{-# LANGUAGE BangPatterns, CPP, MagicHash, NondecreasingIndentation #-}

-------------------------------------------------------------------------------
--
-- | Main API for compiling plain Haskell source code.
--
-- 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.
--
-- (c) The GRASP/AQUA Project, Glasgow University, 1993-2000
--
-------------------------------------------------------------------------------

module HscMain
    (
    -- * Making an HscEnv
      newHscEnv

    -- * Compiling complete source files
    , Messager, batchMsg
    , HscStatus (..)
    , hscCompileOneShot
    , hscCompileCmmFile
    , hscCompileCore

    , genericHscCompileGetFrontendResult

    , genModDetails
    , hscSimpleIface
    , hscWriteIface
    , hscNormalIface
    , hscGenHardCode
    , hscInteractive

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

    -- * Support for interactive evaluation
    , hscParseIdentifier
    , hscTcRcLookupName
    , hscTcRnGetInfo
    , hscCheckSafe
    , hscGetSafe
#ifdef GHCI
    , hscIsGHCiMonad
    , hscGetModuleInterface
    , hscRnImportDecls
    , hscTcRnLookupRdrName
    , hscStmt, hscStmtWithLocation
    , hscDecls, hscDeclsWithLocation
    , hscTcExpr, hscImport, hscKcType
    , hscCompileCoreExpr
    -- * Low-level exports for hooks
    , hscCompileCoreExpr'
#endif
      -- We want to make sure that we export enough to be able to redefine
      -- hscFileFrontEnd in client code
    , hscParse', hscSimplify', hscDesugar', tcRnModule'
    , getHscEnv
    , hscSimpleIface', hscNormalIface'
    , oneShotMsg
    , hscFileFrontEnd, genericHscFrontend, dumpIfaceStats
    ) where

#ifdef GHCI
import Id
import BasicTypes       ( HValue )
import ByteCodeGen      ( byteCodeGen, coreExprToBCOs )
import Linker
import CoreTidy         ( tidyExpr )
import Type             ( Type )
import PrelNames
import {- Kind parts of -} Type         ( Kind )
import CoreLint         ( lintInteractiveExpr )
import DsMeta           ( templateHaskellNames )
import VarEnv           ( emptyTidyEnv )
import Panic
import ConLike

import GHC.Exts
#endif

import Module
import Packages
import RdrName
import HsSyn
import CoreSyn
import StringBuffer
import Parser
import Lexer
import SrcLoc
import TcRnDriver
import TcIface          ( typecheckIface )
import TcRnMonad
import IfaceEnv         ( initNameCache )
import LoadIface        ( ifaceStats, initExternalPackageState )
import PrelInfo
import MkIface
import Desugar
import SimplCore
import TidyPgm
import CorePrep
import CoreToStg        ( coreToStg )
import qualified StgCmm ( codeGen )
import StgSyn
import CostCentre
import ProfInit
import TyCon
import Name
import SimplStg         ( stg2stg )
import Cmm
import CmmParse         ( parseCmmFile )
import CmmBuildInfoTables
import CmmPipeline
import CmmInfo
import CodeOutput
import NameEnv          ( emptyNameEnv )
import NameSet          ( emptyNameSet )
import InstEnv
import FamInstEnv
import Fingerprint      ( Fingerprint )
import Hooks

import DynFlags
import ErrUtils

import Outputable
import HscStats         ( ppSourceStats )
import HscTypes
import FastString
import UniqFM           ( emptyUFM )
import UniqSupply
import Bag
import Exception
import qualified Stream
import Stream (Stream)

import Util

import Data.List
import Control.Monad
import Data.Maybe
import Data.IORef
import System.FilePath as FilePath
import System.Directory
import qualified Data.Map as Map

#include "HsVersions.h"


{- **********************************************************************
%*                                                                      *
                Initialisation
%*                                                                      *
%********************************************************************* -}

newHscEnv :: DynFlags -> IO HscEnv
newHscEnv dflags = do
    eps_var <- newIORef initExternalPackageState
    us      <- mkSplitUniqSupply 'r'
    nc_var  <- newIORef (initNameCache us knownKeyNames)
    fc_var  <- newIORef emptyUFM
    mlc_var <- newIORef emptyModuleEnv
    return HscEnv {  hsc_dflags       = dflags,
                     hsc_targets      = [],
                     hsc_mod_graph    = [],
                     hsc_IC           = emptyInteractiveContext dflags,
                     hsc_HPT          = emptyHomePackageTable,
                     hsc_EPS          = eps_var,
                     hsc_NC           = nc_var,
                     hsc_FC           = fc_var,
                     hsc_MLC          = mlc_var,
                     hsc_type_env_var = Nothing }


knownKeyNames :: [Name]      -- Put here to avoid loops involving DsMeta,
knownKeyNames =              -- where templateHaskellNames are defined
    map getName wiredInThings
        ++ basicKnownKeyNames
#ifdef GHCI
        ++ templateHaskellNames
#endif

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

getWarnings :: Hsc WarningMessages
getWarnings = Hsc $ \_ w -> return (w, w)

clearWarnings :: Hsc ()
clearWarnings = Hsc $ \_ _ -> return ((), emptyBag)

logWarnings :: WarningMessages -> Hsc ()
logWarnings w = Hsc $ \_ w0 -> return ((), w0 `unionBags` w)

getHscEnv :: Hsc HscEnv
getHscEnv = Hsc $ \e w -> return (e, w)

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) $ throwErrors errs

-- | Throw some errors.
throwErrors :: ErrorMessages -> Hsc a
throwErrors = liftIO . throwIO . mkSrcErr

-- | 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
        Nothing -> throwErrors errs
        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 -> Located RdrName -> IO [Name]
hscTcRnLookupRdrName hsc_env0 rdr_name
  = runInteractiveHsc hsc_env0 $
    do { hsc_env <- getHscEnv
       ; ioMsgMaybe $ tcRnLookupRdrName hsc_env rdr_name }
#endif

hscTcRcLookupName :: HscEnv -> Name -> IO (Maybe TyThing)
hscTcRcLookupName hsc_env0 name = runInteractiveHsc hsc_env0 $ do
  hsc_env <- getHscEnv
  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, [ClsInst], [FamInst]))
hscTcRnGetInfo hsc_env0 name
  = runInteractiveHsc hsc_env0 $
    do { hsc_env <- getHscEnv
       ; ioMsgMaybe' $ tcRnGetInfo hsc_env name }

#ifdef GHCI
hscIsGHCiMonad :: HscEnv -> String -> IO Name
hscIsGHCiMonad hsc_env name
  = runHsc hsc_env $ ioMsgMaybe $ isGHCiMonad hsc_env name

hscGetModuleInterface :: HscEnv -> Module -> IO ModIface
hscGetModuleInterface hsc_env0 mod = runInteractiveHsc hsc_env0 $ do
  hsc_env <- getHscEnv
  ioMsgMaybe $ getModuleInterface hsc_env mod

-- -----------------------------------------------------------------------------
-- | Rename some import declarations
hscRnImportDecls :: HscEnv -> [LImportDecl RdrName] -> IO GlobalRdrEnv
hscRnImportDecls hsc_env0 import_decls = runInteractiveHsc hsc_env0 $ do
  hsc_env <- getHscEnv
  ioMsgMaybe $ tcRnImportDecls hsc_env import_decls
#endif

