Add a warning for tabs in source files

compiler/cmm/CmmParse.y

@@ -46,8 +46,9 @@ import Panic
 import Constants
 import Outputable
 
-import Control.Monad	( when )
+import Control.Monad
 import Data.Char	( ord )
+import System.Exit
 
 #include "HsVersions.h"
 }
@@ -918,9 +919,12 @@ parseCmmFile dflags filename = do
 		-- in there we don't want.
   case unP cmmParse init_state of
     PFailed span err -> do printError span err; return Nothing
-    POk _ code -> do
+    POk pst code -> do
 	cmm <- initC dflags no_module (getCmm (unEC code initEnv [] >> return ()))
-	dumpIfSet_dyn dflags Opt_D_dump_cmm "Cmm" (pprCmms [cmm])
+	let ms = getMessages pst
+	printErrorsAndWarnings dflags ms
+        when (errorsFound dflags ms) $ exitWith (ExitFailure 1)
+        dumpIfSet_dyn dflags Opt_D_dump_cmm "Cmm" (pprCmms [cmm])
 	return (Just cmm)
   where
 	no_module = panic "parseCmmFile: no module"

compiler/main/DynFlags.hs

@@ -156,6 +156,7 @@ data DynFlag
    | Opt_WarnDeprecations
    | Opt_WarnDodgyImports
    | Opt_WarnOrphans
+   | Opt_WarnTabs
 
    -- language opts
    | Opt_AllowOverlappingInstances
@@ -1032,6 +1033,7 @@ fFlags = [
   ( "warn-unused-matches",       	Opt_WarnUnusedMatches ),
   ( "warn-deprecations",         	Opt_WarnDeprecations ),
   ( "warn-orphans",	         	Opt_WarnOrphans ),
+  ( "warn-tabs",	         	Opt_WarnTabs ),
   ( "fi",				Opt_FFI ),  -- support `-ffi'...
   ( "ffi",				Opt_FFI ),  -- ...and also `-fffi'
   ( "arrows",				Opt_Arrows ), -- arrow syntax

compiler/main/HeaderInfo.hs

@@ -15,8 +15,7 @@ module HeaderInfo ( getImportsFromFile, getImports
 #include "HsVersions.h"
 
 import Parser		( parseHeader )
-import Lexer		( P(..), ParseResult(..), mkPState, pragState
-                        , lexer, Token(..), PState(..) )
+import Lexer
 import FastString
 import HsSyn		( ImportDecl(..), HsModule(..) )
 import Module		( ModuleName, moduleName )
@@ -25,7 +24,7 @@ import StringBuffer	( StringBuffer(..), hGetStringBuffer, hGetStringBufferBlock
                         , appendStringBuffers )
 import SrcLoc
 import FastString	( mkFastString )
-import DynFlags	( DynFlags )
+import DynFlags
 import ErrUtils
 import Util
 import Outputable
@@ -37,6 +36,8 @@ import Bag		( emptyBag, listToBag )
 import Distribution.Compiler
 
 import Control.Exception
+import Control.Monad
+import System.Exit
 import System.IO
 import Data.List
 
@@ -65,7 +66,10 @@ getImports dflags buf filename = do
   let loc  = mkSrcLoc (mkFastString filename) 1 0
   case unP parseHeader (mkPState buf loc dflags) of
 	PFailed span err -> parseError span err
-	POk _ rdr_module -> 
+	POk pst rdr_module -> do
+          let ms = getMessages pst
+          printErrorsAndWarnings dflags ms
+          when (errorsFound dflags ms) $ exitWith (ExitFailure 1)
 	  case rdr_module of
 	    L _ (HsModule mb_mod _ imps _ _ _ _ _) ->
 	      let

compiler/main/HscMain.lhs

@@ -54,7 +54,7 @@ import HsSyn		( HsModule, LHsBinds, HsGroup, LIE, LImportDecl, HsDoc,
 import SrcLoc		( Located(..) )
 import StringBuffer	( hGetStringBuffer, stringToStringBuffer )
 import Parser
-import Lexer		( P(..), ParseResult(..), mkPState )
+import Lexer
 import SrcLoc		( mkSrcLoc )
 import TcRnDriver	( tcRnModule, tcRnExtCore )
 import TcIface		( typecheckIface )
@@ -93,6 +93,7 @@ import UniqFM		( emptyUFM )
 import Bag		( unitBag )
 
 import Control.Monad
+import System.Exit
 import System.IO
 import Data.IORef
 \end{code}
@@ -737,8 +738,12 @@ myParseModule dflags src_filename maybe_src_buf
 
 	PFailed span err -> return (Left (mkPlainErrMsg span err));
 
-	POk _ rdr_module -> do {
+	POk pst rdr_module -> do {
 
+      let {ms = getMessages pst};
+      printErrorsAndWarnings dflags ms;
+      when (errorsFound dflags ms) $ exitWith (ExitFailure 1);
+      
       dumpIfSet_dyn dflags Opt_D_dump_parsed "Parser" (ppr rdr_module) ;
       
       dumpIfSet_dyn dflags Opt_D_source_stats "Source Statistics"
@@ -893,7 +898,11 @@ hscParseThing parser dflags str
 	PFailed span err -> do { printError span err;
                                  return Nothing };
 
-	POk _ thing -> do {
+	POk pst thing -> do {
+
+      let {ms = getMessages pst};
+      printErrorsAndWarnings dflags ms;
+      when (errorsFound dflags ms) $ exitWith (ExitFailure 1);
 
