content: {-
  (c) The University of Glasgow, 2006
  
  \section[HscTypes]{Types for the per-module compiler}
  -}
  
  {-# LANGUAGE CPP, DeriveDataTypeable, ScopedTypeVariables, RecordWildCards #-}
  
  -- | Types for the per-module compiler
  module Eta.Main.HscTypes (
          -- * compilation state
          HscEnv(..), hscEPS,
          FinderCache, FindResult(..), InstalledFindResult(..), ModLocationCache,
          Target(..), TargetId(..), pprTarget, pprTargetId,
          HscStatus(..),
          IServ(..),
          -- * ModuleGraph
          ModuleGraph, emptyMG, mkModuleGraph, extendMG, mapMG,
          mgModSummaries, mgElemModule, mgLookupModule,
          needsTemplateHaskellOrQQ, mgBootModules,
  
          -- * Hsc monad
          Hsc(..), runHsc, runInteractiveHsc,
  
          -- * Information about modules
          ModDetails(..), emptyModDetails,
          ModGuts(..), CgGuts(..), ForeignStubs(..),
          appendStubC, appendDefs, foreignExportsList, lookupStubs,
          ImportedMods, ImportedBy(..), importedByUser, ImportedModsVal(..),
  
          ModSummary(..), ms_imps, ms_mod_name, showModMsg, isBootSummary,
          msHsFilePath, msHiFilePath, msObjFilePath,
          SourceModified(..), isTemplateHaskellOrQQNonBoot,
  
          -- * Information about the module being compiled
          -- (re-exported from DriverPhases)
          HscSource(..), isHsBootOrSig, hscSourceString,
  
  
          -- * State relating to modules in this package
          HomePackageTable, HomeModInfo(..), emptyHomePackageTable,
          hptInstances, hptRules, hptVectInfo, pprHPT,
          hptObjs,
  
          -- * State relating to known packages
          ExternalPackageState(..), EpsStats(..), addEpsInStats, updNameCacheIO,
          PackageTypeEnv, PackageIfaceTable, emptyPackageIfaceTable,
          lookupIfaceByModule, emptyModIface, lookupHptByModule,
          lookupHpt, lookupHptDirectly, eltsHpt, allHpt, addToHpt, mapHpt,
          delFromHpt, addListToHpt, listToHpt, foldHpt, filterHpt,
  
          PackageInstEnv, PackageFamInstEnv, PackageRuleBase,
  
          mkSOName, mkHsSOName, soExt,
  
          -- * Metaprogramming
          MetaRequest(..),
          MetaResult, -- data constructors not exported to ensure correct response type
          metaRequestE, metaRequestP, metaRequestT, metaRequestD, metaRequestAW,
          MetaHook,
  
          -- * Annotations
          prepareAnnotations,
  
          -- * Interactive context
          InteractiveContext(..), newInteractiveContext,
          icExprCounter, icExprCounterInc, icItCounterInc, icPrintUnqual, icInScopeTTs,
          icExtendGblRdrEnv, extendInteractiveContext, extendInteractiveContextWithIds,
          substInteractiveContext,
          setInteractivePrintName, icInteractiveModule,
          InteractiveImport(..), setInteractivePackage,
          mkPrintUnqualified, pprModulePrefix,
          mkQualPackage, mkQualModule, pkgQual,
  
          -- * Interfaces
          ModIface(..), mkIfaceWarnCache, mkIfaceHashCache, mkIfaceFixCache,
          emptyIfaceWarnCache, mi_boot, mi_semantic_module,
          mi_free_holes, renameFreeHoles,
  
          -- * Fixity
          FixityEnv, FixItem(..), lookupFixity, emptyFixityEnv,
  
          -- * TyThings and type environments
          TyThing(..),  tyThingAvailInfo,
          tyThingTyCon, tyThingDataCon,
          tyThingId, tyThingCoAxiom, tyThingParent_maybe, tyThingsTyVars,
          implicitTyThings, implicitTyConThings, implicitClassThings,
          isImplicitTyThing,
  
          TypeEnv, lookupType, lookupTypeHscEnv, mkTypeEnv, emptyTypeEnv,
          typeEnvFromEntities, mkTypeEnvWithImplicits,
          extendTypeEnv, extendTypeEnvList,
          extendTypeEnvWithIds,
          lookupTypeEnv,
          typeEnvElts, typeEnvTyCons, typeEnvIds, typeEnvPatSyns,
          typeEnvDataCons, typeEnvCoAxioms, typeEnvClasses,
  
          -- * MonadThings
          MonadThings(..),
  
          -- * Information on imports and exports
          WhetherHasOrphans, IsBootInterface, Usage(..),
          Dependencies(..), noDependencies,
          IfaceExport,
  
          -- * Warnings
          Warnings(..), WarningTxt(..), plusWarns,
  
          -- * Linker stuff
          Linkable(..), isObjectLinkable, isInterpretedLinkable, linkableObjs, linkableClasses,
          forceClasses,
          Unlinked(..), CompiledByteCode,
          isObject, nameOfObject, isInterpretable, byteCodeOfObject,
  
          -- * Program coverage
          HpcInfo(..), emptyHpcInfo, isHpcUsed, AnyHpcUsage,
  
          -- * Breakpoints
          ModBreaks (..), BreakIndex, emptyModBreaks,
  
          -- * Vectorisation information
          VectInfo(..), IfaceVectInfo(..), noVectInfo, plusVectInfo,
          noIfaceVectInfo, isNoIfaceVectInfo,
  
          -- * Safe Haskell information
          IfaceTrustInfo, getSafeMode, setSafeMode, noIfaceTrustInfo,
          trustInfoToNum, numToTrustInfo, IsSafeImport,
  
          -- * result of the parser
          HsParsedModule(..),
  
          -- * Compilation errors and warnings
          SourceError, GhcApiError, mkSrcErr, srcErrorMessages, mkApiErr,
          throwOneError, handleSourceError,
          handleFlagWarnings, printOrThrowWarnings,
  
          Reinterpret(..),
          CachedMap(..), ClassIndex, emptyClassIndex, getClassIndex, findInClassIndex,
          addToClassIndex, lookupClassIndex, CachedClassInfo, ClassInfo(..),
  
      ) where
  
  #include "HsVersions.h"
  
  #ifdef ETA_REPL
  import Eta.REPL.Message ( Pipe )
  import Eta.REPL.ClassInfo
  import Eta.REPL.RemoteTypes
  -- import Eta.Interactive.ByteCodeAsm      ( CompiledByteCode )
  import Eta.Main.InteractiveEvalTypes ( Resume )
  #endif
  
  import Eta.Utils.UniqFM
  import Eta.Utils.UniqDSet
  import Eta.HsSyn.HsSyn
  import Eta.BasicTypes.RdrName
  import Eta.BasicTypes.Avail
  import Eta.BasicTypes.Module
  import Eta.Types.InstEnv          ( InstEnv, ClsInst, identicalClsInstHead )
  import Eta.Types.FamInstEnv
  import Eta.Specialise.Rules            ( RuleBase )
  import Eta.Core.CoreSyn          ( CoreProgram, CoreRule, CoreVect )
  import Eta.BasicTypes.Name
  import Eta.BasicTypes.NameEnv
  import Eta.BasicTypes.NameSet
  import Eta.BasicTypes.VarEnv
  import Eta.BasicTypes.VarSet
  import Eta.BasicTypes.Var
  import Eta.BasicTypes.Id
  import Eta.BasicTypes.IdInfo           ( IdDetails(..) )
  import Eta.Types.Type
  import qualified Eta.LanguageExtensions as LangExt
  import Eta.Parser.ApiAnnotation    ( ApiAnns )
  import Eta.Main.Annotations      ( Annotation, AnnEnv, mkAnnEnv, plusAnnEnv )
  import Eta.Types.Class
  import Eta.Types.TyCon
  import Eta.Types.CoAxiom
  import Eta.BasicTypes.ConLike
  import Eta.BasicTypes.DataCon
  import Eta.BasicTypes.PatSyn
  import Eta.Prelude.PrelNames        ( gHC_PRIM, ioTyConName, printName, mkInteractiveModule )
  import Eta.Main.Packages hiding  ( Version(..) )
  import Eta.Main.DynFlags
  import Eta.Main.DriverPhases     ( Phase, HscSource(..), isHsBootOrSig, hscSourceString )
  import Eta.BasicTypes.BasicTypes
  import Eta.Iface.IfaceSyn
  import Eta.Utils.Maybes
  import Eta.Utils.Outputable
  import Eta.BasicTypes.SrcLoc
  import Eta.BasicTypes.Unique
  import Eta.Utils.UniqDFM
  import Eta.Utils.FastString
  import Eta.Utils.StringBuffer     ( StringBuffer )
  import Eta.Utils.Fingerprint
  import Eta.Utils.MonadUtils
  import Eta.Utils.Bag
  import Eta.Utils.Binary
  import Eta.Main.ErrUtils
  import Eta.BasicTypes.NameCache
  import Eta.Utils.Platform
  import Eta.Utils.Util
  import Eta.Serialized       ( Serialized )
  
  import Control.Monad    ( guard, liftM, when, ap )
  import Data.Array       ( Array, array )
  import Data.Map         ( Map )
  import Data.Text        ( Text )
  import Data.IORef
  import Data.Time
  import Data.Word
  import Data.Typeable    ( Typeable )
  import Eta.Utils.Exception
  import Foreign
  import System.FilePath
  import System.IO
  import System.IO.Unsafe
  import System.Process   ( ProcessHandle )
  import Control.Concurrent
  import qualified Data.Map as M
  import Codec.JVM
  import Data.ByteString (ByteString)
  
  -- -----------------------------------------------------------------------------
  -- Compilation state
  -- -----------------------------------------------------------------------------
  
  -- | Status of a compilation to hard-code
  data HscStatus
      = HscNotGeneratingCode
      | HscUpToDate
      | HscUpdateBoot
      | HscUpdateSig
      | HscRecomp CgGuts ModSummary
  
  -- -----------------------------------------------------------------------------
  -- The Hsc monad: Passing an environment and warning state
  
  newtype Hsc a = Hsc (HscEnv -> WarningMessages -> IO (a, WarningMessages))
  
  instance Functor Hsc where
      fmap = liftM
  
  instance Applicative Hsc where
      pure = return
      (<*>) = ap
  
  instance Monad Hsc where
      return a    = Hsc $ \_ w -> return (a, w)
      Hsc m >>= k = Hsc $ \e w -> do (a, w1) <- m e w
                                     case k a of
                                         Hsc k' -> k' e w1
  
  instance MonadIO Hsc where
      liftIO io = Hsc $ \_ w -> do a <- io; return (a, w)
  
  instance HasDynFlags Hsc where
      getDynFlags = Hsc $ \e w -> return (hsc_dflags e, w)
  
  runHsc :: HscEnv -> Hsc a -> IO a
  runHsc hsc_env (Hsc hsc) = do
      (a, w) <- hsc hsc_env emptyBag
      printOrThrowWarnings (hsc_dflags hsc_env) w
      return a
  
  runInteractiveHsc :: HscEnv -> Hsc a -> IO a
  -- A variant of runHsc that switches in the DynFlags from the
  -- InteractiveContext before running the Hsc computation.
  runInteractiveHsc hsc_env
    = runHsc (hsc_env { hsc_dflags = interactive_dflags })
    where
      interactive_dflags = ic_dflags (hsc_IC hsc_env)
  
  -- -----------------------------------------------------------------------------
  -- Source Errors
  
  -- When the compiler (HscMain) discovers errors, it throws an
  -- exception in the IO monad.
  
  mkSrcErr :: ErrorMessages -> SourceError
  mkSrcErr = SourceError
  
  srcErrorMessages :: SourceError -> ErrorMessages
  srcErrorMessages (SourceError msgs) = msgs
  
  mkApiErr :: DynFlags -> SDoc -> GhcApiError
  mkApiErr dflags msg = GhcApiError (showSDoc dflags msg)
  
  throwOneError :: MonadIO m => ErrMsg -> m ab
  throwOneError err = liftIO $ throwIO $ mkSrcErr $ unitBag err
  
  -- | A source error is an error that is caused by one or more errors in the
  -- source code.  A 'SourceError' is thrown by many functions in the
  -- compilation pipeline.  Inside GHC these errors are merely printed via
  -- 'log_action', but API clients may treat them differently, for example,
  -- insert them into a list box.  If you want the default behaviour, use the
  -- idiom:
  --
  -- > handleSourceError printExceptionAndWarnings $ do
  -- >   ... api calls that may fail ...
  --
  -- The 'SourceError's error messages can be accessed via 'srcErrorMessages'.
  -- This list may be empty if the compiler failed due to @-Werror@
  -- ('Opt_WarnIsError').
  --
  -- See 'printExceptionAndWarnings' for more information on what to take care
  -- of when writing a custom error handler.
  newtype SourceError = SourceError ErrorMessages
    deriving Typeable
  
  instance Show SourceError where
    show (SourceError msgs) = unlines . map show . bagToList $ msgs
  
  instance Exception SourceError
  
  -- | Perform the given action and call the exception handler if the action
  -- throws a 'SourceError'.  See 'SourceError' for more information.
  handleSourceError :: (ExceptionMonad m) =>
                       (SourceError -> m a) -- ^ exception handler
                    -> m a -- ^ action to perform
                    -> m a
  handleSourceError handler act =
    gcatch act (\(e :: SourceError) -> handler e)
  
  -- | An error thrown if the GHC API is used in an incorrect fashion.
  newtype GhcApiError = GhcApiError String
    deriving Typeable
  
  instance Show GhcApiError where
    show (GhcApiError msg) = msg
  
  instance Exception GhcApiError
  
  -- | Given a bag of warnings, turn them into an exception if
  -- -Werror is enabled, or print them out otherwise.
  printOrThrowWarnings :: DynFlags -> Bag WarnMsg -> IO ()
  printOrThrowWarnings dflags warns = do
    let (make_error, warns') =
          mapAccumBagL
            (\make_err warn ->
              case isWarnMsgFatal dflags warn of
                Nothing ->
                  (make_err, warn)
                Just err_reason ->
                  (True, warn{ errMsgSeverity = SevError
                             , errMsgReason = ErrReason err_reason
                             }))
            False warns
    if make_error
      then throwIO (mkSrcErr warns')
      else printBagOfErrors dflags warns
  
  handleFlagWarnings :: DynFlags -> [Located String] -> IO ()
  handleFlagWarnings dflags warns
   = when (wopt Opt_WarnDeprecatedFlags dflags) $ do
          -- It would be nicer if warns :: [Located MsgDoc], but that
          -- has circular import problems.
        let bag = listToBag [ mkPlainWarnMsg dflags loc (text warn)
                            | L loc warn <- warns ]
  
        printOrThrowWarnings dflags bag
  
  {-
  ************************************************************************
  *                                                                      *
  \subsection{HscEnv}
  *                                                                      *
  ************************************************************************
  -}
  
  -- | Hscenv is like 'Session', except that some of the fields are immutable.
  -- An HscEnv is used to compile a single module from plain Haskell source
  -- code (after preprocessing) to either C, assembly or C--.  Things like
  -- the module graph don't change during a single compilation.
  --
  -- Historical note: \"hsc\" used to be the name of the compiler binary,
  -- when there was a separate driver and compiler.  To compile a single
  -- module, the driver would invoke hsc on the source code... so nowadays
  -- we think of hsc as the layer of the compiler that deals with compiling
  -- a single module.
  data HscEnv
    = HscEnv {
          hsc_dflags :: DynFlags,
                  -- ^ The dynamic flag settings
  
          hsc_targets :: [Target],
                  -- ^ The targets (or roots) of the current session
  
          hsc_mod_graph :: ModuleGraph,
                  -- ^ The module graph of the current session
  
          hsc_IC :: InteractiveContext,
                  -- ^ The context for evaluating interactive statements
  
          hsc_HPT :: HomePackageTable,
                  -- ^ The home package table describes already-compiled
                  -- home-package modules, /excluding/ the module we
                  -- are compiling right now.
                  -- (In one-shot mode the current module is the only
                  -- home-package module, so hsc_HPT is empty.  All other
                  -- modules count as \"external-package\" modules.
                  -- However, even in GHCi mode, hi-boot interfaces are
                  -- demand-loaded into the external-package table.)
                  --
                  -- 'hsc_HPT' is not mutable because we only demand-load
                  -- external packages; the home package is eagerly
                  -- loaded, module by module, by the compilation manager.
                  --
                  -- The HPT may contain modules compiled earlier by @--make@
                  -- but not actually below the current module in the dependency
                  -- graph.
                  --
                  -- (This changes a previous invariant: changed Jan 05.)
  
          hsc_EPS :: {-# UNPACK #-} !(IORef ExternalPackageState),
                  -- ^ Information about the currently loaded external packages.
                  -- This is mutable because packages will be demand-loaded during
                  -- a compilation run as required.
  
          hsc_NC  :: {-# UNPACK #-} !(IORef NameCache),
                  -- ^ As with 'hsc_EPS', this is side-effected by compiling to
                  -- reflect sucking in interface files.  They cache the state of
                  -- external interface files, in effect.
  
