iface/IfaceEnv.hs

    -- (c) The University of Glasgow 2002-2006

    {-# LANGUAGE CPP, RankNTypes #-}

    module IfaceEnv (
            newGlobalBinder, newImplicitBinder,
            lookupIfaceTop,
            lookupOrig, lookupOrigNameCache, extendNameCache,
            newIfaceName, newIfaceNames,
            extendIfaceIdEnv, extendIfaceTyVarEnv,
            tcIfaceLclId, tcIfaceTyVar, lookupIfaceTyVar,

            ifaceExportNames,

            -- Name-cache stuff
            allocateGlobalBinder, initNameCache, updNameCache,
            getNameCache, mkNameCacheUpdater, NameCacheUpdater(..)
       ) where

    #include "HsVersions.h"

    import TcRnMonad
    import TysWiredIn
    import HscTypes
    import Type
    import Var
    import Name
    import Avail
    import Module
    import UniqFM
    import FastString
    import UniqSupply
    import SrcLoc
    import Util

    import Outputable
    import Exception     ( evaluate )

    import Data.IORef    ( atomicModifyIORef, readIORef )

    {-
    *********************************************************
    *                                                      *
            Allocating new Names in the Name Cache
    *                                                      *
    *********************************************************

    Note [The Name Cache]
    ~~~~~~~~~~~~~~~~~~~~~
    The Name Cache makes sure that, during any invovcation of GHC, each
    External Name "M.x" has one, and only one globally-agreed Unique.

    * The first time we come across M.x we make up a Unique and record that
      association in the Name Cache.

    * When we come across "M.x" again, we look it up in the Name Cache,
      and get a hit.

    The functions newGlobalBinder, allocateGlobalBinder do the main work.
    When you make an External name, you should probably be calling one
    of them.
    -}

    newGlobalBinder :: Module -> OccName -> SrcSpan -> TcRnIf a b Name
    -- Used for source code and interface files, to make the
    -- Name for a thing, given its Module and OccName
    -- See Note [The Name Cache]
    --
    -- The cache may already already have a binding for this thing,
    -- because we may have seen an occurrence before, but now is the
    -- moment when we know its Module and SrcLoc in their full glory

    newGlobalBinder mod occ loc
      = do mod `seq` occ `seq` return ()    -- See notes with lookupOrig
    --     traceIf (text "newGlobalBinder" <+> ppr mod <+> ppr occ <+> ppr loc)
           updNameCache $ \name_cache ->
             allocateGlobalBinder name_cache mod occ loc

    allocateGlobalBinder
      :: NameCache
      -> Module -> OccName -> SrcSpan
      -> (NameCache, Name)
    -- See Note [The Name Cache]
    allocateGlobalBinder name_supply mod occ loc
      = case lookupOrigNameCache (nsNames name_supply) mod occ of
            -- A hit in the cache!  We are at the binding site of the name.
            -- This is the moment when we know the SrcLoc
            -- of the Name, so we set this field in the Name we return.
            --
            -- Then (bogus) multiple bindings of the same Name
            -- get different SrcLocs can can be reported as such.
            --
            -- Possible other reason: it might be in the cache because we
            --      encountered an occurrence before the binding site for an
            --      implicitly-imported Name.  Perhaps the current SrcLoc is
            --      better... but not really: it'll still just say 'imported'
            --
            -- IMPORTANT: Don't mess with wired-in names.
            --            Their wired-in-ness is in their NameSort
            --            and their Module is correct.

            Just name | isWiredInName name
                      -> (name_supply, name)
                      | otherwise
                      -> (new_name_supply, name')
                      where
                        uniq            = nameUnique name
                        name'           = mkExternalName uniq mod occ loc
                                          -- name' is like name, but with the right SrcSpan
                        new_cache       = extendNameCache (nsNames name_supply) mod occ name'
                        new_name_supply = name_supply {nsNames = new_cache}

