\section[HsLit]{Abstract syntax: source-language literals}
\begin{code}
+{-# LANGUAGE DeriveDataTypeable #-}
+
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
-import Ratio ( Rational )
+
+import Data.Data
\end{code}
-- (overloaded literals are done with HsOverLit)
| HsFloatPrim Rational -- Unboxed Float
| HsDoublePrim Rational -- Unboxed Double
+ deriving (Data, Typeable)
instance Eq HsLit where
(HsChar x1) == (HsChar x2) = x1==x2
data HsOverLit id -- An overloaded literal
= OverLit {
ol_val :: OverLitVal,
- ol_rebindable :: Bool, -- True <=> rebindable syntax
- -- False <=> standard syntax
+ ol_rebindable :: Bool, -- Note [ol_rebindable]
ol_witness :: SyntaxExpr id, -- Note [Overloaded literal witnesses]
ol_type :: PostTcType }
+ deriving (Data, Typeable)
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)
overLitType :: HsOverLit a -> Type
overLitType = ol_type
\end{code}
+Note [ol_rebindable]
+~~~~~~~~~~~~~~~~~~~~
+The ol_rebindable field is True if this literal is actually
+using rebindable syntax. Specifically:
+
+ False iff ol_witness is the standard one
+ True iff ol_witness is non-standard
+
+Equivalently it's True if
+ a) RebindableSyntax is on
+ b) the witness for fromInteger/fromRational/fromString
+ that happens to be in scope isn't the standard one
+
Note [Overloaded literal witnesses]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*Before* type checking, the SyntaxExpr in an HsOverLit is the
This dual role is unusual, because we're replacing 'fromInteger' with
a call to fromInteger. Reason: it allows commoning up of the fromInteger
-calls, which wouldn't be possible if the desguarar made the application
+calls, which wouldn't be possible if the desguarar made the application.
The PostTcType in each branch records the type the overload literal is
found to have.
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}