-- -----------------------------------------------------------------------------
-- | parse a file, returning the abstract syntax

hscParse :: HscEnv -> ModSummary -> IO HsParsedModule
hscParse hsc_env mod_summary = runHsc hsc_env $ hscParse' mod_summary

-- internal version, that doesn't fail due to -Werror
hscParse' :: ModSummary -> Hsc HsParsedModule
hscParse' mod_summary = do
    dflags <- getDynFlags
    let src_filename  = ms_hspp_file mod_summary
        maybe_src_buf = ms_hspp_buf  mod_summary

    --------------------------  Parser  ----------------
    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 dflags 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

            -- To get the list of extra source files, we take the list
            -- that the parser gave us,
            --   - eliminate files beginning with '<'.  gcc likes to use
            --     pseudo-filenames like "<built-in>" and "<command-line>"
            --   - normalise them (elimiante differences between ./f and f)
            --   - filter out the preprocessed source file
            --   - filter out anything beginning with tmpdir
            --   - remove duplicates
            --   - filter out the .hs/.lhs source filename if we have one
            --
            let n_hspp  = FilePath.normalise src_filename
                srcs0 = nub $ filter (not . (tmpDir dflags `isPrefixOf`))
                            $ filter (not . (== n_hspp))
                            $ map FilePath.normalise
                            $ filter (not . (isPrefixOf "<"))
                            $ map unpackFS
                            $ srcfiles pst
                srcs1 = case ml_hs_file (ms_location mod_summary) of
                          Just f  -> filter (/= FilePath.normalise f) srcs0
                          Nothing -> srcs0

            -- sometimes we see source files from earlier
            -- preprocessing stages that cannot be found, so just
            -- filter them out:
            srcs2 <- liftIO $ filterM doesFileExist srcs1

            return HsParsedModule {
                      hpm_module    = rdr_module,
                      hpm_src_files = srcs2,
                      hpm_annotations
                              = (Map.fromListWith (++) $ annotations pst,
                                 Map.fromList $ ((noSrcSpan,comment_q pst)
                                                 :(annotations_comments pst)))
                   }

-- 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.
type RenamedStuff =
        (Maybe (HsGroup Name, [LImportDecl Name], Maybe [LIE Name],
                Maybe LHsDocString))

-- | Rename and typecheck a module, additionally returning the renamed syntax
hscTypecheckRename :: HscEnv -> ModSummary -> HsParsedModule
                   -> IO (TcGblEnv, RenamedStuff)
hscTypecheckRename hsc_env mod_summary rdr_module = runHsc hsc_env $ do
    tc_result <- tcRnModule' hsc_env mod_summary True rdr_module

        -- 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)

    return (tc_result, rn_info)

-- wrapper around tcRnModule to handle safe haskell extras
tcRnModule' :: HscEnv -> ModSummary -> Bool -> HsParsedModule
            -> Hsc TcGblEnv
tcRnModule' hsc_env sum save_rn_syntax mod = do
    tcg_res <- {-# SCC "Typecheck-Rename" #-}
               ioMsgMaybe $
                   tcRnModule hsc_env (ms_hsc_src sum) save_rn_syntax mod

    tcSafeOK <- liftIO $ readIORef (tcg_safeInfer tcg_res)
    dflags   <- getDynFlags
    let allSafeOK = safeInferred dflags && tcSafeOK

    -- end of the safe haskell line, how to respond to user?
    if not (safeHaskellOn dflags) || (safeInferOn dflags && not allSafeOK)
        -- if safe Haskell off or safe infer failed, mark unsafe
        then markUnsafeInfer tcg_res emptyBag

        -- module (could be) safe, throw warning if needed
        else do
            tcg_res' <- hscCheckSafeImports tcg_res
            safe <- liftIO $ readIORef (tcg_safeInfer tcg_res')
            when safe $ do
              case wopt Opt_WarnSafe dflags of
                True -> (logWarnings $ unitBag $ mkPlainWarnMsg dflags
                       (warnSafeOnLoc dflags) $ errSafe tcg_res')
                False | safeHaskell dflags == Sf_Trustworthy &&
                        wopt Opt_WarnTrustworthySafe dflags ->
                  (logWarnings $ unitBag $ mkPlainWarnMsg dflags
                    (trustworthyOnLoc dflags) $ errTwthySafe tcg_res')
                False -> return ()
            return tcg_res'
  where
    pprMod t  = ppr $ moduleName $ tcg_mod t
    errSafe t = quotes (pprMod t) <+> text "has been inferred as safe!"
    errTwthySafe t = quotes (pprMod t)
      <+> text "is marked as Trustworthy but has been inferred as safe!"

-- | Convert a typechecked module to Core
hscDesugar :: HscEnv -> ModSummary -> TcGblEnv -> IO ModGuts
hscDesugar hsc_env mod_summary tc_result =
    runHsc hsc_env $ hscDesugar' (ms_location mod_summary) tc_result

hscDesugar' :: ModLocation -> TcGblEnv -> Hsc ModGuts
hscDesugar' mod_location tc_result = do
    hsc_env <- getHscEnv
    r <- ioMsgMaybe $
      {-# SCC "deSugar" #-}
      deSugar hsc_env mod_location tc_result

    -- always check -Werror after desugaring, this is the last opportunity for
    -- warnings to arise before the backend.
    handleWarnings
    return r

-- | 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.
makeSimpleIface :: HscEnv -> Maybe ModIface -> TcGblEnv -> ModDetails
                -> IO (ModIface,Bool)
makeSimpleIface hsc_env maybe_old_iface tc_result details = runHsc hsc_env $ do
    safe_mode <- hscGetSafeMode tc_result
    ioMsgMaybe $ do
        mkIfaceTc hsc_env (fmap mi_iface_hash maybe_old_iface) safe_mode
                  details tc_result

-- | Make a 'ModDetails' from the results of typechecking. Used when
-- typechecking only, as opposed to full compilation.
makeSimpleDetails :: HscEnv -> TcGblEnv -> IO ModDetails
makeSimpleDetails hsc_env tc_result = mkBootModDetailsTc hsc_env tc_result


{- **********************************************************************
%*                                                                      *
                The main compiler pipeline
%*                                                                      *
%********************************************************************* -}

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

It's the task of the compilation proper to compile Haskell, hs-boot and core
files to either byte-code, hard-code (C, asm, LLVM, ect) or to nothing at all
(the module is still parsed and type-checked. This feature is mostly used by
IDE's and the likes). 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:

 * 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 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.

