    -- \section[Hooks]{Low level API hooks}

    -- NB: this module is SOURCE-imported by DynFlags, and should primarily
    --     refer to *types*, rather than *code*
    -- If you import too muchhere , then the revolting compiler_stage2_dll0_MODULES
    -- stuff in compiler/ghc.mk makes DynFlags link to too much stuff

    {-# LANGUAGE CPP #-}
    module Hooks ( Hooks
                 , emptyHooks
                 , lookupHook
                 , getHooked
                   -- the hooks:
                 , dsForeignsHook
                 , tcForeignImportsHook
                 , tcForeignExportsHook
                 , hscFrontendHook
    #ifdef GHCI
                 , hscCompileCoreExprHook
    #endif
                 , ghcPrimIfaceHook
                 , runPhaseHook
                 , runMetaHook
                 , linkHook
                 , runRnSpliceHook
    #ifdef GHCI
                 , getValueSafelyHook
                 , createIservProcessHook
    #endif
                 ) where

    import DynFlags
    import Name
    import PipelineMonad
    import HscTypes
    import HsDecls
    import HsBinds
    import HsExpr
    import OrdList
    import Id
    import TcRnTypes
    import Bag
    import RdrName
    import CoreSyn
    #ifdef GHCI
    import GHCi.RemoteTypes
    import SrcLoc
    import Type
    import System.Process
    #endif
    import BasicTypes

    import Data.Maybe

    {-
    ************************************************************************
    *                                                                      *
    \subsection{Hooks}
    *                                                                      *
    ************************************************************************
    -}

    -- | Hooks can be used by GHC API clients to replace parts of
    --   the compiler pipeline. If a hook is not installed, GHC
    --   uses the default built-in behaviour

    emptyHooks :: Hooks
    emptyHooks = Hooks
      { dsForeignsHook         = Nothing
      , tcForeignImportsHook   = Nothing
      , tcForeignExportsHook   = Nothing
      , hscFrontendHook        = Nothing
    #ifdef GHCI
      , hscCompileCoreExprHook = Nothing
    #endif
      , ghcPrimIfaceHook       = Nothing
      , runPhaseHook           = Nothing
      , runMetaHook            = Nothing
      , linkHook               = Nothing
      , runRnSpliceHook        = Nothing
    #ifdef GHCI
      , getValueSafelyHook     = Nothing
      , createIservProcessHook = Nothing
    #endif
      }

    data Hooks = Hooks
      { dsForeignsHook         :: Maybe ([LForeignDecl Id] -> DsM (ForeignStubs, OrdList (Id, CoreExpr)))
      , tcForeignImportsHook   :: Maybe ([LForeignDecl Name] -> TcM ([Id], [LForeignDecl Id], Bag GlobalRdrElt))
      , tcForeignExportsHook   :: Maybe ([LForeignDecl Name] -> TcM (LHsBinds TcId, [LForeignDecl TcId], Bag GlobalRdrElt))
      , hscFrontendHook        :: Maybe (ModSummary -> Hsc FrontendResult)
    #ifdef GHCI
      , hscCompileCoreExprHook :: Maybe (HscEnv -> SrcSpan -> CoreExpr -> IO ForeignHValue)
    #endif
      , ghcPrimIfaceHook       :: Maybe ModIface
      , runPhaseHook           :: Maybe (PhasePlus -> FilePath -> DynFlags -> CompPipeline (PhasePlus, FilePath))
      , runMetaHook            :: Maybe (MetaHook TcM)
      , linkHook               :: Maybe (GhcLink -> DynFlags -> Bool -> HomePackageTable -> IO SuccessFlag)
      , runRnSpliceHook        :: Maybe (HsSplice Name -> RnM (HsSplice Name))
    #ifdef GHCI
      , getValueSafelyHook     :: Maybe (HscEnv -> Name -> Type -> IO (Maybe HValue))
      , createIservProcessHook :: Maybe (CreateProcess -> IO ProcessHandle)
    #endif
      }

    getHooked :: (Functor f, HasDynFlags f) => (Hooks -> Maybe a) -> a -> f a
    getHooked hook def = fmap (lookupHook hook def) getDynFlags

    lookupHook :: (Hooks -> Maybe a) -> a -> DynFlags -> a
    lookupHook hook def = fromMaybe def . hook . hooks