            -- Miss in the cache!
            -- Build a completely new Name, and put it in the cache
            _ -> (new_name_supply, name)
                      where
                        (uniq, us')     = takeUniqFromSupply (nsUniqs name_supply)
                        name            = mkExternalName uniq mod occ loc
                        new_cache       = extendNameCache (nsNames name_supply) mod occ name
                        new_name_supply = name_supply {nsUniqs = us', nsNames = new_cache}

    newImplicitBinder :: Name                       -- Base name
                      -> (OccName -> OccName)       -- Occurrence name modifier
                      -> TcRnIf m n Name            -- Implicit name
    -- Called in BuildTyCl to allocate the implicit binders of type/class decls
    -- For source type/class decls, this is the first occurrence
    -- For iface ones, the LoadIface has alrady allocated a suitable name in the cache
    newImplicitBinder base_name mk_sys_occ
      | Just mod <- nameModule_maybe base_name
      = newGlobalBinder mod occ loc
      | otherwise           -- When typechecking a [d| decl bracket |],
                            -- TH generates types, classes etc with Internal names,
                            -- so we follow suit for the implicit binders
      = do  { uniq <- newUnique
            ; return (mkInternalName uniq occ loc) }
      where
        occ = mk_sys_occ (nameOccName base_name)
        loc = nameSrcSpan base_name

    ifaceExportNames :: [IfaceExport] -> TcRnIf gbl lcl [AvailInfo]
    ifaceExportNames exports = return exports

    lookupOrig :: Module -> OccName ->  TcRnIf a b Name
    lookupOrig mod occ
      = do  {       -- First ensure that mod and occ are evaluated
                    -- If not, chaos can ensue:
                    --      we read the name-cache
                    --      then pull on mod (say)
                    --      which does some stuff that modifies the name cache
                    -- This did happen, with tycon_mod in TcIface.tcIfaceAlt (DataAlt..)
              mod `seq` occ `seq` return ()
    --      ; traceIf (text "lookup_orig" <+> ppr mod <+> ppr occ)

            ; updNameCache $ \name_cache ->
                case lookupOrigNameCache (nsNames name_cache) mod occ of {
                  Just name -> (name_cache, name);
                  Nothing   ->
                  case takeUniqFromSupply (nsUniqs name_cache) of {
                  (uniq, us) ->
                      let
                        name      = mkExternalName uniq mod occ noSrcSpan
                        new_cache = extendNameCache (nsNames name_cache) mod occ name
                      in (name_cache{ nsUniqs = us, nsNames = new_cache }, name)
        }}}

    {-
    ************************************************************************
    *                                                                      *
                    Name cache access
    *                                                                      *
    ************************************************************************

    See Note [The Name Cache] above.

    Note [Built-in syntax and the OrigNameCache]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    You might think that usin isBuiltInOcc_maybe in lookupOrigNameCache is
    unnecessary because tuple TyCon/DataCons are parsed as Exact RdrNames
    and *don't* appear as original names in interface files (because
    serialization gives them special treatment), so we will never look
    them up in the original name cache.

    However, there are two reasons why we might look up an Orig RdrName:

      * If you use setRdrNameSpace on an Exact RdrName it may be
        turned into an Orig RdrName.

      * Template Haskell turns a BuiltInSyntax Name into a TH.NameG
        (DsMeta.globalVar), and parses a NameG into an Orig RdrName
        (Convert.thRdrName).  So, eg $(do { reify '(,); ... }) will
        go this route (Trac #8954).
    -}

    lookupOrigNameCache :: OrigNameCache -> Module -> OccName -> Maybe Name
    lookupOrigNameCache nc mod occ
      | Just name <- isBuiltInOcc_maybe occ
      =     -- See Note [Known-key names], 3(c) in PrelNames
            -- Special case for tuples; there are too many
            -- of them to pre-populate the original-name cache
        Just name

      | otherwise
      = case lookupModuleEnv nc mod of
            Nothing      -> Nothing
            Just occ_env -> lookupOccEnv occ_env occ

    extendOrigNameCache :: OrigNameCache -> Name -> OrigNameCache
    extendOrigNameCache nc name
      = ASSERT2( isExternalName name, ppr name )
        extendNameCache nc (nameModule name) (nameOccName name) name

    extendNameCache :: OrigNameCache -> Module -> OccName -> Name -> OrigNameCache
    extendNameCache nc mod occ name
      = extendModuleEnvWith combine nc mod (unitOccEnv occ name)
      where
        combine _ occ_env = extendOccEnv occ_env occ name

    getNameCache :: TcRnIf a b NameCache
    getNameCache = do { HscEnv { hsc_NC = nc_var } <- getTopEnv;
                        readMutVar nc_var }

    updNameCache :: (NameCache -> (NameCache, c)) -> TcRnIf a b c
    updNameCache upd_fn = do
      HscEnv { hsc_NC = nc_var } <- getTopEnv
      atomicUpdMutVar' nc_var upd_fn