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.
-}


type Messager = HscEnv -> (Int,Int) -> RecompileRequired -> ModSummary -> IO ()

genericHscCompileGetFrontendResult ::
                     Bool -- always do basic recompilation check?
                  -> Maybe TcGblEnv
                  -> Maybe Messager
                  -> HscEnv
                  -> ModSummary
                  -> SourceModified
                  -> Maybe ModIface  -- Old interface, if available
                  -> (Int,Int)       -- (i,n) = module i of n (for msgs)
                  -> IO (Either ModIface (TcGblEnv, Maybe Fingerprint))

genericHscCompileGetFrontendResult
  always_do_basic_recompilation_check m_tc_result
  mHscMessage hsc_env mod_summary source_modified mb_old_iface mod_index
    = do

    let msg what = case mHscMessage of
                   Just hscMessage -> hscMessage hsc_env mod_index what mod_summary
                   Nothing -> return ()

        skip iface = do
            msg UpToDate
            return $ Left iface

        compile mb_old_hash reason = do
            msg reason
            tc_result <- runHsc hsc_env $ genericHscFrontend mod_summary
            return $ Right (tc_result, mb_old_hash)

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

    case m_tc_result of
         Just tc_result
          | not always_do_basic_recompilation_check ->
             return $ Right (tc_result, Nothing)
         _ -> do
            (recomp_reqd, mb_checked_iface)
                <- {-# SCC "checkOldIface" #-}
                   checkOldIface hsc_env mod_summary
                                source_modified mb_old_iface
            -- 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

            case mb_checked_iface of
                Just iface | not (recompileRequired recomp_reqd) ->
                    -- 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.
                    case m_tc_result of
                    Nothing
                     | mi_used_th iface && not stable ->
                        compile mb_old_hash (RecompBecause "TH")
                    _ ->
                        skip iface
                _ ->
                    case m_tc_result of
                    Nothing -> compile mb_old_hash recomp_reqd
                    Just tc_result ->
                        return $ Right (tc_result, mb_old_hash)

genericHscFrontend :: ModSummary -> Hsc TcGblEnv
genericHscFrontend mod_summary =
  getHooked hscFrontendHook genericHscFrontend' >>= ($ mod_summary)

genericHscFrontend' :: ModSummary -> Hsc TcGblEnv
genericHscFrontend' mod_summary = hscFileFrontEnd mod_summary

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

hscCompileOneShot :: HscEnv
                  -> ModSummary
                  -> SourceModified
                  -> IO HscStatus
hscCompileOneShot env =
  lookupHook hscCompileOneShotHook hscCompileOneShot' (hsc_dflags env) env

-- Compile Haskell/boot in OneShot mode.
hscCompileOneShot' :: HscEnv
                   -> ModSummary
                   -> SourceModified
                   -> IO HscStatus
hscCompileOneShot' hsc_env mod_summary src_changed
  = do
    -- One-shot mode needs a knot-tying mutable variable for interface
    -- files. See TcRnTypes.TcGblEnv.tcg_type_env_var.
    type_env_var <- newIORef emptyNameEnv
    let mod = ms_mod mod_summary
        hsc_env' = hsc_env{ hsc_type_env_var = Just (mod, type_env_var) }

        msg what = oneShotMsg hsc_env' what

        skip = do msg UpToDate
                  dumpIfaceStats hsc_env'
                  return HscUpToDate

        compile mb_old_hash reason = runHsc hsc_env' $ do
            liftIO $ msg reason
            tc_result <- genericHscFrontend mod_summary
            guts0 <- hscDesugar' (ms_location mod_summary) tc_result
            dflags <- getDynFlags
            case hscTarget dflags of
                HscNothing -> do
                    when (gopt Opt_WriteInterface dflags) $ liftIO $ do
                        (iface, changed, _details) <- hscSimpleIface hsc_env tc_result mb_old_hash
                        hscWriteIface dflags iface changed mod_summary
                    return HscNotGeneratingCode
                _ ->
                    case ms_hsc_src mod_summary of
                    t | isHsBootOrSig t ->
                        do (iface, changed, _) <- hscSimpleIface' tc_result mb_old_hash
                           liftIO $ hscWriteIface dflags iface changed mod_summary
                           return (case t of
                                    HsBootFile -> HscUpdateBoot
                                    HsigFile -> HscUpdateSig
                                    HsSrcFile -> panic "hscCompileOneShot Src")
                    _ ->
                        do guts <- hscSimplify' guts0
                           (iface, changed, _details, cgguts) <- hscNormalIface' guts mb_old_hash
                           liftIO $ hscWriteIface dflags iface changed mod_summary
                           return $ HscRecomp cgguts mod_summary

        -- XXX This is always False, because in one-shot mode the
        -- concept of stability does not exist.  The driver never
        -- passes SourceUnmodifiedAndStable in here.
        stable = case src_changed of
                     SourceUnmodifiedAndStable -> True
                     _                         -> False

    (recomp_reqd, mb_checked_iface)
        <- {-# SCC "checkOldIface" #-}
           checkOldIface hsc_env' mod_summary src_changed Nothing
    -- 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

    case mb_checked_iface of
        Just iface | not (recompileRequired recomp_reqd) ->
            -- 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.
            if mi_used_th iface && not stable
            then compile mb_old_hash (RecompBecause "TH")
            else skip
        _ ->
            compile mb_old_hash recomp_reqd

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

genModDetails :: HscEnv -> ModIface -> IO ModDetails
genModDetails hsc_env old_iface
  = do
    new_details <- {-# SCC "tcRnIface" #-}
                   initIfaceCheck hsc_env (typecheckIface old_iface)
    dumpIfaceStats hsc_env
    return new_details

--------------------------------------------------------------
-- Progress displayers.
--------------------------------------------------------------

oneShotMsg :: HscEnv -> RecompileRequired -> IO ()
oneShotMsg hsc_env recomp =
    case recomp of
        UpToDate ->
            compilationProgressMsg (hsc_dflags hsc_env) $
                   "compilation IS NOT required"
        _ ->
            return ()

batchMsg :: Messager
batchMsg hsc_env mod_index recomp mod_summary =
    case recomp of
        MustCompile -> showMsg "Compiling " ""
        UpToDate
            | verbosity (hsc_dflags hsc_env) >= 2 -> showMsg "Skipping  " ""
            | otherwise -> return ()
        RecompBecause reason -> showMsg "Compiling " (" [" ++ reason ++ "]")
    where
        dflags = hsc_dflags hsc_env
        showMsg msg reason =
            compilationProgressMsg dflags $
            (showModuleIndex mod_index ++
            msg ++ showModMsg dflags (hscTarget dflags)
                              (recompileRequired recomp) mod_summary)
                ++ reason

--------------------------------------------------------------
-- FrontEnds
--------------------------------------------------------------

hscFileFrontEnd :: ModSummary -> Hsc TcGblEnv
hscFileFrontEnd mod_summary = do
    hpm <- hscParse' mod_summary
    hsc_env <- getHscEnv
    tcg_env <- tcRnModule' hsc_env mod_summary False hpm
    return tcg_env

--------------------------------------------------------------
-- Safe Haskell
--------------------------------------------------------------

-- 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.


-- 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.
--
-- It used to be that we only did safe inference on modules that had no Safe
-- Haskell flags, but now we perform safe inference on all modules as we want
-- to allow users to set the `--fwarn-safe`, `--fwarn-unsafe` and
-- `--fwarn-trustworthy-safe` flags on Trustworthy and Unsafe modules so that a
-- user can ensure their assumptions are correct and see reasons for why a
-- module is safe or unsafe.
--
-- This is tricky as we must be careful when we should throw an error compared
-- to just warnings. For checking safe imports we manage it as two steps. First
-- we check any imports that are required to be safe, then we check all other
-- imports to see if we can infer them to be safe.