          hsc_FC   :: {-# UNPACK #-} !(IORef FinderCache),
                  -- ^ The cached result of performing finding in the file system
          hsc_MLC  :: {-# UNPACK #-} !(IORef ModLocationCache),
                  -- ^ This caches the location of modules, so we don't have to
                  -- search the filesystem multiple times. See also 'hsc_FC'.
  
          hsc_type_env_var :: Maybe (Module, IORef TypeEnv),
                  -- ^ Used for one-shot compilation only, to initialise
                  -- the 'IfGblEnv'. See 'TcRnTypes.tcg_type_env_var' for
                  -- 'TcRunTypes.TcGblEnv'
          hsc_iserv :: MVar (Maybe IServ),
                -- ^ interactive server process.  Created the first
                -- time it is needed.
          hsc_classIndex :: MVar ClassIndex
   }
  
   -- Note [hsc_type_env_var hack]
   -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   -- hsc_type_env_var is used to initialize tcg_type_env_var, and
   -- eventually it is the mutable variable that is queried from
   -- if_rec_types to get a TypeEnv.  So, clearly, it's something
   -- related to knot-tying (see Note [Tying the knot]).
   -- hsc_type_env_var is used in two places: initTcRn (where
   -- it initializes tcg_type_env_var) and initIfaceCheck
   -- (where it initializes if_rec_types).
   --
   -- But why do we need a way to feed a mutable variable in?  Why
   -- can't we just initialize tcg_type_env_var when we start
   -- typechecking?  The problem is we need to knot-tie the
   -- EPS, and we may start adding things to the EPS before type
   -- checking starts.
   --
   -- Here is a concrete example. Suppose we are running
   -- "ghc -c A.hs", and we have this file system state:
   --
   --  A.hs-boot   A.hi-boot **up to date**
   --  B.hs        B.hi      **up to date**
   --  A.hs        A.hi      **stale**
   --
   -- The first thing we do is run checkOldIface on A.hi.
   -- checkOldIface will call loadInterface on B.hi so it can
   -- get its hands on the fingerprints, to find out if A.hi
   -- needs recompilation.  But loadInterface also populates
   -- the EPS!  And so if compilation turns out to be necessary,
   -- as it is in this case, the thunks we put into the EPS for
   -- B.hi need to have the correct if_rec_types mutable variable
   -- to query.
   --
   -- If the mutable variable is only allocated WHEN we start
   -- typechecking, then that's too late: we can't get the
   -- information to the thunks.  So we need to pre-commit
   -- to a type variable in 'hscIncrementalCompile' BEFORE we
   -- check the old interface.
   --
   -- This is all a massive hack because arguably checkOldIface
   -- should not populate the EPS. But that's a refactor for
   -- another day.
  
  instance ContainsDynFlags HscEnv where
      extractDynFlags env = hsc_dflags env
      replaceDynFlags env dflags = env {hsc_dflags = dflags}
  
  data IServ = IServ
    { iservPipe :: Pipe
    , iservErrors :: Maybe Handle
    , iservProcess :: ProcessHandle
    , iservLookupSymbolCache :: IORef (UniqFM (Ptr ()))
    , iservPendingFrees :: [HValueRef]
    }
  
  -- | Retrieve the ExternalPackageState cache.
  hscEPS :: HscEnv -> IO ExternalPackageState
  hscEPS hsc_env = readIORef (hsc_EPS hsc_env)
  
  -- | A compilation target.
  --
  -- A target may be supplied with the actual text of the
  -- module.  If so, use this instead of the file contents (this
  -- is for use in an IDE where the file hasn't been saved by
  -- the user yet).
  data Target
    = Target {
        targetId           :: TargetId, -- ^ module or filename
        targetAllowObjCode :: Bool,     -- ^ object code allowed?
        targetContents     :: Maybe (StringBuffer,UTCTime)
                                          -- ^ in-memory text buffer?
      }
  
  data TargetId
    = TargetModule ModuleName
          -- ^ A module name: search for the file
    | TargetFile FilePath (Maybe Phase)
          -- ^ A filename: preprocess & parse it to find the module name.
          -- If specified, the Phase indicates how to compile this file
          -- (which phase to start from).  Nothing indicates the starting phase
          -- should be determined from the suffix of the filename.
    deriving Eq
  
  pprTarget :: Target -> SDoc
  pprTarget (Target id obj _) =
      (if obj then char '*' else empty) <> pprTargetId id
  
  instance Outputable Target where
      ppr = pprTarget
  
  pprTargetId :: TargetId -> SDoc
  pprTargetId (TargetModule m) = ppr m
  pprTargetId (TargetFile f _) = text f
  
  instance Outputable TargetId where
      ppr = pprTargetId
  
  {-
  ************************************************************************
  *                                                                      *
  \subsection{Package and Module Tables}
  *                                                                      *
  ************************************************************************
  -}
  
  -- | Helps us find information about modules in the home package
  type HomePackageTable  = DModuleNameEnv HomeModInfo
          -- Domain = modules in the home package that have been fully compiled
          -- "home" package key cached here for convenience
  
  -- | Helps us find information about modules in the imported packages
  type PackageIfaceTable = ModuleEnv ModIface
          -- Domain = modules in the imported packages
  
  -- | Constructs an empty HomePackageTable
  emptyHomePackageTable :: HomePackageTable
  emptyHomePackageTable  = emptyUDFM
  
  -- | Constructs an empty PackageIfaceTable
  emptyPackageIfaceTable :: PackageIfaceTable
  emptyPackageIfaceTable = emptyModuleEnv
  
  pprHPT :: HomePackageTable -> SDoc
  -- A bit aribitrary for now
  pprHPT hpt = pprUDFM hpt $ \hms ->
      vcat [ hang (ppr (mi_module (hm_iface hm)))
                2 (ppr (md_types (hm_details hm)))
           | hm <- hms ]
  
  lookupHptByModule :: HomePackageTable -> Module -> Maybe HomeModInfo
  -- The HPT is indexed by ModuleName, not Module,
  -- we must check for a hit on the right Module
  lookupHptByModule hpt mod
    = case lookupHpt hpt (moduleName mod) of
        Just hm | mi_module (hm_iface hm) == mod -> Just hm
        _otherwise                               -> Nothing
  
  lookupHpt :: HomePackageTable -> ModuleName -> Maybe HomeModInfo
  lookupHpt = lookupUDFM
  
  lookupHptDirectly :: HomePackageTable -> Unique -> Maybe HomeModInfo
  lookupHptDirectly = lookupUDFM_Directly
  
  eltsHpt :: HomePackageTable -> [HomeModInfo]
  eltsHpt = eltsUDFM
  
  filterHpt :: (HomeModInfo -> Bool) -> HomePackageTable -> HomePackageTable
  filterHpt = filterUDFM
  
  addToHpt :: HomePackageTable -> ModuleName -> HomeModInfo -> HomePackageTable
  addToHpt = addToUDFM
  
  allHpt :: (HomeModInfo -> Bool) -> HomePackageTable -> Bool
  allHpt = allUDFM
  
  mapHpt :: (HomeModInfo -> HomeModInfo) -> HomePackageTable -> HomePackageTable
  mapHpt = mapUDFM
  
  delFromHpt :: HomePackageTable -> ModuleName -> HomePackageTable
  delFromHpt = delFromUDFM
  
  foldHpt :: (HomeModInfo -> a -> a) -> a -> HomePackageTable -> a
  foldHpt = foldUDFM
  
  addListToHpt
    :: HomePackageTable -> [(ModuleName, HomeModInfo)] -> HomePackageTable
  addListToHpt = addListToUDFM
  
  listToHpt :: [(ModuleName, HomeModInfo)] -> HomePackageTable
  listToHpt = listToUDFM
  
  -- | Information about modules in the package being compiled
  data HomeModInfo
    = HomeModInfo {
        hm_iface    :: !ModIface,
          -- ^ The basic loaded interface file: every loaded module has one of
          -- these, even if it is imported from another package
        hm_details  :: !ModDetails,
          -- ^ Extra information that has been created from the 'ModIface' for
          -- the module, typically during typechecking
        hm_linkable :: !(Maybe Linkable)
          -- ^ The actual artifact we would like to link to access things in
          -- this module.
          --
          -- 'hm_linkable' might be Nothing:
          --
          --   1. If this is an .hs-boot module
          --
          --   2. Temporarily during compilation if we pruned away
          --      the old linkable because it was out of date.
          --
          -- After a complete compilation ('GHC.load'), all 'hm_linkable' fields
          -- in the 'HomePackageTable' will be @Just@.
          --
          -- When re-linking a module ('HscMain.HscNoRecomp'), we construct the
          -- 'HomeModInfo' by building a new 'ModDetails' from the old
          -- 'ModIface' (only).
      }
  
  -- | Find the 'ModIface' for a 'Module', searching in both the loaded home
  -- and external package module information
  lookupIfaceByModule
          :: DynFlags
          -> HomePackageTable
          -> PackageIfaceTable
          -> Module
          -> Maybe ModIface
  lookupIfaceByModule _dflags hpt pit mod
    = case lookupHptByModule hpt mod of
         Just hm -> Just (hm_iface hm)
         Nothing -> lookupModuleEnv pit mod
  
  -- If the module does come from the home package, why do we look in the PIT as well?
  -- (a) In OneShot mode, even home-package modules accumulate in the PIT
  -- (b) Even in Batch (--make) mode, there is *one* case where a home-package
  --     module is in the PIT, namely GHC.Prim when compiling the base package.
  -- We could eliminate (b) if we wanted, by making GHC.Prim belong to a package
  -- of its own, but it doesn't seem worth the bother.
  
  
  -- | Find all the instance declarations (of classes and families) from
  -- the Home Package Table filtered by the provided predicate function.
  -- Used in @tcRnImports@, to select the instances that are in the
  -- transitive closure of imports from the currently compiled module.
  hptInstances :: HscEnv -> (ModuleName -> Bool) -> ([ClsInst], [FamInst])
  hptInstances hsc_env want_this_module
    = let (insts, famInsts) = unzip $ flip hptAllThings hsc_env $ \mod_info -> do
                  guard (want_this_module (moduleName (mi_module (hm_iface mod_info))))
                  let details = hm_details mod_info
                  return (md_insts details, md_fam_insts details)
      in (concat insts, concat famInsts)
  
  -- | Get the combined VectInfo of all modules in the home package table. In
  -- contrast to instances and rules, we don't care whether the modules are
  -- "below" us in the dependency sense. The VectInfo of those modules not "below"
  -- us does not affect the compilation of the current module.
  hptVectInfo :: HscEnv -> VectInfo
  hptVectInfo = concatVectInfo . hptAllThings ((: []) . md_vect_info . hm_details)
  
  -- | Get rules from modules "below" this one (in the dependency sense)
  hptRules :: HscEnv -> [(ModuleName, IsBootInterface)] -> [CoreRule]
  hptRules = hptSomeThingsBelowUs (md_rules . hm_details) False
  
  
  -- | Get annotations from modules "below" this one (in the dependency sense)
  hptAnns :: HscEnv -> Maybe [(ModuleName, IsBootInterface)] -> [Annotation]
  hptAnns hsc_env (Just deps) = hptSomeThingsBelowUs (md_anns . hm_details) False hsc_env deps
  hptAnns hsc_env Nothing = hptAllThings (md_anns . hm_details) hsc_env
  
  hptAllThings :: (HomeModInfo -> [a]) -> HscEnv -> [a]
  hptAllThings extract hsc_env = concatMap extract (eltsHpt (hsc_HPT hsc_env))
  
  -- | Get things from modules "below" this one (in the dependency sense)
  -- C.f Inst.hptInstances
  hptSomeThingsBelowUs :: (HomeModInfo -> [a]) -> Bool -> HscEnv -> [(ModuleName, IsBootInterface)] -> [a]
  hptSomeThingsBelowUs extract include_hi_boot hsc_env deps
    | isOneShot (ghcMode (hsc_dflags hsc_env)) = []
  
    | otherwise
    = let hpt = hsc_HPT hsc_env
      in
      [ thing
      |   -- Find each non-hi-boot module below me
        (mod, is_boot_mod) <- deps
      , include_hi_boot || not is_boot_mod
  
          -- unsavoury: when compiling the base package with --make, we
          -- sometimes try to look up RULES etc for GHC.Prim. GHC.Prim won't
          -- be in the HPT, because we never compile it; it's in the EPT
          -- instead. ToDo: clean up, and remove this slightly bogus filter:
      , mod /= moduleName gHC_PRIM
  
          -- Look it up in the HPT
      , let things = case lookupHpt hpt mod of
                      Just info -> extract info
                      Nothing -> pprTrace "WARNING in hptSomeThingsBelowUs" msg []
            msg = vcat [ptext (sLit "missing module") <+> ppr mod,
                        ptext (sLit "Probable cause: out-of-date interface files")]
                          -- This really shouldn't happen, but see Trac #962
  
          -- And get its dfuns
      , thing <- things ]
  
  hptObjs :: HomePackageTable -> [FilePath]
  hptObjs hpt = concat (map (maybe [] linkableObjs . hm_linkable) (eltsHpt hpt))
  
  {-
  ************************************************************************
  *                                                                      *
  \subsection{Metaprogramming}
  *                                                                      *
  ************************************************************************
  -}
  
  -- | The supported metaprogramming result types
  data MetaRequest
    = MetaE  (LHsExpr RdrName   -> MetaResult)
    | MetaP  (LPat RdrName      -> MetaResult)
    | MetaT  (LHsType RdrName   -> MetaResult)
    | MetaD  ([LHsDecl RdrName] -> MetaResult)
    | MetaAW (Serialized        -> MetaResult)
  
  -- | data constructors not exported to ensure correct result type
  data MetaResult
    = MetaResE  { unMetaResE  :: LHsExpr RdrName   }
    | MetaResP  { unMetaResP  :: LPat RdrName      }
    | MetaResT  { unMetaResT  :: LHsType RdrName   }
    | MetaResD  { unMetaResD  :: [LHsDecl RdrName] }
    | MetaResAW { unMetaResAW :: Serialized        }
  
  type MetaHook f = MetaRequest -> LHsExpr Id -> f MetaResult
  
  metaRequestE :: Functor f => MetaHook f -> LHsExpr Id -> f (LHsExpr RdrName)
  metaRequestE h = fmap unMetaResE . h (MetaE MetaResE)
  
  metaRequestP :: Functor f => MetaHook f -> LHsExpr Id -> f (LPat RdrName)
  metaRequestP h = fmap unMetaResP . h (MetaP MetaResP)
  
  metaRequestT :: Functor f => MetaHook f -> LHsExpr Id -> f (LHsType RdrName)
  metaRequestT h = fmap unMetaResT . h (MetaT MetaResT)
  
  metaRequestD :: Functor f => MetaHook f -> LHsExpr Id -> f [LHsDecl RdrName]
  metaRequestD h = fmap unMetaResD . h (MetaD MetaResD)
  
  metaRequestAW :: Functor f => MetaHook f -> LHsExpr Id -> f Serialized
  metaRequestAW h = fmap unMetaResAW . h (MetaAW MetaResAW)
  
  {-
  ************************************************************************
  *                                                                      *
  \subsection{Dealing with Annotations}
  *                                                                      *
  ************************************************************************
  -}
  
  -- | Deal with gathering annotations in from all possible places
  --   and combining them into a single 'AnnEnv'
  prepareAnnotations :: HscEnv -> Maybe ModGuts -> IO AnnEnv
  prepareAnnotations hsc_env mb_guts = do
      eps <- hscEPS hsc_env
      let -- Extract annotations from the module being compiled if supplied one
          mb_this_module_anns = fmap (mkAnnEnv . mg_anns) mb_guts
          -- Extract dependencies of the module if we are supplied one,
          -- otherwise load annotations from all home package table
          -- entries regardless of dependency ordering.
          home_pkg_anns  = (mkAnnEnv . hptAnns hsc_env) $ fmap (dep_mods . mg_deps) mb_guts
          other_pkg_anns = eps_ann_env eps
          ann_env        = foldl1' plusAnnEnv $ catMaybes [mb_this_module_anns,
                                                           Just home_pkg_anns,
                                                           Just other_pkg_anns]
      return ann_env
  
  {-
  ************************************************************************
  *                                                                      *
  \subsection{The Finder cache}
  *                                                                      *
  ************************************************************************
  -}
  
  -- | The 'FinderCache' maps home module names to the result of
  -- searching for that module. It records the results of searching for
  -- modules along the search path. On @:load@, we flush the entire
  -- contents of this cache.
  --
  -- Although the @FinderCache@ range is 'FindResult' for convenience,
  -- in fact it will only ever contain 'Found' or 'NotFound' entries.
  --
  type FinderCache = InstalledModuleEnv InstalledFindResult
  
  data InstalledFindResult
    = InstalledFound ModLocation InstalledModule
    | InstalledNoPackage InstalledUnitId
    | InstalledNotFound [FilePath] (Maybe InstalledUnitId)
  
