HscMain.hs 60.5 KB
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%
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% (c) The GRASP/AQUA Project, Glasgow University, 1993-2000
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\begin{code}
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-- | Main API for compiling plain Haskell source code.
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--
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-- This module implements compilation of a Haskell source.  It is
-- /not/ concerned with preprocessing of source files; this is handled
-- in "DriverPipeline".
--
-- There are various entry points depending on what mode we're in:
-- "batch" mode (@--make@), "one-shot" mode (@-c@, @-S@ etc.), and
-- "interactive" mode (GHCi).  There are also entry points for
-- individual passes: parsing, typechecking/renaming, desugaring, and
-- simplification.
--
-- All the functions here take an 'HscEnv' as a parameter, but none of
-- them return a new one: 'HscEnv' is treated as an immutable value
-- from here on in (although it has mutable components, for the
-- caches).
--
-- Warning messages are dealt with consistently throughout this API:
-- during compilation warnings are collected, and before any function
-- in @HscMain@ returns, the warnings are either printed, or turned
-- into a real compialtion error if the @-Werror@ flag is enabled.
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--
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module HscMain
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    ( 
    -- * Making an HscEnv
      newHscEnv

    -- * Compiling complete source files
    , Compiler
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    , HscStatus' (..)
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    , InteractiveStatus, HscStatus
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    , hscCompileOneShot
    , hscCompileBatch
    , hscCompileNothing
    , hscCompileInteractive
    , hscCompileCmmFile
    , hscCompileCore

    -- * Running passes separately
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    , hscParse
    , hscTypecheckRename
    , hscDesugar
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    , makeSimpleIface
    , makeSimpleDetails
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    , hscSimplify -- ToDo, shouldn't really export this

    -- ** Backends
    , hscOneShotBackendOnly
    , hscBatchBackendOnly
    , hscNothingBackendOnly
    , hscInteractiveBackendOnly

    -- * Support for interactive evaluation
    , hscParseIdentifier
    , hscTcRcLookupName
    , hscTcRnGetInfo
#ifdef GHCI
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    , hscGetModuleInterface
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    , hscRnImportDecls
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    , hscTcRnLookupRdrName
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    , hscStmt, hscStmtWithLocation
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    , hscDecls, hscDeclsWithLocation
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    , hscTcExpr, hscImport, hscKcType
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    , hscCompileCoreExpr
#endif

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    ) where
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#ifdef GHCI
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import ByteCodeGen      ( byteCodeGen, coreExprToBCOs )
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import Linker
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import CoreTidy         ( tidyExpr )
import Type             ( Type )
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import PrelNames
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import {- Kind parts of -} Type         ( Kind )
import CoreLint         ( lintUnfolding )
import DsMeta           ( templateHaskellNames )
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import VarSet
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import VarEnv           ( emptyTidyEnv )
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import Panic
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import Class
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import Data.List
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#endif

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import Id
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import Module
import Packages
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import RdrName
import HsSyn
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import CoreSyn
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import StringBuffer
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import Parser
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import Lexer hiding (getDynFlags)
import SrcLoc
import TcRnDriver
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import TcIface          ( typecheckIface )
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import TcRnMonad
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import IfaceEnv         ( initNameCache )
import LoadIface        ( ifaceStats, initExternalPackageState )
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import PrelInfo
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import MkIface
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import Desugar
import SimplCore
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import TidyPgm
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import CorePrep
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import CoreToStg        ( coreToStg )
import qualified StgCmm ( codeGen )
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import StgSyn
import CostCentre
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import ProfInit
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import TyCon
import Name
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import SimplStg         ( stg2stg )
import CodeGen          ( codeGen )
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import OldCmm as Old    ( CmmGroup )
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import PprCmm           ( pprCmms )
import CmmParse         ( parseCmmFile )
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import CmmBuildInfoTables
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import CmmPipeline
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import CmmInfo
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import OptimizationFuel ( initOptFuelState )
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import CmmCvt
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import CodeOutput
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import NameEnv          ( emptyNameEnv )
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import NameSet          ( emptyNameSet )
import InstEnv
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import FamInstEnv
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import Fingerprint      ( Fingerprint )
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import DynFlags
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import ErrUtils
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import UniqSupply       ( mkSplitUniqSupply )
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import Outputable
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import HscStats         ( ppSourceStats )
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import HscTypes
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import MkExternalCore   ( emitExternalCore )
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import FastString
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import UniqFM           ( emptyUFM )
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import UniqSupply       ( initUs_ )
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import Bag
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import Exception
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import Control.Monad
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import Data.Maybe
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import Data.IORef
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\end{code}
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#include "HsVersions.h"
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%************************************************************************
%*									*
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		Initialisation
%*									*
%************************************************************************

