deSugar/Coverage.hs

    {-
    (c) Galois, 2006
    (c) University of Glasgow, 2007
    -}

    {-# LANGUAGE CPP, NondecreasingIndentation, RecordWildCards #-}

    module Coverage (addTicksToBinds, hpcInitCode) where

    import qualified GHCi
    import GHCi.RemoteTypes
    import Data.Array
    import ByteCodeTypes
    #if MIN_VERSION_base(4,9,0)
    import GHC.Stack.CCS
    #else
    import GHC.Stack as GHC.Stack.CCS
    #endif
    import Type
    import HsSyn
    import Module
    import Outputable
    import DynFlags
    import ConLike
    import Control.Monad
    import SrcLoc
    import ErrUtils
    import NameSet hiding (FreeVars)
    import Name
    import Bag
    import CostCentre
    import CoreSyn
    import Id
    import VarSet
    import Data.List
    import FastString
    import HscTypes
    import TyCon
    import UniqSupply
    import BasicTypes
    import MonadUtils
    import Maybes
    import CLabel
    import Util

    import Data.Time
    import System.Directory

    import Trace.Hpc.Mix
    import Trace.Hpc.Util

    import Data.Map (Map)
    import qualified Data.Map as Map

    {-
    ************************************************************************
    *                                                                      *
    *              The main function: addTicksToBinds
    *                                                                      *
    ************************************************************************
    -}

    addTicksToBinds
            :: HscEnv
            -> Module
            -> ModLocation          -- ... off the current module
            -> NameSet              -- Exported Ids.  When we call addTicksToBinds,
                                    -- isExportedId doesn't work yet (the desugarer
                                    -- hasn't set it), so we have to work from this set.
            -> [TyCon]              -- Type constructor in this module
            -> LHsBinds Id
            -> IO (LHsBinds Id, HpcInfo, Maybe ModBreaks)

    addTicksToBinds hsc_env mod mod_loc exports tyCons binds
      | let dflags = hsc_dflags hsc_env
            passes = coveragePasses dflags, not (null passes),
        Just orig_file <- ml_hs_file mod_loc,
        not ("boot" `isSuffixOf` orig_file) = do

         us <- mkSplitUniqSupply 'C' -- for cost centres
         let  orig_file2 = guessSourceFile binds orig_file

              tickPass tickish (binds,st) =
                let env = TTE
                          { fileName     = mkFastString orig_file2
                          , declPath     = []
                          , tte_dflags   = dflags
                          , exports      = exports
                          , inlines      = emptyVarSet
                          , inScope      = emptyVarSet
                          , blackList    = Map.fromList
                                              [ (getSrcSpan (tyConName tyCon),())
                                              | tyCon <- tyCons ]
                          , density      = mkDensity tickish dflags
                          , this_mod     = mod
                          , tickishType  = tickish
    }
                    (binds',_,st') = unTM (addTickLHsBinds binds) env st
                in (binds', st')

              initState = TT { tickBoxCount = 0
                             , mixEntries   = []
                             , uniqSupply   = us
                             }

              (binds1,st) = foldr tickPass (binds, initState) passes

         let tickCount = tickBoxCount st
             entries = reverse $ mixEntries st
         hashNo <- writeMixEntries dflags mod tickCount entries orig_file2
         modBreaks <- mkModBreaks hsc_env mod tickCount entries

         when (dopt Opt_D_dump_ticked dflags) $
             putLogMsg dflags NoReason SevDump noSrcSpan
                 (defaultDumpStyle dflags) (pprLHsBinds binds1)

         return (binds1, HpcInfo tickCount hashNo, Just modBreaks)

      | otherwise = return (binds, emptyHpcInfo False, Nothing)

    guessSourceFile :: LHsBinds Id -> FilePath -> FilePath
    guessSourceFile binds orig_file =
         -- Try look for a file generated from a .hsc file to a
         -- .hs file, by peeking ahead.
         let top_pos = catMaybes $ foldrBag (\ (L pos _) rest ->
                                     srcSpanFileName_maybe pos : rest) [] binds
         in
         case top_pos of
            (file_name:_) | ".hsc" `isSuffixOf` unpackFS file_name
                          -> unpackFS file_name
            _ -> orig_file

    mkModBreaks :: HscEnv -> Module -> Int -> [MixEntry_] -> IO ModBreaks
    mkModBreaks hsc_env mod count entries
      | HscInterpreted <- hscTarget (hsc_dflags hsc_env) = do
        breakArray <- GHCi.newBreakArray hsc_env (length entries)
        ccs <- mkCCSArray hsc_env mod count entries
        let
               locsTicks  = listArray (0,count-1) [ span  | (span,_,_,_)  <- entries ]
               varsTicks  = listArray (0,count-1) [ vars  | (_,_,vars,_)  <- entries ]
               declsTicks = listArray (0,count-1) [ decls | (_,decls,_,_) <- entries ]
        return emptyModBreaks
                           { modBreaks_flags = breakArray
                           , modBreaks_locs  = locsTicks
                           , modBreaks_vars  = varsTicks
                           , modBreaks_decls = declsTicks
                           , modBreaks_ccs   = ccs
                           }
      | otherwise = return emptyModBreaks

    mkCCSArray
      :: HscEnv -> Module -> Int -> [MixEntry_]
      -> IO (Array BreakIndex (RemotePtr GHC.Stack.CCS.CostCentre))
    mkCCSArray hsc_env modul count entries = do
      if interpreterProfiled dflags
        then do
          let module_str = moduleNameString (moduleName modul)
          costcentres <- GHCi.mkCostCentres hsc_env module_str (map mk_one entries)
          return (listArray (0,count-1) costcentres)
        else do
          return (listArray (0,-1) [])
     where
        dflags = hsc_dflags hsc_env
        mk_one (srcspan, decl_path, _, _) = (name, src)
          where name = concat (intersperse "." decl_path)
                src = showSDoc dflags (ppr srcspan)

    writeMixEntries
      :: DynFlags -> Module -> Int -> [MixEntry_] -> FilePath -> IO Int
    writeMixEntries dflags mod count entries filename
      | not (gopt Opt_Hpc dflags) = return 0
      | otherwise   = do
            let
                hpc_dir = hpcDir dflags
                mod_name = moduleNameString (moduleName mod)

                hpc_mod_dir
                  | moduleUnitId mod == mainUnitId  = hpc_dir
                  | otherwise = hpc_dir ++ "/" ++ unitIdString (moduleUnitId mod)

                tabStop = 8 -- <tab> counts as a normal char in GHC's
                            -- location ranges.

            createDirectoryIfMissing True hpc_mod_dir
            modTime <- getModificationUTCTime filename
            let entries' = [ (hpcPos, box)
                           | (span,_,_,box) <- entries, hpcPos <- [mkHpcPos span] ]
            when (length entries' /= count) $ do
              panic "the number of .mix entries are inconsistent"
            let hashNo = mixHash filename modTime tabStop entries'
            mixCreate hpc_mod_dir mod_name
                           $ Mix filename modTime (toHash hashNo) tabStop entries'
            return hashNo

    -- -----------------------------------------------------------------------------
    -- TickDensity: where to insert ticks

    data TickDensity
      = TickForCoverage       -- for Hpc
      | TickForBreakPoints    -- for GHCi
      | TickAllFunctions      -- for -prof-auto-all
      | TickTopFunctions      -- for -prof-auto-top
      | TickExportedFunctions -- for -prof-auto-exported
      | TickCallSites         -- for stack tracing
      deriving Eq

    mkDensity :: TickishType -> DynFlags -> TickDensity
    mkDensity tickish dflags = case tickish of
      HpcTicks             -> TickForCoverage
      SourceNotes          -> TickForCoverage
      Breakpoints          -> TickForBreakPoints
      ProfNotes ->
        case profAuto dflags of
          ProfAutoAll      -> TickAllFunctions
          ProfAutoTop      -> TickTopFunctions
          ProfAutoExports  -> TickExportedFunctions
          ProfAutoCalls    -> TickCallSites
          _other           -> panic "mkDensity"