  -- | The result of searching for an imported module.
  --
  -- NB: FindResult manages both user source-import lookups
  -- (which can result in 'Module') as well as direct imports
  -- for interfaces (which always result in 'VirginModule').
  data FindResult
    = Found ModLocation Module
          -- ^ The module was found
    | NoPackage UnitId
          -- ^ The requested package was not found
    | FoundMultiple [(Module, ModuleOrigin)]
          -- ^ _Error_: both in multiple packages
  
          -- | Not found
    | NotFound
        { fr_paths       :: [FilePath]       -- Places where I looked
  
        , fr_pkg         :: Maybe UnitId  -- Just p => module is in this package's
                                             --           manifest, but couldn't find
                                             --           the .hi file
  
        , fr_mods_hidden :: [UnitId]      -- Module is in these packages,
                                             --   but the *module* is hidden
  
        , fr_pkgs_hidden :: [UnitId]      -- Module is in these packages,
                                             --   but the *package* is hidden
  
        , fr_suggestions :: [ModuleSuggestion] -- Possible mis-spelled modules
        }
  
  -- | Cache that remembers where we found a particular module.  Contains both
  -- home modules and package modules.  On @:load@, only home modules are
  -- purged from this cache.
  type ModLocationCache = ModuleEnv ModLocation
  
  {-
  ************************************************************************
  *                                                                      *
  \subsection{Symbol tables and Module details}
  *                                                                      *
  ************************************************************************
  -}
  
  -- | A 'ModIface' plus a 'ModDetails' summarises everything we know
  -- about a compiled module.  The 'ModIface' is the stuff *before* linking,
  -- and can be written out to an interface file. The 'ModDetails is after
  -- linking and can be completely recovered from just the 'ModIface'.
  --
  -- When we read an interface file, we also construct a 'ModIface' from it,
  -- except that we explicitly make the 'mi_decls' and a few other fields empty;
  -- as when reading we consolidate the declarations etc. into a number of indexed
  -- maps and environments in the 'ExternalPackageState'.
  data ModIface
    = ModIface {
          mi_module     :: !Module,             -- ^ Name of the module we are for
          mi_sig_of     :: !(Maybe Module),     -- ^ Are we a sig of another mod?
          mi_iface_hash :: !Fingerprint,        -- ^ Hash of the whole interface
          mi_mod_hash   :: !Fingerprint,        -- ^ Hash of the ABI only
          mi_flag_hash  :: !Fingerprint,        -- ^ Hash of the important flags
                                                -- used when compiling this module
  
          mi_orphan     :: !WhetherHasOrphans,  -- ^ Whether this module has orphans
          mi_finsts     :: !WhetherHasFamInst,  -- ^ Whether this module has family instances
          mi_hsc_src    :: !HscSource,          -- ^ Boot? Signature?
  
          mi_deps     :: Dependencies,
                  -- ^ The dependencies of the module.  This is
                  -- consulted for directly-imported modules, but not
                  -- for anything else (hence lazy)
  
          mi_usages   :: [Usage],
                  -- ^ Usages; kept sorted so that it's easy to decide
                  -- whether to write a new iface file (changing usages
                  -- doesn't affect the hash of this module)
                  -- NOT STRICT!  we read this field lazily from the interface file
                  -- It is *only* consulted by the recompilation checker
  
          mi_exports  :: ![IfaceExport],
                  -- ^ Exports
                  -- Kept sorted by (mod,occ), to make version comparisons easier
                  -- Records the modules that are the declaration points for things
                  -- exported by this module, and the 'OccName's of those things
  
          mi_exp_hash :: !Fingerprint,
                  -- ^ Hash of export list
  
          mi_used_th  :: !Bool,
                  -- ^ Module required TH splices when it was compiled.
                  -- This disables recompilation avoidance (see #481).
  
          mi_fixities :: [(OccName,Fixity)],
                  -- ^ Fixities
                  -- NOT STRICT!  we read this field lazily from the interface file
  
          mi_warns    :: Warnings,
                  -- ^ Warnings
                  -- NOT STRICT!  we read this field lazily from the interface file
  
          mi_anns     :: [IfaceAnnotation],
                  -- ^ Annotations
                  -- NOT STRICT!  we read this field lazily from the interface file
  
  
          mi_decls    :: [(Fingerprint,IfaceDecl)],
                  -- ^ Type, class and variable declarations
                  -- The hash of an Id changes if its fixity or deprecations change
                  --      (as well as its type of course)
                  -- Ditto data constructors, class operations, except that
                  -- the hash of the parent class/tycon changes
  
          mi_globals  :: !(Maybe GlobalRdrEnv),
                  -- ^ Binds all the things defined at the top level in
                  -- the /original source/ code for this module. which
                  -- is NOT the same as mi_exports, nor mi_decls (which
                  -- may contains declarations for things not actually
                  -- defined by the user).  Used for GHCi and for inspecting
                  -- the contents of modules via the GHC API only.
                  --
                  -- (We need the source file to figure out the
                  -- top-level environment, if we didn't compile this module
                  -- from source then this field contains @Nothing@).
                  --
                  -- Strictly speaking this field should live in the
                  -- 'HomeModInfo', but that leads to more plumbing.
  
                  -- Instance declarations and rules
          mi_insts       :: [IfaceClsInst],     -- ^ Sorted class instance
          mi_fam_insts   :: [IfaceFamInst],  -- ^ Sorted family instances
          mi_rules       :: [IfaceRule],     -- ^ Sorted rules
          mi_orphan_hash :: !Fingerprint,    -- ^ Hash for orphan rules, class and family
                                             -- instances, and vectorise pragmas combined
  
          mi_vect_info :: !IfaceVectInfo,    -- ^ Vectorisation information
  
                  -- Cached environments for easy lookup
                  -- These are computed (lazily) from other fields
                  -- and are not put into the interface file
          mi_warn_fn   :: Name -> Maybe WarningTxt,        -- ^ Cached lookup for 'mi_warns'
          mi_fix_fn    :: OccName -> Fixity,               -- ^ Cached lookup for 'mi_fixities'
          mi_hash_fn   :: OccName -> Maybe (OccName, Fingerprint),
                  -- ^ Cached lookup for 'mi_decls'.
                  -- The @Nothing@ in 'mi_hash_fn' means that the thing
                  -- isn't in decls. It's useful to know that when
                  -- seeing if we are up to date wrt. the old interface.
                  -- The 'OccName' is the parent of the name, if it has one.
  
          mi_hpc       :: !AnyHpcUsage,
                  -- ^ True if this program uses Hpc at any point in the program.
  
          mi_trust     :: !IfaceTrustInfo,
                  -- ^ Safe Haskell Trust information for this module.
  
          mi_trust_pkg :: !Bool
                  -- ^ Do we require the package this module resides in be trusted
                  -- to trust this module? This is used for the situation where a
                  -- module is Safe (so doesn't require the package be trusted
                  -- itself) but imports some trustworthy modules from its own
                  -- package (which does require its own package be trusted).
                  -- See Note [RnNames . Trust Own Package]
       }
  
  -- | The semantic module for this interface; e.g., if it's a interface
  -- for a signature, if 'mi_module' is @p[A=<A>]:A@, 'mi_semantic_module'
  -- will be @<A>@.
  mi_semantic_module :: ModIface -> Module
  mi_semantic_module iface = case mi_sig_of iface of
                             Nothing -> mi_module iface
                             Just mod -> mod
  
  -- | The "precise" free holes, e.g., the signatures that this
  -- 'ModIface' depends on.
  mi_free_holes :: ModIface -> UniqDSet ModuleName
  mi_free_holes iface =
   case splitModuleInsts (mi_module iface) of
     (_, Just indef)
         -- A mini-hack: we rely on the fact that 'renameFreeHoles'
         -- drops things that aren't holes.
         -> renameFreeHoles (mkUniqDSet cands) (indefUnitIdInsts (indefModuleUnitId indef))
     _   -> emptyUniqDSet
   where
     cands = map fst (dep_mods (mi_deps iface))
  
  -- | Given a set of free holes, and a unit identifier, rename
  -- the free holes according to the instantiation of the unit
  -- identifier.  For example, if we have A and B free, and
  -- our unit identity is @p[A=<C>,B=impl:B]@, the renamed free
  -- holes are just C.
  renameFreeHoles :: UniqDSet ModuleName -> [(ModuleName, Module)] -> UniqDSet ModuleName
  renameFreeHoles fhs insts =
     unionManyUniqDSets (map lookup_impl (uniqDSetToList fhs))
   where
     hmap = listToUFM insts
     lookup_impl mod_name
         | Just mod <- lookupUFM hmap mod_name = moduleFreeHoles mod
         -- It wasn't actually a hole
         | otherwise                           = emptyUniqDSet
  
  -- | Old-style accessor for whether or not the ModIface came from an hs-boot
  -- file.
  mi_boot :: ModIface -> Bool
  mi_boot iface = mi_hsc_src iface == HsBootFile
  
  instance Binary ModIface where
     put_ bh (ModIface {
                   mi_module    = mod,
                   mi_sig_of    = sig_of,
                   mi_hsc_src   = hsc_src,
                   mi_iface_hash= iface_hash,
                   mi_mod_hash  = mod_hash,
                   mi_flag_hash = flag_hash,
                   mi_orphan    = orphan,
                   mi_finsts    = hasFamInsts,
                   mi_deps      = deps,
                   mi_usages    = usages,
                   mi_exports   = exports,
                   mi_exp_hash  = exp_hash,
                   mi_used_th   = used_th,
                   mi_fixities  = fixities,
                   mi_warns     = warns,
                   mi_anns      = anns,
                   mi_decls     = decls,
                   mi_insts     = insts,
                   mi_fam_insts = fam_insts,
                   mi_rules     = rules,
                   mi_orphan_hash = orphan_hash,
                   mi_vect_info = vect_info,
                   mi_hpc       = hpc_info,
                   mi_trust     = trust,
                   mi_trust_pkg = trust_pkg }) = do
          put_ bh mod
          put_ bh sig_of
          put_ bh hsc_src
          put_ bh iface_hash
          put_ bh mod_hash
          put_ bh flag_hash
          put_ bh orphan
          put_ bh hasFamInsts
          lazyPut bh deps
          lazyPut bh usages
          put_ bh exports
          put_ bh exp_hash
          put_ bh used_th
          put_ bh fixities
          lazyPut bh warns
          lazyPut bh anns
          put_ bh decls
          put_ bh insts
          put_ bh fam_insts
          lazyPut bh rules
          put_ bh orphan_hash
          put_ bh vect_info
          put_ bh hpc_info
          put_ bh trust
          put_ bh trust_pkg
  
     get bh = do
          mod         <- get bh
          sig_of      <- get bh
          hsc_src     <- get bh
          iface_hash  <- get bh
          mod_hash    <- get bh
          flag_hash   <- get bh
          orphan      <- get bh
          hasFamInsts <- get bh
          deps        <- lazyGet bh
          usages      <- {-# SCC "bin_usages" #-} lazyGet bh
          exports     <- {-# SCC "bin_exports" #-} get bh
          exp_hash    <- get bh
          used_th     <- get bh
          fixities    <- {-# SCC "bin_fixities" #-} get bh
          warns       <- {-# SCC "bin_warns" #-} lazyGet bh
          anns        <- {-# SCC "bin_anns" #-} lazyGet bh
          decls       <- {-# SCC "bin_tycldecls" #-} get bh
          insts       <- {-# SCC "bin_insts" #-} get bh
          fam_insts   <- {-# SCC "bin_fam_insts" #-} get bh
          rules       <- {-# SCC "bin_rules" #-} lazyGet bh
          orphan_hash <- get bh
          vect_info   <- get bh
          hpc_info    <- get bh
          trust       <- get bh
          trust_pkg   <- get bh
          return (ModIface {
                   mi_module      = mod,
                   mi_sig_of      = sig_of,
                   mi_hsc_src     = hsc_src,
                   mi_iface_hash  = iface_hash,
                   mi_mod_hash    = mod_hash,
                   mi_flag_hash   = flag_hash,
                   mi_orphan      = orphan,
                   mi_finsts      = hasFamInsts,
                   mi_deps        = deps,
                   mi_usages      = usages,
                   mi_exports     = exports,
                   mi_exp_hash    = exp_hash,
                   mi_used_th     = used_th,
                   mi_anns        = anns,
                   mi_fixities    = fixities,
                   mi_warns       = warns,
                   mi_decls       = decls,
                   mi_globals     = Nothing,
                   mi_insts       = insts,
                   mi_fam_insts   = fam_insts,
                   mi_rules       = rules,
                   mi_orphan_hash = orphan_hash,
                   mi_vect_info   = vect_info,
                   mi_hpc         = hpc_info,
                   mi_trust       = trust,
                   mi_trust_pkg   = trust_pkg,
                          -- And build the cached values
                   mi_warn_fn     = mkIfaceWarnCache warns,
                   mi_fix_fn      = mkIfaceFixCache fixities,
                   mi_hash_fn     = mkIfaceHashCache decls })
  
  -- | The original names declared of a certain module that are exported
  type IfaceExport = AvailInfo
  
  -- | Constructs an empty ModIface
  emptyModIface :: Module -> ModIface
  emptyModIface mod
    = ModIface { mi_module      = mod,
                 mi_sig_of      = Nothing,
                 mi_iface_hash  = fingerprint0,
                 mi_mod_hash    = fingerprint0,
                 mi_flag_hash   = fingerprint0,
                 mi_orphan      = False,
                 mi_finsts      = False,
                 mi_hsc_src     = HsSrcFile,
                 mi_deps        = noDependencies,
                 mi_usages      = [],
                 mi_exports     = [],
                 mi_exp_hash    = fingerprint0,
                 mi_used_th     = False,
                 mi_fixities    = [],
                 mi_warns       = NoWarnings,
                 mi_anns        = [],
                 mi_insts       = [],
                 mi_fam_insts   = [],
                 mi_rules       = [],
                 mi_decls       = [],
                 mi_globals     = Nothing,
                 mi_orphan_hash = fingerprint0,
                 mi_vect_info   = noIfaceVectInfo,
                 mi_warn_fn     = emptyIfaceWarnCache,
                 mi_fix_fn      = emptyIfaceFixCache,
                 mi_hash_fn     = emptyIfaceHashCache,
                 mi_hpc         = False,
                 mi_trust       = noIfaceTrustInfo,
                 mi_trust_pkg   = False }
  
  
  -- | Constructs cache for the 'mi_hash_fn' field of a 'ModIface'
  mkIfaceHashCache :: [(Fingerprint,IfaceDecl)]
                   -> (OccName -> Maybe (OccName, Fingerprint))
  mkIfaceHashCache pairs
    = \occ -> lookupOccEnv env occ
    where
      env = foldr add_decl emptyOccEnv pairs
      add_decl (v,d) env0 = foldr add env0 (ifaceDeclFingerprints v d)
        where
          add (occ,hash) env0 = extendOccEnv env0 occ (occ,hash)
  
  emptyIfaceHashCache :: OccName -> Maybe (OccName, Fingerprint)
  emptyIfaceHashCache _occ = Nothing
  
  
  -- | The 'ModDetails' is essentially a cache for information in the 'ModIface'
  -- for home modules only. Information relating to packages will be loaded into
  -- global environments in 'ExternalPackageState'.
  data ModDetails
    = ModDetails {
          -- The next two fields are created by the typechecker
          md_exports   :: [AvailInfo],
          md_types     :: !TypeEnv,       -- ^ Local type environment for this particular module
                                          -- Includes Ids, TyCons, PatSyns
          md_insts     :: ![ClsInst],     -- ^ 'DFunId's for the instances in this module
          md_fam_insts :: ![FamInst],
          md_rules     :: ![CoreRule],    -- ^ Domain may include 'Id's from other modules
          md_anns      :: ![Annotation],  -- ^ Annotations present in this module: currently
                                          -- they only annotate things also declared in this module
          md_vect_info :: !VectInfo       -- ^ Module vectorisation information
       }
  
  -- | Constructs an empty ModDetails
  emptyModDetails :: ModDetails
  emptyModDetails
    = ModDetails { md_types     = emptyTypeEnv,
                   md_exports   = [],
                   md_insts     = [],
                   md_rules     = [],
                   md_fam_insts = [],
                   md_anns      = [],
                   md_vect_info = noVectInfo }
  
  -- | Records the modules directly imported by a module for extracting e.g. usage information
  type ImportedMods = ModuleEnv [ImportedBy]
  
  -- | If a module was "imported" by the user, we associate it with
  -- more detailed usage information 'ImportedModsVal'; a module
  -- imported by the system only gets used for usage information.
  data ImportedBy
      = ImportedByUser ImportedModsVal
      | ImportedBySystem
  
  importedByUser :: [ImportedBy] -> [ImportedModsVal]
  importedByUser (ImportedByUser imv : bys) = imv : importedByUser bys
  importedByUser (ImportedBySystem   : bys) =       importedByUser bys
  importedByUser [] = []
  
  data ImportedModsVal
   = ImportedModsVal {
          imv_name :: ModuleName,          -- ^ The name the module is imported with
          imv_span :: SrcSpan,             -- ^ the source span of the whole import
          imv_is_safe :: IsSafeImport,     -- ^ whether this is a safe import
          imv_is_hiding :: Bool,           -- ^ whether this is an "hiding" import
          imv_all_exports :: !GlobalRdrEnv, -- ^ all the things the module could provide
            -- NB. BangPattern here: otherwise this leaks. (#15111)
          imv_qualified :: Bool            -- ^ whether this is a qualified import
          }
  