\begin{code}
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newHscEnv :: DynFlags -> IO HscEnv
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newHscEnv dflags = do
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  { eps_var  <- newIORef initExternalPackageState
  ; us       <- mkSplitUniqSupply 'r'
  ; nc_var   <- newIORef (initNameCache us knownKeyNames)
  ; fc_var   <- newIORef emptyUFM
  ; mlc_var  <- newIORef emptyModuleEnv
  ; optFuel  <- initOptFuelState
  ; safe_var <- newIORef True
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  ; return (HscEnv { hsc_dflags       = dflags,
  		     hsc_targets      = [],
  		     hsc_mod_graph    = [],
  		     hsc_IC           = emptyInteractiveContext,
  		     hsc_HPT          = emptyHomePackageTable,
  		     hsc_EPS          = eps_var,
  		     hsc_NC           = nc_var,
  		     hsc_FC           = fc_var,
  		     hsc_MLC          = mlc_var,
  		     hsc_OptFuel      = optFuel,
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                     hsc_type_env_var = Nothing,
                     hsc_safeInf      = safe_var } ) }
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knownKeyNames :: [Name]      -- Put here to avoid loops involving DsMeta,
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knownKeyNames =              -- where templateHaskellNames are defined
  map getName wiredInThings 
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    ++ basicKnownKeyNames
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#ifdef GHCI
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    ++ templateHaskellNames
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#endif

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-- -----------------------------------------------------------------------------
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-- The Hsc monad: Passing an enviornment and warning state
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newtype Hsc a = Hsc (HscEnv -> WarningMessages -> IO (a, WarningMessages))
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instance Monad Hsc where
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  return a    = Hsc $ \_ w -> return (a, w)
  Hsc m >>= k = Hsc $ \e w -> do (a, w1) <- m e w
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                                 case k a of
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                                   Hsc k' -> k' e w1
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instance MonadIO Hsc where
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  liftIO io = Hsc $ \_ w -> do a <- io; return (a, w)
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runHsc :: HscEnv -> Hsc a -> IO a
runHsc hsc_env (Hsc hsc) = do
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  (a, w) <- hsc hsc_env emptyBag
  printOrThrowWarnings (hsc_dflags hsc_env) w
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  return a

getWarnings :: Hsc WarningMessages
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getWarnings = Hsc $ \_ w -> return (w, w)
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clearWarnings :: Hsc ()
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clearWarnings = Hsc $ \_ _ -> return ((), emptyBag)
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logWarnings :: WarningMessages -> Hsc ()
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logWarnings w = Hsc $ \_ w0 -> return ((), w0 `unionBags` w)
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getHscEnv :: Hsc HscEnv
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getHscEnv = Hsc $ \e w -> return (e, w)
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getDynFlags :: Hsc DynFlags
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getDynFlags = Hsc $ \e w -> return (hsc_dflags e, w)
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handleWarnings :: Hsc ()
handleWarnings = do
  dflags <- getDynFlags
  w <- getWarnings
  liftIO $ printOrThrowWarnings dflags w
  clearWarnings

-- | log warning in the monad, and if there are errors then
-- throw a SourceError exception.
logWarningsReportErrors :: Messages -> Hsc ()
logWarningsReportErrors (warns,errs) = do
  logWarnings warns
  when (not (isEmptyBag errs)) $ do
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    throwErrors errs

-- | Throw some errors.
throwErrors :: ErrorMessages -> Hsc a
throwErrors = liftIO . throwIO . mkSrcErr
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-- | Deal with errors and warnings returned by a compilation step
--
-- In order to reduce dependencies to other parts of the compiler, functions
-- outside the "main" parts of GHC return warnings and errors as a parameter
-- and signal success via by wrapping the result in a 'Maybe' type.  This
-- function logs the returned warnings and propagates errors as exceptions
-- (of type 'SourceError').
--
-- This function assumes the following invariants:
--
--  1. If the second result indicates success (is of the form 'Just x'),
--     there must be no error messages in the first result.
--
--  2. If there are no error messages, but the second result indicates failure
--     there should be warnings in the first result.  That is, if the action
--     failed, it must have been due to the warnings (i.e., @-Werror@).
ioMsgMaybe :: IO (Messages, Maybe a) -> Hsc a
ioMsgMaybe ioA = do
  ((warns,errs), mb_r) <- liftIO $ ioA
  logWarnings warns
  case mb_r of
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    Nothing -> throwErrors errs
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    Just r  -> ASSERT( isEmptyBag errs ) return r

-- | like ioMsgMaybe, except that we ignore error messages and return
-- 'Nothing' instead.
ioMsgMaybe' :: IO (Messages, Maybe a) -> Hsc (Maybe a)
ioMsgMaybe' ioA = do
  ((warns,_errs), mb_r) <- liftIO $ ioA
  logWarnings warns
  return mb_r

-- -----------------------------------------------------------------------------
-- | Lookup things in the compiler's environment

#ifdef GHCI
hscTcRnLookupRdrName :: HscEnv -> RdrName -> IO [Name]
hscTcRnLookupRdrName hsc_env rdr_name = 
  runHsc hsc_env $ ioMsgMaybe $ tcRnLookupRdrName hsc_env rdr_name
#endif

hscTcRcLookupName :: HscEnv -> Name -> IO (Maybe TyThing)
hscTcRcLookupName hsc_env name = 
  runHsc hsc_env $ ioMsgMaybe' $ tcRnLookupName hsc_env name
    -- ignore errors: the only error we're likely to get is
    -- "name not found", and the Maybe in the return type
    -- is used to indicate that.

