module TcPat ( tcLetPat, TcSigFun, TcPragFun
, TcSigInfo(..), TcPatSynInfo(..)
, findScopedTyVars, isPartialSig
, LetBndrSpec(..), addInlinePrags, warnPrags
, tcPat, tcPats, newNoSigLetBndr
, addDataConStupidTheta, badFieldCon, polyPatSig ) where
#include "HsVersions.h"
import TcExpr( tcSyntaxOp, tcInferRho)
import HsSyn
import TcHsSyn
import TcRnMonad
import Inst
import Id
import Var
import Name
import NameSet
import TcEnv
import TcMType
import TcValidity( arityErr )
import TcType
import TcUnify
import TcHsType
import TysWiredIn
import TcEvidence
import TyCon
import DataCon
import PatSyn
import ConLike
import PrelNames
import BasicTypes hiding (SuccessFlag(..))
import DynFlags
import SrcLoc
import Util
import Outputable
import FastString
import Control.Monad
tcLetPat :: TcSigFun -> LetBndrSpec
-> LPat Name -> TcSigmaType
-> TcM a
-> TcM (LPat TcId, a)
tcLetPat sig_fn no_gen pat pat_ty thing_inside
= tc_lpat pat pat_ty penv thing_inside
where
penv = PE { pe_lazy = True
, pe_ctxt = LetPat sig_fn no_gen }
tcPats :: HsMatchContext Name
-> [LPat Name]
-> [TcSigmaType]
-> TcM a
-> TcM ([LPat TcId], a)
tcPats ctxt pats pat_tys thing_inside
= tc_lpats penv pats pat_tys thing_inside
where
penv = PE { pe_lazy = False, pe_ctxt = LamPat ctxt }
tcPat :: HsMatchContext Name
-> LPat Name -> TcSigmaType
-> TcM a
-> TcM (LPat TcId, a)
tcPat ctxt pat pat_ty thing_inside
= tc_lpat pat pat_ty penv thing_inside
where
penv = PE { pe_lazy = False, pe_ctxt = LamPat ctxt }
data PatEnv
= PE { pe_lazy :: Bool
, pe_ctxt :: PatCtxt
}
data PatCtxt
= LamPat
(HsMatchContext Name)
| LetPat
TcSigFun
LetBndrSpec
data LetBndrSpec
= LetLclBndr
| LetGblBndr TcPragFun
makeLazy :: PatEnv -> PatEnv
makeLazy penv = penv { pe_lazy = True }
inPatBind :: PatEnv -> Bool
inPatBind (PE { pe_ctxt = LetPat {} }) = True
inPatBind (PE { pe_ctxt = LamPat {} }) = False
type TcPragFun = Name -> [LSig Name]
type TcSigFun = Name -> Maybe TcSigInfo
data TcSigInfo
= TcSigInfo {
sig_id :: TcId,
sig_tvs :: [(Maybe Name, TcTyVar)],
sig_nwcs :: [(Name, TcTyVar)],
sig_theta :: TcThetaType,
sig_extra_cts :: Maybe SrcSpan,
sig_tau :: TcSigmaType,
sig_loc :: SrcSpan,
sig_partial :: Bool
}
| TcPatSynInfo TcPatSynInfo
data TcPatSynInfo
= TPSI {
patsig_name :: Name,
patsig_tau :: TcSigmaType,
patsig_ex :: [TcTyVar],
patsig_prov :: TcThetaType,
patsig_univ :: [TcTyVar],
patsig_req :: TcThetaType
}
findScopedTyVars
:: LHsType Name
-> TcType
-> [TcTyVar]
-> [(Maybe Name, TcTyVar)]
findScopedTyVars hs_ty sig_ty inst_tvs
= zipWith find sig_tvs inst_tvs
where
find sig_tv inst_tv
| tv_name `elemNameSet` scoped_names = (Just tv_name, inst_tv)
| otherwise = (Nothing, inst_tv)
where
tv_name = tyVarName sig_tv
scoped_names = mkNameSet (hsExplicitTvs hs_ty)
(sig_tvs,_) = tcSplitForAllTys sig_ty
instance NamedThing TcSigInfo where
getName TcSigInfo{ sig_id = id } = idName id
getName (TcPatSynInfo tpsi) = patsig_name tpsi
instance Outputable TcSigInfo where
ppr (TcSigInfo { sig_id = id, sig_tvs = tyvars, sig_theta = theta, sig_tau = tau })
= ppr id <+> dcolon <+> vcat [ pprSigmaType (mkSigmaTy (map snd tyvars) theta tau)
, ppr (map fst tyvars) ]