  -- | A ModGuts is carried through the compiler, accumulating stuff as it goes
  -- There is only one ModGuts at any time, the one for the module
  -- being compiled right now.  Once it is compiled, a 'ModIface' and
  -- 'ModDetails' are extracted and the ModGuts is discarded.
  data ModGuts
    = ModGuts {
          mg_module    :: !Module,         -- ^ Module being compiled
          mg_hsc_src   :: HscSource,       -- ^ Whether it's an hs-boot module
          mg_exports   :: ![AvailInfo],    -- ^ What it exports
          mg_deps      :: !Dependencies,   -- ^ What it depends on, directly or
                                           -- otherwise
          mg_usages    :: ![Usage],        -- ^ What was used?  Used for interfaces.
          mg_used_th   :: !Bool,           -- ^ Did we run a TH splice?
          mg_rdr_env   :: !GlobalRdrEnv,   -- ^ Top-level lexical environment
  
          -- These fields all describe the things **declared in this module**
          mg_fix_env   :: !FixityEnv,      -- ^ Fixities declared in this module.
                                           -- Used for creating interface files.
          mg_tcs       :: ![TyCon],        -- ^ TyCons declared in this module
                                           -- (includes TyCons for classes)
          mg_insts     :: ![ClsInst],      -- ^ Class instances declared in this module
          mg_fam_insts :: ![FamInst],
                                           -- ^ Family instances declared in this module
          mg_patsyns   :: ![PatSyn],       -- ^ Pattern synonyms declared in this module
          mg_rules     :: ![CoreRule],     -- ^ Before the core pipeline starts, contains
                                           -- See Note [Overall plumbing for rules] in Rules.lhs
          mg_binds     :: !CoreProgram,    -- ^ Bindings for this module
          mg_foreign   :: !ForeignStubs,   -- ^ Foreign exports declared in this module
          mg_warns     :: !Warnings,       -- ^ Warnings declared in the module
          mg_anns      :: [Annotation],    -- ^ Annotations declared in this module
          mg_hpc_info  :: !HpcInfo,        -- ^ Coverage tick boxes in the module
          mg_modBreaks :: !ModBreaks,      -- ^ Breakpoints for the module
          mg_vect_decls:: ![CoreVect],     -- ^ Vectorisation declarations in this module
                                           --   (produced by desugarer & consumed by vectoriser)
          mg_vect_info :: !VectInfo,       -- ^ Pool of vectorised declarations in the module
  
          -- The next two fields are unusual, because they give instance
          -- environments for *all* modules in the home package, including
          -- this module, rather than for *just* this module.
          -- Reason: when looking up an instance we don't want to have to
          --        look at each module in the home package in turn
          mg_inst_env     :: InstEnv,
          -- ^ Class instance environment from /home-package/ modules (including
          -- this one); c.f. 'tcg_inst_env'
          mg_fam_inst_env :: FamInstEnv,
          -- ^ Type-family instance environment for /home-package/ modules
          -- (including this one); c.f. 'tcg_fam_inst_env'
          mg_safe_haskell :: SafeHaskellMode,
          -- ^ Safe Haskell mode
          mg_trust_pkg    :: Bool
          -- ^ Do we need to trust our own package for Safe Haskell?
          -- See Note [RnNames . Trust Own Package]
      }
  
  -- The ModGuts takes on several slightly different forms:
  --
  -- After simplification, the following fields change slightly:
  --      mg_rules        Orphan rules only (local ones now attached to binds)
  --      mg_binds        With rules attached
  
  
  ---------------------------------------------------------
  -- The Tidy pass forks the information about this module:
  --      * one lot goes to interface file generation (ModIface)
  --        and later compilations (ModDetails)
  --      * the other lot goes to code generation (CgGuts)
  
  -- | A restricted form of 'ModGuts' for code generation purposes
  data CgGuts
    = CgGuts {
          cg_module    :: !Module,
                  -- ^ Module being compiled
  
          cg_tycons    :: [TyCon],
                  -- ^ Algebraic data types (including ones that started
                  -- life as classes); generate constructors and info
                  -- tables. Includes newtypes, just for the benefit of
                  -- External Core
  
          cg_binds     :: CoreProgram,
                  -- ^ The tidied main bindings, including
                  -- previously-implicit bindings for record and class
                  -- selectors, and data constructor wrappers.  But *not*
                  -- data constructor workers; reason: we we regard them
                  -- as part of the code-gen of tycons
  
          cg_foreign   :: !ForeignStubs,   -- ^ Foreign export stubs
          cg_dep_pkgs  :: ![InstalledUnitId],    -- ^ Dependent packages, used to
                                           -- generate #includes for C code gen
          cg_hpc_info  :: !HpcInfo,        -- ^ Program coverage tick box information
          cg_modBreaks :: !ModBreaks       -- ^ Module breakpoints
      }
  
  -----------------------------------
  type ClassName     = Text
  type ExportMethods = Map ClassName ([MethodDef], [FieldDef])
  
  -- | Foreign export stubs
  data ForeignStubs
    = NoStubs
        -- ^ We don't have any stubs
    | ForeignStubs SDoc SDoc ExportMethods
        -- ^ There are some stubs. Parameters:
        --
        --  1) Header file prototypes for
        --     "foreign exported" functions
        --
        --  2) C stubs to use when calling
        --     "foreign exported" functions
        --
        --  3) Map of class strings to method defintions:
        --     "place.Garage extends place.Home" --> [defs...]
  
  foreignExportsList :: ExportMethods -> [(Text, ([MethodDef], [FieldDef]))]
  foreignExportsList = M.toList
  
  lookupStubs :: ClassName -> ForeignStubs -> Maybe ([MethodDef], [FieldDef])
  lookupStubs cls stubs
    | ForeignStubs _ _ m <- stubs = M.lookup cls m
    | otherwise = Nothing
  
  appendStubC :: ForeignStubs -> SDoc -> ForeignStubs
  appendStubC NoStubs            c_code = ForeignStubs empty c_code M.empty
  appendStubC (ForeignStubs h c m) c_code = ForeignStubs h (c $$ c_code) m
  
  appendDefs :: ForeignStubs -> [(Text, MethodDef, Maybe FieldDef)] -> ForeignStubs
  appendDefs NoStubs defs'
    | length defs' > 0 = ForeignStubs empty empty (M.fromListWith combineExports defs)
    | otherwise = NoStubs
    where defs = createExports defs'
  appendDefs (ForeignStubs h c m) defs' =
    ForeignStubs h c (M.unionWith combineExports m (M.fromListWith combineExports defs))
    where defs = createExports defs'
  
  combineExports ::  ([a], [b]) -> ([a], [b]) -> ([a], [b])
  combineExports (mds, fds) (mds', fds') = (mds ++ mds', fds ++ fds')
  createExports :: [(t, t1, Maybe a)] -> [(t, ([t1], [a]))]
  createExports defs = map (\(t,md,fd) -> (t,([md],maybeToList fd))) defs
  
  {-
  ************************************************************************
  *                                                                      *
  \subsection{The interactive context}
  *                                                                      *
  ************************************************************************
  
  Note [The interactive package]
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  Type, class, and value declarations at the command prompt are treated
  as if they were defined in modules
     interactive:Ghci1
     interactive:Ghci2
     ...etc...
  with each bunch of declarations using a new module, all sharing a
  common package 'interactive' (see Module.interactiveUnitId, and
  PrelNames.mkInteractiveModule).
  
  This scheme deals well with shadowing.  For example:
  
     ghci> data T = A
     ghci> data T = B
     ghci> :i A
     data Ghci1.T = A  -- Defined at <interactive>:2:10
  
  Here we must display info about constructor A, but its type T has been
  shadowed by the second declaration.  But it has a respectable
  qualified name (Ghci1.T), and its source location says where it was
  defined.
  
  So the main invariant continues to hold, that in any session an
  original name M.T only refers to one unique thing.  (In a previous
  iteration both the T's above were called :Interactive.T, albeit with
  different uniques, which gave rise to all sorts of trouble.)
  
  The details are a bit tricky though:
  
   * The field ic_mod_index counts which Ghci module we've got up to.
     It is incremented when extending ic_tythings
  
   * ic_tythings contains only things from the 'interactive' package.
  
   * Module from the 'interactive' package (Ghci1, Ghci2 etc) never go
     in the Home Package Table (HPT).  When you say :load, that's when we
     extend the HPT.
  
   * The 'thisPackage' field of DynFlags is *not* set to 'interactive'.
     It stays as 'main' (or whatever -this-unit-key says), and is the
     package to which :load'ed modules are added to.
  
   * So how do we arrange that declarations at the command prompt get to
     be in the 'interactive' package?  Simply by setting the tcg_mod
     field of the TcGblEnv to "interactive:Ghci1".  This is done by the
     call to initTc in initTcInteractive, which in turn get the module
     from it 'icInteractiveModule' field of the interactive context.
  
     The 'thisPackage' field stays as 'main' (or whatever -this-unit-key says.
  
   * The main trickiness is that the type environment (tcg_type_env) and
     fixity envt (tcg_fix_env), now contain entities from all the
     interactive-package modules (Ghci1, Ghci2, ...) together, rather
     than just a single module as is usually the case.  So you can't use
     "nameIsLocalOrFrom" to decide whether to look in the TcGblEnv vs
     the HPT/PTE.  This is a change, but not a problem provided you
     know.
  
  * However, the tcg_binds, tcg_sigs, tcg_insts, tcg_fam_insts, etc fields
    of the TcGblEnv, which collect "things defined in this module", all
    refer to stuff define in a single GHCi command, *not* all the commands
    so far.
  
    In contrast, tcg_inst_env, tcg_fam_inst_env, have instances from
    all GhciN modules, which makes sense -- they are all "home package"
    modules.
  
  
  Note [Interactively-bound Ids in Eta REPL]
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  The Ids bound by previous Stmts in Eta REPL are currently
          a) GlobalIds, with
          b) An External Name, like Ghci4.foo
             See Note [The interactive package] above
          c) A tidied type
  
   (a) They must be GlobalIds (not LocalIds) otherwise when we come to
       compile an expression using these ids later, the byte code
       generator will consider the occurrences to be free rather than
       global.
  
   (b) Having an External Name is important because of Note
       [GlobalRdrEnv shadowing] in RdrName
  
  Where do interactively-bound Ids come from?
  
    - Eta REPL Stmts   e.g.
           ghci> let foo x = x+1
      These start with an Internal Name because a Stmt is a local
      construct, so the renamer naturally builds an Internal name for
      each of its binders.  Then in tcRnStmt they are externalised via
      TcRnDriver.externaliseAndTidyId, so they get Names like Ghic4.foo.
  
    - Ids bound by the debugger etc have Names constructed by
      IfaceEnv.newInteractiveBinder; at the call sites it is followed by
      mkVanillaGlobal or mkVanillaGlobalWithInfo.  So again, they are
      all Global, External.
  
    - TyCons, Classes, and Ids bound by other top-level declarations in
      GHCi (eg foreign import, record selectors) also get External
      Names, with Ghci9 (or 8, or 7, etc) as the module name.
  