-- | 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
    dflags   <- getDynFlags
    tcg_env' <- checkSafeImports dflags tcg_env
    checkRULES dflags tcg_env'

  where
    checkRULES dflags tcg_env' = do
      case safeLanguageOn dflags of
          True -> do
              -- XSafe: we nuke user written RULES
              logWarnings $ warns dflags (tcg_rules tcg_env')
              return tcg_env' { tcg_rules = [] }
          False
                -- SafeInferred: user defined RULES, so not safe
              | safeInferOn dflags && not (null $ tcg_rules tcg_env')
              -> markUnsafeInfer tcg_env' $ warns dflags (tcg_rules tcg_env')

                -- Trustworthy OR SafeInferred: with no RULES
              | otherwise
              -> return tcg_env'

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

-- | 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 external pacakge
-- is trusted. See the Note [Safe Haskell Trust Check] above for more
-- information.
--
-- 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].
checkSafeImports :: DynFlags -> TcGblEnv -> Hsc TcGblEnv
checkSafeImports dflags tcg_env
    = do
        imps <- mapM condense imports'
        let (safeImps, regImps) = partition (\(_,_,s) -> s) imps

        -- 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

        -- Check safe imports are correct
        safePkgs <- mapM checkSafe safeImps
        safeErrs <- getWarnings
        clearWarnings

        -- Check non-safe imports are correct if inferring safety
        -- See the Note [Safe Haskell Inference]
        (infErrs, infPkgs) <- case (safeInferOn dflags) of
          False -> return (emptyBag, [])
          True -> do infPkgs <- mapM checkSafe regImps
                     infErrs <- getWarnings
                     clearWarnings
                     return (infErrs, infPkgs)

        -- restore old errors
        logWarnings oldErrs

        case (isEmptyBag safeErrs) of
          -- Failed safe check
          False -> liftIO . throwIO . mkSrcErr $ safeErrs

          -- Passed safe check
          True -> do
            let infPassed = isEmptyBag infErrs
            tcg_env' <- case (not infPassed) of
              True  -> markUnsafeInfer tcg_env infErrs
              False -> return tcg_env
            when (packageTrustOn dflags) $ checkPkgTrust dflags pkgReqs
            let newTrust = pkgTrustReqs safePkgs infPkgs infPassed
            return tcg_env' { tcg_imports = impInfo `plusImportAvails` newTrust }

  where
    impInfo  = tcg_imports tcg_env     -- ImportAvails
    imports  = imp_mods impInfo        -- ImportedMods
    imports' = moduleEnvToList imports -- (Module, [ImportedModsVal])
    pkgReqs  = imp_trust_pkgs impInfo  -- [PackageKey]

    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
        = throwErrors $ unitBag $ mkPlainErrMsg dflags l1
              (text "Module" <+> ppr m1 <+>
              (text $ "is imported both as a safe and unsafe import!"))
        | otherwise
        = return v1

    -- easier interface to work with
    checkSafe (m, l, _) = fst `fmap` hscCheckSafe' dflags m l

    -- what pkg's to add to our trust requirements
    pkgTrustReqs req inf infPassed | safeInferOn dflags
                                  && safeHaskell dflags == Sf_None && infPassed
                                   = emptyImportAvails {
                                       imp_trust_pkgs = catMaybes req ++ catMaybes inf
                                   }
    pkgTrustReqs _   _ _ | safeHaskell dflags == Sf_Unsafe
                         = emptyImportAvails
    pkgTrustReqs req _ _ = emptyImportAvails { imp_trust_pkgs = catMaybes req }

-- | Check that a module is safe to import.
--
-- We return True to indicate the import is safe and False otherwise
-- although in the False case an exception may be thrown first.
hscCheckSafe :: HscEnv -> Module -> SrcSpan -> IO Bool
hscCheckSafe hsc_env m l = runHsc hsc_env $ do
    dflags <- getDynFlags
    pkgs <- snd `fmap` hscCheckSafe' dflags m l
    when (packageTrustOn dflags) $ checkPkgTrust dflags pkgs
    errs <- getWarnings
    return $ isEmptyBag errs

-- | Return if a module is trusted and the pkgs it depends on to be trusted.
hscGetSafe :: HscEnv -> Module -> SrcSpan -> IO (Bool, [PackageKey])
hscGetSafe hsc_env m l = runHsc hsc_env $ do
    dflags       <- getDynFlags
    (self, pkgs) <- hscCheckSafe' dflags m l
    good         <- isEmptyBag `fmap` getWarnings
    clearWarnings -- don't want them printed...
    let pkgs' | Just p <- self = p:pkgs
              | otherwise      = pkgs
    return (good, pkgs')

-- | Is a module trusted? If not, throw or log errors depending on the type.
-- Return (regardless of trusted or not) if the trust type requires the modules
-- own package be trusted and a list of other packages required to be trusted
-- (these later ones haven't been checked) but the own package trust has been.
hscCheckSafe' :: DynFlags -> Module -> SrcSpan -> Hsc (Maybe PackageKey, [PackageKey])
hscCheckSafe' dflags m l = do
    (tw, pkgs) <- isModSafe m l
    case tw of
        False              -> return (Nothing, pkgs)
        True | isHomePkg m -> return (Nothing, pkgs)
             | otherwise   -> return (Just $ modulePackageKey m, pkgs)
  where
    isModSafe :: Module -> SrcSpan -> Hsc (Bool, [PackageKey])
    isModSafe m l = do
        iface <- lookup' m
        case iface of
            -- can't load iface to check trust!
            Nothing -> throwErrors $ unitBag $ mkPlainErrMsg dflags l
                         $ 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' ->
                let trust = getSafeMode $ mi_trust iface'
                    trust_own_pkg = mi_trust_pkg iface'
                    -- check module is trusted
                    safeM = trust `elem` [Sf_Safe, Sf_Trustworthy]
                    -- check package is trusted
                    safeP = packageTrusted trust trust_own_pkg m
                    -- pkg trust reqs
                    pkgRs = map fst $ filter snd $ dep_pkgs $ mi_deps iface'
                    -- General errors we throw but Safe errors we log
                    errs = case (safeM, safeP) of
                        (True, True ) -> emptyBag
                        (True, False) -> pkgTrustErr
                        (False, _   ) -> modTrustErr
                in do
                    logWarnings errs
                    return (trust == Sf_Trustworthy, pkgRs)

                where
                    pkgTrustErr = unitBag $ mkErrMsg dflags l (pkgQual dflags) $
                        sep [ ppr (moduleName m)
                                <> text ": Can't be safely imported!"
                            , text "The package (" <> ppr (modulePackageKey m)
                                <> text ") the module resides in isn't trusted."
                            ]
                    modTrustErr = unitBag $ mkErrMsg dflags l (pkgQual dflags) $
                        sep [ ppr (moduleName m)
                                <> text ": Can't be safely imported!"
                            , text "The module itself isn't safe." ]

    -- | Check the package a module resides in is trusted. 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.
    packageTrusted :: SafeHaskellMode -> Bool -> Module -> Bool
    packageTrusted Sf_None             _ _ = False -- shouldn't hit these cases
    packageTrusted Sf_Unsafe           _ _ = False -- prefer for completeness.
    packageTrusted _ _ _
        | not (packageTrustOn dflags)      = True
    packageTrusted Sf_Safe         False _ = True
    packageTrusted _ _ m
        | isHomePkg m = True
        | otherwise   = trusted $ getPackageDetails dflags (modulePackageKey m)

    lookup' :: Module -> Hsc (Maybe ModIface)
    lookup' m = do
        hsc_env <- getHscEnv
        hsc_eps <- liftIO $ hscEPS hsc_env
        let pkgIfaceT = eps_PIT hsc_eps
            homePkgT  = hsc_HPT hsc_env
            iface     = lookupIfaceByModule dflags homePkgT pkgIfaceT m
#ifdef GHCI
        -- the 'lookupIfaceByModule' method will always fail when calling from GHCi
        -- as the compiler hasn't filled in the various module tables
        -- so we need to call 'getModuleInterface' to load from disk
        iface' <- case iface of
            Just _  -> return iface
            Nothing -> snd `fmap` (liftIO $ getModuleInterface hsc_env m)
        return iface'
#else
        return iface
#endif


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

-- | Check the list of packages are trusted.
checkPkgTrust :: DynFlags -> [PackageKey] -> Hsc ()
checkPkgTrust dflags pkgs =
    case errors of
        [] -> return ()
        _  -> (liftIO . throwIO . mkSrcErr . listToBag) errors
    where
        errors = catMaybes $ map go pkgs
        go pkg
            | trusted $ getPackageDetails dflags pkg
            = Nothing
            | otherwise
            = Just $ mkErrMsg dflags noSrcSpan (pkgQual dflags)
                   $ text "The package (" <> ppr pkg <> text ") is required" <>
                     text " to be trusted but it isn't!"

