%
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[RnPat]{Renaming of patterns}
Basically dependency analysis.
Handles @Match@, @GRHSs@, @HsExpr@, and @Qualifier@ datatypes. In
general, all of these functions return a renamed thing, and a set of
free variables.
\begin{code}
module RnPat (
rnPat, rnPats, rnBindPat,
NameMaker, applyNameMaker,
localRecNameMaker, topRecNameMaker,
rnHsRecFields1, HsRecFieldContext(..),
rnLit, rnOverLit,
checkTupSize, patSigErr
) where
import RnExpr ( rnLExpr )
#ifdef GHCI
import TcSplice ( runQuasiQuotePat )
#endif /* GHCI */
#include "HsVersions.h"
import HsSyn
import TcRnMonad
import TcHsSyn ( hsOverLitName )
import RnEnv
import RnTypes
import DynFlags
import PrelNames
import Constants ( mAX_TUPLE_SIZE )
import Name
import NameSet
import RdrName
import BasicTypes
import ListSetOps ( removeDups, minusList )
import Outputable
import SrcLoc
import FastString
import Literal ( inCharRange )
import Control.Monad ( when )
\end{code}
%*********************************************************
%* *
The CpsRn Monad
%* *
%*********************************************************
Note [CpsRn monad]
~~~~~~~~~~~~~~~~~~
The CpsRn monad uses continuation-passing style to support this
style of programming:
do { ...
; ns <- bindNames rs
; ...blah... }
where rs::[RdrName], ns::[Name]
The idea is that '...blah...'
a) sees the bindings of ns
b) returns the free variables it mentions
so that bindNames can report unused ones
In particular,
mapM rnPatAndThen [p1, p2, p3]
has a *left-to-right* scoping: it makes the binders in
p1 scope over p2,p3.
\begin{code}
newtype CpsRn b = CpsRn { unCpsRn :: forall r. (b -> RnM (r, FreeVars))
-> RnM (r, FreeVars) }
instance Monad CpsRn where
return x = CpsRn (\k -> k x)
(CpsRn m) >>= mk = CpsRn (\k -> m (\v -> unCpsRn (mk v) k))
runCps :: CpsRn a -> RnM (a, FreeVars)
runCps (CpsRn m) = m (\r -> return (r, emptyFVs))
liftCps :: RnM a -> CpsRn a
liftCps rn_thing = CpsRn (\k -> rn_thing >>= k)
liftCpsFV :: RnM (a, FreeVars) -> CpsRn a
liftCpsFV rn_thing = CpsRn (\k -> do { (v,fvs1) <- rn_thing
; (r,fvs2) <- k v
; return (r, fvs1 `plusFV` fvs2) })
wrapSrcSpanCps :: (a -> CpsRn b) -> Located a -> CpsRn (Located b)
wrapSrcSpanCps fn (L loc a)
= CpsRn (\k -> setSrcSpan loc $
unCpsRn (fn a) $ \v ->
k (L loc v))
lookupConCps :: Located RdrName -> CpsRn (Located Name)
lookupConCps con_rdr
= CpsRn (\k -> do { con_name <- lookupLocatedOccRn con_rdr
; (r, fvs) <- k con_name
; return (r, fvs `plusFV` unitFV (unLoc con_name)) })
\end{code}
%*********************************************************
%* *
Name makers
%* *
%*********************************************************
Externally abstract type of name makers,
which is how you go from a RdrName to a Name
\begin{code}
data NameMaker
= LamMk
Bool
| LetMk
TopLevelFlag
MiniFixityEnv
topRecNameMaker :: MiniFixityEnv -> NameMaker
topRecNameMaker fix_env = LetMk TopLevel fix_env
localRecNameMaker :: MiniFixityEnv -> NameMaker
localRecNameMaker fix_env = LetMk NotTopLevel fix_env
matchNameMaker :: HsMatchContext a -> NameMaker
matchNameMaker ctxt = LamMk report_unused
where
report_unused = case ctxt of
StmtCtxt GhciStmt -> False
_ -> True
newName :: NameMaker -> Located RdrName -> CpsRn Name
newName (LamMk report_unused) rdr_name
= CpsRn (\ thing_inside ->
do { name <- newLocalBndrRn rdr_name
; (res, fvs) <- bindLocalName name (thing_inside name)
; when report_unused $ warnUnusedMatches [name] fvs
; return (res, name `delFV` fvs) })
newName (LetMk is_top fix_env) rdr_name
= CpsRn (\ thing_inside ->
do { name <- case is_top of
NotTopLevel -> newLocalBndrRn rdr_name
TopLevel -> newTopSrcBinder rdr_name
; bindLocalName name $
addLocalFixities fix_env [name] $
thing_inside name })
\end{code}
Note [View pattern usage]
~~~~~~~~~~~~~~~~~~~~~~~~~
Consider
let (r, (r -> x)) = x in ...
