%
% (c) The University of Glasgow 2006
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
Utilities for desugaring
This module exports some utility functions of no great interest.
\begin{code}
module DsUtils (
EquationInfo(..),
firstPat, shiftEqns,
MatchResult(..), CanItFail(..),
cantFailMatchResult, alwaysFailMatchResult,
extractMatchResult, combineMatchResults,
adjustMatchResult, adjustMatchResultDs,
mkCoLetMatchResult, mkViewMatchResult, mkGuardedMatchResult,
matchCanFail, mkEvalMatchResult,
mkCoPrimCaseMatchResult, mkCoAlgCaseMatchResult,
wrapBind, wrapBinds,
mkErrorAppDs, mkCoreAppDs, mkCoreAppsDs,
seqVar,
mkLHsVarPatTup, mkLHsPatTup, mkVanillaTuplePat,
mkBigLHsVarTup, mkBigLHsTup, mkBigLHsVarPatTup, mkBigLHsPatTup,
mkSelectorBinds,
dsSyntaxTable, lookupEvidence,
selectSimpleMatchVarL, selectMatchVars, selectMatchVar,
mkTickBox, mkOptTickBox, mkBinaryTickBox
) where
#include "HsVersions.h"
import Match ( matchSimply )
import DsExpr( dsExpr )
import HsSyn
import TcHsSyn
import TcType( tcSplitTyConApp )
import CoreSyn
import DsMonad
import CoreUtils
import MkCore
import MkId
import Id
import Var
import Name
import Literal
import TyCon
import DataCon
import Type
import Coercion
import TysPrim
import TysWiredIn
import BasicTypes
import UniqSet
import UniqSupply
import PrelNames
import Outputable
import SrcLoc
import Util
import ListSetOps
import FastString
import StaticFlags
\end{code}
%************************************************************************
%* *
Rebindable syntax
%* *
%************************************************************************
\begin{code}
dsSyntaxTable :: SyntaxTable Id
-> DsM ([CoreBind],
[(Name,Id)])
dsSyntaxTable rebound_ids = do
(binds_s, prs) <- mapAndUnzipM mk_bind rebound_ids
return (concat binds_s, prs)
where
mk_bind (std_name, HsVar id) = return ([], (std_name, id))
mk_bind (std_name, expr) = do
rhs <- dsExpr expr
id <- newSysLocalDs (exprType rhs)
return ([NonRec id rhs], (std_name, id))
lookupEvidence :: [(Name, Id)] -> Name -> Id
lookupEvidence prs std_name
= assocDefault (mk_panic std_name) prs std_name
where
mk_panic std_name = pprPanic "dsSyntaxTable" (ptext (sLit "Not found:") <+> ppr std_name)
\end{code}
%************************************************************************
%* *
\subsection{ Selecting match variables}
%* *
%************************************************************************
We're about to match against some patterns. We want to make some
@Ids@ to use as match variables. If a pattern has an @Id@ readily at
hand, which should indeed be bound to the pattern as a whole, then use it;
otherwise, make one up.
\begin{code}
selectSimpleMatchVarL :: LPat Id -> DsM Id
selectSimpleMatchVarL pat = selectMatchVar (unLoc pat)
selectMatchVars :: [Pat Id] -> DsM [Id]
selectMatchVars ps = mapM selectMatchVar ps
selectMatchVar :: Pat Id -> DsM Id
selectMatchVar (BangPat pat) = selectMatchVar (unLoc pat)
selectMatchVar (LazyPat pat) = selectMatchVar (unLoc pat)
selectMatchVar (ParPat pat) = selectMatchVar (unLoc pat)
selectMatchVar (VarPat var) = return (localiseId var)
selectMatchVar (AsPat var _) = return (unLoc var)
selectMatchVar other_pat = newSysLocalDs (hsPatType other_pat)
\end{code}
Note [Localise pattern binders]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider module M where
[Just a] = e
After renaming it looks like
module M where
[Just M.a] = e
We don't generalise, since it's a pattern binding, monomorphic, etc,
so after desugaring we may get something like
M.a = case e of (v:_) ->
case v of Just M.a -> M.a
Notice the "M.a" in the pattern; after all, it was in the original
pattern. However, after optimisation those pattern binders can become
let-binders, and then end up floated to top level. They have a
different *unique* by then (the simplifier is good about maintaining
proper scoping), but it's BAD to have two top-level bindings with the
External Name M.a, because that turns into two linker symbols for M.a.