-- | Set module to unsafe and (potentially) wipe trust information.
--
-- Make sure to call this method to set a module to inferred unsafe, it should
-- be a central and single failure method. We only wipe the trust information
-- when we aren't in a specific Safe Haskell mode.
--
-- While we only use this for recording that a module was inferred unsafe, we
-- may call it on modules using Trustworthy or Unsafe flags so as to allow
-- warning flags for safety to function correctly. See Note [Safe Haskell
-- Inference].
markUnsafeInfer :: TcGblEnv -> WarningMessages -> Hsc TcGblEnv
markUnsafeInfer tcg_env whyUnsafe = do
    dflags <- getDynFlags

    when (wopt Opt_WarnUnsafe dflags)
         (logWarnings $ unitBag $
             mkPlainWarnMsg dflags (warnUnsafeOnLoc dflags) (whyUnsafe' dflags))

    liftIO $ writeIORef (tcg_safeInfer tcg_env) False
    -- NOTE: Only wipe trust when not in an explicity safe haskell mode. Other
    -- times inference may be on but we are in Trustworthy mode -- so we want
    -- to record safe-inference failed but not wipe the trust dependencies.
    case safeHaskell dflags == Sf_None of
      True  -> return $ tcg_env { tcg_imports = wiped_trust }
      False -> return tcg_env

  where
    wiped_trust   = (tcg_imports tcg_env) { imp_trust_pkgs = [] }
    pprMod        = ppr $ moduleName $ tcg_mod tcg_env
    whyUnsafe' df = vcat [ quotes pprMod <+> text "has been inferred as unsafe!"
                         , text "Reason:"
                         , nest 4 $ (vcat $ badFlags df) $+$
                                    (vcat $ pprErrMsgBagWithLoc whyUnsafe) $+$
                                    (vcat $ badInsts $ tcg_insts tcg_env)
                         ]
    badFlags df   = concat $ map (badFlag df) unsafeFlagsForInfer
    badFlag df (str,loc,on,_)
        | on df     = [mkLocMessage SevOutput (loc df) $
                            text str <+> text "is not allowed in Safe Haskell"]
        | otherwise = []
    badInsts insts = concat $ map badInst insts

    checkOverlap (NoOverlap _) = False
    checkOverlap _             = True

    badInst ins | checkOverlap (overlapMode (is_flag ins))
                = [mkLocMessage SevOutput (nameSrcSpan $ getName $ is_dfun ins) $
                      ppr (overlapMode $ is_flag ins) <+>
                      text "overlap mode isn't allowed in Safe Haskell"]
                | otherwise = []


-- | Figure out the final correct safe haskell mode
hscGetSafeMode :: TcGblEnv -> Hsc SafeHaskellMode
hscGetSafeMode tcg_env = do
    dflags  <- getDynFlags
    liftIO $ finalSafeMode dflags tcg_env

--------------------------------------------------------------
-- Simplifiers
--------------------------------------------------------------

hscSimplify :: HscEnv -> ModGuts -> IO ModGuts
hscSimplify hsc_env modguts = runHsc hsc_env $ hscSimplify' modguts

hscSimplify' :: ModGuts -> Hsc ModGuts
hscSimplify' ds_result = do
    hsc_env <- getHscEnv
    {-# SCC "Core2Core" #-}
      liftIO $ core2core hsc_env ds_result

--------------------------------------------------------------
-- Interface generators
--------------------------------------------------------------

hscSimpleIface :: HscEnv
               -> TcGblEnv
               -> Maybe Fingerprint
               -> IO (ModIface, Bool, ModDetails)
hscSimpleIface hsc_env tc_result mb_old_iface
    = runHsc hsc_env $ hscSimpleIface' tc_result mb_old_iface

hscSimpleIface' :: TcGblEnv
                -> Maybe Fingerprint
                -> Hsc (ModIface, Bool, ModDetails)
hscSimpleIface' tc_result mb_old_iface = do
    hsc_env   <- getHscEnv
    details   <- liftIO $ mkBootModDetailsTc hsc_env tc_result
    safe_mode <- hscGetSafeMode tc_result
    (new_iface, no_change)
        <- {-# SCC "MkFinalIface" #-}
           ioMsgMaybe $
               mkIfaceTc hsc_env mb_old_iface safe_mode details tc_result
    -- And the answer is ...
    liftIO $ dumpIfaceStats hsc_env
    return (new_iface, no_change, details)

hscNormalIface :: HscEnv
               -> ModGuts
               -> Maybe Fingerprint
               -> IO (ModIface, Bool, ModDetails, CgGuts)
hscNormalIface hsc_env simpl_result mb_old_iface =
    runHsc hsc_env $ hscNormalIface' simpl_result mb_old_iface

hscNormalIface' :: ModGuts
                -> Maybe Fingerprint
                -> Hsc (ModIface, Bool, ModDetails, CgGuts)
hscNormalIface' simpl_result mb_old_iface = do
    hsc_env <- getHscEnv
    (cg_guts, details) <- {-# SCC "CoreTidy" #-}
                          liftIO $ tidyProgram hsc_env simpl_result

    -- BUILD THE NEW ModIface and ModDetails
    --  and emit external core if necessary
    -- This has to happen *after* code gen so that the back-end
    -- info has been set. Not yet clear if it matters waiting
    -- until after code output
    (new_iface, no_change)
        <- {-# SCC "MkFinalIface" #-}
           ioMsgMaybe $
               mkIface hsc_env mb_old_iface details simpl_result

    liftIO $ dumpIfaceStats hsc_env

    -- Return the prepared code.
    return (new_iface, no_change, details, cg_guts)

--------------------------------------------------------------
-- BackEnd combinators
--------------------------------------------------------------

hscWriteIface :: DynFlags -> ModIface -> Bool -> ModSummary -> IO ()
hscWriteIface dflags iface no_change mod_summary = do
    let ifaceFile = ml_hi_file (ms_location mod_summary)
    unless no_change $
        {-# SCC "writeIface" #-}
        writeIfaceFile dflags ifaceFile iface
    whenGeneratingDynamicToo dflags $ do
        -- TODO: We should do a no_change check for the dynamic
        --       interface file too
        -- TODO: Should handle the dynamic hi filename properly
        let dynIfaceFile = replaceExtension ifaceFile (dynHiSuf dflags)
            dynIfaceFile' = addBootSuffix_maybe (mi_boot iface) dynIfaceFile
            dynDflags = dynamicTooMkDynamicDynFlags dflags
        writeIfaceFile dynDflags dynIfaceFile' iface