Here the pattern binds 'r', and then uses it *only* in the view pattern.
We want to "see" this use, and in let-bindings we collect all uses and
report unused variables at the binding level. So we must use bindLocalName
here, *not* bindLocalNameFV. Trac #3943.
%*********************************************************
%* *
External entry points
%* *
%*********************************************************
There are various entry points to renaming patterns, depending on
(1) whether the names created should be top-level names or local names
(2) whether the scope of the names is entirely given in a continuation
(e.g., in a case or lambda, but not in a let or at the top-level,
because of the way mutually recursive bindings are handled)
(3) whether the a type signature in the pattern can bind
lexically-scoped type variables (for unpacking existential
type vars in data constructors)
(4) whether we do duplicate and unused variable checking
(5) whether there are fixity declarations associated with the names
bound by the patterns that need to be brought into scope with them.
Rather than burdening the clients of this module with all of these choices,
we export the three points in this design space that we actually need:
\begin{code}
rnPats :: HsMatchContext Name
-> [LPat RdrName]
-> ([LPat Name] -> RnM (a, FreeVars))
-> RnM (a, FreeVars)
rnPats ctxt pats thing_inside
= do { envs_before <- getRdrEnvs
; bindPatSigTyVarsFV (collectSigTysFromPats pats) $
unCpsRn (rnLPatsAndThen (matchNameMaker ctxt) pats) $ \ pats' -> do
{
; let names = collectPatsBinders pats'
; addErrCtxt doc_pat $ checkDupAndShadowedNames envs_before names
; thing_inside pats' } }
where
doc_pat = ptext (sLit "In") <+> pprMatchContext ctxt
rnPat :: HsMatchContext Name
-> LPat RdrName
-> (LPat Name -> RnM (a, FreeVars))
-> RnM (a, FreeVars)
rnPat ctxt pat thing_inside
= rnPats ctxt [pat] (\pats' -> let [pat'] = pats' in thing_inside pat')
applyNameMaker :: NameMaker -> Located RdrName -> RnM Name
applyNameMaker mk rdr = do { (n, _fvs) <- runCps (newName mk rdr); return n }
rnBindPat :: NameMaker
-> LPat RdrName
-> RnM (LPat Name, FreeVars)
rnBindPat name_maker pat = runCps (rnLPatAndThen name_maker pat)
\end{code}
%*********************************************************
%* *
The main event
%* *
%*********************************************************
\begin{code}
rnLPatsAndThen :: NameMaker -> [LPat RdrName] -> CpsRn [LPat Name]
rnLPatsAndThen mk = mapM (rnLPatAndThen mk)
rnLPatAndThen :: NameMaker -> LPat RdrName -> CpsRn (LPat Name)
rnLPatAndThen nm lpat = wrapSrcSpanCps (rnPatAndThen nm) lpat
rnPatAndThen :: NameMaker -> Pat RdrName -> CpsRn (Pat Name)
rnPatAndThen _ (WildPat _) = return (WildPat placeHolderType)
rnPatAndThen mk (ParPat pat) = do { pat' <- rnLPatAndThen mk pat; return (ParPat pat') }
rnPatAndThen mk (LazyPat pat) = do { pat' <- rnLPatAndThen mk pat; return (LazyPat pat') }
rnPatAndThen mk (BangPat pat) = do { pat' <- rnLPatAndThen mk pat; return (BangPat pat') }
rnPatAndThen mk (VarPat rdr) = do { loc <- liftCps getSrcSpanM
; name <- newName mk (L loc rdr)
; return (VarPat name) }
rnPatAndThen mk (SigPatIn pat ty)
= do { patsigs <- liftCps (xoptM Opt_ScopedTypeVariables)
; if patsigs
then do { pat' <- rnLPatAndThen mk pat
; ty' <- liftCpsFV (rnHsTypeFVs tvdoc ty)