hscTcRnGetInfo :: HscEnv -> Name -> IO (Maybe (TyThing, Fixity, [Instance]))
hscTcRnGetInfo hsc_env name =
  runHsc hsc_env $ ioMsgMaybe' $ tcRnGetInfo hsc_env name

#ifdef GHCI
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hscGetModuleInterface :: HscEnv -> Module -> IO ModIface
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hscGetModuleInterface hsc_env mod =
  runHsc hsc_env $ ioMsgMaybe $ getModuleInterface hsc_env mod
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-- -----------------------------------------------------------------------------
-- | Rename some import declarations
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hscRnImportDecls :: HscEnv -> [LImportDecl RdrName] -> IO GlobalRdrEnv
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hscRnImportDecls hsc_env import_decls
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  = runHsc hsc_env $ ioMsgMaybe $ tcRnImportDecls hsc_env import_decls
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#endif

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-- -----------------------------------------------------------------------------
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-- | parse a file, returning the abstract syntax
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hscParse :: HscEnv -> ModSummary -> IO (Located (HsModule RdrName))
hscParse hsc_env mod_summary = runHsc hsc_env $ hscParse' mod_summary

-- internal version, that doesn't fail due to -Werror
hscParse' :: ModSummary -> Hsc (Located (HsModule RdrName))
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hscParse' mod_summary = do
  dflags <- getDynFlags
  let src_filename  = ms_hspp_file mod_summary
      maybe_src_buf = ms_hspp_buf  mod_summary
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   --------------------------  Parser  ----------------
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  liftIO $ showPass dflags "Parser"
  {-# SCC "Parser" #-} do

    -- sometimes we already have the buffer in memory, perhaps
    -- because we needed to parse the imports out of it, or get the
    -- module name.
  buf <- case maybe_src_buf of
           Just b  -> return b
           Nothing -> liftIO $ hGetStringBuffer src_filename

  let loc = mkRealSrcLoc (mkFastString src_filename) 1 1

  case unP parseModule (mkPState dflags buf loc) of
    PFailed span err ->
      liftIO $ throwOneError (mkPlainErrMsg span err)

    POk pst rdr_module -> do
      logWarningsReportErrors (getMessages pst)
      liftIO $ dumpIfSet_dyn dflags Opt_D_dump_parsed "Parser" $
                             ppr rdr_module
      liftIO $ dumpIfSet_dyn dflags Opt_D_source_stats "Source Statistics" $
                             ppSourceStats False rdr_module
      return rdr_module
       -- ToDo: free the string buffer later.
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-- XXX: should this really be a Maybe X?  Check under which circumstances this
-- can become a Nothing and decide whether this should instead throw an
-- exception/signal an error.
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type RenamedStuff = 
        (Maybe (HsGroup Name, [LImportDecl Name], Maybe [LIE Name],
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                Maybe LHsDocString))
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-- | Rename and typecheck a module, additionally returning the renamed syntax
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hscTypecheckRename :: HscEnv -> ModSummary -> Located (HsModule RdrName)
                   -> IO (TcGblEnv, RenamedStuff)
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hscTypecheckRename hsc_env mod_summary rdr_module =
  runHsc hsc_env $ do
    tc_result <- {-# SCC "Typecheck-Rename" #-}
                 ioMsgMaybe $ 
                   tcRnModule hsc_env (ms_hsc_src mod_summary) True rdr_module
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        -- This 'do' is in the Maybe monad!
    let rn_info = do decl <- tcg_rn_decls tc_result
                     let imports = tcg_rn_imports tc_result
                         exports = tcg_rn_exports tc_result
                         doc_hdr = tcg_doc_hdr tc_result
                     return (decl,imports,exports,doc_hdr)
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    return (tc_result, rn_info)
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-- | Convert a typechecked module to Core
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hscDesugar :: HscEnv -> ModSummary -> TcGblEnv -> IO ModGuts
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hscDesugar hsc_env mod_summary tc_result =
  runHsc hsc_env $ hscDesugar' mod_summary tc_result
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hscDesugar' :: ModSummary -> TcGblEnv -> Hsc ModGuts
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hscDesugar' mod_summary tc_result = do
  hsc_env <- getHscEnv
  r <- ioMsgMaybe $ deSugar hsc_env (ms_location mod_summary) tc_result
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  -- always check -Werror after desugaring, this is the last opportunity for
  -- warnings to arise before the backend.
  handleWarnings
  return r
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-- | Make a 'ModIface' from the results of typechecking.  Used when
-- not optimising, and the interface doesn't need to contain any
-- unfoldings or other cross-module optimisation info.
-- ToDo: the old interface is only needed to get the version numbers,
-- we should use fingerprint versions instead.
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makeSimpleIface :: HscEnv -> Maybe ModIface -> TcGblEnv -> ModDetails
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                -> IO (ModIface,Bool)
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makeSimpleIface hsc_env maybe_old_iface tc_result details =
  runHsc hsc_env $ ioMsgMaybe $ 
      mkIfaceTc hsc_env (fmap mi_iface_hash maybe_old_iface) details tc_result
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-- | Make a 'ModDetails' from the results of typechecking.  Used when
-- typechecking only, as opposed to full compilation.
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makeSimpleDetails :: HscEnv -> TcGblEnv -> IO ModDetails
makeSimpleDetails hsc_env tc_result = mkBootModDetailsTc hsc_env tc_result
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\end{code}