  
  Note [ic_tythings]
  ~~~~~~~~~~~~~~~~~~
  The ic_tythings field contains
    * The TyThings declared by the user at the command prompt
      (eg Ids, TyCons, Classes)
  
    * The user-visible Ids that arise from such things, which
      *don't* come from 'implicitTyThings', notably:
         - record selectors
         - class ops
      The implicitTyThings are readily obtained from the TyThings
      but record selectors etc are not
  
  It does *not* contain
    * DFunIds (they can be gotten from ic_instances)
    * CoAxioms (ditto)
  
  See also Note [Interactively-bound Ids in GHCi]
  
  Note [Override identical instances in GHCi]
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  If you declare a new instance in GHCi that is identical to a previous one,
  we simply override the previous one; we don't regard it as overlapping.
  e.g.    Prelude> data T = A | B
          Prelude> instance Eq T where ...
          Prelude> instance Eq T where ...   -- This one overrides
  
  It's exactly the same for type-family instances.  See Trac #7102
  -}
  
  -- | Interactive context, recording information about the state of the
  -- context in which statements are executed in a GHC session.
  data InteractiveContext
    = InteractiveContext {
           ic_dflags     :: DynFlags,
               -- ^ The 'DynFlags' used to evaluate interative expressions
               -- and statements.
  
           ic_mod_index :: Int,
               -- ^ Each GHCi stmt or declaration brings some new things into
               -- scope. We give them names like interactive:Ghci9.T,
               -- where the ic_index is the '9'.  The ic_mod_index is
               -- incremented whenever we add something to ic_tythings
               -- See Note [The interactive package]
  
           ic_imports :: [InteractiveImport],
               -- ^ The GHCi top-level scope (ic_rn_gbl_env) is extended with
               -- these imports
               --
               -- This field is only stored here so that the client
               -- can retrieve it with GHC.getContext. GHC itself doesn't
               -- use it, but does reset it to empty sometimes (such
               -- as before a GHC.load). The context is set with GHC.setContext.
  
           ic_tythings   :: [TyThing],
               -- ^ TyThings defined by the user, in reverse order of
               -- definition (ie most recent at the front)
               -- See Note [ic_tythings]
  
           ic_rn_gbl_env :: GlobalRdrEnv,
               -- ^ The cached 'GlobalRdrEnv', built by
               -- 'InteractiveEval.setContext' and updated regularly
               -- It contains everything in scope at the command line,
               -- including everything in ic_tythings
  
           ic_instances  :: ([ClsInst], [FamInst]),
               -- ^ All instances and family instances created during
               -- this session.  These are grabbed en masse after each
               -- update to be sure that proper overlapping is retained.
               -- That is, rather than re-check the overlapping each
               -- time we update the context, we just take the results
               -- from the instance code that already does that.
  
           ic_fix_env :: FixityEnv,
              -- ^ Fixities declared in let statements
  
           ic_default :: Maybe [Type],
               -- ^ The current default types, set by a 'default' declaration
  
  #ifdef ETA_REPL
            ic_resume :: [Resume],
               -- ^ The stack of breakpoint contexts
  #endif
  
           ic_monad      :: Name,
               -- ^ The monad that GHCi is executing in
  
           ic_int_print  :: Name,
               -- ^ The function that is used for printing results
               -- of expressions in ghci and -e mode.
  
           ic_cwd :: Maybe FilePath,
               -- virtual CWD of the program
  
           ic_expr_counter :: IORef Int64,
               -- ^ A thread-safe counter used to identify distinct expressions.
               --   Should be large enough such that it shouldn't overflow.
  
           ic_it_counter :: IORef Int64
               -- ^ A thread-safe counter used to identify distinct repl expressions.
               --   Should be large enough such that it shouldn't overflow.
      }
  
  data InteractiveImport
    = IIDecl (ImportDecl RdrName)
        -- ^ Bring the exports of a particular module
        -- (filtered by an import decl) into scope
  
    | IIModule ModuleName
        -- ^ Bring into scope the entire top-level envt of
        -- of this module, including the things imported
        -- into it.
  
  newInteractiveContext :: (MonadIO m) => DynFlags -> m InteractiveContext
  newInteractiveContext dflags = do
      itCounter <- liftIO $ newIORef 0
      return $ InteractiveContext {
         ic_dflags       = dflags,
         ic_imports      = [],
         ic_rn_gbl_env   = emptyGlobalRdrEnv,
         ic_mod_index    = 1,
         ic_tythings     = [],
         ic_instances    = ([],[]),
         ic_fix_env      = emptyNameEnv,
         ic_monad        = ioTyConName,  -- IO monad by default
         ic_int_print    = printName,    -- System.IO.print by default
         ic_default      = Nothing,
  #ifdef ETA_REPL
         ic_resume       = [],
  #endif
         ic_cwd          = Nothing,
         ic_expr_counter = exprCounter,
         ic_it_counter   = itCounter
         }
  
  {-# NOINLINE exprCounter #-}
  exprCounter :: IORef Int64
  exprCounter = unsafePerformIO (newIORef 0)
  
  icExprCounter :: (MonadIO m) => InteractiveContext -> m Int64
  icExprCounter (InteractiveContext { ic_expr_counter = ctr }) =
    liftIO $ readIORef ctr
  
  -- | Atomically increment the expression counter.
  icExprCounterInc :: (MonadIO m) => InteractiveContext -> m Int64
  icExprCounterInc (InteractiveContext { ic_expr_counter = ctr }) =
    liftIO $ atomicModifyIORef' ctr (\x -> (x + 1, x))
  
  -- | Atomically increment the expression counter.
  icItCounterInc :: (MonadIO m) => InteractiveContext -> m Int64
  icItCounterInc (InteractiveContext { ic_it_counter = ctr }) =
    liftIO $ atomicModifyIORef' ctr (\x -> (x + 1, x))
  
  icInteractiveModule :: InteractiveContext -> Module
  icInteractiveModule (InteractiveContext { ic_mod_index = index })
    = mkInteractiveModule index
  
  -- | This function returns the list of visible TyThings (useful for
  -- e.g. showBindings)
  icInScopeTTs :: InteractiveContext -> [TyThing]
  icInScopeTTs = ic_tythings
  
  -- | Get the PrintUnqualified function based on the flags and this InteractiveContext
  icPrintUnqual :: DynFlags -> InteractiveContext -> PrintUnqualified
  icPrintUnqual dflags InteractiveContext{ ic_rn_gbl_env = grenv } =
      mkPrintUnqualified dflags grenv
  
  -- | extendInteractiveContext is called with new TyThings recently defined to update the
  -- InteractiveContext to include them.  Ids are easily removed when shadowed,
  -- but Classes and TyCons are not.  Some work could be done to determine
  -- whether they are entirely shadowed, but as you could still have references
  -- to them (e.g. instances for classes or values of the type for TyCons), it's
  -- not clear whether removing them is even the appropriate behavior.
  extendInteractiveContext :: InteractiveContext
                           -> [TyThing]
                           -> [ClsInst] -> [FamInst]
                           -> Maybe [Type]
                           -> FixityEnv
                           -> InteractiveContext
  extendInteractiveContext ictxt new_tythings new_cls_insts new_fam_insts defaults fix_env
    = ictxt { ic_mod_index  = ic_mod_index ictxt + 1
                              -- Always bump this; even instances should create
                              -- a new mod_index (Trac #9426)
            , ic_tythings   = new_tythings ++ old_tythings
            , ic_rn_gbl_env = ic_rn_gbl_env ictxt `icExtendGblRdrEnv` new_tythings
            , ic_instances  = ( new_cls_insts ++ old_cls_insts
                              , new_fam_insts ++ fam_insts )
                              -- we don't shadow old family instances (#7102),
                              -- so don't need to remove them here
            , ic_default    = defaults
            , ic_fix_env    = fix_env  -- See Note [Fixity declarations in GHCi]
            }
    where
      new_ids = [id | AnId id <- new_tythings]
      old_tythings = filterOut (shadowed_by new_ids) (ic_tythings ictxt)
  
      -- Discard old instances that have been fully overridden
      -- See Note [Override identical instances in GHCi]
      (cls_insts, fam_insts) = ic_instances ictxt
      old_cls_insts = filterOut (\i -> any (identicalClsInstHead i) new_cls_insts) cls_insts
  
  extendInteractiveContextWithIds :: InteractiveContext -> [Id] -> InteractiveContext
  -- Just a specialised version
  extendInteractiveContextWithIds ictxt new_ids
    | null new_ids  = ictxt
    | otherwise = ictxt { ic_mod_index  = ic_mod_index ictxt + 1
                        , ic_tythings   = new_tythings ++ old_tythings
                        , ic_rn_gbl_env = ic_rn_gbl_env ictxt `icExtendGblRdrEnv` new_tythings }
    where
      new_tythings = map AnId new_ids
      old_tythings = filterOut (shadowed_by new_ids) (ic_tythings ictxt)
  
  shadowed_by :: [Id] -> TyThing -> Bool
  shadowed_by ids = shadowed
    where
      shadowed id = getOccName id `elemOccSet` new_occs
      new_occs = mkOccSet (map getOccName ids)
  
  setInteractivePackage :: HscEnv -> HscEnv
  -- Set the 'thisPackage' DynFlag to 'interactive'
  setInteractivePackage hsc_env
     = hsc_env { hsc_dflags = (hsc_dflags hsc_env)
                 { thisInstalledUnitId = toInstalledUnitId interactiveUnitId } }
  
  setInteractivePrintName :: InteractiveContext -> Name -> InteractiveContext
  setInteractivePrintName ic n = ic{ic_int_print = n}
  
      -- ToDo: should not add Ids to the gbl env here
  
  -- | Add TyThings to the GlobalRdrEnv, earlier ones in the list shadowing
  -- later ones, and shadowing existing entries in the GlobalRdrEnv.
  icExtendGblRdrEnv :: GlobalRdrEnv -> [TyThing] -> GlobalRdrEnv
  icExtendGblRdrEnv env tythings
    = foldr add env tythings  -- Foldr makes things in the front of
                              -- the list shadow things at the back
    where
      add thing env = extendGlobalRdrEnv True {- Shadowing please -} env
                                         [tyThingAvailInfo thing]
         -- One at a time, to ensure each shadows the previous ones
  
  substInteractiveContext :: InteractiveContext -> TvSubst -> InteractiveContext
  substInteractiveContext ictxt@InteractiveContext{ ic_tythings = tts } subst
    | isEmptyTvSubst subst = ictxt
    | otherwise            = ictxt { ic_tythings = map subst_ty tts }
    where
      subst_ty (AnId id)
        = AnId $ id `setIdType` substTyAddInScope subst (idType id)
        -- Variables in the interactive context *can* mention free type variables
        -- because of the runtime debugger. Otherwise you'd expect all
        -- variables bound in the interactive context to be closed.
      subst_ty tt
        = tt
  
  instance Outputable InteractiveImport where
    ppr (IIModule m) = char '*' <> ppr m
    ppr (IIDecl d)   = ppr d
  
  {-
  ************************************************************************
  *                                                                      *
          Building a PrintUnqualified
  *                                                                      *
  ************************************************************************
  
  Note [Printing original names]
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  Deciding how to print names is pretty tricky.  We are given a name
  P:M.T, where P is the package name, M is the defining module, and T is
  the occurrence name, and we have to decide in which form to display
  the name given a GlobalRdrEnv describing the current scope.
  
  Ideally we want to display the name in the form in which it is in
  scope.  However, the name might not be in scope at all, and that's
  where it gets tricky.  Here are the cases:
  
   1. T uniquely maps to  P:M.T      --->  "T"      NameUnqual
   2. There is an X for which X.T
         uniquely maps to  P:M.T     --->  "X.T"    NameQual X
   3. There is no binding for "M.T"  --->  "M.T"    NameNotInScope1
   4. Otherwise                      --->  "P:M.T"  NameNotInScope2
  
  (3) and (4) apply when the entity P:M.T is not in the GlobalRdrEnv at
  all. In these cases we still want to refer to the name as "M.T", *but*
  "M.T" might mean something else in the current scope (e.g. if there's
  an "import X as M"), so to avoid confusion we avoid using "M.T" if
  there's already a binding for it.  Instead we write P:M.T.
  
  There's one further subtlety: in case (3), what if there are two
  things around, P1:M.T and P2:M.T?  Then we don't want to print both of
  them as M.T!  However only one of the modules P1:M and P2:M can be
  exposed (say P2), so we use M.T for that, and P1:M.T for the other one.
  This is handled by the qual_mod component of PrintUnqualified, inside
  the (ppr mod) of case (3), in Name.pprModulePrefix
  
  Note [Printing unit ids]
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  In the old days, original names were tied to PackageIds, which directly
  corresponded to the entities that users wrote in Cabal files, and were perfectly
  suitable for printing when we need to disambiguate packages.  However, with
  UnitId, the situation can be different: if the key is instantiated with
  some holes, we should try to give the user some more useful information.
  -}
  
  -- | Creates some functions that work out the best ways to format
  -- names for the user according to a set of heuristics.
  mkPrintUnqualified :: DynFlags -> GlobalRdrEnv -> PrintUnqualified
  mkPrintUnqualified dflags env = QueryQualify qual_name
                                               (mkQualModule dflags)
                                               (mkQualPackage dflags)
    where
    qual_name mod occ
          | [gre] <- unqual_gres
          , right_name gre
          = NameUnqual
                  -- If there's a unique entity that's in scope unqualified with 'occ'
                  -- AND that entity is the right one, then we can use the unqualified name
  
          | [gre] <- qual_gres
          = NameQual (get_qual_mod (gre_prov gre))
  
          | null qual_gres
          = if null (lookupGRE_RdrName (mkRdrQual (moduleName mod) occ) env)
            then NameNotInScope1
            else NameNotInScope2
  
          | otherwise
          = NameNotInScope1   -- Can happen if 'f' is bound twice in the module
                              -- Eg  f = True; g = 0; f = False
        where
          right_name gre = nameModule_maybe (gre_name gre) == Just mod
  
          unqual_gres = lookupGRE_RdrName (mkRdrUnqual occ) env
          qual_gres   = filter right_name (lookupGlobalRdrEnv env occ)
  
          get_qual_mod LocalDef      = moduleName mod
          get_qual_mod (Imported is) = ASSERT( not (null is) ) is_as (is_decl (head is))
  
      -- we can mention a module P:M without the P: qualifier iff
      -- "import M" would resolve unambiguously to P:M.  (if P is the
      -- current package we can just assume it is unqualified).
  
  -- | Creates a function for formatting modules based on two heuristics:
  -- (1) if the module is the current module, don't qualify, and (2) if there
  -- is only one exposed package which exports this module, don't qualify.
  mkQualModule :: DynFlags -> QueryQualifyModule
  mkQualModule dflags mod
       | moduleUnitId mod == thisPackage dflags = False
  
       | [(_, pkgconfig)] <- lookup,
         packageConfigId pkgconfig == moduleUnitId mod
          -- this says: we are given a module P:M, is there just one exposed package
          -- that exposes a module M, and is it package P?
       = False
  
       | otherwise = True
       where lookup = lookupModuleInAllPackages dflags (moduleName mod)
  
  -- | Creates a function for formatting packages based on two heuristics:
  -- (1) don't qualify if the package in question is "main", and (2) only qualify
  -- with a package key if the package ID would be ambiguous.
  mkQualPackage :: DynFlags -> QueryQualifyPackage
  mkQualPackage dflags pkg_key
       | pkg_key == mainUnitId || pkg_key == interactiveUnitId
          -- Skip the lookup if it's main, since it won't be in the package
          -- database!
       = False
       | Just pkgid <- mb_pkgid
       , searchPackageId dflags pkgid `lengthIs` 1
          -- this says: we are given a package pkg-0.1@MMM, are there only one
          -- exposed packages whose package ID is pkg-0.1?
       = False
       | otherwise
       = True
       where mb_pkgid = fmap sourcePackageId (lookupPackage dflags pkg_key)
  
  -- | A function which only qualifies package names if necessary; but
  -- qualifies all other identifiers.
  pkgQual :: DynFlags -> PrintUnqualified
  pkgQual dflags = alwaysQualify {
          queryQualifyPackage = mkQualPackage dflags
      }
  
  {-
  ************************************************************************
  *                                                                      *
                  Implicit TyThings
  *                                                                      *
  ************************************************************************
  
  Note [Implicit TyThings]
  ~~~~~~~~~~~~~~~~~~~~~~~~
    DEFINITION: An "implicit" TyThing is one that does not have its own
    IfaceDecl in an interface file.  Instead, its binding in the type
    environment is created as part of typechecking the IfaceDecl for
    some other thing.
  
  Examples:
    * All DataCons are implicit, because they are generated from the
      IfaceDecl for the data/newtype.  Ditto class methods.
  
    * Record selectors are *not* implicit, because they get their own
      free-standing IfaceDecl.
  
    * Associated data/type families are implicit because they are
      included in the IfaceDecl of the parent class.  (NB: the
      IfaceClass decl happens to use IfaceDecl recursively for the
      associated types, but that's irrelevant here.)
  
    * Dictionary function Ids are not implicit.
  
    * Axioms for newtypes are implicit (same as above), but axioms
      for data/type family instances are *not* implicit (like DFunIds).
  -}
  
  -- | Determine the 'TyThing's brought into scope by another 'TyThing'
  -- /other/ than itself. For example, Id's don't have any implicit TyThings
  -- as they just bring themselves into scope, but classes bring their
  -- dictionary datatype, type constructor and some selector functions into
  -- scope, just for a start!
  
  -- N.B. the set of TyThings returned here *must* match the set of
  -- names returned by LoadIface.ifaceDeclImplicitBndrs, in the sense that
  -- TyThing.getOccName should define a bijection between the two lists.
  -- This invariant is used in LoadIface.loadDecl (see note [Tricky iface loop])
  -- The order of the list does not matter.
  implicitTyThings :: TyThing -> [TyThing]
  implicitTyThings (AnId _)       = []
  implicitTyThings (ACoAxiom _cc) = []
  implicitTyThings (ATyCon tc)    = implicitTyConThings tc
  implicitTyThings (AConLike cl)  = implicitConLikeThings cl
  
  implicitConLikeThings :: ConLike -> [TyThing]
  implicitConLikeThings (RealDataCon dc)
    = map AnId (dataConImplicitIds dc)
      -- For data cons add the worker and (possibly) wrapper
  
  implicitConLikeThings (PatSynCon {})
    = []  -- Pattern synonyms have no implicit Ids; the wrapper and matcher
          -- are not "implicit"; they are simply new top-level bindings,
          -- and they have their own declaration in an interface file
  
  implicitClassThings :: Class -> [TyThing]
  implicitClassThings cl
    = -- Does not include default methods, because those Ids may have
      --    their own pragmas, unfoldings etc, not derived from the Class object
      -- associated types
      --    No extras_plus (recursive call) for the classATs, because they
      --    are only the family decls; they have no implicit things
      map ATyCon (classATs cl) ++
      -- superclass and operation selectors
      map AnId (classAllSelIds cl)
  
  implicitTyConThings :: TyCon -> [TyThing]
  implicitTyConThings tc
    = class_stuff ++
        -- fields (names of selectors)
  
        -- (possibly) implicit newtype coercion
      implicitCoTyCon tc ++
  
        -- for each data constructor in order,
        --   the contructor, worker, and (possibly) wrapper
      concatMap (extras_plus . AConLike . RealDataCon) (tyConDataCons tc)
        -- NB. record selectors are *not* implicit, they have fully-fledged
        -- bindings that pass through the compilation pipeline as normal.
    where
      class_stuff = case tyConClass_maybe tc of
          Nothing -> []
          Just cl -> implicitClassThings cl
  
  -- add a thing and recursive call
  extras_plus :: TyThing -> [TyThing]
  extras_plus thing = thing : implicitTyThings thing
  
  -- For newtypes and closed type families (only) add the implicit coercion tycon
  implicitCoTyCon :: TyCon -> [TyThing]
  implicitCoTyCon tc
    | Just co <- newTyConCo_maybe tc = [ACoAxiom $ toBranchedAxiom co]
    | Just co <- isClosedSynFamilyTyCon_maybe tc
                                     = [ACoAxiom co]
    | otherwise                      = []
  
  -- | Returns @True@ if there should be no interface-file declaration
  -- for this thing on its own: either it is built-in, or it is part
  -- of some other declaration, or it is generated implicitly by some
  -- other declaration.
  isImplicitTyThing :: TyThing -> Bool
  isImplicitTyThing (AConLike cl) = case cl of
                                      RealDataCon {} -> True
                                      PatSynCon {}   -> False
  isImplicitTyThing (AnId id)     = isImplicitId id
  isImplicitTyThing (ATyCon tc)   = isImplicitTyCon tc
  isImplicitTyThing (ACoAxiom ax) = isImplicitCoAxiom ax
  
  -- | tyThingParent_maybe x returns (Just p)
  -- when pprTyThingInContext sould print a declaration for p
  -- (albeit with some "..." in it) when asked to show x
  -- It returns the *immediate* parent.  So a datacon returns its tycon
  -- but the tycon could be the associated type of a class, so it in turn
  -- might have a parent.
  tyThingParent_maybe :: TyThing -> Maybe TyThing
  tyThingParent_maybe (AConLike cl) = case cl of
      RealDataCon dc  -> Just (ATyCon (dataConTyCon dc))
      PatSynCon{}     -> Nothing
  tyThingParent_maybe (ATyCon tc)   = case tyConAssoc_maybe tc of
                                        Just cls -> Just (ATyCon (classTyCon cls))
                                        Nothing  -> Nothing
  tyThingParent_maybe (AnId id)     = case idDetails id of
                                           RecSelId { sel_tycon = tc } -> Just (ATyCon tc)
                                           ClassOpId cls               -> Just (ATyCon (classTyCon cls))
                                           _other                      -> Nothing
  tyThingParent_maybe _other = Nothing
  
  tyThingsTyVars :: [TyThing] -> TyVarSet
  tyThingsTyVars tts =
      unionVarSets $ map ttToVarSet tts
      where
          ttToVarSet (AnId id)     = tyVarsOfType $ idType id
          ttToVarSet (AConLike cl) = case cl of
              RealDataCon dc  -> tyVarsOfType $ dataConRepType dc
              PatSynCon{}     -> emptyVarSet
          ttToVarSet (ATyCon tc)
            = case tyConClass_maybe tc of
                Just cls -> (mkVarSet . fst . classTvsFds) cls
                Nothing  -> tyVarsOfType $ tyConKind tc
          ttToVarSet _             = emptyVarSet
  