    -- | Decide whether to add a tick to a binding or not.
    shouldTickBind  :: TickDensity
                    -> Bool         -- top level?
                    -> Bool         -- exported?
                    -> Bool         -- simple pat bind?
                    -> Bool         -- INLINE pragma?
                    -> Bool

    shouldTickBind density top_lev exported _simple_pat inline
     = case density of
          TickForBreakPoints    -> False
            -- we never add breakpoints to simple pattern bindings
            -- (there's always a tick on the rhs anyway).
          TickAllFunctions      -> not inline
          TickTopFunctions      -> top_lev && not inline
          TickExportedFunctions -> exported && not inline
          TickForCoverage       -> True
          TickCallSites         -> False

    shouldTickPatBind :: TickDensity -> Bool -> Bool
    shouldTickPatBind density top_lev
      = case density of
          TickForBreakPoints    -> False
          TickAllFunctions      -> True
          TickTopFunctions      -> top_lev
          TickExportedFunctions -> False
          TickForCoverage       -> False
          TickCallSites         -> False

    -- -----------------------------------------------------------------------------
    -- Adding ticks to bindings

    addTickLHsBinds :: LHsBinds Id -> TM (LHsBinds Id)
    addTickLHsBinds = mapBagM addTickLHsBind

    addTickLHsBind :: LHsBind Id -> TM (LHsBind Id)
    addTickLHsBind (L pos bind@(AbsBinds { abs_binds   = binds,
                                           abs_exports = abs_exports })) = do
      withEnv add_exports $ do
      withEnv add_inlines $ do
      binds' <- addTickLHsBinds binds
      return $ L pos $ bind { abs_binds = binds' }
     where
       -- in AbsBinds, the Id on each binding is not the actual top-level
       -- Id that we are defining, they are related by the abs_exports
       -- field of AbsBinds.  So if we're doing TickExportedFunctions we need
       -- to add the local Ids to the set of exported Names so that we know to
       -- tick the right bindings.
       add_exports env =
         env{ exports = exports env `extendNameSetList`
                          [ idName mid
                          | ABE{ abe_poly = pid, abe_mono = mid } <- abs_exports
                          , idName pid `elemNameSet` (exports env) ] }

       add_inlines env =
         env{ inlines = inlines env `extendVarSetList`
                          [ mid
                          | ABE{ abe_poly = pid, abe_mono = mid } <- abs_exports
                          , isAnyInlinePragma (idInlinePragma pid) ] }

    addTickLHsBind (L pos bind@(AbsBindsSig { abs_sig_bind   = val_bind
                                            , abs_sig_export = poly_id }))
      | L _ FunBind { fun_id = L _ mono_id } <- val_bind
      = do withEnv (add_export  mono_id) $ do
           withEnv (add_inlines mono_id) $ do
           val_bind' <- addTickLHsBind val_bind
           return $ L pos $ bind { abs_sig_bind = val_bind' }

      | otherwise
      = pprPanic "addTickLHsBind" (ppr bind)
     where
      -- see AbsBinds comments
      add_export mono_id env
        | idName poly_id `elemNameSet` exports env
        = env { exports = exports env `extendNameSet` idName mono_id }
        | otherwise
        = env

      add_inlines mono_id env
        | isAnyInlinePragma (idInlinePragma poly_id)
        = env { inlines = inlines env `extendVarSet` mono_id }
        | otherwise
        = env

    addTickLHsBind (L pos (funBind@(FunBind { fun_id = (L _ id)  }))) = do
      let name = getOccString id
      decl_path <- getPathEntry
      density <- getDensity

      inline_ids <- liftM inlines getEnv
      let inline   = isAnyInlinePragma (idInlinePragma id)
                     || id `elemVarSet` inline_ids

      -- See Note [inline sccs]
      tickish <- tickishType `liftM` getEnv
      if inline && tickish == ProfNotes then return (L pos funBind) else do

      (fvs, mg@(MG { mg_alts = matches' })) <-
            getFreeVars $
            addPathEntry name $
            addTickMatchGroup False (fun_matches funBind)

      blackListed <- isBlackListed pos
      exported_names <- liftM exports getEnv

      -- We don't want to generate code for blacklisted positions
      -- We don't want redundant ticks on simple pattern bindings
      -- We don't want to tick non-exported bindings in TickExportedFunctions
      let simple = isSimplePatBind funBind
          toplev = null decl_path
          exported = idName id `elemNameSet` exported_names

      tick <- if not blackListed &&
                   shouldTickBind density toplev exported simple inline
                 then
                    bindTick density name pos fvs
                 else
                    return Nothing

      let mbCons = maybe Prelude.id (:)
      return $ L pos $ funBind { fun_matches = mg { mg_alts = matches' }
                               , fun_tick = tick `mbCons` fun_tick funBind }

       where
       -- a binding is a simple pattern binding if it is a funbind with
       -- zero patterns
       isSimplePatBind :: HsBind a -> Bool
       isSimplePatBind funBind = matchGroupArity (fun_matches funBind) == 0

    -- TODO: Revisit this
    addTickLHsBind (L pos (pat@(PatBind { pat_lhs = lhs, pat_rhs = rhs }))) = do
      let name = "(...)"
      (fvs, rhs') <- getFreeVars $ addPathEntry name $ addTickGRHSs False False rhs
      let pat' = pat { pat_rhs = rhs'}

      -- Should create ticks here?
      density <- getDensity
      decl_path <- getPathEntry
      let top_lev = null decl_path
      if not (shouldTickPatBind density top_lev) then return (L pos pat') else do

        -- Allocate the ticks
        rhs_tick <- bindTick density name pos fvs
        let patvars = map getOccString (collectPatBinders lhs)
        patvar_ticks <- mapM (\v -> bindTick density v pos fvs) patvars

        -- Add to pattern
        let mbCons = maybe id (:)
            rhs_ticks = rhs_tick `mbCons` fst (pat_ticks pat')
            patvar_tickss = zipWith mbCons patvar_ticks
                            (snd (pat_ticks pat') ++ repeat [])
        return $ L pos $ pat' { pat_ticks = (rhs_ticks, patvar_tickss) }

    -- Only internal stuff, not from source, uses VarBind, so we ignore it.
    addTickLHsBind var_bind@(L _ (VarBind {})) = return var_bind
    addTickLHsBind patsyn_bind@(L _ (PatSynBind {})) = return patsyn_bind

    bindTick
      :: TickDensity -> String -> SrcSpan -> FreeVars -> TM (Maybe (Tickish Id))
    bindTick density name pos fvs = do
      decl_path <- getPathEntry
      let
          toplev        = null decl_path
          count_entries = toplev || density == TickAllFunctions
          top_only      = density /= TickAllFunctions
          box_label     = if toplev then TopLevelBox [name]
                                    else LocalBox (decl_path ++ [name])
      --
      allocATickBox box_label count_entries top_only pos fvs

    -- Note [inline sccs]
    --
    -- It should be reasonable to add ticks to INLINE functions; however
    -- currently this tickles a bug later on because the SCCfinal pass
    -- does not look inside unfoldings to find CostCentres.  It would be
    -- difficult to fix that, because SCCfinal currently works on STG and
    -- not Core (and since it also generates CostCentres for CAFs,
    -- changing this would be difficult too).
    --
    -- Another reason not to add ticks to INLINE functions is that this
    -- sometimes handy for avoiding adding a tick to a particular function
    -- (see #6131)
    --
    -- So for now we do not add any ticks to INLINE functions at all.