; return (SigPatIn pat' ty') }
else do { liftCps (addErr (patSigErr ty))
; rnPatAndThen mk (unLoc pat) } }
where
tvdoc = text "In a pattern type-signature"
rnPatAndThen mk (LitPat lit)
| HsString s <- lit
= do { ovlStr <- liftCps (xoptM Opt_OverloadedStrings)
; if ovlStr
then rnPatAndThen mk (mkNPat (mkHsIsString s placeHolderType) Nothing)
else normal_lit }
| otherwise = normal_lit
where
normal_lit = do { liftCps (rnLit lit); return (LitPat lit) }
rnPatAndThen _ (NPat lit mb_neg _eq)
= do { lit' <- liftCpsFV $ rnOverLit lit
; mb_neg' <- liftCpsFV $ case mb_neg of
Nothing -> return (Nothing, emptyFVs)
Just _ -> do { (neg, fvs) <- lookupSyntaxName negateName
; return (Just neg, fvs) }
; eq' <- liftCpsFV $ lookupSyntaxName eqName
; return (NPat lit' mb_neg' eq') }
rnPatAndThen mk (NPlusKPat rdr lit _ _)
= do { new_name <- newName mk rdr
; lit' <- liftCpsFV $ rnOverLit lit
; minus <- liftCpsFV $ lookupSyntaxName minusName
; ge <- liftCpsFV $ lookupSyntaxName geName
; return (NPlusKPat (L (nameSrcSpan new_name) new_name) lit' ge minus) }
rnPatAndThen mk (AsPat rdr pat)
= do { new_name <- newName mk rdr
; pat' <- rnLPatAndThen mk pat
; return (AsPat (L (nameSrcSpan new_name) new_name) pat') }
rnPatAndThen mk p@(ViewPat expr pat ty)
= do { liftCps $ do { vp_flag <- xoptM Opt_ViewPatterns
; checkErr vp_flag (badViewPat p) }
; expr' <- liftCpsFV $ rnLExpr expr
; pat' <- rnLPatAndThen mk pat
; return (ViewPat expr' pat' ty) }
rnPatAndThen mk (ConPatIn con stuff)
= rnConPatAndThen mk con stuff
rnPatAndThen mk (ListPat pats _)
= do { pats' <- rnLPatsAndThen mk pats
; return (ListPat pats' placeHolderType) }
rnPatAndThen mk (PArrPat pats _)
= do { pats' <- rnLPatsAndThen mk pats
; return (PArrPat pats' placeHolderType) }
rnPatAndThen mk (TuplePat pats boxed _)
= do { liftCps $ checkTupSize (length pats)
; pats' <- rnLPatsAndThen mk pats
; return (TuplePat pats' boxed placeHolderType) }
rnPatAndThen _ (TypePat ty)
= do { ty' <- liftCpsFV $ rnHsTypeFVs (text "In a type pattern") ty
; return (TypePat ty') }
#ifndef GHCI
rnPatAndThen _ p@(QuasiQuotePat {})
= pprPanic "Can't do QuasiQuotePat without GHCi" (ppr p)
#else
rnPatAndThen mk (QuasiQuotePat qq)
= do { pat <- liftCps $ runQuasiQuotePat qq
; L _ pat' <- rnLPatAndThen mk pat
; return pat' }
#endif /* GHCI */
rnPatAndThen _ pat = pprPanic "rnLPatAndThen" (ppr pat)
rnConPatAndThen :: NameMaker
-> Located RdrName
-> HsConPatDetails RdrName
-> CpsRn (Pat Name)
rnConPatAndThen mk con (PrefixCon pats)
= do { con' <- lookupConCps con
; pats' <- rnLPatsAndThen mk pats
; return (ConPatIn con' (PrefixCon pats')) }
rnConPatAndThen mk con (InfixCon pat1 pat2)
= do { con' <- lookupConCps con
; pat1' <- rnLPatAndThen mk pat1
; pat2' <- rnLPatAndThen mk pat2
; fixity <- liftCps $ lookupFixityRn (unLoc con')
; liftCps $ mkConOpPatRn con' fixity pat1' pat2' }
rnConPatAndThen mk con (RecCon rpats)
= do { con' <- lookupConCps con
; rpats' <- rnHsRecPatsAndThen mk con' rpats
; return (ConPatIn con' (RecCon rpats')) }
rnHsRecPatsAndThen :: NameMaker
-> Located Name
-> HsRecFields RdrName (LPat RdrName)
-> CpsRn (HsRecFields Name (LPat Name))
rnHsRecPatsAndThen mk (L _ con) hs_rec_fields@(HsRecFields { rec_dotdot = dd })
= do { flds <- liftCpsFV $ rnHsRecFields1 (HsRecFieldPat con) VarPat hs_rec_fields
; flds' <- mapM rn_field (flds `zip` [1..])
