prelude/PrelInfo.hs

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

    \section[PrelInfo]{The @PrelInfo@ interface to the compiler's prelude knowledge}
    -}

    {-# LANGUAGE CPP #-}
    module PrelInfo (
            wiredInIds, ghcPrimIds,
            primOpRules, builtinRules,

            ghcPrimExports,
            wiredInThings, basicKnownKeyNames,
            primOpId,

            -- Random other things
            maybeCharLikeCon, maybeIntLikeCon,

            -- Class categories
            isNumericClass, isStandardClass

        ) where

    #include "HsVersions.h"

    import PrelNames
    import PrelRules
    import Avail
    import PrimOp
    import DataCon
    import Id
    import MkId
    import TysPrim
    import TysWiredIn
    import HscTypes
    import Class
    import TyCon
    import Util
    import {-# SOURCE #-} TcTypeNats ( typeNatTyCons )

    import Data.Array

    {-
    ************************************************************************
    *                                                                      *
    \subsection[builtinNameInfo]{Lookup built-in names}
    *                                                                      *
    ************************************************************************

    Notes about wired in things
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~
    * Wired-in things are Ids\/TyCons that are completely known to the compiler.
      They are global values in GHC, (e.g.  listTyCon :: TyCon).

    * A wired in Name contains the thing itself inside the Name:
            see Name.wiredInNameTyThing_maybe
      (E.g. listTyConName contains listTyCon.

    * The name cache is initialised with (the names of) all wired-in things

    * The type checker sees if the Name is wired in before looking up
      the name in the type environment.  So the type envt itself contains
      no wired in things.

    * MkIface prunes out wired-in things before putting them in an interface file.
      So interface files never contain wired-in things.
    -}

    wiredInThings :: [TyThing]
    -- This list is used only to initialise HscMain.knownKeyNames
    -- to ensure that when you say "Prelude.map" in your source code, you
    -- get a Name with the correct known key (See Note [Known-key names])
    wiredInThings
      = concat
        [           -- Wired in TyCons and their implicit Ids
              tycon_things
            , concatMap implicitTyThings tycon_things

                    -- Wired in Ids
            , map AnId wiredInIds

                    -- PrimOps
            , map (AnId . primOpId) allThePrimOps
        ]
      where
        tycon_things = map ATyCon ([funTyCon] ++ primTyCons ++ wiredInTyCons
                                        ++ typeNatTyCons)

    {-
    We let a lot of "non-standard" values be visible, so that we can make
    sense of them in interface pragmas. It's cool, though they all have
    "non-standard" names, so they won't get past the parser in user code.

    ************************************************************************
    *                                                                      *
                    PrimOpIds
    *                                                                      *
    ************************************************************************
    -}

    primOpIds :: Array Int Id
    -- A cache of the PrimOp Ids, indexed by PrimOp tag
    primOpIds = array (1,maxPrimOpTag) [ (primOpTag op, mkPrimOpId op)
                                       | op <- allThePrimOps ]

    primOpId :: PrimOp -> Id
    primOpId op = primOpIds ! primOpTag op

    {-
    ************************************************************************
    *                                                                      *
    \subsection{Export lists for pseudo-modules (GHC.Prim)}
    *                                                                      *
    ************************************************************************

    GHC.Prim "exports" all the primops and primitive types, some
    wired-in Ids.
    -}

    ghcPrimExports :: [IfaceExport]
    ghcPrimExports
     = map (Avail . idName) ghcPrimIds ++
       map (Avail . idName . primOpId) allThePrimOps ++
       [ AvailTC n [n]
       | tc <- funTyCon : primTyCons, let n = tyConName tc  ]

    {-
    ************************************************************************
    *                                                                      *
    \subsection{Built-in keys}
    *                                                                      *
    ************************************************************************

    ToDo: make it do the ``like'' part properly (as in 0.26 and before).
    -}

    maybeCharLikeCon, maybeIntLikeCon :: DataCon -> Bool
    maybeCharLikeCon con = con `hasKey` charDataConKey
    maybeIntLikeCon  con = con `hasKey` intDataConKey

    {-
    ************************************************************************
    *                                                                      *
    \subsection{Class predicates}
    *                                                                      *
    ************************************************************************
    -}

    isNumericClass, isStandardClass :: Class -> Bool

    isNumericClass     clas = classKey clas `is_elem` numericClassKeys
    isStandardClass    clas = classKey clas `is_elem` standardClassKeys

    is_elem :: Eq a => a -> [a] -> Bool
    is_elem = isIn "is_X_Class"