    -- -----------------------------------------------------------------------------
    -- Decorate an LHsExpr with ticks

    -- selectively add ticks to interesting expressions
    addTickLHsExpr :: LHsExpr Id -> TM (LHsExpr Id)
    addTickLHsExpr e@(L pos e0) = do
      d <- getDensity
      case d of
        TickForBreakPoints | isGoodBreakExpr e0 -> tick_it
        TickForCoverage    -> tick_it
        TickCallSites      | isCallSite e0      -> tick_it
        _other             -> dont_tick_it
     where
       tick_it      = allocTickBox (ExpBox False) False False pos $ addTickHsExpr e0
       dont_tick_it = addTickLHsExprNever e

    -- Add a tick to an expression which is the RHS of an equation or a binding.
    -- We always consider these to be breakpoints, unless the expression is a 'let'
    -- (because the body will definitely have a tick somewhere).  ToDo: perhaps
    -- we should treat 'case' and 'if' the same way?
    addTickLHsExprRHS :: LHsExpr Id -> TM (LHsExpr Id)
    addTickLHsExprRHS e@(L pos e0) = do
      d <- getDensity
      case d of
         TickForBreakPoints | HsLet{} <- e0 -> dont_tick_it
                            | otherwise     -> tick_it
         TickForCoverage -> tick_it
         TickCallSites   | isCallSite e0 -> tick_it
         _other          -> dont_tick_it
     where
       tick_it      = allocTickBox (ExpBox False) False False pos $ addTickHsExpr e0
       dont_tick_it = addTickLHsExprNever e

    -- The inner expression of an evaluation context:
    --    let binds in [], ( [] )
    -- we never tick these if we're doing HPC, but otherwise
    -- we treat it like an ordinary expression.
    addTickLHsExprEvalInner :: LHsExpr Id -> TM (LHsExpr Id)
    addTickLHsExprEvalInner e = do
       d <- getDensity
       case d of
         TickForCoverage -> addTickLHsExprNever e
         _otherwise      -> addTickLHsExpr e

    -- | A let body is treated differently from addTickLHsExprEvalInner
    -- above with TickForBreakPoints, because for breakpoints we always
    -- want to tick the body, even if it is not a redex.  See test
    -- break012.  This gives the user the opportunity to inspect the
    -- values of the let-bound variables.
    addTickLHsExprLetBody :: LHsExpr Id -> TM (LHsExpr Id)
    addTickLHsExprLetBody e@(L pos e0) = do
      d <- getDensity
      case d of
         TickForBreakPoints | HsLet{} <- e0 -> dont_tick_it
                            | otherwise     -> tick_it
         _other -> addTickLHsExprEvalInner e
     where
       tick_it      = allocTickBox (ExpBox False) False False pos $ addTickHsExpr e0
       dont_tick_it = addTickLHsExprNever e

    -- version of addTick that does not actually add a tick,
    -- because the scope of this tick is completely subsumed by
    -- another.
    addTickLHsExprNever :: LHsExpr Id -> TM (LHsExpr Id)
    addTickLHsExprNever (L pos e0) = do
        e1 <- addTickHsExpr e0
        return $ L pos e1

    -- general heuristic: expressions which do not denote values are good
    -- break points
    isGoodBreakExpr :: HsExpr Id -> Bool
    isGoodBreakExpr (HsApp {})        = True
    isGoodBreakExpr (HsAppTypeOut {}) = True
    isGoodBreakExpr (OpApp {})        = True
    isGoodBreakExpr _other            = False

    isCallSite :: HsExpr Id -> Bool
    isCallSite HsApp{}        = True
    isCallSite HsAppTypeOut{} = True
    isCallSite OpApp{}        = True
    isCallSite _ = False

    addTickLHsExprOptAlt :: Bool -> LHsExpr Id -> TM (LHsExpr Id)
    addTickLHsExprOptAlt oneOfMany (L pos e0)
      = ifDensity TickForCoverage
            (allocTickBox (ExpBox oneOfMany) False False pos $ addTickHsExpr e0)
            (addTickLHsExpr (L pos e0))

    addBinTickLHsExpr :: (Bool -> BoxLabel) -> LHsExpr Id -> TM (LHsExpr Id)
    addBinTickLHsExpr boxLabel (L pos e0)
      = ifDensity TickForCoverage
            (allocBinTickBox boxLabel pos $ addTickHsExpr e0)
            (addTickLHsExpr (L pos e0))

    -- -----------------------------------------------------------------------------
    -- Decorate the body of an HsExpr with ticks.
    -- (Whether to put a tick around the whole expression was already decided,
    -- in the addTickLHsExpr family of functions.)

    addTickHsExpr :: HsExpr Id -> TM (HsExpr Id)
    addTickHsExpr e@(HsVar (L _ id)) = do freeVar id; return e
    addTickHsExpr (HsUnboundVar {})  = panic "addTickHsExpr.HsUnboundVar"
    addTickHsExpr e@(HsConLikeOut con)
      | Just id <- conLikeWrapId_maybe con = do freeVar id; return e
    addTickHsExpr e@(HsIPVar _)      = return e
    addTickHsExpr e@(HsOverLit _)    = return e
    addTickHsExpr e@(HsOverLabel{})  = return e
    addTickHsExpr e@(HsLit _)        = return e
    addTickHsExpr (HsLam matchgroup) = liftM HsLam (addTickMatchGroup True matchgroup)
    addTickHsExpr (HsLamCase mgs)    = liftM HsLamCase (addTickMatchGroup True mgs)
    addTickHsExpr (HsApp e1 e2)      = liftM2 HsApp (addTickLHsExprNever e1)
                                                    (addTickLHsExpr      e2)
    addTickHsExpr (HsAppTypeOut e ty) = liftM2 HsAppTypeOut (addTickLHsExprNever e)
                                                            (return ty)

