (at the time of writing), to try to
-avoid suppressing warnings for bugs in our own code.
-
-TODO. Reevaluate this situation once Alex >3.1.4 is released. Hopefully you
-can remove these flags from all (Lexer).x files in the repository, and also
-delete this Note. Don't forget to update aclocal.m4, and send a HEADS UP
-message to ghc-devs.
-
-The first release of Alex after 3.1.4 will either suppress all warnings itself
-[1] (bad), or most warnings will be fixed and only a few select ones will be
-suppressed by default [2] (better).
-
-[1] https://github.com/simonmar/alex/commit/1eefcde22ba1bb9b51d523814415714e20f0761e
-[2] https://github.com/simonmar/alex/pull/69
--}
 }