  -- | The Names that a TyThing should bring into scope.  Used to build
  -- the GlobalRdrEnv for the InteractiveContext.
  tyThingAvailInfo :: TyThing -> AvailInfo
  tyThingAvailInfo (ATyCon t)
     = case tyConClass_maybe t of
          Just c  -> AvailTC n (n : map getName (classMethods c)
                    ++ map getName (classATs c))
               where n = getName c
          Nothing -> AvailTC n (n : map getName dcs ++
                                     concatMap dataConFieldLabels dcs)
               where n = getName t
                     dcs = tyConDataCons t
  tyThingAvailInfo t
     = Avail (getName t)
  
  {-
  ************************************************************************
  *                                                                      *
                  TypeEnv
  *                                                                      *
  ************************************************************************
  -}
  
  -- | A map from 'Name's to 'TyThing's, constructed by typechecking
  -- local declarations or interface files
  type TypeEnv = NameEnv TyThing
  
  emptyTypeEnv    :: TypeEnv
  typeEnvElts     :: TypeEnv -> [TyThing]
  typeEnvTyCons   :: TypeEnv -> [TyCon]
  typeEnvCoAxioms :: TypeEnv -> [CoAxiom Branched]
  typeEnvIds      :: TypeEnv -> [Id]
  typeEnvPatSyns  :: TypeEnv -> [PatSyn]
  typeEnvDataCons :: TypeEnv -> [DataCon]
  typeEnvClasses  :: TypeEnv -> [Class]
  lookupTypeEnv   :: TypeEnv -> Name -> Maybe TyThing
  
  emptyTypeEnv        = emptyNameEnv
  typeEnvElts     env = nameEnvElts env
  typeEnvTyCons   env = [tc | ATyCon tc   <- typeEnvElts env]
  typeEnvCoAxioms env = [ax | ACoAxiom ax <- typeEnvElts env]
  typeEnvIds      env = [id | AnId id     <- typeEnvElts env]
  typeEnvPatSyns  env = [ps | AConLike (PatSynCon ps) <- typeEnvElts env]
  typeEnvDataCons env = [dc | AConLike (RealDataCon dc) <- typeEnvElts env]
  typeEnvClasses  env = [cl | tc <- typeEnvTyCons env,
                              Just cl <- [tyConClass_maybe tc]]
  
  mkTypeEnv :: [TyThing] -> TypeEnv
  mkTypeEnv things = extendTypeEnvList emptyTypeEnv things
  
  mkTypeEnvWithImplicits :: [TyThing] -> TypeEnv
  mkTypeEnvWithImplicits things =
    mkTypeEnv things
      `plusNameEnv`
    mkTypeEnv (concatMap implicitTyThings things)
  
  typeEnvFromEntities :: [Id] -> [TyCon] -> [FamInst] -> TypeEnv
  typeEnvFromEntities ids tcs famInsts =
    mkTypeEnv (   map AnId ids
               ++ map ATyCon all_tcs
               ++ concatMap implicitTyConThings all_tcs
               ++ map (ACoAxiom . toBranchedAxiom . famInstAxiom) famInsts
              )
   where
    all_tcs = tcs ++ famInstsRepTyCons famInsts
  
  lookupTypeEnv = lookupNameEnv
  
  -- Extend the type environment
  extendTypeEnv :: TypeEnv -> TyThing -> TypeEnv
  extendTypeEnv env thing = extendNameEnv env (getName thing) thing
  
  extendTypeEnvList :: TypeEnv -> [TyThing] -> TypeEnv
  extendTypeEnvList env things = foldl extendTypeEnv env things
  
  extendTypeEnvWithIds :: TypeEnv -> [Id] -> TypeEnv
  extendTypeEnvWithIds env ids
    = extendNameEnvList env [(getName id, AnId id) | id <- ids]
  
  -- | Find the 'TyThing' for the given 'Name' by using all the resources
  -- at our disposal: the compiled modules in the 'HomePackageTable' and the
  -- compiled modules in other packages that live in 'PackageTypeEnv'. Note
  -- that this does NOT look up the 'TyThing' in the module being compiled: you
  -- have to do that yourself, if desired
  lookupType :: DynFlags
             -> HomePackageTable
             -> PackageTypeEnv
             -> Name
             -> Maybe TyThing
  
  lookupType dflags hpt pte name
    | isOneShot (ghcMode dflags)  -- in one-shot, we don't use the HPT
    = lookupNameEnv pte name
    | otherwise
    = case lookupHptByModule hpt mod of
         Just hm -> lookupNameEnv (md_types (hm_details hm)) name
         Nothing -> lookupNameEnv pte name
    where
      mod = ASSERT2( isExternalName name, ppr name )
            if isHoleName name
              then mkModule (thisPackage dflags) (moduleName (nameModule name))
              else nameModule name
  
  -- | As 'lookupType', but with a marginally easier-to-use interface
  -- if you have a 'HscEnv'
  lookupTypeHscEnv :: HscEnv -> Name -> IO (Maybe TyThing)
  lookupTypeHscEnv hsc_env name = do
      eps <- readIORef (hsc_EPS hsc_env)
      return $! lookupType dflags hpt (eps_PTE eps) name
    where
      dflags = hsc_dflags hsc_env
      hpt = hsc_HPT hsc_env
  
  -- | Get the 'TyCon' from a 'TyThing' if it is a type constructor thing. Panics otherwise
  tyThingTyCon :: TyThing -> TyCon
  tyThingTyCon (ATyCon tc) = tc
  tyThingTyCon other       = pprPanic "tyThingTyCon" (pprTyThing other)
  
  -- | Get the 'CoAxiom' from a 'TyThing' if it is a coercion axiom thing. Panics otherwise
  tyThingCoAxiom :: TyThing -> CoAxiom Branched
  tyThingCoAxiom (ACoAxiom ax) = ax
  tyThingCoAxiom other         = pprPanic "tyThingCoAxiom" (pprTyThing other)
  
  -- | Get the 'DataCon' from a 'TyThing' if it is a data constructor thing. Panics otherwise
  tyThingDataCon :: TyThing -> DataCon
  tyThingDataCon (AConLike (RealDataCon dc)) = dc
  tyThingDataCon other                       = pprPanic "tyThingDataCon" (pprTyThing other)
  
  -- | Get the 'Id' from a 'TyThing' if it is a id *or* data constructor thing. Panics otherwise
  tyThingId :: TyThing -> Id
  tyThingId (AnId id)                   = id
  tyThingId (AConLike (RealDataCon dc)) = dataConWrapId dc
  tyThingId other                       = pprPanic "tyThingId" (pprTyThing other)
  
  {-
  ************************************************************************
  *                                                                      *
  \subsection{MonadThings and friends}
  *                                                                      *
  ************************************************************************
  -}
  
  -- | Class that abstracts out the common ability of the monads in GHC
  -- to lookup a 'TyThing' in the monadic environment by 'Name'. Provides
  -- a number of related convenience functions for accessing particular
  -- kinds of 'TyThing'
  class Monad m => MonadThings m where
          lookupThing :: Name -> m TyThing
  
          lookupId :: Name -> m Id
          lookupId = liftM tyThingId . lookupThing
  
          lookupDataCon :: Name -> m DataCon
          lookupDataCon = liftM tyThingDataCon . lookupThing
  
          lookupTyCon :: Name -> m TyCon
          lookupTyCon = liftM tyThingTyCon . lookupThing
  
  {-
  ************************************************************************
  *                                                                      *
  \subsection{Auxiliary types}
  *                                                                      *
  ************************************************************************
  
  These types are defined here because they are mentioned in ModDetails,
  but they are mostly elaborated elsewhere
  -}
  
  ------------------ Warnings -------------------------
  -- | Warning information for a module
  data Warnings
    = NoWarnings                          -- ^ Nothing deprecated
    | WarnAll WarningTxt                  -- ^ Whole module deprecated
    | WarnSome [(OccName,WarningTxt)]     -- ^ Some specific things deprecated
  
       -- Only an OccName is needed because
       --    (1) a deprecation always applies to a binding
       --        defined in the module in which the deprecation appears.
       --    (2) deprecations are only reported outside the defining module.
       --        this is important because, otherwise, if we saw something like
       --
       --        {-# DEPRECATED f "" #-}
       --        f = ...
       --        h = f
       --        g = let f = undefined in f
       --
       --        we'd need more information than an OccName to know to say something
       --        about the use of f in h but not the use of the locally bound f in g
       --
       --        however, because we only report about deprecations from the outside,
       --        and a module can only export one value called f,
       --        an OccName suffices.
       --
       --        this is in contrast with fixity declarations, where we need to map
       --        a Name to its fixity declaration.
    deriving( Eq )
  
  instance Binary Warnings where
      put_ bh NoWarnings     = putByte bh 0
      put_ bh (WarnAll t) = do
              putByte bh 1
              put_ bh t
      put_ bh (WarnSome ts) = do
              putByte bh 2
              put_ bh ts
  
      get bh = do
              h <- getByte bh
              case h of
                0 -> return NoWarnings
                1 -> do aa <- get bh
                        return (WarnAll aa)
                _ -> do aa <- get bh
                        return (WarnSome aa)
  
  -- | Constructs the cache for the 'mi_warn_fn' field of a 'ModIface'
  mkIfaceWarnCache :: Warnings -> Name -> Maybe WarningTxt
  mkIfaceWarnCache NoWarnings  = \_ -> Nothing
  mkIfaceWarnCache (WarnAll t) = \_ -> Just t
  mkIfaceWarnCache (WarnSome pairs) = lookupOccEnv (mkOccEnv pairs) . nameOccName
  
  emptyIfaceWarnCache :: Name -> Maybe WarningTxt
  emptyIfaceWarnCache _ = Nothing
  
  plusWarns :: Warnings -> Warnings -> Warnings
  plusWarns d NoWarnings = d
  plusWarns NoWarnings d = d
  plusWarns _ (WarnAll t) = WarnAll t
  plusWarns (WarnAll t) _ = WarnAll t
  plusWarns (WarnSome v1) (WarnSome v2) = WarnSome (v1 ++ v2)
  
  -- | Creates cached lookup for the 'mi_fix_fn' field of 'ModIface'
  mkIfaceFixCache :: [(OccName, Fixity)] -> OccName -> Fixity
  mkIfaceFixCache pairs
    = \n -> lookupOccEnv env n `orElse` defaultFixity
    where
     env = mkOccEnv pairs
  
  emptyIfaceFixCache :: OccName -> Fixity
  emptyIfaceFixCache _ = defaultFixity
  
  -- | Fixity environment mapping names to their fixities
  type FixityEnv = NameEnv FixItem
  
  -- | Fixity information for an 'Name'. We keep the OccName in the range
  -- so that we can generate an interface from it
  data FixItem = FixItem OccName Fixity
  
  instance Outputable FixItem where
    ppr (FixItem occ fix) = ppr fix <+> ppr occ
  
  emptyFixityEnv :: FixityEnv
  emptyFixityEnv = emptyNameEnv
  
  lookupFixity :: FixityEnv -> Name -> Fixity
  lookupFixity env n = case lookupNameEnv env n of
                          Just (FixItem _ fix) -> fix
                          Nothing         -> defaultFixity
  
  {-
  ************************************************************************
  *                                                                      *
  \subsection{WhatsImported}
  *                                                                      *
  ************************************************************************
  -}
  
  -- | Records whether a module has orphans. An \"orphan\" is one of:
  --
  -- * An instance declaration in a module other than the definition
  --   module for one of the type constructors or classes in the instance head
  --
  -- * A transformation rule in a module other than the one defining
  --   the function in the head of the rule
  --
  -- * A vectorisation pragma
  type WhetherHasOrphans   = Bool
  
  -- | Does this module define family instances?
  type WhetherHasFamInst = Bool
  
  -- | Did this module originate from a *-boot file?
  type IsBootInterface = Bool
  
  -- | Dependency information about ALL modules and packages below this one
  -- in the import hierarchy.
  --
  -- Invariant: the dependencies of a module @M@ never includes @M@.
  --
  -- Invariant: none of the lists contain duplicates.
  data Dependencies
    = Deps { dep_mods   :: [(ModuleName, IsBootInterface)]
                          -- ^ All home-package modules transitively below this one
                          -- I.e. modules that this one imports, or that are in the
                          --      dep_mods of those directly-imported modules
  
           , dep_pkgs   :: [(InstalledUnitId, Bool)]
                          -- ^ All packages transitively below this module
                          -- I.e. packages to which this module's direct imports belong,
                          --      or that are in the dep_pkgs of those modules
                          -- The bool indicates if the package is required to be
                          -- trusted when the module is imported as a safe import
                          -- (Safe Haskell). See Note [RnNames . Tracking Trust Transitively]
  
           , dep_orphs  :: [Module]
                          -- ^ Transitive closure of orphan modules (whether
                          -- home or external pkg).
                          --
                          -- (Possible optimization: don't include family
                          -- instance orphans as they are anyway included in
                          -- 'dep_finsts'.  But then be careful about code
                          -- which relies on dep_orphs having the complete list!)
  
           , dep_finsts :: [Module]
                          -- ^ Modules that contain family instances (whether the
                          -- instances are from the home or an external package)
           }
    deriving( Eq )
          -- Equality used only for old/new comparison in MkIface.addFingerprints
          -- See 'TcRnTypes.ImportAvails' for details on dependencies.
  
  instance Binary Dependencies where
      put_ bh deps = do put_ bh (dep_mods deps)
                        put_ bh (dep_pkgs deps)
                        put_ bh (dep_orphs deps)
                        put_ bh (dep_finsts deps)
  
      get bh = do ms <- get bh
                  ps <- get bh
                  os <- get bh
                  fis <- get bh
                  return (Deps { dep_mods = ms, dep_pkgs = ps, dep_orphs = os,
                                 dep_finsts = fis })
  
  noDependencies :: Dependencies
  noDependencies = Deps [] [] [] []
  
  -- | Records modules for which changes may force recompilation of this module
  -- See wiki: http://ghc.haskell.org/trac/ghc/wiki/Commentary/Compiler/RecompilationAvoidance
  --
  -- This differs from Dependencies.  A module X may be in the dep_mods of this
  -- module (via an import chain) but if we don't use anything from X it won't
  -- appear in our Usage
  data Usage
    -- | Module from another package
    = UsagePackageModule {
          usg_mod      :: Module,
             -- ^ External package module depended on
          usg_mod_hash :: Fingerprint,
              -- ^ Cached module fingerprint
          usg_safe :: IsSafeImport
              -- ^ Was this module imported as a safe import
      }
    -- | Module from the current package
    | UsageHomeModule {
          usg_mod_name :: ModuleName,
              -- ^ Name of the module
          usg_mod_hash :: Fingerprint,
              -- ^ Cached module fingerprint
          usg_entities :: [(OccName,Fingerprint)],
              -- ^ Entities we depend on, sorted by occurrence name and fingerprinted.
              -- NB: usages are for parent names only, e.g. type constructors
              -- but not the associated data constructors.
          usg_exports  :: Maybe Fingerprint,
              -- ^ Fingerprint for the export list of this module,
              -- if we directly imported it (and hence we depend on its export list)
          usg_safe :: IsSafeImport
              -- ^ Was this module imported as a safe import
      }                                           -- ^ Module from the current package
    -- | A file upon which the module depends, e.g. a CPP #include, or using TH's
    -- 'addDependentFile'
    | UsageFile {
          usg_file_path  :: FilePath,
          -- ^ External file dependency. From a CPP #include or TH
          -- addDependentFile. Should be absolute.
          usg_file_hash  :: Fingerprint
          -- ^ 'Fingerprint' of the file contents.
  
