Record the original text along with parsed Rationals: fixes #2245

compiler/basicTypes/BasicTypes.lhs

@@ -72,13 +72,16 @@ module BasicTypes(
         inlinePragmaActivation, inlinePragmaRuleMatchInfo,
         setInlinePragmaActivation, setInlinePragmaRuleMatchInfo,
 
-	SuccessFlag(..), succeeded, failed, successIf
+	SuccessFlag(..), succeeded, failed, successIf,
+	
+	FractionalLit(..)
    ) where
 
 import FastString
 import Outputable
 
 import Data.Data hiding (Fixity)
+import Data.Function (on)
 \end{code}
 
 %************************************************************************
@@ -862,3 +865,25 @@ isEarlyActive (ActiveBefore {}) = True
 isEarlyActive _		        = False
 \end{code}
 
+
+
+\begin{code}
+-- Used to represent exactly the floating point literal that we encountered in
+-- the user's source program. This allows us to pretty-print exactly what the user
+-- wrote, which is important e.g. for floating point numbers that can't represented
+-- as Doubles (we used to via Double for pretty-printing). See also #2245.
+data FractionalLit
+  = FL { fl_text :: String         -- How the value was written in the source
+       , fl_value :: Rational      -- Numeric value of the literal
+       }
+  deriving (Data, Typeable)
+
+-- Comparison operations are needed when grouping literals
+-- for compiling pattern-matching (module MatchLit)
+
+instance Eq FractionalLit where
+  (==) = (==) `on` fl_value
+
+instance Ord FractionalLit where
+  compare = compare `on` fl_value
+\end{code}

compiler/deSugar/Check.lhs

@@ -30,6 +30,7 @@ import Type
 import SrcLoc
 import UniqSet
 import Util
+import BasicTypes
 import Outputable
 import FastString
 \end{code}
@@ -437,7 +438,7 @@ get_lit :: Pat id -> Maybe HsLit
 -- with other HsLits gotten in the same way
 get_lit (LitPat lit)				          = Just lit
 get_lit (NPat (OverLit { ol_val = HsIntegral i})    mb _) = Just (HsIntPrim   (mb_neg mb i))
-get_lit (NPat (OverLit { ol_val = HsFractional f }) mb _) = Just (HsFloatPrim (mb_neg mb f))
+get_lit (NPat (OverLit { ol_val = HsFractional f }) mb _) = Just (HsFloatPrim (mb_neg mb (fl_value f)))
 get_lit (NPat (OverLit { ol_val = HsIsString s })   _  _) = Just (HsStringPrim s)
 get_lit _                                	          = Nothing
 

compiler/deSugar/DsMeta.hs

@@ -1595,7 +1595,7 @@ repOverloadedLiteral (OverLit { ol_val = val})
 
 mk_lit :: OverLitVal -> DsM HsLit
 mk_lit (HsIntegral i)   = mk_integer  i
-mk_lit (HsFractional f) = mk_rational f
+mk_lit (HsFractional f) = mk_rational (fl_value f)
 mk_lit (HsIsString s)   = mk_string   s
               
 --------------- Miscellaneous -------------------

compiler/deSugar/MatchLit.lhs

@@ -33,6 +33,7 @@ import Literal
 import SrcLoc
 import Data.Ratio
 import Outputable
+import BasicTypes
 import Util
 import FastString
 \end{code}
@@ -124,8 +125,8 @@ hsOverLitKey (OverLit { ol_val = l }) neg = litValKey l neg
 litValKey :: OverLitVal -> Bool -> Literal
 litValKey (HsIntegral i)   False = MachInt i
 litValKey (HsIntegral i)   True  = MachInt (-i)
-litValKey (HsFractional r) False = MachFloat r
-litValKey (HsFractional r) True  = MachFloat (-r)
+litValKey (HsFractional r) False = MachFloat (fl_value r)
+litValKey (HsFractional r) True  = MachFloat (negate (fl_value r))
 litValKey (HsIsString s)   neg   = ASSERT( not neg) MachStr s
 \end{code}
 
@@ -190,8 +191,8 @@ tidyNPat tidy_lit_pat (OverLit val False _ ty) mb_neg _
     mb_rat_lit = case (mb_neg, val) of
 		   (Nothing, HsIntegral   i) -> Just (fromInteger i)
 		   (Just _,  HsIntegral   i) -> Just (fromInteger (-i))
-		   (Nothing, HsFractional f) -> Just f
-		   (Just _, HsFractional f)  -> Just (-f)
+		   (Nothing, HsFractional f) -> Just (fl_value f)
+		   (Just _, HsFractional f)  -> Just (negate (fl_value f))
 		   _ -> Nothing
 	
     mb_str_lit :: Maybe FastString

compiler/hsSyn/Convert.lhs

@@ -568,7 +568,7 @@ cvtOverLit :: Lit -> CvtM (HsOverLit RdrName)
 cvtOverLit (IntegerL i)  
   = do { force i; return $ mkHsIntegral i placeHolderType}
 cvtOverLit (RationalL r) 
-  = do { force r; return $ mkHsFractional r placeHolderType}
+  = do { force r; return $ mkHsFractional (FL { fl_text = show (fromRational r :: Double), fl_value = r }) placeHolderType}
 cvtOverLit (StringL s)   
   = do { let { s' = mkFastString s }
        ; force s'