    addTickHsExpr (OpApp e1 e2 fix e3) =
            liftM4 OpApp
                    (addTickLHsExpr e1)
                    (addTickLHsExprNever e2)
                    (return fix)
                    (addTickLHsExpr e3)
    addTickHsExpr (NegApp e neg) =
            liftM2 NegApp
                    (addTickLHsExpr e)
                    (addTickSyntaxExpr hpcSrcSpan neg)
    addTickHsExpr (HsPar e) =
            liftM HsPar (addTickLHsExprEvalInner e)
    addTickHsExpr (SectionL e1 e2) =
            liftM2 SectionL
                    (addTickLHsExpr e1)
                    (addTickLHsExprNever e2)
    addTickHsExpr (SectionR e1 e2) =
            liftM2 SectionR
                    (addTickLHsExprNever e1)
                    (addTickLHsExpr e2)
    addTickHsExpr (ExplicitTuple es boxity) =
            liftM2 ExplicitTuple
                    (mapM addTickTupArg es)
                    (return boxity)
    addTickHsExpr (ExplicitSum tag arity e ty) = do
            e' <- addTickLHsExpr e
            return (ExplicitSum tag arity e' ty)
    addTickHsExpr (HsCase e mgs) =
            liftM2 HsCase
                    (addTickLHsExpr e) -- not an EvalInner; e might not necessarily
                                       -- be evaluated.
                    (addTickMatchGroup False mgs)
    addTickHsExpr (HsIf cnd e1 e2 e3) =
            liftM3 (HsIf cnd)
                    (addBinTickLHsExpr (BinBox CondBinBox) e1)
                    (addTickLHsExprOptAlt True e2)
                    (addTickLHsExprOptAlt True e3)
    addTickHsExpr (HsMultiIf ty alts)
      = do { let isOneOfMany = case alts of [_] -> False; _ -> True
           ; alts' <- mapM (liftL $ addTickGRHS isOneOfMany False) alts
           ; return $ HsMultiIf ty alts' }
    addTickHsExpr (HsLet (L l binds) e) =
            bindLocals (collectLocalBinders binds) $
              liftM2 (HsLet . L l)
                      (addTickHsLocalBinds binds) -- to think about: !patterns.
                      (addTickLHsExprLetBody e)
    addTickHsExpr (HsDo cxt (L l stmts) srcloc)
      = do { (stmts', _) <- addTickLStmts' forQual stmts (return ())
           ; return (HsDo cxt (L l stmts') srcloc) }
      where
            forQual = case cxt of
                        ListComp -> Just $ BinBox QualBinBox
                        _        -> Nothing
    addTickHsExpr (ExplicitList ty wit es) =
            liftM3 ExplicitList
                    (return ty)
                    (addTickWit wit)
                    (mapM (addTickLHsExpr) es)
                 where addTickWit Nothing = return Nothing
                       addTickWit (Just fln)
                         = do fln' <- addTickSyntaxExpr hpcSrcSpan fln
                              return (Just fln')
    addTickHsExpr (ExplicitPArr ty es) =
            liftM2 ExplicitPArr
                    (return ty)
                    (mapM (addTickLHsExpr) es)

    addTickHsExpr (HsStatic fvs e) = HsStatic fvs <$> addTickLHsExpr e

    addTickHsExpr expr@(RecordCon { rcon_flds = rec_binds })
      = do { rec_binds' <- addTickHsRecordBinds rec_binds
           ; return (expr { rcon_flds = rec_binds' }) }

    addTickHsExpr expr@(RecordUpd { rupd_expr = e, rupd_flds = flds })
      = do { e' <- addTickLHsExpr e
           ; flds' <- mapM addTickHsRecField flds
           ; return (expr { rupd_expr = e', rupd_flds = flds' }) }

    addTickHsExpr (ExprWithTySig e ty) =
            liftM2 ExprWithTySig
                    (addTickLHsExprNever e) -- No need to tick the inner expression
                                        -- for expressions with signatures
                    (return ty)
    addTickHsExpr (ArithSeq  ty wit arith_seq) =
            liftM3 ArithSeq
                    (return ty)
                    (addTickWit wit)
                    (addTickArithSeqInfo arith_seq)
                 where addTickWit Nothing = return Nothing
                       addTickWit (Just fl) = do fl' <- addTickSyntaxExpr hpcSrcSpan fl
                                                 return (Just fl')

    -- We might encounter existing ticks (multiple Coverage passes)
    addTickHsExpr (HsTick t e) =
            liftM (HsTick t) (addTickLHsExprNever e)
    addTickHsExpr (HsBinTick t0 t1 e) =
            liftM (HsBinTick t0 t1) (addTickLHsExprNever e)

    addTickHsExpr (HsTickPragma _ _ _ (L pos e0)) = do
        e2 <- allocTickBox (ExpBox False) False False pos $
                    addTickHsExpr e0
        return $ unLoc e2
    addTickHsExpr (PArrSeq   ty arith_seq) =
            liftM2 PArrSeq
                    (return ty)
                    (addTickArithSeqInfo arith_seq)
    addTickHsExpr (HsSCC src nm e) =
            liftM3 HsSCC
                    (return src)
                    (return nm)
                    (addTickLHsExpr e)
    addTickHsExpr (HsCoreAnn src nm e) =
            liftM3 HsCoreAnn
                    (return src)
                    (return nm)
                    (addTickLHsExpr e)
    addTickHsExpr e@(HsBracket     {})   = return e
    addTickHsExpr e@(HsTcBracketOut  {}) = return e
    addTickHsExpr e@(HsRnBracketOut  {}) = return e
    addTickHsExpr e@(HsSpliceE  {})      = return e
    addTickHsExpr (HsProc pat cmdtop) =
            liftM2 HsProc
                    (addTickLPat pat)
                    (liftL (addTickHsCmdTop) cmdtop)
    addTickHsExpr (HsWrap w e) =
            liftM2 HsWrap
                    (return w)
                    (addTickHsExpr e)       -- Explicitly no tick on inside

    addTickHsExpr (ExprWithTySigOut e ty) =
            liftM2 ExprWithTySigOut
                   (addTickLHsExprNever e) -- No need to tick the inner expression
                   (return ty)             -- for expressions with signatures

    -- Others should never happen in expression content.
    addTickHsExpr e  = pprPanic "addTickHsExpr" (ppr e)

    addTickTupArg :: LHsTupArg Id -> TM (LHsTupArg Id)
    addTickTupArg (L l (Present e))  = do { e' <- addTickLHsExpr e
                                          ; return (L l (Present e')) }
    addTickTupArg (L l (Missing ty)) = return (L l (Missing ty))

    addTickMatchGroup :: Bool{-is lambda-} -> MatchGroup Id (LHsExpr Id) -> TM (MatchGroup Id (LHsExpr Id))
    addTickMatchGroup is_lam mg@(MG { mg_alts = L l matches }) = do
      let isOneOfMany = matchesOneOfMany matches
      matches' <- mapM (liftL (addTickMatch isOneOfMany is_lam)) matches
      return $ mg { mg_alts = L l matches' }

    addTickMatch :: Bool -> Bool -> Match Id (LHsExpr Id) -> TM (Match Id (LHsExpr Id))
    addTickMatch isOneOfMany isLambda (Match mf pats opSig gRHSs) =
      bindLocals (collectPatsBinders pats) $ do
        gRHSs' <- addTickGRHSs isOneOfMany isLambda gRHSs
        return $ Match mf pats opSig gRHSs'

    addTickGRHSs :: Bool -> Bool -> GRHSs Id (LHsExpr Id) -> TM (GRHSs Id (LHsExpr Id))
    addTickGRHSs isOneOfMany isLambda (GRHSs guarded (L l local_binds)) = do
      bindLocals binders $ do
        local_binds' <- addTickHsLocalBinds local_binds
        guarded' <- mapM (liftL (addTickGRHS isOneOfMany isLambda)) guarded
        return $ GRHSs guarded' (L l local_binds')
      where
        binders = collectLocalBinders local_binds

    addTickGRHS :: Bool -> Bool -> GRHS Id (LHsExpr Id) -> TM (GRHS Id (LHsExpr Id))
    addTickGRHS isOneOfMany isLambda (GRHS stmts expr) = do
      (stmts',expr') <- addTickLStmts' (Just $ BinBox $ GuardBinBox) stmts
                            (addTickGRHSBody isOneOfMany isLambda expr)
      return $ GRHS stmts' expr'

    addTickGRHSBody :: Bool -> Bool -> LHsExpr Id -> TM (LHsExpr Id)
    addTickGRHSBody isOneOfMany isLambda expr@(L pos e0) = do
      d <- getDensity
      case d of
        TickForCoverage  -> addTickLHsExprOptAlt isOneOfMany expr
        TickAllFunctions | isLambda ->
           addPathEntry "\\" $
             allocTickBox (ExpBox False) True{-count-} False{-not top-} pos $
               addTickHsExpr e0
        _otherwise ->
           addTickLHsExprRHS expr