    -- | A function that atomically updates the name cache given a modifier
    -- function.  The second result of the modifier function will be the result
    -- of the IO action.
    newtype NameCacheUpdater = NCU { updateNameCache :: forall c. (NameCache -> (NameCache, c)) -> IO c }

    -- | Return a function to atomically update the name cache.
    mkNameCacheUpdater :: TcRnIf a b NameCacheUpdater
    mkNameCacheUpdater = do
      nc_var <- hsc_NC `fmap` getTopEnv
      let update_nc f = do r <- atomicModifyIORef nc_var f
                           _ <- evaluate =<< readIORef nc_var
                           return r
      return (NCU update_nc)

    initNameCache :: UniqSupply -> [Name] -> NameCache
    initNameCache us names
      = NameCache { nsUniqs = us,
                    nsNames = initOrigNames names }

    initOrigNames :: [Name] -> OrigNameCache
    initOrigNames names = foldl extendOrigNameCache emptyModuleEnv names

    {-
    ************************************************************************
    *                                                                      *
                    Type variables and local Ids
    *                                                                      *
    ************************************************************************
    -}

    tcIfaceLclId :: FastString -> IfL Id
    tcIfaceLclId occ
      = do  { lcl <- getLclEnv
            ; case (lookupUFM (if_id_env lcl) occ) of
                Just ty_var -> return ty_var
                Nothing     -> failIfM (text "Iface id out of scope: " <+> ppr occ)
            }

    extendIfaceIdEnv :: [Id] -> IfL a -> IfL a
    extendIfaceIdEnv ids thing_inside
      = do  { env <- getLclEnv
            ; let { id_env' = addListToUFM (if_id_env env) pairs
                  ; pairs   = [(occNameFS (getOccName id), id) | id <- ids] }
            ; setLclEnv (env { if_id_env = id_env' }) thing_inside }

    tcIfaceTyVar :: FastString -> IfL TyVar
    tcIfaceTyVar occ
      = do  { lcl <- getLclEnv
            ; case (lookupUFM (if_tv_env lcl) occ) of
                Just ty_var -> return ty_var
                Nothing     -> failIfM (text "Iface type variable out of scope: " <+> ppr occ)
            }

    lookupIfaceTyVar :: FastString -> IfL (Maybe TyVar)
    lookupIfaceTyVar occ
      = do  { lcl <- getLclEnv
            ; return (lookupUFM (if_tv_env lcl) occ) }

    extendIfaceTyVarEnv :: [TyVar] -> IfL a -> IfL a
    extendIfaceTyVarEnv tyvars thing_inside
      = do  { env <- getLclEnv
            ; let { tv_env' = addListToUFM (if_tv_env env) pairs
                  ; pairs   = [(occNameFS (getOccName tv), tv) | tv <- tyvars] }
            ; setLclEnv (env { if_tv_env = tv_env' }) thing_inside }

    {-
    ************************************************************************
    *                                                                      *
                    Getting from RdrNames to Names
    *                                                                      *
    ************************************************************************
    -}

    lookupIfaceTop :: OccName -> IfL Name
    -- Look up a top-level name from the current Iface module
    lookupIfaceTop occ
      = do  { env <- getLclEnv; lookupOrig (if_mod env) occ }

    newIfaceName :: OccName -> IfL Name
    newIfaceName occ
      = do  { uniq <- newUnique
            ; return $! mkInternalName uniq occ noSrcSpan }

    newIfaceNames :: [OccName] -> IfL [Name]
    newIfaceNames occs
      = do  { uniqs <- newUniqueSupply
            ; return [ mkInternalName uniq occ noSrcSpan
                     | (occ,uniq) <- occs `zip` uniqsFromSupply uniqs] }