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%************************************************************************
%*									*
		The main compiler pipeline
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%*									*
%************************************************************************

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                   --------------------------------
                        The compilation proper
                   --------------------------------

It's the task of the compilation proper to compile Haskell, hs-boot and
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core files to either byte-code, hard-code (C, asm, LLVM, ect) or to
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nothing at all (the module is still parsed and type-checked. This
feature is mostly used by IDE's and the likes).
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Compilation can happen in either 'one-shot', 'batch', 'nothing',
or 'interactive' mode. 'One-shot' mode targets hard-code, 'batch' mode
targets hard-code, 'nothing' mode targets nothing and 'interactive' mode
targets byte-code.
The modes are kept separate because of their different types and meanings.
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In 'one-shot' mode, we're only compiling a single file and can therefore
discard the new ModIface and ModDetails. This is also the reason it only
targets hard-code; compiling to byte-code or nothing doesn't make sense
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when we discard the result.
'Batch' mode is like 'one-shot' except that we keep the resulting ModIface
and ModDetails. 'Batch' mode doesn't target byte-code since that require
us to return the newly compiled byte-code.
'Nothing' mode has exactly the same type as 'batch' mode but they're still
kept separate. This is because compiling to nothing is fairly special: We
don't output any interface files, we don't run the simplifier and we don't
generate any code.
'Interactive' mode is similar to 'batch' mode except that we return the
compiled byte-code together with the ModIface and ModDetails.

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Trying to compile a hs-boot file to byte-code will result in a run-time
error. This is the only thing that isn't caught by the type-system.

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\begin{code}
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-- Status of a compilation to hard-code or nothing.
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data HscStatus' a
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    = HscNoRecomp
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    | HscRecomp
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       (Maybe FilePath)
            -- Has stub files.  This is a hack. We can't compile C files here
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            -- since it's done in DriverPipeline. For now we just return True
            -- if we want the caller to compile them for us.
       a

-- This is a bit ugly.  Since we use a typeclass below and would like to avoid
-- functional dependencies, we have to parameterise the typeclass over the
-- result type.  Therefore we need to artificially distinguish some types.  We
-- do this by adding type tags which will simply be ignored by the caller.
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type HscStatus         = HscStatus' ()
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type InteractiveStatus = HscStatus' (Maybe (CompiledByteCode, ModBreaks))
    -- INVARIANT: result is @Nothing@ <=> input was a boot file
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type OneShotResult     = HscStatus
type BatchResult       = (HscStatus, ModIface, ModDetails)
type NothingResult     = (HscStatus, ModIface, ModDetails)
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type InteractiveResult = (InteractiveStatus, ModIface, ModDetails)
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-- ToDo: The old interface and module index are only using in 'batch' and
--       'interactive' mode. They should be removed from 'oneshot' mode.
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type Compiler result =  HscEnv
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                     -> ModSummary
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                     -> SourceModified
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                     -> Maybe ModIface  -- Old interface, if available
                     -> Maybe (Int,Int) -- Just (i,n) <=> module i of n (for msgs)
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                     -> IO result
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data HsCompiler a
  = HsCompiler {
    -- | Called when no recompilation is necessary.
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    hscNoRecomp :: ModIface
                -> Hsc a,
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    -- | Called to recompile the module.
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    hscRecompile :: ModSummary -> Maybe Fingerprint
                 -> Hsc a,
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    hscBackend :: TcGblEnv -> ModSummary -> Maybe Fingerprint
               -> Hsc a,
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    -- | Code generation for Boot modules.
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    hscGenBootOutput :: TcGblEnv -> ModSummary -> Maybe Fingerprint
                     -> Hsc a,
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    -- | Code generation for normal modules.
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    hscGenOutput :: ModGuts  -> ModSummary -> Maybe Fingerprint
                 -> Hsc a
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  }

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genericHscCompile :: HsCompiler a
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                  -> (HscEnv -> Maybe (Int,Int) -> RecompReason -> ModSummary -> IO ())
                  -> HscEnv -> ModSummary -> SourceModified
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                  -> Maybe ModIface -> Maybe (Int, Int)
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                  -> IO a
genericHscCompile compiler hscMessage hsc_env
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                  mod_summary source_modified
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                  mb_old_iface0 mb_mod_index
 = do
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     (recomp_reqd, mb_checked_iface)
         <- {-# SCC "checkOldIface" #-}
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            checkOldIface hsc_env mod_summary 
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                          source_modified mb_old_iface0
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     -- save the interface that comes back from checkOldIface.
     -- In one-shot mode we don't have the old iface until this
     -- point, when checkOldIface reads it from the disk.
     let mb_old_hash = fmap mi_iface_hash mb_checked_iface
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     let
       skip iface = do
         hscMessage hsc_env mb_mod_index RecompNotRequired mod_summary
         runHsc hsc_env $ hscNoRecomp compiler iface

       compile reason = do
         hscMessage hsc_env mb_mod_index reason mod_summary
         runHsc hsc_env $ hscRecompile compiler mod_summary mb_old_hash

       stable = case source_modified of
                  SourceUnmodifiedAndStable -> True
                  _ -> False