    addTickLStmts :: (Maybe (Bool -> BoxLabel)) -> [ExprLStmt Id] -> TM [ExprLStmt Id]
    addTickLStmts isGuard stmts = do
      (stmts, _) <- addTickLStmts' isGuard stmts (return ())
      return stmts

    addTickLStmts' :: (Maybe (Bool -> BoxLabel)) -> [ExprLStmt Id] -> TM a
                   -> TM ([ExprLStmt Id], a)
    addTickLStmts' isGuard lstmts res
      = bindLocals (collectLStmtsBinders lstmts) $
        do { lstmts' <- mapM (liftL (addTickStmt isGuard)) lstmts
           ; a <- res
           ; return (lstmts', a) }

    addTickStmt :: (Maybe (Bool -> BoxLabel)) -> Stmt Id (LHsExpr Id) -> TM (Stmt Id (LHsExpr Id))
    addTickStmt _isGuard (LastStmt e noret ret) = do
            liftM3 LastStmt
                    (addTickLHsExpr e)
                    (pure noret)
                    (addTickSyntaxExpr hpcSrcSpan ret)
    addTickStmt _isGuard (BindStmt pat e bind fail ty) = do
            liftM5 BindStmt
                    (addTickLPat pat)
                    (addTickLHsExprRHS e)
                    (addTickSyntaxExpr hpcSrcSpan bind)
                    (addTickSyntaxExpr hpcSrcSpan fail)
                    (return ty)
    addTickStmt isGuard (BodyStmt e bind' guard' ty) = do
            liftM4 BodyStmt
                    (addTick isGuard e)
                    (addTickSyntaxExpr hpcSrcSpan bind')
                    (addTickSyntaxExpr hpcSrcSpan guard')
                    (return ty)
    addTickStmt _isGuard (LetStmt (L l binds)) = do
            liftM (LetStmt . L l)
                    (addTickHsLocalBinds binds)
    addTickStmt isGuard (ParStmt pairs mzipExpr bindExpr ty) = do
        liftM4 ParStmt
            (mapM (addTickStmtAndBinders isGuard) pairs)
            (unLoc <$> addTickLHsExpr (L hpcSrcSpan mzipExpr))
            (addTickSyntaxExpr hpcSrcSpan bindExpr)
            (return ty)
    addTickStmt isGuard (ApplicativeStmt args mb_join body_ty) = do
        args' <- mapM (addTickApplicativeArg isGuard) args
        return (ApplicativeStmt args' mb_join body_ty)

    addTickStmt isGuard stmt@(TransStmt { trS_stmts = stmts
                                        , trS_by = by, trS_using = using
                                        , trS_ret = returnExpr, trS_bind = bindExpr
                                        , trS_fmap = liftMExpr }) = do
        t_s <- addTickLStmts isGuard stmts
        t_y <- fmapMaybeM  addTickLHsExprRHS by
        t_u <- addTickLHsExprRHS using
        t_f <- addTickSyntaxExpr hpcSrcSpan returnExpr
        t_b <- addTickSyntaxExpr hpcSrcSpan bindExpr
        L _ t_m <- addTickLHsExpr (L hpcSrcSpan liftMExpr)
        return $ stmt { trS_stmts = t_s, trS_by = t_y, trS_using = t_u
                      , trS_ret = t_f, trS_bind = t_b, trS_fmap = t_m }

    addTickStmt isGuard stmt@(RecStmt {})
      = do { stmts' <- addTickLStmts isGuard (recS_stmts stmt)
           ; ret'   <- addTickSyntaxExpr hpcSrcSpan (recS_ret_fn stmt)
           ; mfix'  <- addTickSyntaxExpr hpcSrcSpan (recS_mfix_fn stmt)
           ; bind'  <- addTickSyntaxExpr hpcSrcSpan (recS_bind_fn stmt)
           ; return (stmt { recS_stmts = stmts', recS_ret_fn = ret'
                          , recS_mfix_fn = mfix', recS_bind_fn = bind' }) }

    addTick :: Maybe (Bool -> BoxLabel) -> LHsExpr Id -> TM (LHsExpr Id)
    addTick isGuard e | Just fn <- isGuard = addBinTickLHsExpr fn e
                      | otherwise          = addTickLHsExprRHS e

    addTickApplicativeArg
      :: Maybe (Bool -> BoxLabel) -> (SyntaxExpr Id, ApplicativeArg Id Id)
      -> TM (SyntaxExpr Id, ApplicativeArg Id Id)
    addTickApplicativeArg isGuard (op, arg) =
      liftM2 (,) (addTickSyntaxExpr hpcSrcSpan op) (addTickArg arg)
     where
      addTickArg (ApplicativeArgOne pat expr) =
        ApplicativeArgOne <$> addTickLPat pat <*> addTickLHsExpr expr
      addTickArg (ApplicativeArgMany stmts ret pat) =
        ApplicativeArgMany
          <$> addTickLStmts isGuard stmts
          <*> (unLoc <$> addTickLHsExpr (L hpcSrcSpan ret))
          <*> addTickLPat pat

    addTickStmtAndBinders :: Maybe (Bool -> BoxLabel) -> ParStmtBlock Id Id
                          -> TM (ParStmtBlock Id Id)
    addTickStmtAndBinders isGuard (ParStmtBlock stmts ids returnExpr) =
        liftM3 ParStmtBlock
            (addTickLStmts isGuard stmts)
            (return ids)
            (addTickSyntaxExpr hpcSrcSpan returnExpr)

    addTickHsLocalBinds :: HsLocalBinds Id -> TM (HsLocalBinds Id)
    addTickHsLocalBinds (HsValBinds binds) =
            liftM HsValBinds
                    (addTickHsValBinds binds)
    addTickHsLocalBinds (HsIPBinds binds)  =
            liftM HsIPBinds
                    (addTickHsIPBinds binds)
    addTickHsLocalBinds (EmptyLocalBinds)  = return EmptyLocalBinds

    addTickHsValBinds :: HsValBindsLR Id a -> TM (HsValBindsLR Id b)
    addTickHsValBinds (ValBindsOut binds sigs) =
            liftM2 ValBindsOut
                    (mapM (\ (rec,binds') ->
                                    liftM2 (,)
                                            (return rec)
                                            (addTickLHsBinds binds'))
                            binds)
                    (return sigs)
    addTickHsValBinds _ = panic "addTickHsValBinds"

    addTickHsIPBinds :: HsIPBinds Id -> TM (HsIPBinds Id)
    addTickHsIPBinds (IPBinds ipbinds dictbinds) =
            liftM2 IPBinds
                    (mapM (liftL (addTickIPBind)) ipbinds)
                    (return dictbinds)

    addTickIPBind :: IPBind Id -> TM (IPBind Id)
    addTickIPBind (IPBind nm e) =
            liftM2 IPBind
                    (return nm)
                    (addTickLHsExpr e)