It's quite rare for this to actually *happen* -- the only case I know
of is tc003 compiled with the 'hpc' way -- but that only makes it
all the more annoying.
To avoid this, we craftily call 'localiseId' in the desugarer, which
simply turns the External Name for the Id into an Internal one, but
doesn't change the unique. So the desugarer produces this:
M.a{r8} = case e of (v:_) ->
case v of Just a{r8} -> M.a{r8}
The unique is still 'r8', but the binding site in the pattern
is now an Internal Name. Now the simplifier's usual mechanisms
will propagate that Name to all the occurrence sites, as well as
un-shadowing it, so we'll get
M.a{r8} = case e of (v:_) ->
case v of Just a{s77} -> a{s77}
In fact, even CoreSubst.simplOptExpr will do this, and simpleOptExpr
runs on the output of the desugarer, so all is well by the end of
the desugaring pass.
%************************************************************************
%* *
%* type synonym EquationInfo and access functions for its pieces *
%* *
%************************************************************************
\subsection[EquationInfo-synonym]{@EquationInfo@: a useful synonym}
The ``equation info'' used by @match@ is relatively complicated and
worthy of a type synonym and a few handy functions.
\begin{code}
firstPat :: EquationInfo -> Pat Id
firstPat eqn = ASSERT( notNull (eqn_pats eqn) ) head (eqn_pats eqn)
shiftEqns :: [EquationInfo] -> [EquationInfo]
shiftEqns eqns = [ eqn { eqn_pats = tail (eqn_pats eqn) } | eqn <- eqns ]
\end{code}
Functions on MatchResults
\begin{code}
matchCanFail :: MatchResult -> Bool
matchCanFail (MatchResult CanFail _) = True
matchCanFail (MatchResult CantFail _) = False
alwaysFailMatchResult :: MatchResult
alwaysFailMatchResult = MatchResult CanFail (\fail -> return fail)
cantFailMatchResult :: CoreExpr -> MatchResult
cantFailMatchResult expr = MatchResult CantFail (\_ -> return expr)
extractMatchResult :: MatchResult -> CoreExpr -> DsM CoreExpr
extractMatchResult (MatchResult CantFail match_fn) _
= match_fn (error "It can't fail!")
extractMatchResult (MatchResult CanFail match_fn) fail_expr = do
(fail_bind, if_it_fails) <- mkFailurePair fail_expr
body <- match_fn if_it_fails
return (mkCoreLet fail_bind body)
combineMatchResults :: MatchResult -> MatchResult -> MatchResult
combineMatchResults (MatchResult CanFail body_fn1)
(MatchResult can_it_fail2 body_fn2)
= MatchResult can_it_fail2 body_fn
where
body_fn fail = do body2 <- body_fn2 fail
(fail_bind, duplicatable_expr) <- mkFailurePair body2
body1 <- body_fn1 duplicatable_expr
return (Let fail_bind body1)
combineMatchResults match_result1@(MatchResult CantFail _) _
= match_result1
adjustMatchResult :: DsWrapper -> MatchResult -> MatchResult
adjustMatchResult encl_fn (MatchResult can_it_fail body_fn)
= MatchResult can_it_fail (\fail -> encl_fn <$> body_fn fail)
adjustMatchResultDs :: (CoreExpr -> DsM CoreExpr) -> MatchResult -> MatchResult
adjustMatchResultDs encl_fn (MatchResult can_it_fail body_fn)
= MatchResult can_it_fail (\fail -> encl_fn =<< body_fn fail)
wrapBinds :: [(Var,Var)] -> CoreExpr -> CoreExpr
wrapBinds [] e = e
wrapBinds ((new,old):prs) e = wrapBind new old (wrapBinds prs e)
wrapBind :: Var -> Var -> CoreExpr -> CoreExpr
wrapBind new old body
| new==old = body
| isTyCoVar new = Let (mkTyBind new (mkTyVarTy old)) body
