prelude/PrelInfo.hs

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

    -}

    {-# LANGUAGE CPP #-}

    -- | The @PrelInfo@ interface to the compiler's prelude knowledge.
    --
    -- This module serves as the central gathering point for names which the
    -- compiler knows something about. This includes functions for,
    --
    --  * discerning whether a 'Name' is known-key
    --
    --  * given a 'Unique', looking up its corresponding known-key 'Name'
    --
    -- See Note [Known-key names] and Note [About wired-in things] for information
    -- about the two types of prelude things in GHC.
    --
    module PrelInfo (
            -- * Known-key names
            isKnownKeyName,
            lookupKnownKeyName,
            lookupKnownNameInfo,

            -- ** Internal use
            -- | 'knownKeyNames' is exported to seed the original name cache only;
            -- if you find yourself wanting to look at it you might consider using
            -- 'lookupKnownKeyName' or 'isKnownKeyName'.
            knownKeyNames,

            -- * Miscellaneous
            wiredInIds, ghcPrimIds,
            primOpRules, builtinRules,

            ghcPrimExports,
            primOpId,

            -- * Random other things
            maybeCharLikeCon, maybeIntLikeCon,

            -- * Class categories
            isNumericClass, isStandardClass

        ) where

    #include "HsVersions.h"

    import GhcPrelude

    import KnownUniques
    import Unique           ( isValidKnownKeyUnique )

    import ConLike          ( ConLike(..) )
    import THNames          ( templateHaskellNames )
    import PrelNames
    import PrelRules
    import Avail
    import PrimOp
    import DataCon
    import Id
    import Name
    import NameEnv
    import MkId
    import Outputable
    import TysPrim
    import TysWiredIn
    import HscTypes
    import Class
    import TyCon
    import UniqFM
    import Util
    import TcTypeNats ( typeNatTyCons )

    import Control.Applicative ((<|>))
    import Data.List        ( intercalate )
    import Data.Array
    import Data.Maybe

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

    Note [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
      (except tuples and sums; see Note [Known-])

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

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

    -- | This list is used to ensure that when you say "Prelude.map" in your source
    -- code, or in an interface file, you get a Name with the correct known key (See
    -- Note [Known-key names] in PrelNames)
    knownKeyNames :: [Name]
    knownKeyNames
      | debugIsOn
      , Just badNamesStr <- knownKeyNamesOkay all_names
      = panic ("badAllKnownKeyNames:\n" ++ badNamesStr)
           -- NB: We can't use ppr here, because this is sometimes evaluated in a
           -- context where there are no DynFlags available, leading to a cryptic
           -- "<<details unavailable>>" error. (This seems to happen only in the
           -- stage 2 compiler, for reasons I [Richard] have no clue of.)
      | otherwise
      = all_names
      where
        all_names =
          concat [ wired_tycon_kk_names funTyCon
                 , concatMap wired_tycon_kk_names primTyCons

                 , concatMap wired_tycon_kk_names wiredInTyCons
                   -- Does not include tuples

                 , concatMap wired_tycon_kk_names typeNatTyCons

                 , map idName wiredInIds
                 , map (idName . primOpId) allThePrimOps
                 , map (idName . primOpWrapperId) allThePrimOps
                 , basicKnownKeyNames
                 , templateHaskellNames
                 ]
        -- All of the names associated with a wired-in TyCon.
        -- This includes the TyCon itself, its DataCons and promoted TyCons.
        wired_tycon_kk_names :: TyCon -> [Name]
        wired_tycon_kk_names tc =
            tyConName tc : (rep_names tc ++ implicits)
          where implicits = concatMap thing_kk_names (implicitTyConThings tc)

        wired_datacon_kk_names :: DataCon -> [Name]
        wired_datacon_kk_names dc =
          dataConName dc : rep_names (promoteDataCon dc)

        thing_kk_names :: TyThing -> [Name]
        thing_kk_names (ATyCon tc)                 = wired_tycon_kk_names tc
        thing_kk_names (AConLike (RealDataCon dc)) = wired_datacon_kk_names dc
        thing_kk_names thing                       = [getName thing]

        -- The TyConRepName for a known-key TyCon has a known key,
        -- but isn't itself an implicit thing.  Yurgh.
        -- NB: if any of the wired-in TyCons had record fields, the record
        --     field names would be in a similar situation.  Ditto class ops.
        --     But it happens that there aren't any
        rep_names tc = case tyConRepName_maybe tc of
                            Just n  -> [n]
                            Nothing -> []

    -- | Check the known-key names list of consistency.
    knownKeyNamesOkay :: [Name] -> Maybe String
    knownKeyNamesOkay all_names
      | ns@(_:_) <- filter (not . isValidKnownKeyUnique . getUnique) all_names
      = Just $ "    Out-of-range known-key uniques: ["
            ++ intercalate ", " (map (occNameString . nameOccName) ns) ++
             "]"
      | null badNamesPairs
      = Nothing
      | otherwise
      = Just badNamesStr
      where
        namesEnv      = foldl' (\m n -> extendNameEnv_Acc (:) singleton m n n)
                               emptyUFM all_names
        badNamesEnv   = filterNameEnv (\ns -> ns `lengthExceeds` 1) namesEnv
        badNamesPairs = nonDetUFMToList badNamesEnv
          -- It's OK to use nonDetUFMToList here because the ordering only affects
          -- the message when we get a panic
        badNamesStrs  = map pairToStr badNamesPairs
        badNamesStr   = unlines badNamesStrs

        pairToStr (uniq, ns) = "        " ++
                               show uniq ++
                               ": [" ++
                               intercalate ", " (map (occNameString . nameOccName) ns) ++
                               "]"

    -- | Given a 'Unique' lookup its associated 'Name' if it corresponds to a
    -- known-key thing.
    lookupKnownKeyName :: Unique -> Maybe Name
    lookupKnownKeyName u =
        knownUniqueName u <|> lookupUFM knownKeysMap u

    -- | Is a 'Name' known-key?
    isKnownKeyName :: Name -> Bool
    isKnownKeyName n =
        isJust (knownUniqueName $ nameUnique n) || elemUFM n knownKeysMap

    knownKeysMap :: UniqFM Name
    knownKeysMap = listToUFM [ (nameUnique n, n) | n <- knownKeyNames ]

    -- | Given a 'Unique' lookup any associated arbitrary SDoc's to be displayed by
    -- GHCi's ':info' command.
    lookupKnownNameInfo :: Name -> SDoc
    lookupKnownNameInfo name = case lookupNameEnv knownNamesInfo name of
        -- If we do find a doc, we add comment delimeters to make the output
        -- of ':info' valid Haskell.
        Nothing  -> empty
        Just doc -> vcat [text "{-", doc, text "-}"]

    -- A map from Uniques to SDocs, used in GHCi's ':info' command. (#12390)
    knownNamesInfo :: NameEnv SDoc
    knownNamesInfo = unitNameEnv coercibleTyConName $
        vcat [ text "Coercible is a special constraint with custom solving rules."
             , text "It is not a class."
             , text "Please see section `The Coercible constraint`"
             , text "of the user's guide for details." ]

    {-
    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

    {-
    ************************************************************************
    *                                                                      *
                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 : exposedPrimTyCons, let n = tyConName tc  ]

    {-
    ************************************************************************
    *                                                                      *
                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

    {-
    ************************************************************************
    *                                                                      *
                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"