-- | Compile to hard-code.
hscGenHardCode :: HscEnv -> CgGuts -> ModSummary -> FilePath
               -> IO (FilePath, Maybe FilePath) -- ^ @Just f@ <=> _stub.c is f
hscGenHardCode hsc_env cgguts mod_summary output_filename = do
        let CgGuts{ -- This is the last use of the ModGuts in a compilation.
                    -- From now on, we just use the bits we need.
                    cg_module   = this_mod,
                    cg_binds    = core_binds,
                    cg_tycons   = tycons,
                    cg_foreign  = foreign_stubs0,
                    cg_dep_pkgs = dependencies,
                    cg_hpc_info = hpc_info } = cgguts
            dflags = hsc_dflags hsc_env
            location = ms_location mod_summary
            data_tycons = filter isDataTyCon tycons
            -- cg_tycons includes newtypes, for the benefit of External Core,
            -- but we don't generate any code for newtypes

        -------------------
        -- PREPARE FOR CODE GENERATION
        -- Do saturation and convert to A-normal form
        prepd_binds <- {-# SCC "CorePrep" #-}
                       corePrepPgm hsc_env location core_binds data_tycons ;
        -----------------  Convert to STG ------------------
        (stg_binds, cost_centre_info)
            <- {-# SCC "CoreToStg" #-}
               myCoreToStg dflags this_mod prepd_binds

        let prof_init = profilingInitCode this_mod cost_centre_info
            foreign_stubs = foreign_stubs0 `appendStubC` prof_init

        ------------------  Code generation ------------------

        -- The back-end is streamed: each top-level function goes
        -- from Stg all the way to asm before dealing with the next
        -- top-level function, so showPass isn't very useful here.
        -- Hence we have one showPass for the whole backend, the
        -- next showPass after this will be "Assembler".
        showPass dflags "CodeGen"

        cmms <- {-# SCC "StgCmm" #-}
                         doCodeGen hsc_env this_mod data_tycons
                             cost_centre_info
                             stg_binds hpc_info

        ------------------  Code output -----------------------
        rawcmms0 <- {-# SCC "cmmToRawCmm" #-}
                   cmmToRawCmm dflags cmms

        let dump a = do dumpIfSet_dyn dflags Opt_D_dump_cmm_raw "Raw Cmm"
                           (ppr a)
                        return a
            rawcmms1 = Stream.mapM dump rawcmms0

        (output_filename, (_stub_h_exists, stub_c_exists))
            <- {-# SCC "codeOutput" #-}
               codeOutput dflags this_mod output_filename location
               foreign_stubs dependencies rawcmms1
        return (output_filename, stub_c_exists)


hscInteractive :: HscEnv
               -> CgGuts
               -> ModSummary
               -> IO (Maybe FilePath, CompiledByteCode, ModBreaks)
#ifdef GHCI
hscInteractive hsc_env cgguts mod_summary = do
    let dflags = hsc_dflags hsc_env
    let CgGuts{ -- This is the last use of the ModGuts in a compilation.
                -- From now on, we just use the bits we need.
               cg_module   = this_mod,
               cg_binds    = core_binds,
               cg_tycons   = tycons,
               cg_foreign  = foreign_stubs,
               cg_modBreaks = mod_breaks } = cgguts

        location = ms_location mod_summary
        data_tycons = filter isDataTyCon tycons
        -- cg_tycons includes newtypes, for the benefit of External Core,
        -- but we don't generate any code for newtypes

    -------------------
    -- PREPARE FOR CODE GENERATION
    -- Do saturation and convert to A-normal form
    prepd_binds <- {-# SCC "CorePrep" #-}
                   corePrepPgm hsc_env location core_binds data_tycons
    -----------------  Generate byte code ------------------
    comp_bc <- byteCodeGen dflags this_mod prepd_binds data_tycons mod_breaks
    ------------------ Create f-x-dynamic C-side stuff ---
    (_istub_h_exists, istub_c_exists)
        <- outputForeignStubs dflags this_mod location foreign_stubs
    return (istub_c_exists, comp_bc, mod_breaks)
#else
hscInteractive _ _ = panic "GHC not compiled with interpreter"
#endif

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

hscCompileCmmFile :: HscEnv -> FilePath -> FilePath -> IO ()
hscCompileCmmFile hsc_env filename output_filename = runHsc hsc_env $ do
    let dflags = hsc_dflags hsc_env
    cmm <- ioMsgMaybe $ parseCmmFile dflags filename
    liftIO $ do
        us <- mkSplitUniqSupply 'S'
        let initTopSRT = initUs_ us emptySRT
        dumpIfSet_dyn dflags Opt_D_dump_cmm "Parsed Cmm" (ppr cmm)
        (_, cmmgroup) <- cmmPipeline hsc_env initTopSRT cmm
        rawCmms <- cmmToRawCmm dflags (Stream.yield cmmgroup)
        _ <- codeOutput dflags no_mod output_filename no_loc NoStubs [] rawCmms
        return ()
  where
    no_mod = panic "hscCmmFile: no_mod"
    no_loc = ModLocation{ ml_hs_file  = Just filename,
                          ml_hi_file  = panic "hscCmmFile: no hi file",
                          ml_obj_file = panic "hscCmmFile: no obj file" }

-------------------- Stuff for new code gen ---------------------

doCodeGen   :: HscEnv -> Module -> [TyCon]
            -> CollectedCCs
            -> [StgBinding]
            -> HpcInfo
            -> IO (Stream IO CmmGroup ())
         -- Note we produce a 'Stream' of CmmGroups, so that the
         -- backend can be run incrementally.  Otherwise it generates all
         -- the C-- up front, which has a significant space cost.
doCodeGen hsc_env this_mod data_tycons
              cost_centre_info stg_binds hpc_info = do
    let dflags = hsc_dflags hsc_env

    let cmm_stream :: Stream IO CmmGroup ()
        cmm_stream = {-# SCC "StgCmm" #-}
            StgCmm.codeGen dflags this_mod data_tycons
                           cost_centre_info stg_binds hpc_info

        -- codegen consumes a stream of CmmGroup, and produces a new
        -- stream of CmmGroup (not necessarily synchronised: one
        -- CmmGroup on input may produce many CmmGroups on output due
        -- to proc-point splitting).

    let dump1 a = do dumpIfSet_dyn dflags Opt_D_dump_cmm
                       "Cmm produced by new codegen" (ppr a)
                     return a

        ppr_stream1 = Stream.mapM dump1 cmm_stream

    -- We are building a single SRT for the entire module, so
    -- we must thread it through all the procedures as we cps-convert them.
    us <- mkSplitUniqSupply 'S'

    -- When splitting, we generate one SRT per split chunk, otherwise
    -- we generate one SRT for the whole module.
    let
     pipeline_stream
      | gopt Opt_SplitObjs dflags
        = {-# SCC "cmmPipeline" #-}
          let run_pipeline us cmmgroup = do
                let (topSRT', us') = initUs us emptySRT
                (topSRT, cmmgroup) <- cmmPipeline hsc_env topSRT' cmmgroup
                let srt | isEmptySRT topSRT = []
                        | otherwise         = srtToData topSRT
                return (us', srt ++ cmmgroup)

          in do _ <- Stream.mapAccumL run_pipeline us ppr_stream1
                return ()

      | otherwise
        = {-# SCC "cmmPipeline" #-}
          let initTopSRT = initUs_ us emptySRT
              run_pipeline = cmmPipeline hsc_env
          in do topSRT <- Stream.mapAccumL run_pipeline initTopSRT ppr_stream1
                Stream.yield (srtToData topSRT)

    let
        dump2 a = do dumpIfSet_dyn dflags Opt_D_dump_cmm "Output Cmm" $ ppr a
                     return a

        ppr_stream2 = Stream.mapM dump2 pipeline_stream

    return ppr_stream2



myCoreToStg :: DynFlags -> Module -> CoreProgram
            -> IO ( [StgBinding] -- output program
                  , CollectedCCs) -- cost centre info (declared and used)
myCoreToStg dflags this_mod prepd_binds = do
    stg_binds
        <- {-# SCC "Core2Stg" #-}
           coreToStg dflags this_mod prepd_binds