          -- Note: We don't consider things like modification timestamps
          -- here, because there's no reason to recompile if the actual
          -- contents don't change.  This previously lead to odd
          -- recompilation behaviors; see #8114
    }
    -- | A requirement which was merged into this one.
    | UsageMergedRequirement {
          usg_mod :: Module,
          usg_mod_hash :: Fingerprint
    }
      deriving( Eq )
          -- The export list field is (Just v) if we depend on the export list:
          --      i.e. we imported the module directly, whether or not we
          --           enumerated the things we imported, or just imported
          --           everything
          -- We need to recompile if M's exports change, because
          -- if the import was    import M,       we might now have a name clash
          --                                      in the importing module.
          -- if the import was    import M(x)     M might no longer export x
          -- The only way we don't depend on the export list is if we have
          --                      import M()
          -- And of course, for modules that aren't imported directly we don't
          -- depend on their export lists
  
  instance Binary Usage where
      put_ bh usg@UsagePackageModule{} = do
          putByte bh 0
          put_ bh (usg_mod usg)
          put_ bh (usg_mod_hash usg)
          put_ bh (usg_safe     usg)
  
      put_ bh usg@UsageHomeModule{} = do
          putByte bh 1
          put_ bh (usg_mod_name usg)
          put_ bh (usg_mod_hash usg)
          put_ bh (usg_exports  usg)
          put_ bh (usg_entities usg)
          put_ bh (usg_safe     usg)
  
      put_ bh usg@UsageFile{} = do
          putByte bh 2
          put_ bh (usg_file_path usg)
          put_ bh (usg_file_hash usg)
  
      put_ bh usg@UsageMergedRequirement{} = do
         putByte bh 3
         put_ bh (usg_mod      usg)
         put_ bh (usg_mod_hash usg)
  
      get bh = do
          h <- getByte bh
          case h of
            0 -> do
              nm    <- get bh
              mod   <- get bh
              safe  <- get bh
              return UsagePackageModule { usg_mod = nm, usg_mod_hash = mod, usg_safe = safe }
            1 -> do
              nm    <- get bh
              mod   <- get bh
              exps  <- get bh
              ents  <- get bh
              safe  <- get bh
              return UsageHomeModule { usg_mod_name = nm, usg_mod_hash = mod,
                       usg_exports = exps, usg_entities = ents, usg_safe = safe }
            2 -> do
              fp   <- get bh
              hash <- get bh
              return UsageFile { usg_file_path = fp, usg_file_hash = hash }
  
            3 -> do
              mod <- get bh
              hash <- get bh
              return UsageMergedRequirement { usg_mod = mod, usg_mod_hash = hash }
  
            i -> error ("Binary.get(Usage): " ++ show i)
  
  {-
  ************************************************************************
  *                                                                      *
                  The External Package State
  *                                                                      *
  ************************************************************************
  -}
  
  type PackageTypeEnv    = TypeEnv
  type PackageRuleBase   = RuleBase
  type PackageInstEnv    = InstEnv
  type PackageFamInstEnv = FamInstEnv
  type PackageVectInfo   = VectInfo
  type PackageAnnEnv     = AnnEnv
  
  -- | Information about other packages that we have slurped in by reading
  -- their interface files
  data ExternalPackageState
    = EPS {
          eps_is_boot :: !(ModuleNameEnv (ModuleName, IsBootInterface)),
                  -- ^ In OneShot mode (only), home-package modules
                  -- accumulate in the external package state, and are
                  -- sucked in lazily.  For these home-pkg modules
                  -- (only) we need to record which are boot modules.
                  -- We set this field after loading all the
                  -- explicitly-imported interfaces, but before doing
                  -- anything else
                  --
                  -- The 'ModuleName' part is not necessary, but it's useful for
                  -- debug prints, and it's convenient because this field comes
                  -- direct from 'TcRnTypes.imp_dep_mods'
  
          eps_PIT :: !PackageIfaceTable,
                  -- ^ The 'ModIface's for modules in external packages
                  -- whose interfaces we have opened.
                  -- The declarations in these interface files are held in the
                  -- 'eps_decls', 'eps_inst_env', 'eps_fam_inst_env' and 'eps_rules'
                  -- fields of this record, not in the 'mi_decls' fields of the
                  -- interface we have sucked in.
                  --
                  -- What /is/ in the PIT is:
                  --
                  -- * The Module
                  --
                  -- * Fingerprint info
                  --
                  -- * Its exports
                  --
                  -- * Fixities
                  --
  
                  -- * Deprecations and warnings
          eps_free_holes :: InstalledModuleEnv (UniqDSet ModuleName),
                  -- ^ Cache for 'mi_free_holes'.  Ordinarily, we can rely on
                  -- the 'eps_PIT' for this information, EXCEPT that when
                  -- we do dependency analysis, we need to look at the
                  -- 'Dependencies' of our imports to determine what their
                  -- precise free holes are ('moduleFreeHolesPrecise').  We
                  -- don't want to repeatedly reread in the interface
                  -- for every import, so cache it here.  When the PIT
                  -- gets filled in we can drop these entries.
  
          eps_PTE :: !PackageTypeEnv,
                  -- ^ Result of typechecking all the external package
                  -- interface files we have sucked in. The domain of
                  -- the mapping is external-package modules
  
          eps_inst_env     :: !PackageInstEnv,   -- ^ The total 'InstEnv' accumulated
                                                 -- from all the external-package modules
          eps_fam_inst_env :: !PackageFamInstEnv,-- ^ The total 'FamInstEnv' accumulated
                                                 -- from all the external-package modules
          eps_rule_base    :: !PackageRuleBase,  -- ^ The total 'RuleEnv' accumulated
                                                 -- from all the external-package modules
          eps_vect_info    :: !PackageVectInfo,  -- ^ The total 'VectInfo' accumulated
                                                 -- from all the external-package modules
          eps_ann_env      :: !PackageAnnEnv,    -- ^ The total 'AnnEnv' accumulated
                                                 -- from all the external-package modules
  
          eps_mod_fam_inst_env :: !(ModuleEnv FamInstEnv), -- ^ The family instances accumulated from external
                                                           -- packages, keyed off the module that declared them
  
          eps_stats :: !EpsStats                 -- ^ Stastics about what was loaded from external packages
    }
  
  -- | Accumulated statistics about what we are putting into the 'ExternalPackageState'.
  -- \"In\" means stuff that is just /read/ from interface files,
  -- \"Out\" means actually sucked in and type-checked
  data EpsStats = EpsStats { n_ifaces_in
                           , n_decls_in, n_decls_out
                           , n_rules_in, n_rules_out
                           , n_insts_in, n_insts_out :: !Int }
  
  addEpsInStats :: EpsStats -> Int -> Int -> Int -> EpsStats
  -- ^ Add stats for one newly-read interface
  addEpsInStats stats n_decls n_insts n_rules
    = stats { n_ifaces_in = n_ifaces_in stats + 1
            , n_decls_in  = n_decls_in stats + n_decls
            , n_insts_in  = n_insts_in stats + n_insts
            , n_rules_in  = n_rules_in stats + n_rules }
  
  {-
  Names in a NameCache are always stored as a Global, and have the SrcLoc
  of their binding locations.
  
  Actually that's not quite right.  When we first encounter the original
  name, we might not be at its binding site (e.g. we are reading an
  interface file); so we give it 'noSrcLoc' then.  Later, when we find
  its binding site, we fix it up.
  -}
  
  updNameCacheIO :: HscEnv
                 -> (NameCache -> (NameCache, c))  -- The updating function
                 -> IO c
  updNameCacheIO hsc_env upd_fn
    = atomicModifyIORef' (hsc_NC hsc_env) upd_fn
  
  -- | The NameCache makes sure that there is just one Unique assigned for
  -- each original name; i.e. (module-name, occ-name) pair and provides
  -- something of a lookup mechanism for those names.
  
  mkSOName :: Platform -> FilePath -> FilePath
  mkSOName _platform root = ("lib" ++ root) <.> "so"
  
  mkHsSOName :: Platform -> FilePath -> FilePath
  mkHsSOName platform root = ("lib" ++ root) <.> soExt platform
  
  soExt :: Platform -> FilePath
  soExt _platform = "so"
  
  {-
  ************************************************************************
  *                                                                      *
                  The module graph and ModSummary type
          A ModSummary is a node in the compilation manager's
          dependency graph, and it's also passed to hscMain
  *                                                                      *
  ************************************************************************
  -}
  
  -- | A ModuleGraph contains all the nodes from the home package (only).
  -- There will be a node for each source module, plus a node for each hi-boot
  -- module.
  --
  -- The graph is not necessarily stored in topologically-sorted order.  Use
  -- 'GHC.topSortModuleGraph' and 'Digraph.flattenSCC' to achieve this.
  -- | A ModuleGraph contains all the nodes from the home package (only).
  -- There will be a node for each source module, plus a node for each hi-boot
  -- module.
  --
  -- The graph is not necessarily stored in topologically-sorted order.  Use
  -- 'GHC.topSortModuleGraph' and 'Digraph.flattenSCC' to achieve this.
  data ModuleGraph = ModuleGraph
    { mg_mss :: [ModSummary]
    , mg_non_boot :: ModuleEnv ModSummary
      -- a map of all non-boot ModSummaries keyed by Modules
    , mg_boots :: ModuleSet
      -- a set of boot Modules
    , mg_needs_th_or_qq :: !Bool
      -- does any of the modules in mg_mss require TemplateHaskell or
      -- QuasiQuotes?
    }
  
  -- | Determines whether a set of modules requires Template Haskell or
  -- Quasi Quotes
  --
  -- Note that if the session's 'DynFlags' enabled Template Haskell when
  -- 'depanal' was called, then each module in the returned module graph will
  -- have Template Haskell enabled whether it is actually needed or not.
  needsTemplateHaskellOrQQ :: ModuleGraph -> Bool
  needsTemplateHaskellOrQQ mg = mg_needs_th_or_qq mg
  
  mapMG :: (ModSummary -> ModSummary) -> ModuleGraph -> ModuleGraph
  mapMG f mg@ModuleGraph{..} = mg
    { mg_mss = map f mg_mss
    , mg_non_boot = mapModuleEnv f mg_non_boot
    }
  
  mgBootModules :: ModuleGraph -> ModuleSet
  mgBootModules ModuleGraph{..} = mg_boots
  
  mgModSummaries :: ModuleGraph -> [ModSummary]
  mgModSummaries = mg_mss
  
  mgElemModule :: ModuleGraph -> Module -> Bool
  mgElemModule ModuleGraph{..} m = elemModuleEnv m mg_non_boot
  
  -- | Look up a ModSummary in the ModuleGraph
  mgLookupModule :: ModuleGraph -> Module -> Maybe ModSummary
  mgLookupModule ModuleGraph{..} m = lookupModuleEnv mg_non_boot m
  
  emptyMG :: ModuleGraph
  emptyMG = ModuleGraph [] emptyModuleEnv emptyModuleSet False
  
  isTemplateHaskellOrQQNonBoot :: ModSummary -> Bool
  isTemplateHaskellOrQQNonBoot ms =
    (xopt LangExt.TemplateHaskell (ms_hspp_opts ms)
      || xopt LangExt.QuasiQuotes (ms_hspp_opts ms)) &&
    not (isBootSummary ms)
  
  -- | Add a ModSummary to ModuleGraph. Assumes that the new ModSummary is
  -- not an element of the ModuleGraph.
  extendMG :: ModuleGraph -> ModSummary -> ModuleGraph
  extendMG ModuleGraph{..} ms = ModuleGraph
    { mg_mss = ms:mg_mss
    , mg_non_boot = if isBootSummary ms
        then mg_non_boot
        else extendModuleEnv mg_non_boot (ms_mod ms) ms
    , mg_boots = if isBootSummary ms
        then extendModuleSet mg_boots (ms_mod ms)
        else mg_boots
    , mg_needs_th_or_qq = mg_needs_th_or_qq || isTemplateHaskellOrQQNonBoot ms
    }
  
  mkModuleGraph :: [ModSummary] -> ModuleGraph
  mkModuleGraph = foldr (flip extendMG) emptyMG
  
  -- | A single node in a 'ModuleGraph'. The nodes of the module graph
  -- are one of:
  --
  -- * A regular Haskell source module
  -- * A hi-boot source module
  -- * An external-core source module
  --
  data ModSummary
     = ModSummary {
          ms_mod          :: Module,
            -- ^ Identity of the module
          ms_hsc_src      :: HscSource,
            -- ^ The module source either plain Haskell, hs-boot or external core
          ms_location     :: ModLocation,
            -- ^ Location of the various files belonging to the module
          ms_hs_date      :: UTCTime,
            -- ^ Timestamp of source file
          ms_obj_date     :: Maybe UTCTime,
            -- ^ Timestamp of object, if we have one
          ms_iface_date   :: Maybe UTCTime,
            -- ^ Timestamp of hi file, if we *only* are typechecking (it is
            -- 'Nothing' otherwise.
            -- See Note [Recompilation checking when typechecking only] and #9243
          ms_srcimps      :: [(Maybe FastString, Located ModuleName)],
            -- ^ Source imports of the module
          ms_textual_imps :: [(Maybe FastString, Located ModuleName)],
            -- ^ Non-source imports of the module from the module *text*
          ms_parsed_mod   :: Maybe HsParsedModule,
            -- ^ The parsed, nonrenamed source, if we have it.  This is also
            -- used to support "inline module syntax" in Backpack files.
          ms_hspp_file    :: FilePath,
            -- ^ Filename of preprocessed source file
          ms_hspp_opts    :: DynFlags,
            -- ^ Cached flags from @OPTIONS@, @INCLUDE@ and @LANGUAGE@
            -- pragmas in the modules source code
          ms_hspp_buf     :: Maybe StringBuffer
            -- ^ The actual preprocessed source, if we have it
       }
  
  ms_mod_name :: ModSummary -> ModuleName
  ms_mod_name = moduleName . ms_mod
  
  ms_imps :: ModSummary -> [(Maybe FastString, Located ModuleName)]
  ms_imps ms =
    ms_textual_imps ms ++
    map mk_additional_import (dynFlagDependencies (ms_hspp_opts ms))
    where
      mk_additional_import mod_nm = (Nothing, noLoc mod_nm)
  
  -- The ModLocation contains both the original source filename and the
  -- filename of the cleaned-up source file after all preprocessing has been
  -- done.  The point is that the summariser will have to cpp/unlit/whatever
  -- all files anyway, and there's no point in doing this twice -- just
  -- park the result in a temp file, put the name of it in the location,
  -- and let @compile@ read from that file on the way back up.
  
  -- The ModLocation is stable over successive up-sweeps in GHCi, wheres
  -- the ms_hs_date and imports can, of course, change
  
  msHsFilePath, msHiFilePath, msObjFilePath :: ModSummary -> FilePath
  msHsFilePath  ms = expectJust "msHsFilePath" (ml_hs_file  (ms_location ms))
  msHiFilePath  ms = ml_hi_file  (ms_location ms)
  msObjFilePath ms = ml_obj_file (ms_location ms)
  
  -- | Did this 'ModSummary' originate from a hs-boot file?
  isBootSummary :: ModSummary -> Bool
  isBootSummary ms = ms_hsc_src ms == HsBootFile
  
  instance Outputable ModSummary where
     ppr ms
        = sep [text "ModSummary {",
               nest 3 (sep [text "ms_hs_date = " <> text (show (ms_hs_date ms)),
                            text "ms_mod =" <+> ppr (ms_mod ms)
                                  <> text (hscSourceString (ms_hsc_src ms)) <> comma,
                            text "ms_textual_imps =" <+> ppr (ms_textual_imps ms),
                            text "ms_srcimps =" <+> ppr (ms_srcimps ms)]),
               char '}'
              ]
  
  showModMsg :: DynFlags -> HscTarget -> Bool -> ModSummary -> String
  showModMsg dflags target recomp mod_summary
    = showSDoc dflags $
          hsep $ [text (mod_str ++ replicate (max 0 (16 - length mod_str)) ' ')]
             ++ fileDetails
   where
      mod     = moduleName (ms_mod mod_summary)
      mod_str = showPpr dflags mod
                  ++ hscSourceString (ms_hsc_src mod_summary)
      fileDetails
        | gopt Opt_ShowSourcePaths dflags || verbosity dflags > 1 =
          [char '(', text (normalise $ msHsFilePath mod_summary) <> comma,
          case target of
              HscInterpreted | recomp
                         -> text "interpreted"
              HscNothing -> text "nothing"
              _ -> text (normalise $ msObjFilePath mod_summary),
          char ')']
        | otherwise = []
  
  -- -- | Variant of hscSourceString which prints more information for signatures.
  -- -- This can't live in DriverPhases because this would cause a module loop.
  -- hscSourceString' :: DynFlags -> ModuleName -> HscSource -> String
  -- hscSourceString' _ _ HsSrcFile   = ""
  -- hscSourceString' _ _ HsBootFile  = "[boot]"
  -- hscSourceString' dflags mod HsigFile =
  --      "[" ++ (maybe "abstract sig"
  --                (("sig of "++).showPpr dflags)
  --                (getSigOf dflags mod)) ++ "]"
      -- NB: -sig-of could be missing if we're just typechecking
  
  {-
  ************************************************************************
  *                                                                      *
  \subsection{Recmpilation}
  *                                                                      *
  ************************************************************************
  -}
  
  -- | Indicates whether a given module's source has been modified since it
  -- was last compiled.
  data SourceModified
    = SourceModified
         -- ^ the source has been modified
    | SourceUnmodified
         -- ^ the source has not been modified.  Compilation may or may
         -- not be necessary, depending on whether any dependencies have
         -- changed since we last compiled.
    | SourceUnmodifiedAndStable
         -- ^ the source has not been modified, and furthermore all of
         -- its (transitive) dependencies are up to date; it definitely
         -- does not need to be recompiled.  This is important for two
         -- reasons: (a) we can omit the version check in checkOldIface,
         -- and (b) if the module used TH splices we don't need to force
         -- recompilation.
  