        -- If the module used TH splices when it was last compiled,
        -- then the recompilation check is not accurate enough (#481)
        -- and we must ignore it.  However, if the module is stable
        -- (none of the modules it depends on, directly or indirectly,
        -- changed), then we *can* skip recompilation.  This is why
        -- the SourceModified type contains SourceUnmodifiedAndStable,
        -- and it's pretty important: otherwise ghc --make would
        -- always recompile TH modules, even if nothing at all has
        -- changed.  Stability is just the same check that make is
        -- doing for us in one-shot mode.

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     case mb_checked_iface of
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       Just iface | not recomp_reqd ->
           if mi_used_th iface && not stable
               then compile RecompForcedByTH
               else skip iface
       _otherwise ->
           compile RecompRequired

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hscCheckRecompBackend :: HsCompiler a -> TcGblEnv -> Compiler a
hscCheckRecompBackend compiler tc_result 
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                   hsc_env mod_summary source_modified mb_old_iface _m_of_n
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  = do
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     (recomp_reqd, mb_checked_iface)
         <- {-# SCC "checkOldIface" #-}
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            checkOldIface hsc_env mod_summary
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                          source_modified mb_old_iface
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     let mb_old_hash = fmap mi_iface_hash mb_checked_iface
     case mb_checked_iface of
       Just iface | not recomp_reqd
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           -> runHsc hsc_env $ 
                 hscNoRecomp compiler
                             iface{ mi_globals = Just (tcg_rdr_env tc_result) }
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       _otherwise
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           -> runHsc hsc_env $
                 hscBackend compiler tc_result mod_summary mb_old_hash
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genericHscRecompile :: HsCompiler a
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                    -> ModSummary -> Maybe Fingerprint
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                    -> Hsc a
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genericHscRecompile compiler mod_summary mb_old_hash
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  | ExtCoreFile <- ms_hsc_src mod_summary =
      panic "GHC does not currently support reading External Core files"
  | otherwise = do
      tc_result <- hscFileFrontEnd mod_summary
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      hscBackend compiler tc_result mod_summary mb_old_hash

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genericHscBackend :: HsCompiler a
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                  -> TcGblEnv -> ModSummary -> Maybe Fingerprint
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                  -> Hsc a
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genericHscBackend compiler tc_result mod_summary mb_old_hash
  | HsBootFile <- ms_hsc_src mod_summary =
      hscGenBootOutput compiler tc_result mod_summary mb_old_hash
  | otherwise = do
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      guts <- hscDesugar' mod_summary tc_result
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      hscGenOutput compiler guts mod_summary mb_old_hash
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compilerBackend :: HsCompiler a -> TcGblEnv -> Compiler a
compilerBackend comp tcg hsc_env ms' _ _mb_old_iface _ =
  runHsc hsc_env $
    hscBackend comp tcg ms' Nothing

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--------------------------------------------------------------
-- Compilers
--------------------------------------------------------------

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hscOneShotCompiler :: HsCompiler OneShotResult
hscOneShotCompiler =
  HsCompiler {

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    hscNoRecomp = \_old_iface -> do
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      hsc_env <- getHscEnv
      liftIO $ dumpIfaceStats hsc_env
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      return HscNoRecomp

  , hscRecompile = genericHscRecompile hscOneShotCompiler

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  , hscBackend = \tc_result mod_summary mb_old_hash -> do
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       dflags <- getDynFlags
       case hscTarget dflags of
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         HscNothing -> return (HscRecomp Nothing ())
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         _otherw    -> genericHscBackend hscOneShotCompiler
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                                         tc_result mod_summary mb_old_hash
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  , hscGenBootOutput = \tc_result mod_summary mb_old_iface -> do
       (iface, changed, _) <- hscSimpleIface tc_result mb_old_iface
       hscWriteIface iface changed mod_summary
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       return (HscRecomp Nothing ())
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  , hscGenOutput = \guts0 mod_summary mb_old_iface -> do
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       guts <- hscSimplify' guts0
       (iface, changed, _details, cgguts) <- hscNormalIface guts mb_old_iface
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       hscWriteIface iface changed mod_summary
       hasStub <- hscGenHardCode cgguts mod_summary
       return (HscRecomp hasStub ())
  }
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-- Compile Haskell, boot and extCore in OneShot mode.
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hscCompileOneShot :: Compiler OneShotResult
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hscCompileOneShot hsc_env mod_summary src_changed mb_old_iface mb_i_of_n
  = do
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       -- One-shot mode needs a knot-tying mutable variable for interface
       -- files.  See TcRnTypes.TcGblEnv.tcg_type_env_var.
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      type_env_var <- newIORef emptyNameEnv
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      let
         mod = ms_mod mod_summary
         hsc_env' = hsc_env{ hsc_type_env_var = Just (mod, type_env_var) }
      ---
      genericHscCompile hscOneShotCompiler
                        oneShotMsg hsc_env' mod_summary src_changed
                        mb_old_iface mb_i_of_n