; return (HsRecFields { rec_flds = flds', rec_dotdot = dd }) }
where
rn_field (fld, n') = do { arg' <- rnLPatAndThen (nested_mk dd mk n')
(hsRecFieldArg fld)
; return (fld { hsRecFieldArg = arg' }) }
nested_mk Nothing mk _ = mk
nested_mk (Just _) mk@(LetMk {}) _ = mk
nested_mk (Just n) (LamMk report_unused) n' = LamMk (report_unused && (n' <= n))
\end{code}
%************************************************************************
%* *
Record fields
%* *
%************************************************************************
\begin{code}
data HsRecFieldContext
= HsRecFieldCon Name
| HsRecFieldPat Name
| HsRecFieldUpd
rnHsRecFields1
:: HsRecFieldContext
-> (RdrName -> arg)
-> HsRecFields RdrName (Located arg)
-> RnM ([HsRecField Name (Located arg)], FreeVars)
rnHsRecFields1 ctxt mk_arg (HsRecFields { rec_flds = flds, rec_dotdot = dotdot })
= do { pun_ok <- xoptM Opt_RecordPuns
; disambig_ok <- xoptM Opt_DisambiguateRecordFields
; parent <- check_disambiguation disambig_ok mb_con
; flds1 <- mapM (rn_fld pun_ok parent) flds
; mapM_ (addErr . dupFieldErr ctxt) dup_flds
; flds2 <- rn_dotdot dotdot mb_con flds1
; return (flds2, mkFVs (getFieldIds flds2)) }
where
mb_con = case ctxt of
HsRecFieldUpd -> Nothing
HsRecFieldCon con -> Just con
HsRecFieldPat con -> Just con
doc = case mb_con of
Nothing -> ptext (sLit "constructor field name")
Just con -> ptext (sLit "field of constructor") <+> quotes (ppr con)
name_to_arg (L loc n) = L loc (mk_arg (mkRdrUnqual (nameOccName n)))
rn_fld pun_ok parent (HsRecField { hsRecFieldId = fld
, hsRecFieldArg = arg
, hsRecPun = pun })
= do { fld' <- wrapLocM (lookupSubBndr parent doc) fld
; arg' <- if pun
then do { checkErr pun_ok (badPun fld)
; return (name_to_arg fld') }
else return arg
; return (HsRecField { hsRecFieldId = fld'
, hsRecFieldArg = arg'
, hsRecPun = pun }) }
rn_dotdot Nothing _mb_con flds
= return flds
rn_dotdot (Just {}) Nothing flds
= do { addErr (badDotDot ctxt); return flds }
rn_dotdot (Just n) (Just con) flds
= ASSERT( n == length flds )
do { loc <- getSrcSpanM
; dd_flag <- xoptM Opt_RecordWildCards
; checkErr dd_flag (needFlagDotDot ctxt)
; con_fields <- lookupConstructorFields con
; let present_flds = getFieldIds flds
absent_flds = con_fields `minusList` present_flds
extras = [ HsRecField
{ hsRecFieldId = L loc f
, hsRecFieldArg = name_to_arg (L loc f)
, hsRecPun = False }
| f <- absent_flds ]
; return (flds ++ extras) }
check_disambiguation :: Bool -> Maybe Name -> RnM Parent
check_disambiguation disambig_ok mb_con
| disambig_ok, Just con <- mb_con
= do { env <- getGlobalRdrEnv
; return (case lookupGRE_Name env con of
[gre] -> gre_par gre
gres -> WARN( True, ppr con <+> ppr gres ) NoParent) }
| otherwise = return NoParent
dup_flds :: [[RdrName]]
(_, dup_flds) = removeDups compare (getFieldIds flds)