  {-
  ************************************************************************
  *                                                                      *
  \subsection{Hpc Support}
  *                                                                      *
  ************************************************************************
  -}
  
  -- | Information about a modules use of Haskell Program Coverage
  data HpcInfo
    = HpcInfo
       { hpcInfoTickCount :: Int
       , hpcInfoHash      :: Int
       }
    | NoHpcInfo
       { hpcUsed          :: AnyHpcUsage  -- ^ Is hpc used anywhere on the module \*tree\*?
       }
  
  -- | This is used to signal if one of my imports used HPC instrumentation
  -- even if there is no module-local HPC usage
  type AnyHpcUsage = Bool
  
  emptyHpcInfo :: AnyHpcUsage -> HpcInfo
  emptyHpcInfo = NoHpcInfo
  
  -- | Find out if HPC is used by this module or any of the modules
  -- it depends upon
  isHpcUsed :: HpcInfo -> AnyHpcUsage
  isHpcUsed (HpcInfo {})                   = True
  isHpcUsed (NoHpcInfo { hpcUsed = used }) = used
  
  {-
  ************************************************************************
  *                                                                      *
  \subsection{Vectorisation Support}
  *                                                                      *
  ************************************************************************
  
  The following information is generated and consumed by the vectorisation
  subsystem.  It communicates the vectorisation status of declarations from one
  module to another.
  
  Why do we need both f and f_v in the ModGuts/ModDetails/EPS version VectInfo
  below?  We need to know `f' when converting to IfaceVectInfo.  However, during
  vectorisation, we need to know `f_v', whose `Var' we cannot lookup based
  on just the OccName easily in a Core pass.
  -}
  
  -- |Vectorisation information for 'ModGuts', 'ModDetails' and 'ExternalPackageState'; see also
  -- documentation at 'Vectorise.Env.GlobalEnv'.
  --
  -- NB: The following tables may also include 'Var's, 'TyCon's and 'DataCon's from imported modules,
  --     which have been subsequently vectorised in the current module.
  --
  data VectInfo
    = VectInfo
      { vectInfoVar            :: VarEnv  (Var    , Var  )    -- ^ @(f, f_v)@ keyed on @f@
      , vectInfoTyCon          :: NameEnv (TyCon  , TyCon)    -- ^ @(T, T_v)@ keyed on @T@
      , vectInfoDataCon        :: NameEnv (DataCon, DataCon)  -- ^ @(C, C_v)@ keyed on @C@
      , vectInfoParallelVars   :: VarSet                      -- ^ set of parallel variables
      , vectInfoParallelTyCons :: NameSet                     -- ^ set of parallel type constructors
      }
  
  -- |Vectorisation information for 'ModIface'; i.e, the vectorisation information propagated
  -- across module boundaries.
  --
  -- NB: The field 'ifaceVectInfoVar' explicitly contains the workers of data constructors as well as
  --     class selectors — i.e., their mappings are /not/ implicitly generated from the data types.
  --     Moreover, whether the worker of a data constructor is in 'ifaceVectInfoVar' determines
  --     whether that data constructor was vectorised (or is part of an abstractly vectorised type
  --     constructor).
  --
  data IfaceVectInfo
    = IfaceVectInfo
      { ifaceVectInfoVar            :: [Name]  -- ^ All variables in here have a vectorised variant
      , ifaceVectInfoTyCon          :: [Name]  -- ^ All 'TyCon's in here have a vectorised variant;
                                               -- the name of the vectorised variant and those of its
                                               -- data constructors are determined by
                                               -- 'OccName.mkVectTyConOcc' and
                                               -- 'OccName.mkVectDataConOcc'; the names of the
                                               -- isomorphisms are determined by 'OccName.mkVectIsoOcc'
      , ifaceVectInfoTyConReuse     :: [Name]  -- ^ The vectorised form of all the 'TyCon's in here
                                               -- coincides with the unconverted form; the name of the
                                               -- isomorphisms is determined by 'OccName.mkVectIsoOcc'
      , ifaceVectInfoParallelVars   :: [Name]  -- iface version of 'vectInfoParallelVar'
      , ifaceVectInfoParallelTyCons :: [Name]  -- iface version of 'vectInfoParallelTyCon'
      }
  
  noVectInfo :: VectInfo
  noVectInfo
    = VectInfo emptyVarEnv emptyNameEnv emptyNameEnv emptyVarSet emptyNameSet
  
  plusVectInfo :: VectInfo -> VectInfo -> VectInfo
  plusVectInfo vi1 vi2 =
    VectInfo (vectInfoVar            vi1 `plusVarEnv`    vectInfoVar            vi2)
             (vectInfoTyCon          vi1 `plusNameEnv`   vectInfoTyCon          vi2)
             (vectInfoDataCon        vi1 `plusNameEnv`   vectInfoDataCon        vi2)
             (vectInfoParallelVars   vi1 `unionVarSet`   vectInfoParallelVars   vi2)
             (vectInfoParallelTyCons vi1 `unionNameSet` vectInfoParallelTyCons vi2)
  
  concatVectInfo :: [VectInfo] -> VectInfo
  concatVectInfo = foldr plusVectInfo noVectInfo
  
  noIfaceVectInfo :: IfaceVectInfo
  noIfaceVectInfo = IfaceVectInfo [] [] [] [] []
  
  isNoIfaceVectInfo :: IfaceVectInfo -> Bool
  isNoIfaceVectInfo (IfaceVectInfo l1 l2 l3 l4 l5)
    = null l1 && null l2 && null l3 && null l4 && null l5
  
  instance Outputable VectInfo where
    ppr info = vcat
               [ ptext (sLit "variables       :") <+> ppr (vectInfoVar            info)
               , ptext (sLit "tycons          :") <+> ppr (vectInfoTyCon          info)
               , ptext (sLit "datacons        :") <+> ppr (vectInfoDataCon        info)
               , ptext (sLit "parallel vars   :") <+> ppr (vectInfoParallelVars   info)
               , ptext (sLit "parallel tycons :") <+> ppr (vectInfoParallelTyCons info)
               ]
  
  instance Outputable IfaceVectInfo where
    ppr info = vcat
               [ ptext (sLit "variables       :") <+> ppr (ifaceVectInfoVar            info)
               , ptext (sLit "tycons          :") <+> ppr (ifaceVectInfoTyCon          info)
               , ptext (sLit "tycons reuse    :") <+> ppr (ifaceVectInfoTyConReuse     info)
               , ptext (sLit "parallel vars   :") <+> ppr (ifaceVectInfoParallelVars   info)
               , ptext (sLit "parallel tycons :") <+> ppr (ifaceVectInfoParallelTyCons info)
               ]
  
  
  instance Binary IfaceVectInfo where
      put_ bh (IfaceVectInfo a1 a2 a3 a4 a5) = do
          put_ bh a1
          put_ bh a2
          put_ bh a3
          put_ bh a4
          put_ bh a5
      get bh = do
          a1 <- get bh
          a2 <- get bh
          a3 <- get bh
          a4 <- get bh
          a5 <- get bh
          return (IfaceVectInfo a1 a2 a3 a4 a5)
  
  {-
  ************************************************************************
  *                                                                      *
  \subsection{Safe Haskell Support}
  *                                                                      *
  ************************************************************************
  
  This stuff here is related to supporting the Safe Haskell extension,
  primarily about storing under what trust type a module has been compiled.
  -}
  
  -- | Is an import a safe import?
  type IsSafeImport = Bool
  
  -- | Safe Haskell information for 'ModIface'
  -- Simply a wrapper around SafeHaskellMode to sepperate iface and flags
  newtype IfaceTrustInfo = TrustInfo SafeHaskellMode
  
  getSafeMode :: IfaceTrustInfo -> SafeHaskellMode
  getSafeMode (TrustInfo x) = x
  
  setSafeMode :: SafeHaskellMode -> IfaceTrustInfo
  setSafeMode = TrustInfo
  
  noIfaceTrustInfo :: IfaceTrustInfo
  noIfaceTrustInfo = setSafeMode Sf_None
  
  trustInfoToNum :: IfaceTrustInfo -> Word8
  trustInfoToNum it
    = case getSafeMode it of
              Sf_None         -> 0
              Sf_Unsafe       -> 1
              Sf_Trustworthy  -> 2
              Sf_Safe         -> 3
  
  numToTrustInfo :: Word8 -> IfaceTrustInfo
  numToTrustInfo 0 = setSafeMode Sf_None
  numToTrustInfo 1 = setSafeMode Sf_Unsafe
  numToTrustInfo 2 = setSafeMode Sf_Trustworthy
  numToTrustInfo 3 = setSafeMode Sf_Safe
  numToTrustInfo 4 = setSafeMode Sf_Safe -- retained for backwards compat, used
                                         -- to be Sf_SafeInfered but we no longer
                                         -- differentiate.
  numToTrustInfo n = error $ "numToTrustInfo: bad input number! (" ++ show n ++ ")"
  
  instance Outputable IfaceTrustInfo where
      ppr (TrustInfo Sf_None)          = ptext $ sLit "none"
      ppr (TrustInfo Sf_Unsafe)        = ptext $ sLit "unsafe"
      ppr (TrustInfo Sf_Trustworthy)   = ptext $ sLit "trustworthy"
      ppr (TrustInfo Sf_Safe)          = ptext $ sLit "safe"
  
  instance Binary IfaceTrustInfo where
      put_ bh iftrust = putByte bh $ trustInfoToNum iftrust
      get bh = getByte bh >>= (return . numToTrustInfo)
  
  {-
  ************************************************************************
  *                                                                      *
  \subsection{Parser result}
  *                                                                      *
  ************************************************************************
  -}
  
  data HsParsedModule = HsParsedModule {
      hpm_module    :: Located (HsModule RdrName),
      hpm_src_files :: [FilePath],
         -- ^ extra source files (e.g. from #includes).  The lexer collects
         -- these from '# <file> <line>' pragmas, which the C preprocessor
         -- leaves behind.  These files and their timestamps are stored in
         -- the .hi file, so that we can force recompilation if any of
         -- them change (#3589)
      hpm_annotations :: ApiAnns
      -- See note [Api annotations] in ApiAnnotation.hs
    }
  
  {-
  ************************************************************************
  *                                                                      *
  \subsection{Linkable stuff}
  *                                                                      *
  ************************************************************************
  
  This stuff is in here, rather than (say) in Linker.lhs, because the Linker.lhs
  stuff is the *dynamic* linker, and isn't present in a stage-1 compiler
  -}
  
  -- | Information we can use to dynamically link modules into the compiler
  data Linkable = LM {
    linkableTime     :: UTCTime,          -- ^ Time at which this linkable was built
                                          -- (i.e. when the bytecodes were produced,
                                          --       or the mod date on the files)
    linkableModule   :: Module,           -- ^ The linkable module itself
    linkableUnlinked :: [Unlinked]
      -- ^ Those files and chunks of code we have yet to link.
      --
      -- INVARIANT: A valid linkable always has at least one 'Unlinked' item.
      -- If this list is empty, the Linkable represents a fake linkable, which
      -- is generated in HscNothing mode to avoid recompiling modules.
      --
      -- ToDo: Do items get removed from this list when they get linked?
   }
  
  isObjectLinkable :: Linkable -> Bool
  isObjectLinkable l = not (null unlinked) && all isObject unlinked
    where unlinked = linkableUnlinked l
          -- A linkable with no Unlinked's is treated as a BCO.  We can
          -- generate a linkable with no Unlinked's as a result of
          -- compiling a module in HscNothing mode, and this choice
          -- happens to work well with checkStability in module GHC.
  
  isInterpretedLinkable :: Linkable -> Bool
  isInterpretedLinkable l = not (null unlinked) && all isInterpretable unlinked
    where unlinked = linkableUnlinked l
  
  linkableObjs :: Linkable -> [FilePath]
  linkableObjs l = [ f | DotO f <- linkableUnlinked l ]
  
  linkableClasses :: Linkable -> [(String, String, ByteString)]
  linkableClasses l = concat [ classes | Classes classes <- linkableUnlinked l ]
  
  instance Outputable Linkable where
     ppr (LM when_made mod unlinkeds)
        = (text "LinkableM" <+> parens (text (show when_made)) <+> ppr mod)
          $$ nest 3 (ppr unlinkeds)
  
  -------------------------------------------
  
  -- | Objects which have yet to be linked by the compiler
  data Unlinked
     = DotO FilePath      -- ^ An object file (.o)
     | DotA FilePath      -- ^ Static archive file (.a)
     | DotDLL FilePath    -- ^ Dynamically linked library file (.so, .dll, .dylib)
     | Classes [(String, String, ByteString)] -- ^ List of interpreted class files
  
  #ifdef ETA_REPL
  data CompiledByteCode = CompiledByteCodeUndefined
  
  instance Outputable CompiledByteCode where
    ppr _ = text "Unlinked"
  
  _unused :: CompiledByteCode
  _unused = CompiledByteCodeUndefined
  #endif
  
  instance Outputable Unlinked where
     ppr (DotO path)   = text "DotO" <+> text path
     ppr (DotA path)   = text "DotA" <+> text path
     ppr (DotDLL path) = text "DotDLL" <+> text path
     ppr (Classes _classes) = text "Classes"
  
  -- | Is this an actual file on disk we can link in somehow?
  isObject :: Unlinked -> Bool
  isObject (DotO _)   = True
  isObject (DotA _)   = True
  isObject (DotDLL _) = True
  isObject _          = False
  
  -- | Is this a bytecode linkable with no file on disk?
  isInterpretable :: Unlinked -> Bool
  isInterpretable = not . isObject
  
  -- | Retrieve the filename of the linkable if possible. Panic if it is a byte-code object
  nameOfObject :: Unlinked -> FilePath
  nameOfObject (DotO fn)   = fn
  nameOfObject (DotA fn)   = fn
  nameOfObject (DotDLL fn) = fn
  nameOfObject other       = pprPanic "nameOfObject" (ppr other)
  
  -- | Retrieve the compiled byte-code if possible. Panic if it is a file-based linkable
  byteCodeOfObject :: Unlinked -> [(String, String, ByteString)]
  byteCodeOfObject (Classes classes) = classes
  byteCodeOfObject other             = pprPanic "byteCodeOfObject" (ppr other)
  
  forceClasses :: [ClassFile] -> [(String, String, ByteString)]
  forceClasses classes =  map (\d -> let !a = classFileName d
                                         !b = superClassName d
                                         !c = classFileBS d
                                     in (a, b, c)) classes
  
  {-
  ************************************************************************
  *                                                                      *
  \subsection{Breakpoint Support}
  *                                                                      *
  ************************************************************************
  -}
  
  -- | Breakpoint index
  type BreakIndex = Int
  
  -- | All the information about the breakpoints for a given module
  data ModBreaks
     = ModBreaks
     { modBreaks_flags :: ForeignRef ()
          -- ^ The array of flags, one per breakpoint,
          -- indicating which breakpoints are enabled.
     , modBreaks_locs :: !(Array BreakIndex SrcSpan)
          -- ^ An array giving the source span of each breakpoint.
     , modBreaks_vars :: !(Array BreakIndex [OccName])
          -- ^ An array giving the names of the free variables at each breakpoint.
     , modBreaks_decls :: !(Array BreakIndex [String])
          -- ^ An array giving the names of the declarations enclosing each breakpoint.
     }
  
  -- | Construct an empty ModBreaks
  emptyModBreaks :: ModBreaks
  emptyModBreaks = ModBreaks
     { modBreaks_flags = error "ModBreaks.modBreaks_array not initialised"
           -- ToDo: can we avoid this?
     , modBreaks_locs  = array (0,-1) []
     , modBreaks_vars  = array (0,-1) []
     , modBreaks_decls = array (0,-1) []
     }
  
  data Reinterpret = ReinterpretDecl
                   | ReinterpretAsWrappedDecl
                   | ReinterpretSplice
                   | ReinterpretRunQ
  
  toCachedClassInfo :: PreClassInfo -> CachedClassInfo
  toCachedClassInfo ClassInfo {..} =
    ClassInfo { ciMethods = CachedMap $ M.fromListWith (++) [ (miName m, [m]) | m <- ciMethods ]
              , ciFields  = CachedMap $ M.fromListWith (++) [ (fiName f, [f]) | f <- ciFields ]
              , .. }
  
  newtype ClassIndex = ClassIndex (Map String CachedClassInfo)
  
  newtype CachedMap a = CachedMap { unCachedMap :: Map String [a] }
  
  type CachedClassInfo = ClassInfo CachedMap
  
  emptyClassIndex :: ClassIndex
  emptyClassIndex = ClassIndex M.empty
  
  lookupClassIndex :: String -> ClassIndex -> Maybe CachedClassInfo
  lookupClassIndex cls (ClassIndex clsIndex) = M.lookup cls clsIndex
  
  getClassIndex :: HscEnv -> IO ClassIndex
  getClassIndex = readMVar . hsc_classIndex
  
  findInClassIndex :: HscEnv -> [String] -> IO [String]
  findInClassIndex hsc_env classes = do
    let var = hsc_classIndex hsc_env
    withMVar var $ \(ClassIndex index) ->
      return $ filter (not . flip M.member index) classes
  
  addToClassIndex :: HscEnv -> [PreClassInfo] -> IO ()
  addToClassIndex hsc_env classInfos = do
    let var = hsc_classIndex hsc_env
    modifyMVar_ var $ \(ClassIndex idx) ->
      return $ ClassIndex $ M.union idx $
                 M.fromList [ (ciName classInfo, toCachedClassInfo classInfo)
                            | classInfo <- classInfos ]
  