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hscOneShotBackendOnly :: TcGblEnv -> Compiler OneShotResult
hscOneShotBackendOnly = compilerBackend hscOneShotCompiler

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--------------------------------------------------------------

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hscBatchCompiler :: HsCompiler BatchResult
hscBatchCompiler =
  HsCompiler {
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    hscNoRecomp = \iface -> do
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       details <- genModDetails iface
       return (HscNoRecomp, iface, details)
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  , hscRecompile = genericHscRecompile hscBatchCompiler
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  , hscBackend = genericHscBackend hscBatchCompiler

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  , hscGenBootOutput = \tc_result mod_summary mb_old_iface -> do
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       (iface, changed, details) <- hscSimpleIface tc_result mb_old_iface
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       hscWriteIface iface changed mod_summary
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       return (HscRecomp Nothing (), iface, details)
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  , hscGenOutput = \guts0 mod_summary mb_old_iface -> do
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       guts <- hscSimplify' guts0
       (iface, changed, details, cgguts) <- hscNormalIface guts mb_old_iface
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       hscWriteIface iface changed mod_summary
       hasStub <- hscGenHardCode cgguts mod_summary
       return (HscRecomp hasStub (), iface, details)
  }
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-- Compile Haskell, boot and extCore in batch mode.
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hscCompileBatch :: Compiler (HscStatus, ModIface, ModDetails)
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hscCompileBatch = genericHscCompile hscBatchCompiler batchMsg
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hscBatchBackendOnly :: TcGblEnv -> Compiler BatchResult
hscBatchBackendOnly = hscCheckRecompBackend hscBatchCompiler

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--------------------------------------------------------------

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hscInteractiveCompiler :: HsCompiler InteractiveResult
hscInteractiveCompiler =
  HsCompiler {
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    hscNoRecomp = \iface -> do
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       details <- genModDetails iface
       return (HscNoRecomp, iface, details)
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  , hscRecompile = genericHscRecompile hscInteractiveCompiler
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  , hscBackend = genericHscBackend hscInteractiveCompiler

  , hscGenBootOutput = \tc_result _mod_summary mb_old_iface -> do
       (iface, _changed, details) <- hscSimpleIface tc_result mb_old_iface
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       return (HscRecomp Nothing Nothing, iface, details)
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  , hscGenOutput = \guts0 mod_summary mb_old_iface -> do
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       guts <- hscSimplify' guts0
       (iface, _changed, details, cgguts) <- hscNormalIface guts mb_old_iface
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       hscInteractive (iface, details, cgguts) mod_summary
  }
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-- Compile Haskell, extCore to bytecode.
hscCompileInteractive :: Compiler (InteractiveStatus, ModIface, ModDetails)
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hscCompileInteractive = genericHscCompile hscInteractiveCompiler batchMsg
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hscInteractiveBackendOnly :: TcGblEnv -> Compiler InteractiveResult
hscInteractiveBackendOnly = compilerBackend hscInteractiveCompiler

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--------------------------------------------------------------

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hscNothingCompiler :: HsCompiler NothingResult
hscNothingCompiler =
  HsCompiler {
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    hscNoRecomp = \iface -> do
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       details <- genModDetails iface
       return (HscNoRecomp, iface, details)
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  , hscRecompile = genericHscRecompile hscNothingCompiler
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  , hscBackend = \tc_result _mod_summary mb_old_iface -> do
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       handleWarnings
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       (iface, _changed, details) <- hscSimpleIface tc_result mb_old_iface
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       return (HscRecomp Nothing (), iface, details)
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  , hscGenBootOutput = \_ _ _ ->
        panic "hscCompileNothing: hscGenBootOutput should not be called"

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  , hscGenOutput = \_ _ _ ->
        panic "hscCompileNothing: hscGenOutput should not be called"
  }
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-- Type-check Haskell and .hs-boot only (no external core)
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hscCompileNothing :: Compiler (HscStatus, ModIface, ModDetails)
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hscCompileNothing = genericHscCompile hscNothingCompiler batchMsg
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hscNothingBackendOnly :: TcGblEnv -> Compiler NothingResult
hscNothingBackendOnly = compilerBackend hscNothingCompiler

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--------------------------------------------------------------
-- NoRecomp handlers
--------------------------------------------------------------

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genModDetails :: ModIface -> Hsc ModDetails
genModDetails old_iface
  = do
      hsc_env <- getHscEnv
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      new_details <- {-# SCC "tcRnIface" #-}
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                     liftIO $ initIfaceCheck hsc_env $
                              typecheckIface old_iface
      liftIO $ dumpIfaceStats hsc_env
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      return new_details
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--------------------------------------------------------------
-- Progress displayers.
--------------------------------------------------------------