getFieldIds :: [HsRecField id arg] -> [id]
getFieldIds flds = map (unLoc . hsRecFieldId) flds
needFlagDotDot :: HsRecFieldContext -> SDoc
needFlagDotDot ctxt = vcat [ptext (sLit "Illegal `..' in record") <+> pprRFC ctxt,
ptext (sLit "Use -XRecordWildCards to permit this")]
badDotDot :: HsRecFieldContext -> SDoc
badDotDot ctxt = ptext (sLit "You cannot use `..' in a record") <+> pprRFC ctxt
badPun :: Located RdrName -> SDoc
badPun fld = vcat [ptext (sLit "Illegal use of punning for field") <+> quotes (ppr fld),
ptext (sLit "Use -XNamedFieldPuns to permit this")]
dupFieldErr :: HsRecFieldContext -> [RdrName] -> SDoc
dupFieldErr ctxt dups
= hsep [ptext (sLit "duplicate field name"),
quotes (ppr (head dups)),
ptext (sLit "in record"), pprRFC ctxt]
pprRFC :: HsRecFieldContext -> SDoc
pprRFC (HsRecFieldCon {}) = ptext (sLit "construction")
pprRFC (HsRecFieldPat {}) = ptext (sLit "pattern")
pprRFC (HsRecFieldUpd {}) = ptext (sLit "update")
\end{code}
%************************************************************************
%* *
\subsubsection{Literals}
%* *
%************************************************************************
When literals occur we have to make sure
that the types and classes they involve
are made available.
\begin{code}
rnLit :: HsLit -> RnM ()
rnLit (HsChar c) = checkErr (inCharRange c) (bogusCharError c)
rnLit _ = return ()
rnOverLit :: HsOverLit t -> RnM (HsOverLit Name, FreeVars)
rnOverLit lit@(OverLit {ol_val=val})
= do { let std_name = hsOverLitName val
; (from_thing_name, fvs) <- lookupSyntaxName std_name
; let rebindable = case from_thing_name of
HsVar v -> v /= std_name
_ -> panic "rnOverLit"
; return (lit { ol_witness = from_thing_name
, ol_rebindable = rebindable }, fvs) }
\end{code}
%************************************************************************
%* *
\subsubsection{Errors}
%* *
%************************************************************************
\begin{code}
checkTupSize :: Int -> RnM ()
checkTupSize tup_size
| tup_size <= mAX_TUPLE_SIZE
= return ()
| otherwise
= addErr (sep [ptext (sLit "A") <+> int tup_size <> ptext (sLit "-tuple is too large for GHC"),
nest 2 (parens (ptext (sLit "max size is") <+> int mAX_TUPLE_SIZE)),
nest 2 (ptext (sLit "Workaround: use nested tuples or define a data type"))])
patSigErr :: Outputable a => a -> SDoc
patSigErr ty
= (ptext (sLit "Illegal signature in pattern:") <+> ppr ty)
$$ nest 4 (ptext (sLit "Use -XScopedTypeVariables to permit it"))
bogusCharError :: Char -> SDoc
bogusCharError c
= ptext (sLit "character literal out of range: '\\") <> char c <> char '\''
badViewPat :: Pat RdrName -> SDoc
badViewPat pat = vcat [ptext (sLit "Illegal view pattern: ") <+> ppr pat,
ptext (sLit "Use -XViewPatterns to enable view patterns")]
\end{code}