       --ToDo: can't free the string buffer until we've finished this
       -- compilation sweep and all the identifiers have gone away.

compiler/parser/Lexer.x

@@ -25,6 +25,7 @@ module Lexer (
    Token(..), lexer, pragState, mkPState, PState(..),
    P(..), ParseResult(..), getSrcLoc, 
    failLocMsgP, failSpanMsgP, srcParseFail,
+   getMessages,
    popContext, pushCurrentContext, setLastToken, setSrcLoc,
    getLexState, popLexState, pushLexState,
    extension, glaExtsEnabled, bangPatEnabled
@@ -32,7 +33,8 @@ module Lexer (
 
 #include "HsVersions.h"
 
-import ErrUtils		( Message )
+import Bag
+import ErrUtils
 import Outputable
 import StringBuffer
 import FastString
@@ -43,6 +45,7 @@ import DynFlags
 import Ctype
 import Util		( maybePrefixMatch, readRational )
 
+import Control.Monad
 import Data.Bits
 import Data.Char 	( chr, isSpace )
 import Data.Ratio
@@ -56,8 +59,9 @@ import Compat.Unicode	( GeneralCategory(..), generalCategory, isPrint, isUpper )
 }
 
 $unispace    = \x05
-$whitechar   = [\ \t\n\r\f\v\xa0 $unispace]
+$whitechar   = [\ \n\r\f\v\xa0 $unispace]
 $white_no_nl = $whitechar # \n
+$tab         = \t
 
 $ascdigit  = 0-9
 $unidigit  = \x03
@@ -108,6 +112,7 @@ haskell :-
 
 -- everywhere: skip whitespace and comments
 $white_no_nl+ 				;
+$tab+         { warn Opt_WarnTabs (text "Tab character") }
 
 -- Everywhere: deal with nested comments.  We explicitly rule out
 -- pragmas, "{-#", so that we don't accidentally treat them as comments.
@@ -1298,6 +1303,14 @@ getCharOrFail =  do
 	Nothing -> lexError "unexpected end-of-file in string/character literal"
 	Just (c,i)  -> do setInput i; return c
 
+-- -----------------------------------------------------------------------------
+-- Warnings
+
+warn :: DynFlag -> SDoc -> Action
+warn option warning span _buf _len = do
+    addWarning option (mkWarnMsg span alwaysQualify warning)
+    lexToken
+
 -- -----------------------------------------------------------------------------
 -- The Parse Monad
 
@@ -1316,6 +1329,8 @@ data ParseResult a
 
 data PState = PState { 
 	buffer	   :: StringBuffer,
+    dflags     :: DynFlags,
+    messages   :: Messages,
         last_loc   :: SrcSpan,	-- pos of previous token
         last_offs  :: !Int, 	-- offset of the previous token from the
 				-- beginning of  the current line.
@@ -1500,6 +1515,10 @@ pragState :: StringBuffer -> SrcLoc -> PState
 pragState buf loc  = 
   PState {
       buffer	      = buf,
+      messages      = emptyMessages,
+      -- XXX defaultDynFlags is not right, but we don't have a real
+      -- dflags handy
+      dflags        = defaultDynFlags,
       last_loc      = mkSrcSpan loc loc,
       last_offs     = 0,
       last_len      = 0,
@@ -1517,6 +1536,8 @@ mkPState :: StringBuffer -> SrcLoc -> DynFlags -> PState
 mkPState buf loc flags  = 
   PState {
       buffer	      = buf,
+      dflags        = flags,
+      messages      = emptyMessages,
       last_loc      = mkSrcSpan loc loc,
       last_offs     = 0,
       last_len      = 0,
@@ -1543,6 +1564,15 @@ mkPState buf loc flags  =
       b `setBitIf` cond | cond      = bit b
 			| otherwise = 0
 
+addWarning :: DynFlag -> WarnMsg -> P ()
+addWarning option w
+ = P $ \s@PState{messages=(ws,es), dflags=d} ->
+       let ws' = if dopt option d then ws `snocBag` w else ws
+       in POk s{messages=(ws', es)} ()
+
+getMessages :: PState -> Messages
+getMessages PState{messages=ms} = ms
+
 getContext :: P [LayoutContext]
 getContext = P $ \s@PState{context=ctx} -> POk s ctx
 

docs/users_guide/flags.xml

@@ -813,6 +813,13 @@
 	    <entry><option>-fno-warn-simple-patterns</option></entry>
 	  </row>
 
+	  <row>
+	    <entry><option>-fwarn-tabs</option></entry>
+	    <entry>warn if there are tabs in the source file</entry>
+	    <entry>dynamic</entry>
+	    <entry><option>-fno-warn-tabs</option></entry>
+	  </row>
+
 	  <row>
 	    <entry><option>-fwarn-type-defaults</option></entry>
 	    <entry>warn when defaulting happens</entry>

docs/users_guide/using.xml

@@ -1096,6 +1096,18 @@ f "2"    = 2
 	</listitem>
       </varlistentry>
 
+      <varlistentry>
+	<term><option>-fwarn-tabs</option>:</term>
+	<listitem>
+	  <indexterm><primary><option>-fwarn-tabs</option></primary></indexterm>
+	  <indexterm><primary>tabs, warning</primary></indexterm>
+	  <para>Have the compiler warn if there are tabs in your source
+          file.</para>
+
+	  <para>This warning is off by default.</para>
+	</listitem>
+      </varlistentry>
+
       <varlistentry>
 	<term><option>-fwarn-type-defaults</option>:</term>
 	<listitem>