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data RecompReason = RecompNotRequired | RecompRequired | RecompForcedByTH
  deriving Eq
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oneShotMsg :: HscEnv -> Maybe (Int,Int) -> RecompReason -> ModSummary -> IO ()
oneShotMsg hsc_env _mb_mod_index recomp _mod_summary =
  case recomp of
    RecompNotRequired ->
            compilationProgressMsg (hsc_dflags hsc_env) $
                   "compilation IS NOT required"
    _other ->
            return ()

batchMsg :: HscEnv -> Maybe (Int,Int) -> RecompReason -> ModSummary -> IO ()
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batchMsg hsc_env mb_mod_index recomp mod_summary
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 = case recomp of
     RecompRequired -> showMsg "Compiling "
     RecompNotRequired
       | verbosity (hsc_dflags hsc_env) >= 2 -> showMsg "Skipping  "
       | otherwise -> return ()
     RecompForcedByTH -> showMsg "Compiling [TH] "
   where
     showMsg msg =
        compilationProgressMsg (hsc_dflags hsc_env) $
         (showModuleIndex mb_mod_index ++
         msg ++ showModMsg (hscTarget (hsc_dflags hsc_env)) (recomp == RecompRequired) mod_summary)
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--------------------------------------------------------------
-- FrontEnds
--------------------------------------------------------------
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hscFileFrontEnd :: ModSummary -> Hsc TcGblEnv
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hscFileFrontEnd mod_summary = do
    rdr_module <- hscParse' mod_summary
    hsc_env <- getHscEnv
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    dflags  <- getDynFlags
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    tcg_env <-
        {-# SCC "Typecheck-Rename" #-}
        ioMsgMaybe $
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            tcRnModule hsc_env (ms_hsc_src mod_summary) False rdr_module
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    tcSafeOK <- liftIO $ readIORef (tcg_safeInfer tcg_env)
    -- if safe haskell off or safe infer failed, wipe trust
    if not (safeHaskellOn dflags) || (safeInferOn dflags && not tcSafeOK)
        then wipeTrust tcg_env
        else hscCheckSafeImports tcg_env
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--------------------------------------------------------------
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-- Safe Haskell
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--------------------------------------------------------------

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-- Note [Safe Haskell Trust Check]
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- Safe Haskell checks that an import is trusted according to the following
-- rules for an import of module M that resides in Package P:
--
--   * If M is recorded as Safe and all its trust dependencies are OK
--     then M is considered safe.
--   * If M is recorded as Trustworthy and P is considered trusted and
--     all M's trust dependencies are OK then M is considered safe.
--
-- By trust dependencies we mean that the check is transitive. So if
-- a module M that is Safe relies on a module N that is trustworthy,
-- importing module M will first check (according to the second case)
-- that N is trusted before checking M is trusted.
--
-- This is a minimal description, so please refer to the user guide
-- for more details. The user guide is also considered the authoritative
-- source in this matter, not the comments or code.


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-- Note [Safe Haskell Inference]
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- Safe Haskell does Safe inference on modules that don't have any specific
-- safe haskell mode flag. The basic aproach to this is:
--   * When deciding if we need to do a Safe language check, treat
--     an unmarked module as having -XSafe mode specified.
--   * For checks, don't throw errors but return them to the caller.
--   * Caller checks if there are errors:
--     * For modules explicitly marked -XSafe, we throw the errors.
--     * For unmarked modules (inference mode), we drop the errors
--       and mark the module as being Unsafe.


-- | Check that the safe imports of the module being compiled are valid.
-- If not we either issue a compilation error if the module is explicitly
-- using Safe Haskell, or mark the module as unsafe if we're in safe
-- inference mode.
hscCheckSafeImports :: TcGblEnv -> Hsc TcGblEnv
hscCheckSafeImports tcg_env = do
    hsc_env  <- getHscEnv
    dflags   <- getDynFlags
    tcg_env' <- checkSafeImports dflags hsc_env tcg_env
    case safeLanguageOn dflags of
        True -> do
            -- we nuke user written RULES in -XSafe
            logWarnings $ warns (tcg_rules tcg_env')
            return tcg_env' { tcg_rules = [] }
        False
              -- user defined RULES, so not safe or already unsafe
            | safeInferOn dflags && not (null $ tcg_rules tcg_env') ||
              safeHaskell dflags == Sf_None
            -> wipeTrust tcg_env'

              -- trustworthy
            | otherwise
            -> return tcg_env'

    where
        warns rules = listToBag $ map warnRules rules
        warnRules (L loc (HsRule n _ _ _ _ _ _)) =
            mkPlainWarnMsg loc $
                text "Rule \"" <> ftext n <> text "\" ignored" $+$
                text "User defined rules are disabled under Safe Haskell"