    (stg_binds2, cost_centre_info)
        <- {-# SCC "Stg2Stg" #-}
           stg2stg dflags this_mod stg_binds

    return (stg_binds2, cost_centre_info)


{- **********************************************************************
%*                                                                      *
\subsection{Compiling a do-statement}
%*                                                                      *
%********************************************************************* -}

{-
When the UnlinkedBCOExpr is linked you get an HValue of type *IO [HValue]* When
you run it you get a list of HValues that should be the same length as the list
of names; add them to the ClosureEnv.

A naked expression returns a singleton Name [it]. The stmt is lifted into the
IO monad as explained in Note [Interactively-bound Ids in GHCi] in HscTypes
-}

#ifdef GHCI
-- | Compile a stmt all the way to an HValue, but don't run it
--
-- We return Nothing to indicate an empty statement (or comment only), not a
-- parse error.
hscStmt :: HscEnv -> String -> IO (Maybe ([Id], IO [HValue], FixityEnv))
hscStmt hsc_env stmt = hscStmtWithLocation hsc_env stmt "<interactive>" 1

-- | Compile a stmt all the way to an HValue, but don't run it
--
-- We return Nothing to indicate an empty statement (or comment only), not a
-- parse error.
hscStmtWithLocation :: HscEnv
                    -> String -- ^ The statement
                    -> String -- ^ The source
                    -> Int    -- ^ Starting line
                    -> IO (Maybe ([Id], IO [HValue], FixityEnv))
hscStmtWithLocation hsc_env0 stmt source linenumber =
 runInteractiveHsc hsc_env0 $ do
    maybe_stmt <- hscParseStmtWithLocation source linenumber stmt
    case maybe_stmt of
        Nothing -> return Nothing

        Just parsed_stmt -> do
            -- Rename and typecheck it
            hsc_env <- getHscEnv
            (ids, tc_expr, fix_env) <- ioMsgMaybe $ tcRnStmt hsc_env parsed_stmt

            -- Desugar it
            ds_expr <- ioMsgMaybe $ deSugarExpr hsc_env tc_expr
            liftIO (lintInteractiveExpr "desugar expression" hsc_env ds_expr)
            handleWarnings

            -- Then code-gen, and link it
            -- It's important NOT to have package 'interactive' as thisPackageKey
            -- for linking, else we try to link 'main' and can't find it.
            -- Whereas the linker already knows to ignore 'interactive'
            let  src_span     = srcLocSpan interactiveSrcLoc
            hval <- liftIO $ hscCompileCoreExpr hsc_env src_span ds_expr
            let hval_io = unsafeCoerce# hval :: IO [HValue]

            return $ Just (ids, hval_io, fix_env)

-- | Compile a decls
hscDecls :: HscEnv
         -> String -- ^ The statement
         -> IO ([TyThing], InteractiveContext)
hscDecls hsc_env str = hscDeclsWithLocation hsc_env str "<interactive>" 1

-- | Compile a decls
hscDeclsWithLocation :: HscEnv
                     -> String -- ^ The statement
                     -> String -- ^ The source
                     -> Int    -- ^ Starting line
                     -> IO ([TyThing], InteractiveContext)
hscDeclsWithLocation hsc_env0 str source linenumber =
 runInteractiveHsc hsc_env0 $ do
    L _ (HsModule{ hsmodDecls = decls }) <-
        hscParseThingWithLocation source linenumber parseModule str

    {- Rename and typecheck it -}
    hsc_env <- getHscEnv
    tc_gblenv <- ioMsgMaybe $ tcRnDeclsi hsc_env decls

    {- Grab the new instances -}
    -- We grab the whole environment because of the overlapping that may have
    -- been done. See the notes at the definition of InteractiveContext
    -- (ic_instances) for more details.
    let defaults = tcg_default tc_gblenv

    {- Desugar it -}
    -- We use a basically null location for iNTERACTIVE
    let iNTERACTIVELoc = ModLocation{ ml_hs_file   = Nothing,
                                      ml_hi_file   = panic "hsDeclsWithLocation:ml_hi_file",
                                      ml_obj_file  = panic "hsDeclsWithLocation:ml_hi_file"}
    ds_result <- hscDesugar' iNTERACTIVELoc tc_gblenv

    {- Simplify -}
    simpl_mg <- liftIO $ hscSimplify hsc_env ds_result

    {- Tidy -}
    (tidy_cg, mod_details) <- liftIO $ tidyProgram hsc_env simpl_mg

    let dflags = hsc_dflags hsc_env
        !CgGuts{ cg_module    = this_mod,
                 cg_binds     = core_binds,
                 cg_tycons    = tycons,
                 cg_modBreaks = mod_breaks } = tidy_cg

        !ModDetails { md_insts     = cls_insts
                    , md_fam_insts = fam_insts } = mod_details
            -- Get the *tidied* cls_insts and fam_insts

        data_tycons = filter isDataTyCon tycons

    {- Prepare For Code Generation -}
    -- Do saturation and convert to A-normal form
    prepd_binds <- {-# SCC "CorePrep" #-}
      liftIO $ corePrepPgm hsc_env iNTERACTIVELoc core_binds data_tycons

    {- Generate byte code -}
    cbc <- liftIO $ byteCodeGen dflags this_mod
                                prepd_binds data_tycons mod_breaks

    let src_span = srcLocSpan interactiveSrcLoc
    liftIO $ linkDecls hsc_env src_span cbc

    let tcs = filterOut isImplicitTyCon (mg_tcs simpl_mg)
        patsyns = mg_patsyns simpl_mg

        ext_ids = [ id | id <- bindersOfBinds core_binds
                       , isExternalName (idName id)
                       , not (isDFunId id || isImplicitId id) ]
            -- We only need to keep around the external bindings
            -- (as decided by TidyPgm), since those are the only ones
            -- that might be referenced elsewhere.
            -- The DFunIds are in 'cls_insts' (see Note [ic_tythings] in HscTypes
            -- Implicit Ids are implicit in tcs

        tythings =  map AnId ext_ids ++ map ATyCon tcs ++ map (AConLike . PatSynCon) patsyns

    let icontext = hsc_IC hsc_env
        ictxt    = extendInteractiveContext icontext ext_ids tcs
                                            cls_insts fam_insts defaults patsyns
    return (tythings, ictxt)

hscImport :: HscEnv -> String -> IO (ImportDecl RdrName)
hscImport hsc_env str = runInteractiveHsc hsc_env $ do
    (L _ (HsModule{hsmodImports=is})) <-
       hscParseThing parseModule str
    case is of
        [L _ i] -> return i
        _ -> liftIO $ throwOneError $
                 mkPlainErrMsg (hsc_dflags hsc_env) noSrcSpan $
                     ptext (sLit "parse error in import declaration")