| otherwise = Let (NonRec new (Var old)) body
seqVar :: Var -> CoreExpr -> CoreExpr
seqVar var body = Case (Var var) var (exprType body)
[(DEFAULT, [], body)]
mkCoLetMatchResult :: CoreBind -> MatchResult -> MatchResult
mkCoLetMatchResult bind = adjustMatchResult (mkCoreLet bind)
mkViewMatchResult :: Id -> CoreExpr -> Id -> MatchResult -> MatchResult
mkViewMatchResult var' viewExpr var =
adjustMatchResult (mkCoreLet (NonRec var' (mkCoreAppDs viewExpr (Var var))))
mkEvalMatchResult :: Id -> Type -> MatchResult -> MatchResult
mkEvalMatchResult var ty
= adjustMatchResult (\e -> Case (Var var) var ty [(DEFAULT, [], e)])
mkGuardedMatchResult :: CoreExpr -> MatchResult -> MatchResult
mkGuardedMatchResult pred_expr (MatchResult _ body_fn)
= MatchResult CanFail (\fail -> do body <- body_fn fail
return (mkIfThenElse pred_expr body fail))
mkCoPrimCaseMatchResult :: Id
-> Type
-> [(Literal, MatchResult)]
-> MatchResult
mkCoPrimCaseMatchResult var ty match_alts
= MatchResult CanFail mk_case
where
mk_case fail = do
alts <- mapM (mk_alt fail) sorted_alts
return (Case (Var var) var ty ((DEFAULT, [], fail) : alts))
sorted_alts = sortWith fst match_alts
mk_alt fail (lit, MatchResult _ body_fn) = do body <- body_fn fail
return (LitAlt lit, [], body)
mkCoAlgCaseMatchResult :: Id
-> Type
-> [(DataCon, [CoreBndr], MatchResult)]
-> MatchResult
mkCoAlgCaseMatchResult var ty match_alts
| isNewTyCon tycon
= ASSERT( null (tail match_alts) && null (tail arg_ids1) )
mkCoLetMatchResult (NonRec arg_id1 newtype_rhs) match_result1
| isPArrFakeAlts match_alts
= MatchResult CanFail mk_parrCase
| otherwise
= MatchResult fail_flag mk_case
where
tycon = dataConTyCon con1
(con1, arg_ids1, match_result1) = ASSERT( notNull match_alts ) head match_alts
arg_id1 = ASSERT( notNull arg_ids1 ) head arg_ids1
var_ty = idType var
(tc, ty_args) = tcSplitTyConApp var_ty
newtype_rhs = unwrapNewTypeBody tc ty_args (Var var)
data_cons = tyConDataCons tycon
match_results = [match_result | (_,_,match_result) <- match_alts]
fail_flag | exhaustive_case
= foldr1 orFail [can_it_fail | MatchResult can_it_fail _ <- match_results]
| otherwise
= CanFail
sorted_alts = sortWith get_tag match_alts
get_tag (con, _, _) = dataConTag con
mk_case fail = do alts <- mapM (mk_alt fail) sorted_alts
return (mkWildCase (Var var) (idType var) ty (mk_default fail ++ alts))
mk_alt fail (con, args, MatchResult _ body_fn) = do
body <- body_fn fail
us <- newUniqueSupply
return (mkReboxingAlt (uniqsFromSupply us) con args body)
mk_default fail | exhaustive_case = []
| otherwise = [(DEFAULT, [], fail)]
un_mentioned_constructors
= mkUniqSet data_cons `minusUniqSet` mkUniqSet [ con | (con, _, _) <- match_alts]
exhaustive_case = isEmptyUniqSet un_mentioned_constructors
isPArrFakeAlts [(dcon, _, _)] = isPArrFakeCon dcon
isPArrFakeAlts ((dcon, _, _):alts) =
case (isPArrFakeCon dcon, isPArrFakeAlts alts) of
(True , True ) -> True
(False, False) -> False
_ -> panic "DsUtils: you may not mix `[:...:]' with `PArr' patterns"
isPArrFakeAlts [] = panic "DsUtils: unexpectedly found an empty list of PArr fake alternatives"
mk_parrCase fail = do
lengthP <- dsLookupGlobalId lengthPName
alt <- unboxAlt
return (mkWildCase (len lengthP) intTy ty [alt])
where
elemTy = case splitTyConApp (idType var) of
(_, [elemTy]) -> elemTy
_ -> panic panicMsg
panicMsg = "DsUtils.mkCoAlgCaseMatchResult: not a parallel array?"