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-- | Validate that safe imported modules are actually safe.
-- For modules in the HomePackage (the package the module we
-- are compiling in resides) this just involves checking its
-- trust type is 'Safe' or 'Trustworthy'. For modules that
-- reside in another package we also must check that the
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-- external pacakge is trusted. See the Note [Safe Haskell
-- Trust Check] above for more information.
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--
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-- The code for this is quite tricky as the whole algorithm
-- is done in a few distinct phases in different parts of the
-- code base. See RnNames.rnImportDecl for where package trust
-- dependencies for a module are collected and unioned.
-- Specifically see the Note [RnNames . Tracking Trust Transitively]
-- and the Note [RnNames . Trust Own Package].
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checkSafeImports :: DynFlags -> HscEnv -> TcGblEnv -> Hsc TcGblEnv
checkSafeImports dflags hsc_env tcg_env
    = do
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        -- We want to use the warning state specifically for detecting if safe
        -- inference has failed, so store and clear any existing warnings.
        oldErrs <- getWarnings
        clearWarnings

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        imps <- mapM condense imports'
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        pkgs <- mapM checkSafe imps
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        -- grab any safe haskell specific errors and restore old warnings
        errs <- getWarnings
        clearWarnings
        logWarnings oldErrs

        -- See the Note [ Safe Haskell Inference]
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        case (not $ isEmptyBag errs) of

            -- We have errors!
            True ->
                -- did we fail safe inference or fail -XSafe?
                case safeInferOn dflags of
                    True  -> wipeTrust tcg_env
                    False -> liftIO . throwIO . mkSrcErr $ errs
            
            -- All good matey!
            False -> do
                when (packageTrustOn dflags) $ checkPkgTrust pkg_reqs
                -- add in trusted package requirements for this module
                let new_trust = emptyImportAvails { imp_trust_pkgs = catMaybes pkgs }
                return tcg_env { tcg_imports = imp_info `plusImportAvails` new_trust }
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    where
        imp_info = tcg_imports tcg_env     -- ImportAvails
        imports  = imp_mods imp_info       -- ImportedMods
        imports' = moduleEnvToList imports -- (Module, [ImportedModsVal])
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        pkg_reqs = imp_trust_pkgs imp_info -- [PackageId]
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        condense :: (Module, [ImportedModsVal]) -> Hsc (Module, SrcSpan, IsSafeImport)
        condense (_, [])   = panic "HscMain.condense: Pattern match failure!"
        condense (m, x:xs) = do (_,_,l,s) <- foldlM cond' x xs
                                return (m, l, s)
        
        -- ImportedModsVal = (ModuleName, Bool, SrcSpan, IsSafeImport)
        cond' :: ImportedModsVal -> ImportedModsVal -> Hsc ImportedModsVal
        cond' v1@(m1,_,l1,s1) (_,_,_,s2)
            | s1 /= s2
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            = throwErrors $ unitBag $ mkPlainErrMsg l1
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                    (text "Module" <+> ppr m1 <+> (text $ "is imported"
                        ++ " both as a safe and unsafe import!"))
            | otherwise
            = return v1

        lookup' :: Module -> Hsc (Maybe ModIface)
        lookup' m = do
            hsc_eps <- liftIO $ hscEPS hsc_env
            let pkgIfaceT = eps_PIT hsc_eps
                homePkgT = hsc_HPT hsc_env
                iface = lookupIfaceByModule dflags homePkgT pkgIfaceT m
            return iface

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        isHomePkg :: Module -> Bool
        isHomePkg m
            | thisPackage dflags == modulePackageId m = True
            | otherwise                               = False

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        -- | Check the package a module resides in is trusted.
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        -- Safe compiled modules are trusted without requiring
        -- that their package is trusted. For trustworthy modules,
        -- modules in the home package are trusted but otherwise
        -- we check the package trust flag.
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        packageTrusted :: SafeHaskellMode -> Bool -> Module -> Bool
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        packageTrusted _ _ _
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            | not (packageTrustOn dflags)     = True
        packageTrusted Sf_Safe        False _ = True
        packageTrusted Sf_SafeInfered False _ = True
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        packageTrusted _ _ m
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            | isHomePkg m = True
            | otherwise   = trusted $ getPackageDetails (pkgState dflags)
                                                        (modulePackageId m)
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        -- Is a module trusted? Return Nothing if True, or a String
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        -- if it isn't, containing the reason it isn't. Also return
        -- if the module trustworthy (true) or safe (false) so we know
        -- if we should check if the package itself is trusted in the
        -- future.
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        isModSafe :: Module -> SrcSpan -> Hsc (Bool)
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        isModSafe m l = do
            iface <- lookup' m
            case iface of
                -- can't load iface to check trust!
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                Nothing -> throwErrors $ unitBag $ mkPlainErrMsg l
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                            $ text "Can't load the interface file for" <+> ppr m <>
                              text ", to check that it can be safely imported"

                -- got iface, check trust
                Just iface' -> do
                    let trust = getSafeMode $ mi_trust iface'
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                        trust_own_pkg = mi_trust_pkg iface'
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                        -- check module is trusted
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                        safeM = trust `elem` [Sf_SafeInfered, Sf_Safe, Sf_Trustworthy]
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                        -- check package is trusted
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                        safeP = packageTrusted trust trust_own_pkg m