    -- \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

    module Hooks ( Hooks
                 , emptyHooks
                 , lookupHook
                 , getHooked
                   -- the hooks:
                 , dsForeignsHook
                 , tcForeignImportsHook
                 , tcForeignExportsHook
                 , hscFrontendHook
                 , hscCompileOneShotHook
                 , hscCompileCoreExprHook
                 , ghcPrimIfaceHook
                 , runPhaseHook
                 , runMetaHook
                 , linkHook
                 , runQuasiQuoteHook
                 , runRnSpliceHook
                 , getValueSafelyHook
                 ) where

    import DynFlags
    import HsTypes
    import Name
    import PipelineMonad
    import HscTypes
    import HsDecls
    import HsBinds
    import HsExpr
    import OrdList
    import Id
    import TcRnTypes
    import Bag
    import RdrName
    import CoreSyn
    import BasicTypes
    import Type
    import SrcLoc

    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 Nothing Nothing Nothing Nothing Nothing Nothing
                       Nothing Nothing Nothing Nothing Nothing Nothing
                       Nothing

    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 TcGblEnv)
      , hscCompileOneShotHook  :: Maybe (HscEnv -> ModSummary -> SourceModified -> IO HscStatus)
      , hscCompileCoreExprHook :: Maybe (HscEnv -> SrcSpan -> CoreExpr -> IO HValue)
      , ghcPrimIfaceHook       :: Maybe ModIface
      , runPhaseHook           :: Maybe (PhasePlus -> FilePath -> DynFlags -> CompPipeline (PhasePlus, FilePath))
      , runMetaHook            :: Maybe (MetaHook TcM)
      , linkHook               :: Maybe (GhcLink -> DynFlags -> Bool -> HomePackageTable -> IO SuccessFlag)
      , runQuasiQuoteHook      :: Maybe (HsQuasiQuote Name -> RnM (HsQuasiQuote Name))
      , runRnSpliceHook        :: Maybe (LHsExpr Name -> RnM (LHsExpr Name))
      , getValueSafelyHook     :: Maybe (HscEnv -> Name -> Type -> IO (Maybe HValue))
      }

    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