    -- There is no location here, so we might need to use a context location??
    addTickSyntaxExpr :: SrcSpan -> SyntaxExpr Id -> TM (SyntaxExpr Id)
    addTickSyntaxExpr pos syn@(SyntaxExpr { syn_expr = x }) = do
            L _ x' <- addTickLHsExpr (L pos x)
            return $ syn { syn_expr = x' }
    -- we do not walk into patterns.
    addTickLPat :: LPat Id -> TM (LPat Id)
    addTickLPat pat = return pat

    addTickHsCmdTop :: HsCmdTop Id -> TM (HsCmdTop Id)
    addTickHsCmdTop (HsCmdTop cmd tys ty syntaxtable) =
            liftM4 HsCmdTop
                    (addTickLHsCmd cmd)
                    (return tys)
                    (return ty)
                    (return syntaxtable)

    addTickLHsCmd ::  LHsCmd Id -> TM (LHsCmd Id)
    addTickLHsCmd (L pos c0) = do
            c1 <- addTickHsCmd c0
            return $ L pos c1

    addTickHsCmd :: HsCmd Id -> TM (HsCmd Id)
    addTickHsCmd (HsCmdLam matchgroup) =
            liftM HsCmdLam (addTickCmdMatchGroup matchgroup)
    addTickHsCmd (HsCmdApp c e) =
            liftM2 HsCmdApp (addTickLHsCmd c) (addTickLHsExpr e)
    {-
    addTickHsCmd (OpApp e1 c2 fix c3) =
            liftM4 OpApp
                    (addTickLHsExpr e1)
                    (addTickLHsCmd c2)
                    (return fix)
                    (addTickLHsCmd c3)
    -}
    addTickHsCmd (HsCmdPar e) = liftM HsCmdPar (addTickLHsCmd e)
    addTickHsCmd (HsCmdCase e mgs) =
            liftM2 HsCmdCase
                    (addTickLHsExpr e)
                    (addTickCmdMatchGroup mgs)
    addTickHsCmd (HsCmdIf cnd e1 c2 c3) =
            liftM3 (HsCmdIf cnd)
                    (addBinTickLHsExpr (BinBox CondBinBox) e1)
                    (addTickLHsCmd c2)
                    (addTickLHsCmd c3)
    addTickHsCmd (HsCmdLet (L l binds) c) =
            bindLocals (collectLocalBinders binds) $
              liftM2 (HsCmdLet . L l)
                       (addTickHsLocalBinds binds) -- to think about: !patterns.
                       (addTickLHsCmd c)
    addTickHsCmd (HsCmdDo (L l stmts) srcloc)
      = do { (stmts', _) <- addTickLCmdStmts' stmts (return ())
           ; return (HsCmdDo (L l stmts') srcloc) }

    addTickHsCmd (HsCmdArrApp   e1 e2 ty1 arr_ty lr) =
            liftM5 HsCmdArrApp
                   (addTickLHsExpr e1)
                   (addTickLHsExpr e2)
                   (return ty1)
                   (return arr_ty)
                   (return lr)
    addTickHsCmd (HsCmdArrForm e f fix cmdtop) =
            liftM4 HsCmdArrForm
                   (addTickLHsExpr e)
                   (return f)
                   (return fix)
                   (mapM (liftL (addTickHsCmdTop)) cmdtop)

    addTickHsCmd (HsCmdWrap w cmd)
      = liftM2 HsCmdWrap (return w) (addTickHsCmd cmd)

    -- Others should never happen in a command context.
    --addTickHsCmd e  = pprPanic "addTickHsCmd" (ppr e)

    addTickCmdMatchGroup :: MatchGroup Id (LHsCmd Id) -> TM (MatchGroup Id (LHsCmd Id))
    addTickCmdMatchGroup mg@(MG { mg_alts = L l matches }) = do
      matches' <- mapM (liftL addTickCmdMatch) matches
      return $ mg { mg_alts = L l matches' }

    addTickCmdMatch :: Match Id (LHsCmd Id) -> TM (Match Id (LHsCmd Id))
    addTickCmdMatch (Match mf pats opSig gRHSs) =
      bindLocals (collectPatsBinders pats) $ do
        gRHSs' <- addTickCmdGRHSs gRHSs
        return $ Match mf pats opSig gRHSs'

    addTickCmdGRHSs :: GRHSs Id (LHsCmd Id) -> TM (GRHSs Id (LHsCmd Id))
    addTickCmdGRHSs (GRHSs guarded (L l local_binds)) = do
      bindLocals binders $ do
        local_binds' <- addTickHsLocalBinds local_binds
        guarded' <- mapM (liftL addTickCmdGRHS) guarded
        return $ GRHSs guarded' (L l local_binds')
      where
        binders = collectLocalBinders local_binds

    addTickCmdGRHS :: GRHS Id (LHsCmd Id) -> TM (GRHS Id (LHsCmd Id))
    -- The *guards* are *not* Cmds, although the body is
    -- C.f. addTickGRHS for the BinBox stuff
    addTickCmdGRHS (GRHS stmts cmd)
      = do { (stmts',expr') <- addTickLStmts' (Just $ BinBox $ GuardBinBox)
                                       stmts (addTickLHsCmd cmd)
           ; return $ GRHS stmts' expr' }

    addTickLCmdStmts :: [LStmt Id (LHsCmd Id)] -> TM [LStmt Id (LHsCmd Id)]
    addTickLCmdStmts stmts = do
      (stmts, _) <- addTickLCmdStmts' stmts (return ())
      return stmts

    addTickLCmdStmts' :: [LStmt Id (LHsCmd Id)] -> TM a -> TM ([LStmt Id (LHsCmd Id)], a)
    addTickLCmdStmts' lstmts res
      = bindLocals binders $ do
            lstmts' <- mapM (liftL addTickCmdStmt) lstmts
            a <- res
            return (lstmts', a)
      where
            binders = collectLStmtsBinders lstmts

    addTickCmdStmt :: Stmt Id (LHsCmd Id) -> TM (Stmt Id (LHsCmd Id))
    addTickCmdStmt (BindStmt pat c bind fail ty) = do
            liftM5 BindStmt
                    (addTickLPat pat)
                    (addTickLHsCmd c)
                    (return bind)
                    (return fail)
                    (return ty)
    addTickCmdStmt (LastStmt c noret ret) = do
            liftM3 LastStmt
                    (addTickLHsCmd c)
                    (pure noret)
                    (addTickSyntaxExpr hpcSrcSpan ret)
    addTickCmdStmt (BodyStmt c bind' guard' ty) = do
            liftM4 BodyStmt
                    (addTickLHsCmd c)
                    (addTickSyntaxExpr hpcSrcSpan bind')
                    (addTickSyntaxExpr hpcSrcSpan guard')
                    (return ty)
    addTickCmdStmt (LetStmt (L l binds)) = do
            liftM (LetStmt . L l)
                    (addTickHsLocalBinds binds)
    addTickCmdStmt stmt@(RecStmt {})
      = do { stmts' <- addTickLCmdStmts (recS_stmts stmt)
           ; ret'   <- addTickSyntaxExpr hpcSrcSpan (recS_ret_fn stmt)
           ; mfix'  <- addTickSyntaxExpr hpcSrcSpan (recS_mfix_fn stmt)
           ; bind'  <- addTickSyntaxExpr hpcSrcSpan (recS_bind_fn stmt)
           ; return (stmt { recS_stmts = stmts', recS_ret_fn = ret'
                          , recS_mfix_fn = mfix', recS_bind_fn = bind' }) }
    addTickCmdStmt ApplicativeStmt{} =
      panic "ToDo: addTickCmdStmt ApplicativeLastStmt"

