hsSyn/HsLit.hs

    {-
    (c) The University of Glasgow 2006
    (c) The GRASP/AQUA Project, Glasgow University, 1992-1998

    \section[HsLit]{Abstract syntax: source-language literals}
    -}

    {-# LANGUAGE CPP, DeriveDataTypeable #-}
    {-# LANGUAGE TypeSynonymInstances #-}
    {-# LANGUAGE StandaloneDeriving #-}
    {-# LANGUAGE FlexibleInstances #-}
    {-# LANGUAGE FlexibleContexts #-}
    {-# LANGUAGE UndecidableInstances #-} -- Note [Pass sensitive types]
                                          -- in module PlaceHolder
    {-# LANGUAGE ConstraintKinds #-}

    module HsLit where

    #include "HsVersions.h"

    import {-# SOURCE #-} HsExpr( HsExpr, pprExpr )
    import BasicTypes ( FractionalLit(..),SourceText(..),pprWithSourceText )
    import Type       ( Type )
    import Outputable
    import FastString
    import PlaceHolder ( PostTc,PostRn,DataId,OutputableBndrId )

    import Data.ByteString (ByteString)
    import Data.Data hiding ( Fixity )

    {-
    ************************************************************************
    *                                                                      *
    \subsection[HsLit]{Literals}
    *                                                                      *
    ************************************************************************
    -}

    -- Note [Literal source text] in BasicTypes for SourceText fields in
    -- the following
    -- | Haskell Literal
    data HsLit
      = HsChar          SourceText Char
          -- ^ Character
      | HsCharPrim      SourceText Char
          -- ^ Unboxed character
      | HsString        SourceText FastString
          -- ^ String
      | HsStringPrim    SourceText ByteString
          -- ^ Packed bytes
      | HsInt           SourceText Integer
          -- ^ Genuinely an Int; arises from
          -- @TcGenDeriv@, and from TRANSLATION
      | HsIntPrim       SourceText Integer
          -- ^ literal @Int#@
      | HsWordPrim      SourceText Integer
          -- ^ literal @Word#@
      | HsInt64Prim     SourceText Integer
          -- ^ literal @Int64#@
      | HsWord64Prim    SourceText Integer
          -- ^ literal @Word64#@
      | HsInteger       SourceText Integer Type
          -- ^ Genuinely an integer; arises only
          -- from TRANSLATION (overloaded
          -- literals are done with HsOverLit)
      | HsRat           FractionalLit Type
          -- ^ Genuinely a rational; arises only from
          -- TRANSLATION (overloaded literals are
          -- done with HsOverLit)
      | HsFloatPrim     FractionalLit
          -- ^ Unboxed Float
      | HsDoublePrim    FractionalLit
          -- ^ Unboxed Double
      deriving Data

    instance Eq HsLit where
      (HsChar _ x1)       == (HsChar _ x2)       = x1==x2
      (HsCharPrim _ x1)   == (HsCharPrim _ x2)   = x1==x2
      (HsString _ x1)     == (HsString _ x2)     = x1==x2
      (HsStringPrim _ x1) == (HsStringPrim _ x2) = x1==x2
      (HsInt _ x1)        == (HsInt _ x2)        = x1==x2
      (HsIntPrim _ x1)    == (HsIntPrim _ x2)    = x1==x2
      (HsWordPrim _ x1)   == (HsWordPrim _ x2)   = x1==x2
      (HsInt64Prim _ x1)  == (HsInt64Prim _ x2)  = x1==x2
      (HsWord64Prim _ x1) == (HsWord64Prim _ x2) = x1==x2
      (HsInteger _ x1 _)  == (HsInteger _ x2 _)  = x1==x2
      (HsRat x1 _)        == (HsRat x2 _)        = x1==x2
      (HsFloatPrim x1)    == (HsFloatPrim x2)    = x1==x2
      (HsDoublePrim x1)   == (HsDoublePrim x2)   = x1==x2
      _                   == _                   = False

    -- | Haskell Overloaded Literal
    data HsOverLit id
      = OverLit {
            ol_val :: OverLitVal,
            ol_rebindable :: PostRn id Bool, -- Note [ol_rebindable]
            ol_witness :: HsExpr id,     -- Note [Overloaded literal witnesses]
            ol_type :: PostTc id Type }
    deriving instance (DataId id) => Data (HsOverLit id)

    -- Note [Literal source text] in BasicTypes for SourceText fields in
    -- the following
    -- | Overloaded Literal Value
    data OverLitVal
      = HsIntegral   !SourceText !Integer    -- ^ Integer-looking literals;
      | HsFractional !FractionalLit          -- ^ Frac-looking literals
      | HsIsString   !SourceText !FastString -- ^ String-looking literals
      deriving Data

    overLitType :: HsOverLit a -> PostTc a Type
    overLitType = ol_type

    {-
    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 HsExpr in an HsOverLit is the
    name of the coercion function, 'fromInteger' or 'fromRational'.
    *After* type checking, it is a witness for the literal, such as
            (fromInteger 3) or lit_78
    This witness should replace the literal.