len lengthP = mkApps (Var lengthP) [Type elemTy, Var var]
unboxAlt = do
l <- newSysLocalDs intPrimTy
indexP <- dsLookupGlobalId indexPName
alts <- mapM (mkAlt indexP) sorted_alts
return (DataAlt intDataCon, [l], mkWildCase (Var l) intPrimTy ty (dft : alts))
where
dft = (DEFAULT, [], fail)
mkAlt indexP (con, args, MatchResult _ bodyFun) = do
body <- bodyFun fail
return (LitAlt lit, [], mkCoreLets binds body)
where
lit = MachInt $ toInteger (dataConSourceArity con)
binds = [NonRec arg (indexExpr i) | (i, arg) <- zip [1..] args]
indexExpr i = mkApps (Var indexP) [Type elemTy, Var var, mkIntExpr i]
\end{code}
%************************************************************************
%* *
\subsection{Desugarer's versions of some Core functions}
%* *
%************************************************************************
\begin{code}
mkErrorAppDs :: Id
-> Type
-> SDoc
-> DsM CoreExpr
mkErrorAppDs err_id ty msg = do
src_loc <- getSrcSpanDs
let
full_msg = showSDoc (hcat [ppr src_loc, text "|", msg])
core_msg = Lit (mkMachString full_msg)
return (mkApps (Var err_id) [Type ty, core_msg])
\end{code}
'mkCoreAppDs' and 'mkCoreAppsDs' hand the special-case desugaring of 'seq'.
Note [Desugaring seq (1)] cf Trac #1031
~~~~~~~~~~~~~~~~~~~~~~~~~
f x y = x `seq` (y `seq` (# x,y #))
The [CoreSyn let/app invariant] means that, other things being equal, because
the argument to the outer 'seq' has an unlifted type, we'll use call-by-value thus:
f x y = case (y `seq` (# x,y #)) of v -> x `seq` v
But that is bad for two reasons:
(a) we now evaluate y before x, and
(b) we can't bind v to an unboxed pair
Seq is very, very special! So we recognise it right here, and desugar to
case x of _ -> case y of _ -> (# x,y #)
Note [Desugaring seq (2)] cf Trac #2273
~~~~~~~~~~~~~~~~~~~~~~~~~
Consider
let chp = case b of { True -> fst x; False -> 0 }
in chp `seq` ...chp...
Here the seq is designed to plug the space leak of retaining (snd x)
for too long.
If we rely on the ordinary inlining of seq, we'll get
let chp = case b of { True -> fst x; False -> 0 }
case chp of _ { I# -> ...chp... }
But since chp is cheap, and the case is an alluring contet, we'll
inline chp into the case scrutinee. Now there is only one use of chp,
so we'll inline a second copy. Alas, we've now ruined the purpose of
the seq, by re-introducing the space leak:
case (case b of {True -> fst x; False -> 0}) of
I# _ -> ...case b of {True -> fst x; False -> 0}...
We can try to avoid doing this by ensuring that the binder-swap in the
case happens, so we get his at an early stage:
case chp of chp2 { I# -> ...chp2... }
But this is fragile. The real culprit is the source program. Perhaps we
should have said explicitly
let !chp2 = chp in ...chp2...
But that's painful. So the code here does a little hack to make seq
more robust: a saturated application of 'seq' is turned *directly* into
the case expression, thus:
x `seq` e2 ==> case x of x -> e2 -- Note shadowing!
e1 `seq` e2 ==> case x of _ -> e2
So we desugar our example to:
let chp = case b of { True -> fst x; False -> 0 }
case chp of chp { I# -> ...chp... }
And now all is well.
The reason it's a hack is because if you define mySeq=seq, the hack
won't work on mySeq.
Note [Desugaring seq (3)] cf Trac #2409
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The isLocalId ensures that we don't turn
True `seq` e
into
case True of True { ... }
which stupidly tries to bind the datacon 'True'.
\begin{code}
mkCoreAppDs :: CoreExpr -> CoreExpr -> CoreExpr
mkCoreAppDs (Var f `App` Type ty1 `App` Type ty2 `App` arg1) arg2
| f `hasKey` seqIdKey
= Case arg1 case_bndr ty2 [(DEFAULT,[],arg2)]
where
case_bndr = case arg1 of
Var v1 | isLocalId v1 -> v1
_ -> mkWildValBinder ty1
mkCoreAppDs fun arg = mkCoreApp fun arg
mkCoreAppsDs :: CoreExpr -> [CoreExpr] -> CoreExpr
mkCoreAppsDs fun args = foldl mkCoreAppDs fun args
\end{code}
%************************************************************************
%* *
\subsection[mkSelectorBind]{Make a selector bind}
%* *
%************************************************************************
This is used in various places to do with lazy patterns.