    -- Others should never happen in a command context.
    addTickCmdStmt stmt  = pprPanic "addTickHsCmd" (ppr stmt)

    addTickHsRecordBinds :: HsRecordBinds Id -> TM (HsRecordBinds Id)
    addTickHsRecordBinds (HsRecFields fields dd)
      = do  { fields' <- mapM addTickHsRecField fields
            ; return (HsRecFields fields' dd) }

    addTickHsRecField :: LHsRecField' id (LHsExpr Id) -> TM (LHsRecField' id (LHsExpr Id))
    addTickHsRecField (L l (HsRecField id expr pun))
            = do { expr' <- addTickLHsExpr expr
                 ; return (L l (HsRecField id expr' pun)) }

    addTickArithSeqInfo :: ArithSeqInfo Id -> TM (ArithSeqInfo Id)
    addTickArithSeqInfo (From e1) =
            liftM From
                    (addTickLHsExpr e1)
    addTickArithSeqInfo (FromThen e1 e2) =
            liftM2 FromThen
                    (addTickLHsExpr e1)
                    (addTickLHsExpr e2)
    addTickArithSeqInfo (FromTo e1 e2) =
            liftM2 FromTo
                    (addTickLHsExpr e1)
                    (addTickLHsExpr e2)
    addTickArithSeqInfo (FromThenTo e1 e2 e3) =
            liftM3 FromThenTo
                    (addTickLHsExpr e1)
                    (addTickLHsExpr e2)
                    (addTickLHsExpr e3)

    liftL :: (Monad m) => (a -> m a) -> Located a -> m (Located a)
    liftL f (L loc a) = do
      a' <- f a
      return $ L loc a'

    data TickTransState = TT { tickBoxCount:: Int
                             , mixEntries  :: [MixEntry_]
                             , uniqSupply  :: UniqSupply
                             }

    data TickTransEnv = TTE { fileName     :: FastString
                            , density      :: TickDensity
                            , tte_dflags   :: DynFlags
                            , exports      :: NameSet
                            , inlines      :: VarSet
                            , declPath     :: [String]
                            , inScope      :: VarSet
                            , blackList    :: Map SrcSpan ()
                            , this_mod     :: Module
                            , tickishType  :: TickishType
                            }

    --      deriving Show

    data TickishType = ProfNotes | HpcTicks | Breakpoints | SourceNotes
                     deriving (Eq)

    coveragePasses :: DynFlags -> [TickishType]
    coveragePasses dflags =
        ifa (hscTarget dflags == HscInterpreted) Breakpoints $
        ifa (gopt Opt_Hpc dflags)                HpcTicks $
        ifa (gopt Opt_SccProfilingOn dflags &&
             profAuto dflags /= NoProfAuto)      ProfNotes $
        ifa (debugLevel dflags > 0)              SourceNotes []
      where ifa f x xs | f         = x:xs
                       | otherwise = xs

    -- | Tickishs that only make sense when their source code location
    -- refers to the current file. This might not always be true due to
    -- LINE pragmas in the code - which would confuse at least HPC.
    tickSameFileOnly :: TickishType -> Bool
    tickSameFileOnly HpcTicks = True
    tickSameFileOnly _other   = False

    type FreeVars = OccEnv Id
    noFVs :: FreeVars
    noFVs = emptyOccEnv

    -- Note [freevars]
    --   For breakpoints we want to collect the free variables of an
    --   expression for pinning on the HsTick.  We don't want to collect
    --   *all* free variables though: in particular there's no point pinning
    --   on free variables that are will otherwise be in scope at the GHCi
    --   prompt, which means all top-level bindings.  Unfortunately detecting
    --   top-level bindings isn't easy (collectHsBindsBinders on the top-level
    --   bindings doesn't do it), so we keep track of a set of "in-scope"
    --   variables in addition to the free variables, and the former is used
    --   to filter additions to the latter.  This gives us complete control
    --   over what free variables we track.

    data TM a = TM { unTM :: TickTransEnv -> TickTransState -> (a,FreeVars,TickTransState) }
            -- a combination of a state monad (TickTransState) and a writer
            -- monad (FreeVars).

    instance Functor TM where
        fmap = liftM

    instance Applicative TM where
        pure a = TM $ \ _env st -> (a,noFVs,st)
        (<*>) = ap

    instance Monad TM where
      (TM m) >>= k = TM $ \ env st ->
                                    case m env st of
                                      (r1,fv1,st1) ->
                                         case unTM (k r1) env st1 of
                                           (r2,fv2,st2) ->
                                              (r2, fv1 `plusOccEnv` fv2, st2)

    instance HasDynFlags TM where
      getDynFlags = TM $ \ env st -> (tte_dflags env, noFVs, st)

    instance MonadUnique TM where
      getUniqueSupplyM = TM $ \_ st -> (uniqSupply st, noFVs, st)
      getUniqueM = TM $ \_ st -> let (u, us') = takeUniqFromSupply (uniqSupply st)
                                 in (u, noFVs, st { uniqSupply = us' })

    getState :: TM TickTransState
    getState = TM $ \ _ st -> (st, noFVs, st)

    setState :: (TickTransState -> TickTransState) -> TM ()
    setState f = TM $ \ _ st -> ((), noFVs, f st)

    getEnv :: TM TickTransEnv
    getEnv = TM $ \ env st -> (env, noFVs, st)

    withEnv :: (TickTransEnv -> TickTransEnv) -> TM a -> TM a
    withEnv f (TM m) = TM $ \ env st ->
                                     case m (f env) st of
                                       (a, fvs, st') -> (a, fvs, st')

    getDensity :: TM TickDensity
    getDensity = TM $ \env st -> (density env, noFVs, st)

    ifDensity :: TickDensity -> TM a -> TM a -> TM a
    ifDensity d th el = do d0 <- getDensity; if d == d0 then th else el

    getFreeVars :: TM a -> TM (FreeVars, a)
    getFreeVars (TM m)
      = TM $ \ env st -> case m env st of (a, fv, st') -> ((fv,a), fv, st')

    freeVar :: Id -> TM ()
    freeVar id = TM $ \ env st ->
                    if id `elemVarSet` inScope env
                       then ((), unitOccEnv (nameOccName (idName id)) id, st)
                       else ((), noFVs, st)

    addPathEntry :: String -> TM a -> TM a
    addPathEntry nm = withEnv (\ env -> env { declPath = declPath env ++ [nm] })

    getPathEntry :: TM [String]
    getPathEntry = declPath `liftM` getEnv

    getFileName :: TM FastString
    getFileName = fileName `liftM` getEnv

    isGoodSrcSpan' :: SrcSpan -> Bool
    isGoodSrcSpan' pos@(RealSrcSpan _) = srcSpanStart pos /= srcSpanEnd pos
    isGoodSrcSpan' (UnhelpfulSpan _) = False

    isGoodTickSrcSpan :: SrcSpan -> TM Bool
    isGoodTickSrcSpan pos = do
      file_name <- getFileName
      tickish <- tickishType `liftM` getEnv
      let need_same_file = tickSameFileOnly tickish
          same_file      = Just file_name == srcSpanFileName_maybe pos
      return (isGoodSrcSpan' pos && (not need_same_file || same_file))

    ifGoodTickSrcSpan :: SrcSpan -> TM a -> TM a -> TM a
    ifGoodTickSrcSpan pos then_code else_code = do
      good <- isGoodTickSrcSpan pos
      if good then then_code else else_code

    bindLocals :: [Id] -> TM a -> TM a
    bindLocals new_ids (TM m)
      = TM $ \ env st ->
                     case m env{ inScope = inScope env `extendVarSetList` new_ids } st of
                       (r, fv, st') -> (r, fv `delListFromOccEnv` occs, st')
      where occs = [ nameOccName (idName id) | id <- new_ids ]

    isBlackListed :: SrcSpan -> TM Bool
    isBlackListed pos = TM $ \ env st ->
                  case Map.lookup pos (blackList env) of
                    Nothing -> (False,noFVs,st)
                    Just () -> (True,noFVs,st)