    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.

    The PostTcType in each branch records the type the overload literal is
    found to have.
    -}

    -- Comparison operations are needed when grouping literals
    -- for compiling pattern-matching (module MatchLit)
    instance Eq (HsOverLit id) where
      (OverLit {ol_val = val1}) == (OverLit {ol_val=val2}) = val1 == val2

    instance Eq OverLitVal where
      (HsIntegral _ i1)   == (HsIntegral _ i2)   = i1 == i2
      (HsFractional f1)   == (HsFractional f2)   = f1 == f2
      (HsIsString _ s1)   == (HsIsString _ s2)   = s1 == s2
      _                   == _                   = False

    instance Ord (HsOverLit id) where
      compare (OverLit {ol_val=val1}) (OverLit {ol_val=val2}) = val1 `compare` val2

    instance Ord OverLitVal where
      compare (HsIntegral _ i1)   (HsIntegral _ i2)   = i1 `compare` i2
      compare (HsIntegral _ _)    (HsFractional _)    = LT
      compare (HsIntegral _ _)    (HsIsString _ _)    = LT
      compare (HsFractional f1)   (HsFractional f2)   = f1 `compare` f2
      compare (HsFractional _)    (HsIntegral _ _)    = GT
      compare (HsFractional _)    (HsIsString _ _)    = LT
      compare (HsIsString _ s1)   (HsIsString _ s2)   = s1 `compare` s2
      compare (HsIsString _ _)    (HsIntegral _ _)    = GT
      compare (HsIsString _ _)    (HsFractional _)    = GT

    instance Outputable HsLit where
        ppr (HsChar st c)       = pprWithSourceText st (pprHsChar c)
        ppr (HsCharPrim st c)   = pp_st_suffix st primCharSuffix (pprPrimChar c)
        ppr (HsString st s)     = pprWithSourceText st (pprHsString s)
        ppr (HsStringPrim st s) = pprWithSourceText st (pprHsBytes s)
        ppr (HsInt st i)        = pprWithSourceText st (integer i)
        ppr (HsInteger st i _)  = pprWithSourceText st (integer i)
        ppr (HsRat f _)         = ppr f
        ppr (HsFloatPrim f)     = ppr f <> primFloatSuffix
        ppr (HsDoublePrim d)    = ppr d <> primDoubleSuffix
        ppr (HsIntPrim st i)    = pprWithSourceText st (pprPrimInt i)
        ppr (HsWordPrim st w)   = pprWithSourceText st (pprPrimWord w)
        ppr (HsInt64Prim st i)  = pp_st_suffix st primInt64Suffix  (pprPrimInt64 i)
        ppr (HsWord64Prim st w) = pp_st_suffix st primWord64Suffix (pprPrimWord64 w)

    pp_st_suffix :: SourceText -> SDoc -> SDoc -> SDoc
    pp_st_suffix NoSourceText         _ doc = doc
    pp_st_suffix (SourceText st) suffix _   = text st <> suffix

    -- in debug mode, print the expression that it's resolved to, too
    instance (OutputableBndrId id) => Outputable (HsOverLit id) where
      ppr (OverLit {ol_val=val, ol_witness=witness})
            = ppr val <+> (ifPprDebug (parens (pprExpr witness)))

    instance Outputable OverLitVal where
      ppr (HsIntegral st i)  = pprWithSourceText st (integer i)
      ppr (HsFractional f)   = ppr f
      ppr (HsIsString st s)  = pprWithSourceText st (pprHsString s)

    -- | pmPprHsLit pretty prints literals and is used when pretty printing pattern
    -- match warnings. All are printed the same (i.e., without hashes if they are
    -- primitive and not wrapped in constructors if they are boxed). This happens
    -- mainly for too reasons:
    --  * We do not want to expose their internal representation
    --  * The warnings become too messy
    pmPprHsLit :: HsLit -> SDoc
    pmPprHsLit (HsChar _ c)       = pprHsChar c
    pmPprHsLit (HsCharPrim _ c)   = pprHsChar c
    pmPprHsLit (HsString st s)    = pprWithSourceText st (pprHsString s)
    pmPprHsLit (HsStringPrim _ s) = pprHsBytes s
    pmPprHsLit (HsInt _ i)        = integer i
    pmPprHsLit (HsIntPrim _ i)    = integer i
    pmPprHsLit (HsWordPrim _ w)   = integer w
    pmPprHsLit (HsInt64Prim _ i)  = integer i
    pmPprHsLit (HsWord64Prim _ w) = integer w
    pmPprHsLit (HsInteger _ i _)  = integer i
    pmPprHsLit (HsRat f _)        = ppr f
    pmPprHsLit (HsFloatPrim f)    = ppr f
    pmPprHsLit (HsDoublePrim d)   = ppr d