For each binder $b$ in the pattern, we create a binding:
\begin{verbatim}
b = case v of pat' -> b'
\end{verbatim}
where @pat'@ is @pat@ with each binder @b@ cloned into @b'@.
ToDo: making these bindings should really depend on whether there's
much work to be done per binding. If the pattern is complex, it
should be de-mangled once, into a tuple (and then selected from).
Otherwise the demangling can be in-line in the bindings (as here).
Boring! Boring! One error message per binder. The above ToDo is
even more helpful. Something very similar happens for pattern-bound
expressions.
\begin{code}
mkSelectorBinds :: LPat Id
-> CoreExpr
-> DsM [(Id,CoreExpr)]
mkSelectorBinds (L _ (VarPat v)) val_expr
= return [(v, val_expr)]
mkSelectorBinds pat val_expr
| isSingleton binders || is_simple_lpat pat = do
val_var <- newSysLocalDs (hsLPatType pat)
err_expr <- mkErrorAppDs iRREFUT_PAT_ERROR_ID unitTy (ppr pat)
err_var <- newSysLocalDs unitTy
binds <- mapM (mk_bind val_var err_var) binders
return ( (val_var, val_expr) :
(err_var, err_expr) :
binds )
| otherwise = do
error_expr <- mkErrorAppDs iRREFUT_PAT_ERROR_ID tuple_ty (ppr pat)
tuple_expr <- matchSimply val_expr PatBindRhs pat local_tuple error_expr
tuple_var <- newSysLocalDs tuple_ty
let mk_tup_bind binder
= (binder, mkTupleSelector local_binders binder tuple_var (Var tuple_var))
return ( (tuple_var, tuple_expr) : map mk_tup_bind binders )
where
binders = collectPatBinders pat
local_binders = map localiseId binders
local_tuple = mkBigCoreVarTup binders
tuple_ty = exprType local_tuple
mk_bind scrut_var err_var bndr_var = do
rhs_expr <- matchSimply (Var scrut_var) PatBindRhs pat
(Var bndr_var) error_expr
return (bndr_var, rhs_expr)
where
error_expr = mkCoerce co (Var err_var)
co = mkUnsafeCoercion (exprType (Var err_var)) (idType bndr_var)
is_simple_lpat p = is_simple_pat (unLoc p)
is_simple_pat (TuplePat ps Boxed _) = all is_triv_lpat ps
is_simple_pat (ConPatOut{ pat_args = ps }) = all is_triv_lpat (hsConPatArgs ps)
is_simple_pat (VarPat _) = True
is_simple_pat (ParPat p) = is_simple_lpat p
is_simple_pat _ = False
is_triv_lpat p = is_triv_pat (unLoc p)
is_triv_pat (VarPat _) = True
is_triv_pat (WildPat _) = True
is_triv_pat (ParPat p) = is_triv_lpat p
is_triv_pat _ = False
\end{code}
Creating big tuples and their types for full Haskell expressions.
They work over *Ids*, and create tuples replete with their types,
which is whey they are not in HsUtils.
\begin{code}
mkLHsPatTup :: [LPat Id] -> LPat Id
mkLHsPatTup [] = noLoc $ mkVanillaTuplePat [] Boxed
mkLHsPatTup [lpat] = lpat
mkLHsPatTup lpats = L (getLoc (head lpats)) $
mkVanillaTuplePat lpats Boxed
mkLHsVarPatTup :: [Id] -> LPat Id
mkLHsVarPatTup bs = mkLHsPatTup (map nlVarPat bs)
mkVanillaTuplePat :: [OutPat Id] -> Boxity -> Pat Id
mkVanillaTuplePat pats box
= TuplePat pats box (mkTupleTy box (map hsLPatType pats))
mkBigLHsVarTup :: [Id] -> LHsExpr Id
mkBigLHsVarTup ids = mkBigLHsTup (map nlHsVar ids)
mkBigLHsTup :: [LHsExpr Id] -> LHsExpr Id
mkBigLHsTup = mkChunkified mkLHsTupleExpr
mkBigLHsVarPatTup :: [Id] -> LPat Id
mkBigLHsVarPatTup bs = mkBigLHsPatTup (map nlVarPat bs)
mkBigLHsPatTup :: [LPat Id] -> LPat Id
mkBigLHsPatTup = mkChunkified mkLHsPatTup
\end{code}
%************************************************************************
%* *
\subsection[mkFailurePair]{Code for pattern-matching and other failures}
%* *
%************************************************************************
Generally, we handle pattern matching failure like this: let-bind a
fail-variable, and use that variable if the thing fails:
\begin{verbatim}
let fail.33 = error "Help"
in
case x of
p1 -> ...
p2 -> fail.33
p3 -> fail.33
p4 -> ...