    -- the tick application inherits the source position of its
    -- expression argument to support nested box allocations
    allocTickBox :: BoxLabel -> Bool -> Bool -> SrcSpan -> TM (HsExpr Id)
                 -> TM (LHsExpr Id)
    allocTickBox boxLabel countEntries topOnly pos m =
      ifGoodTickSrcSpan pos (do
        (fvs, e) <- getFreeVars m
        env <- getEnv
        tickish <- mkTickish boxLabel countEntries topOnly pos fvs (declPath env)
        return (L pos (HsTick tickish (L pos e)))
      ) (do
        e <- m
        return (L pos e)
      )

    -- the tick application inherits the source position of its
    -- expression argument to support nested box allocations
    allocATickBox :: BoxLabel -> Bool -> Bool -> SrcSpan -> FreeVars
                  -> TM (Maybe (Tickish Id))
    allocATickBox boxLabel countEntries topOnly  pos fvs =
      ifGoodTickSrcSpan pos (do
        let
          mydecl_path = case boxLabel of
                          TopLevelBox x -> x
                          LocalBox xs  -> xs
                          _ -> panic "allocATickBox"
        tickish <- mkTickish boxLabel countEntries topOnly pos fvs mydecl_path
        return (Just tickish)
      ) (return Nothing)

    mkTickish :: BoxLabel -> Bool -> Bool -> SrcSpan -> OccEnv Id -> [String]
              -> TM (Tickish Id)
    mkTickish boxLabel countEntries topOnly pos fvs decl_path = do

      let ids = filter (not . isUnliftedType . idType) $ occEnvElts fvs
              -- unlifted types cause two problems here:
              --   * we can't bind them  at the GHCi prompt
              --     (bindLocalsAtBreakpoint already fliters them out),
              --   * the simplifier might try to substitute a literal for
              --     the Id, and we can't handle that.

          me = (pos, decl_path, map (nameOccName.idName) ids, boxLabel)

          cc_name | topOnly   = head decl_path
                  | otherwise = concat (intersperse "." decl_path)

      dflags <- getDynFlags
      env <- getEnv
      case tickishType env of
        HpcTicks -> do
          c <- liftM tickBoxCount getState
          setState $ \st -> st { tickBoxCount = c + 1
                               , mixEntries = me : mixEntries st }
          return $ HpcTick (this_mod env) c

        ProfNotes -> do
          ccUnique <- getUniqueM
          let cc = mkUserCC (mkFastString cc_name) (this_mod env) pos ccUnique
              count = countEntries && gopt Opt_ProfCountEntries dflags
          return $ ProfNote cc count True{-scopes-}

        Breakpoints -> do
          c <- liftM tickBoxCount getState
          setState $ \st -> st { tickBoxCount = c + 1
                               , mixEntries = me:mixEntries st }
          return $ Breakpoint c ids

        SourceNotes | RealSrcSpan pos' <- pos ->
          return $ SourceNote pos' cc_name

        _otherwise -> panic "mkTickish: bad source span!"

    allocBinTickBox :: (Bool -> BoxLabel) -> SrcSpan -> TM (HsExpr Id)
                    -> TM (LHsExpr Id)
    allocBinTickBox boxLabel pos m = do
      env <- getEnv
      case tickishType env of
        HpcTicks -> do e <- liftM (L pos) m
                       ifGoodTickSrcSpan pos
                         (mkBinTickBoxHpc boxLabel pos e)
                         (return e)
        _other   -> allocTickBox (ExpBox False) False False pos m

    mkBinTickBoxHpc :: (Bool -> BoxLabel) -> SrcSpan -> LHsExpr Id
                    -> TM (LHsExpr Id)
    mkBinTickBoxHpc boxLabel pos e =
     TM $ \ env st ->
      let meT = (pos,declPath env, [],boxLabel True)
          meF = (pos,declPath env, [],boxLabel False)
          meE = (pos,declPath env, [],ExpBox False)
          c = tickBoxCount st
          mes = mixEntries st
      in
                 ( L pos $ HsTick (HpcTick (this_mod env) c) $ L pos $ HsBinTick (c+1) (c+2) e
               -- notice that F and T are reversed,
               -- because we are building the list in
               -- reverse...
                 , noFVs
                 , st {tickBoxCount=c+3 , mixEntries=meF:meT:meE:mes}
                 )

    mkHpcPos :: SrcSpan -> HpcPos
    mkHpcPos pos@(RealSrcSpan s)
       | isGoodSrcSpan' pos = toHpcPos (srcSpanStartLine s,
                                        srcSpanStartCol s,
                                        srcSpanEndLine s,
                                        srcSpanEndCol s - 1)
                                  -- the end column of a SrcSpan is one
                                  -- greater than the last column of the
                                  -- span (see SrcLoc), whereas HPC
                                  -- expects to the column range to be
                                  -- inclusive, hence we subtract one above.
    mkHpcPos _ = panic "bad source span; expected such spans to be filtered out"

    hpcSrcSpan :: SrcSpan
    hpcSrcSpan = mkGeneralSrcSpan (fsLit "Haskell Program Coverage internals")

    matchesOneOfMany :: [LMatch Id body] -> Bool
    matchesOneOfMany lmatches = sum (map matchCount lmatches) > 1
      where
            matchCount (L _ (Match _ _pats _ty (GRHSs grhss _binds))) = length grhss

    type MixEntry_ = (SrcSpan, [String], [OccName], BoxLabel)

    -- For the hash value, we hash everything: the file name,
    --  the timestamp of the original source file, the tab stop,
    --  and the mix entries. We cheat, and hash the show'd string.
    -- This hash only has to be hashed at Mix creation time,
    -- and is for sanity checking only.

    mixHash :: FilePath -> UTCTime -> Int -> [MixEntry] -> Int
    mixHash file tm tabstop entries = fromIntegral $ hashString
            (show $ Mix file tm 0 tabstop entries)

    {-
    ************************************************************************
    *                                                                      *
    *              initialisation
    *                                                                      *
    ************************************************************************

    Each module compiled with -fhpc declares an initialisation function of
    the form `hpc_init_<module>()`, which is emitted into the _stub.c file
    and annotated with __attribute__((constructor)) so that it gets
    executed at startup time.

    The function's purpose is to call hs_hpc_module to register this
    module with the RTS, and it looks something like this:

    static void hpc_init_Main(void) __attribute__((constructor));
    static void hpc_init_Main(void)
    {extern StgWord64 _hpc_tickboxes_Main_hpc[];
     hs_hpc_module("Main",8,1150288664,_hpc_tickboxes_Main_hpc);}
    -}

    hpcInitCode :: Module -> HpcInfo -> SDoc
    hpcInitCode _ (NoHpcInfo {}) = Outputable.empty
    hpcInitCode this_mod (HpcInfo tickCount hashNo)
     = vcat
        [ text "static void hpc_init_" <> ppr this_mod
             <> text "(void) __attribute__((constructor));"
        , text "static void hpc_init_" <> ppr this_mod <> text "(void)"
        , braces (vcat [
            text "extern StgWord64 " <> tickboxes <>
                   text "[]" <> semi,
            text "hs_hpc_module" <>
              parens (hcat (punctuate comma [
                  doubleQuotes full_name_str,
                  int tickCount, -- really StgWord32
                  int hashNo,    -- really StgWord32
                  tickboxes
                ])) <> semi
           ])
        ]
      where
        tickboxes = ppr (mkHpcTicksLabel $ this_mod)

        module_name  = hcat (map (text.charToC) $
                             bytesFS (moduleNameFS (Module.moduleName this_mod)))
        package_name = hcat (map (text.charToC) $
                             bytesFS (unitIdFS  (moduleUnitId this_mod)))
        full_name_str
           | moduleUnitId this_mod == mainUnitId
           = module_name
           | otherwise
           = package_name <> char '/' <> module_name