-- | Typecheck an expression (but don't run it)
-- Returns its most general type
hscTcExpr :: HscEnv
          -> String -- ^ The expression
          -> IO Type
hscTcExpr hsc_env0 expr = runInteractiveHsc hsc_env0 $ do
    hsc_env <- getHscEnv
    maybe_stmt <- hscParseStmt expr
    case maybe_stmt of
        Just (L _ (BodyStmt expr _ _ _)) ->
            ioMsgMaybe $ tcRnExpr hsc_env expr
        _ ->
            throwErrors $ unitBag $ mkPlainErrMsg (hsc_dflags hsc_env) noSrcSpan
                (text "not an expression:" <+> quotes (text expr))

-- | Find the kind of a type
-- Currently this does *not* generalise the kinds of the type
hscKcType
  :: HscEnv
  -> Bool            -- ^ Normalise the type
  -> String          -- ^ The type as a string
  -> IO (Type, Kind) -- ^ Resulting type (possibly normalised) and kind
hscKcType hsc_env0 normalise str = runInteractiveHsc hsc_env0 $ do
    hsc_env <- getHscEnv
    ty <- hscParseType str
    ioMsgMaybe $ tcRnType hsc_env normalise ty

hscParseStmt :: String -> Hsc (Maybe (GhciLStmt RdrName))
hscParseStmt = hscParseThing parseStmt

hscParseStmtWithLocation :: String -> Int -> String
                         -> Hsc (Maybe (GhciLStmt RdrName))
hscParseStmtWithLocation source linenumber stmt =
    hscParseThingWithLocation source linenumber parseStmt stmt

hscParseType :: String -> Hsc (LHsType RdrName)
hscParseType = hscParseThing parseType
#endif

hscParseIdentifier :: HscEnv -> String -> IO (Located RdrName)
hscParseIdentifier hsc_env str =
    runInteractiveHsc hsc_env $ hscParseThing parseIdentifier str

hscParseThing :: (Outputable thing) => Lexer.P thing -> String -> Hsc thing
hscParseThing = hscParseThingWithLocation "<interactive>" 1

hscParseThingWithLocation :: (Outputable thing) => String -> Int
                          -> Lexer.P thing -> String -> Hsc thing
hscParseThingWithLocation source linenumber parser str
  = {-# SCC "Parser" #-} do
    dflags <- getDynFlags
    liftIO $ showPass dflags "Parser"

    let buf = stringToStringBuffer str
        loc = mkRealSrcLoc (fsLit source) linenumber 1

    case unP parser (mkPState dflags buf loc) of
        PFailed span err -> do
            let msg = mkPlainErrMsg dflags span err
            throwErrors $ unitBag msg

        POk pst thing -> do
            logWarningsReportErrors (getMessages pst)
            liftIO $ dumpIfSet_dyn dflags Opt_D_dump_parsed "Parser" (ppr thing)
            return thing

hscCompileCore :: HscEnv -> Bool -> SafeHaskellMode -> ModSummary
               -> CoreProgram -> FilePath -> IO ()
hscCompileCore hsc_env simplify safe_mode mod_summary binds output_filename
  = runHsc hsc_env $ do
        guts <- maybe_simplify (mkModGuts (ms_mod mod_summary) safe_mode binds)
        (iface, changed, _details, cgguts) <- hscNormalIface' guts Nothing
        liftIO $ hscWriteIface (hsc_dflags hsc_env) iface changed mod_summary
        _ <- liftIO $ hscGenHardCode hsc_env cgguts mod_summary output_filename
        return ()

  where
    maybe_simplify mod_guts | simplify = hscSimplify' mod_guts
                            | otherwise = return mod_guts

-- Makes a "vanilla" ModGuts.
mkModGuts :: Module -> SafeHaskellMode -> CoreProgram -> ModGuts
mkModGuts mod safe binds =
    ModGuts {
        mg_module       = mod,
        mg_boot         = False,
        mg_exports      = [],
        mg_deps         = noDependencies,
        mg_dir_imps     = emptyModuleEnv,
        mg_used_names   = emptyNameSet,
        mg_used_th      = False,
        mg_rdr_env      = emptyGlobalRdrEnv,
        mg_fix_env      = emptyFixityEnv,
        mg_tcs          = [],
        mg_insts        = [],
        mg_fam_insts    = [],
        mg_patsyns      = [],
        mg_rules        = [],
        mg_vect_decls   = [],
        mg_binds        = binds,
        mg_foreign      = NoStubs,
        mg_warns        = NoWarnings,
        mg_anns         = [],
        mg_hpc_info     = emptyHpcInfo False,
        mg_modBreaks    = emptyModBreaks,
        mg_vect_info    = noVectInfo,
        mg_inst_env     = emptyInstEnv,
        mg_fam_inst_env = emptyFamInstEnv,
        mg_safe_haskell = safe,
        mg_trust_pkg    = False,
        mg_dependent_files = []
    }


{- **********************************************************************
%*                                                                      *
        Desugar, simplify, convert to bytecode, and link an expression
%*                                                                      *
%********************************************************************* -}

#ifdef GHCI
hscCompileCoreExpr :: HscEnv -> SrcSpan -> CoreExpr -> IO HValue
hscCompileCoreExpr hsc_env =
  lookupHook hscCompileCoreExprHook hscCompileCoreExpr' (hsc_dflags hsc_env) hsc_env

hscCompileCoreExpr' :: HscEnv -> SrcSpan -> CoreExpr -> IO HValue
hscCompileCoreExpr' hsc_env srcspan ds_expr
    | rtsIsProfiled
    = throwIO (InstallationError "You can't call hscCompileCoreExpr in a profiled compiler")
            -- Otherwise you get a seg-fault when you run it

    | otherwise
    = do { let dflags = hsc_dflags hsc_env

           {- Simplify it -}
         ; simpl_expr <- simplifyExpr dflags ds_expr

           {- Tidy it (temporary, until coreSat does cloning) -}
         ; let tidy_expr = tidyExpr emptyTidyEnv simpl_expr

           {- Prepare for codegen -}
         ; prepd_expr <- corePrepExpr dflags hsc_env tidy_expr

           {- Lint if necessary -}
         ; lintInteractiveExpr "hscCompileExpr" hsc_env prepd_expr

           {- Convert to BCOs -}
         ; bcos <- coreExprToBCOs dflags (icInteractiveModule (hsc_IC hsc_env)) prepd_expr

           {- link it -}
         ; hval <- linkExpr hsc_env srcspan bcos

         ; return hval }
#endif


{- **********************************************************************
%*                                                                      *
        Statistics on reading interfaces
%*                                                                      *
%********************************************************************* -}

dumpIfaceStats :: HscEnv -> IO ()
dumpIfaceStats hsc_env = do
    eps <- readIORef (hsc_EPS hsc_env)
    dumpIfSet dflags (dump_if_trace || dump_rn_stats)
              "Interface statistics"
              (ifaceStats eps)
  where
    dflags = hsc_dflags hsc_env
    dump_rn_stats = dopt Opt_D_dump_rn_stats dflags
    dump_if_trace = dopt Opt_D_dump_if_trace dflags


{- **********************************************************************
%*                                                                      *
        Progress Messages: Module i of n
%*                                                                      *
%********************************************************************* -}

showModuleIndex :: (Int, Int) -> String
showModuleIndex (i,n) = "[" ++ padded ++ " of " ++ n_str ++ "] "
  where
    n_str = show n
    i_str = show i
    padded = replicate (length n_str - length i_str) ' ' ++ i_str