\end{verbatim}
Then
\begin{itemize}
\item
If the case can't fail, then there'll be no mention of @fail.33@, and the
simplifier will later discard it.
\item
If it can fail in only one way, then the simplifier will inline it.
\item
Only if it is used more than once will the let-binding remain.
\end{itemize}
There's a problem when the result of the case expression is of
unboxed type. Then the type of @fail.33@ is unboxed too, and
there is every chance that someone will change the let into a case:
\begin{verbatim}
case error "Help" of
fail.33 -> case ....
\end{verbatim}
which is of course utterly wrong. Rather than drop the condition that
only boxed types can be let-bound, we just turn the fail into a function
for the primitive case:
\begin{verbatim}
let fail.33 :: Void -> Int#
fail.33 = \_ -> error "Help"
in
case x of
p1 -> ...
p2 -> fail.33 void
p3 -> fail.33 void
p4 -> ...
\end{verbatim}
Now @fail.33@ is a function, so it can be let-bound.
\begin{code}
mkFailurePair :: CoreExpr
-> DsM (CoreBind,
CoreExpr)
mkFailurePair expr
= do { fail_fun_var <- newFailLocalDs (realWorldStatePrimTy `mkFunTy` ty)
; fail_fun_arg <- newSysLocalDs realWorldStatePrimTy
; return (NonRec fail_fun_var (Lam fail_fun_arg expr),
App (Var fail_fun_var) (Var realWorldPrimId)) }
where
ty = exprType expr
\end{code}
Note [Failure thunks and CPR]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
When we make a failure point we ensure that it
does not look like a thunk. Example:
let fail = \rw -> error "urk"
in case x of
[] -> fail realWorld#
(y:ys) -> case ys of
[] -> fail realWorld#
(z:zs) -> (y,z)
Reason: we know that a failure point is always a "join point" and is
entered at most once. Adding a dummy 'realWorld' token argument makes
it clear that sharing is not an issue. And that in turn makes it more
CPR-friendly. This matters a lot: if you don't get it right, you lose
the tail call property. For example, see Trac #3403.
\begin{code}
mkOptTickBox :: Maybe (Int,[Id]) -> CoreExpr -> DsM CoreExpr
mkOptTickBox Nothing e = return e
mkOptTickBox (Just (ix,ids)) e = mkTickBox ix ids e
mkTickBox :: Int -> [Id] -> CoreExpr -> DsM CoreExpr
mkTickBox ix vars e = do
uq <- newUnique
mod <- getModuleDs
let tick | opt_Hpc = mkTickBoxOpId uq mod ix
| otherwise = mkBreakPointOpId uq mod ix
uq2 <- newUnique
let occName = mkVarOcc "tick"
let name = mkInternalName uq2 occName noSrcSpan
let var = Id.mkLocalId name realWorldStatePrimTy
scrut <-
if opt_Hpc
then return (Var tick)
else do
let tickVar = Var tick
let tickType = mkFunTys (map idType vars) realWorldStatePrimTy
let scrutApTy = App tickVar (Type tickType)
return (mkApps scrutApTy (map Var vars) :: Expr Id)
return $ Case scrut var ty [(DEFAULT,[],e)]
where
ty = exprType e
mkBinaryTickBox :: Int -> Int -> CoreExpr -> DsM CoreExpr
mkBinaryTickBox ixT ixF e = do
uq <- newUnique
let bndr1 = mkSysLocal (fsLit "t1") uq boolTy
falseBox <- mkTickBox ixF [] $ Var falseDataConId
trueBox <- mkTickBox ixT [] $ Var trueDataConId
return $ Case e bndr1 boolTy
[ (DataAlt falseDataCon, [], falseBox)
, (DataAlt trueDataCon, [], trueBox)
]
\end{code}