compiler/hsSyn/HsLit.lhs

@@ -12,7 +12,8 @@ module HsLit where
 #include "HsVersions.h"
 
 import {-# SOURCE #-} HsExpr( SyntaxExpr, pprExpr )
-import HsTypes (PostTcType)
+import BasicTypes ( FractionalLit(..) )
+import HsTypes  ( PostTcType )
 import Type	( Type )
 import Outputable
 import FastString
@@ -70,7 +71,7 @@ data HsOverLit id 	-- An overloaded literal
 
 data OverLitVal
   = HsIntegral   !Integer   	-- Integer-looking literals;
-  | HsFractional !Rational   	-- Frac-looking literals
+  | HsFractional !FractionalLit	-- Frac-looking literals
   | HsIsString   !FastString 	-- String-looking literals
   deriving (Data, Typeable)
 
@@ -155,6 +156,6 @@ instance OutputableBndr id => Outputable (HsOverLit id) where
 
 instance Outputable OverLitVal where
   ppr (HsIntegral i)   = integer i 
-  ppr (HsFractional f) = rational f
+  ppr (HsFractional f) = text (fl_text f)
   ppr (HsIsString s)   = pprHsString s
 \end{code}

compiler/hsSyn/HsUtils.lhs

@@ -187,7 +187,7 @@ mkSimpleHsAlt pat expr
 -- See RnEnv.lookupSyntaxName
 
 mkHsIntegral   :: Integer -> PostTcType -> HsOverLit id
-mkHsFractional :: Rational -> PostTcType -> HsOverLit id
+mkHsFractional :: FractionalLit -> PostTcType -> HsOverLit id
 mkHsIsString   :: FastString -> PostTcType -> HsOverLit id
 mkHsDo         :: HsStmtContext Name -> [LStmt id] -> HsExpr id
 mkHsComp       :: HsStmtContext Name -> [LStmt id] -> LHsExpr id -> HsExpr id

compiler/parser/Lexer.x

@@ -68,7 +68,7 @@ import UniqFM
 import DynFlags
 import Module
 import Ctype
-import BasicTypes	( InlineSpec(..), RuleMatchInfo(..) )
+import BasicTypes	( InlineSpec(..), RuleMatchInfo(..), FractionalLit(..) )
 import Util		( readRational )
 
 import Control.Monad
@@ -541,7 +541,7 @@ data Token
   | ITchar       Char
   | ITstring     FastString
   | ITinteger    Integer
-  | ITrational   Rational
+  | ITrational   FractionalLit
 
   | ITprimchar   Char
   | ITprimstring FastString
@@ -1061,7 +1061,7 @@ hexadecimal = (16,hexDigit)
 
 -- readRational can understand negative rationals, exponents, everything.
 tok_float, tok_primfloat, tok_primdouble :: String -> Token
-tok_float        str = ITrational   $! readRational str
+tok_float        str = ITrational   $! FL { fl_text = str, fl_value = readRational str }
 tok_primfloat    str = ITprimfloat  $! readRational str
 tok_primdouble   str = ITprimdouble $! readRational str
 

compiler/typecheck/Inst.lhs

@@ -56,6 +56,7 @@ import PrelNames
 import SrcLoc
 import DynFlags
 import Bag
+import BasicTypes
 import Maybes
 import Util
 import Outputable
@@ -276,7 +277,7 @@ mkOverLit (HsIntegral i)
 
 mkOverLit (HsFractional r)
   = do	{ rat_ty <- tcMetaTy rationalTyConName
-	; return (HsRat r rat_ty) }
+	; return (HsRat (fl_value r) rat_ty) }
 
 mkOverLit (HsIsString s) = return (HsString s)
 \end{code}

compiler/typecheck/TcHsSyn.lhs

@@ -121,7 +121,7 @@ shortCutLit (HsIntegral i) ty
   | isIntTy ty && inIntRange i   = Just (HsLit (HsInt i))
   | isWordTy ty && inWordRange i = Just (mkLit wordDataCon (HsWordPrim i))
   | isIntegerTy ty 	       	 = Just (HsLit (HsInteger i ty))
-  | otherwise		       	 = shortCutLit (HsFractional (fromInteger i)) ty
+  | otherwise		       	 = shortCutLit (HsFractional (FL { fl_text = show i, fl_value = fromInteger i })) ty
 	-- The 'otherwise' case is important
 	-- Consider (3 :: Float).  Syntactically it looks like an IntLit,
 	-- so we'll call shortCutIntLit, but of course it's a float
@@ -129,8 +129,8 @@ shortCutLit (HsIntegral i) ty
 	-- literals, compiled without -O
 
 shortCutLit (HsFractional f) ty
-  | isFloatTy ty  = Just (mkLit floatDataCon  (HsFloatPrim f))
-  | isDoubleTy ty = Just (mkLit doubleDataCon (HsDoublePrim f))
+  | isFloatTy ty  = Just (mkLit floatDataCon  (HsFloatPrim (fl_value f)))
+  | isDoubleTy ty = Just (mkLit doubleDataCon (HsDoublePrim (fl_value f)))
   | otherwise     = Nothing
 
 shortCutLit (HsIsString s) ty