ppr (TcPatSynInfo tpsi) = text "TcPatSynInfo" <+> ppr tpsi
instance Outputable TcPatSynInfo where
ppr (TPSI{ patsig_name = name}) = ppr name
isPartialSig :: TcSigInfo -> Bool
isPartialSig = sig_partial
tcPatBndr :: PatEnv -> Name -> TcSigmaType -> TcM (TcCoercion, TcId)
tcPatBndr (PE { pe_ctxt = LetPat lookup_sig no_gen}) bndr_name pat_ty
| LetGblBndr prags <- no_gen
, Just sig <- lookup_sig bndr_name
= do { bndr_id <- addInlinePrags (sig_id sig) (prags bndr_name)
; traceTc "tcPatBndr(gbl,sig)" (ppr bndr_id $$ ppr (idType bndr_id))
; co <- unifyPatType (idType bndr_id) pat_ty
; return (co, bndr_id) }
| otherwise
= do { bndr_id <- newNoSigLetBndr no_gen bndr_name pat_ty
; traceTc "tcPatBndr(no-sig)" (ppr bndr_id $$ ppr (idType bndr_id))
; return (mkTcNomReflCo pat_ty, bndr_id) }
tcPatBndr (PE { pe_ctxt = _lam_or_proc }) bndr_name pat_ty
= do { bndr <- mkLocalBinder bndr_name pat_ty
; return (mkTcNomReflCo pat_ty, bndr) }
newNoSigLetBndr :: LetBndrSpec -> Name -> TcType -> TcM TcId
newNoSigLetBndr LetLclBndr name ty
=do { mono_name <- newLocalName name
; mkLocalBinder mono_name ty }
newNoSigLetBndr (LetGblBndr prags) name ty
= do { id <- mkLocalBinder name ty
; addInlinePrags id (prags name) }
addInlinePrags :: TcId -> [LSig Name] -> TcM TcId
addInlinePrags poly_id prags
= do { traceTc "addInlinePrags" (ppr poly_id $$ ppr prags)
; tc_inl inl_sigs }
where
inl_sigs = filter isInlineLSig prags
tc_inl [] = return poly_id
tc_inl (L loc (InlineSig _ prag) : other_inls)
= do { unless (null other_inls) (setSrcSpan loc warn_dup_inline)
; traceTc "addInlinePrag" (ppr poly_id $$ ppr prag)
; return (poly_id `setInlinePragma` prag) }
tc_inl _ = panic "tc_inl"
warn_dup_inline = warnPrags poly_id inl_sigs $
ptext (sLit "Duplicate INLINE pragmas for")
warnPrags :: Id -> [LSig Name] -> SDoc -> TcM ()
warnPrags id bad_sigs herald
= addWarnTc (hang (herald <+> quotes (ppr id))
2 (ppr_sigs bad_sigs))
where
ppr_sigs sigs = vcat (map (ppr . getLoc) sigs)
mkLocalBinder :: Name -> TcType -> TcM TcId
mkLocalBinder name ty
= return (Id.mkLocalId name ty)
type Checker inp out = forall r.
inp
-> PatEnv
-> TcM r
-> TcM (out, r)
tcMultiple :: Checker inp out -> Checker [inp] [out]
tcMultiple tc_pat args penv thing_inside
= do { err_ctxt <- getErrCtxt
; let loop _ []
= do { res <- thing_inside
; return ([], res) }
loop penv (arg:args)
= do { (p', (ps', res))
<- tc_pat arg penv $
setErrCtxt err_ctxt $
loop penv args
; return (p':ps', res) }
; loop penv args }
tc_lpat :: LPat Name
-> TcSigmaType
-> PatEnv
-> TcM a
-> TcM (LPat TcId, a)
tc_lpat (L span pat) pat_ty penv thing_inside
= setSrcSpan span $
do { (pat', res) <- maybeWrapPatCtxt pat (tc_pat penv pat pat_ty)
thing_inside
; return (L span pat', res) }
tc_lpats :: PatEnv
-> [LPat Name] -> [TcSigmaType]
-> TcM a
-> TcM ([LPat TcId], a)
tc_lpats penv pats tys thing_inside
= ASSERT2( equalLength pats tys, ppr pats $$ ppr tys )
tcMultiple (\(p,t) -> tc_lpat p t)
(zipEqual "tc_lpats" pats tys)
penv thing_inside
tc_pat :: PatEnv
-> Pat Name
-> TcSigmaType
-> TcM a
-> TcM (Pat TcId,
a)
tc_pat penv (VarPat name) pat_ty thing_inside
= do { (co, id) <- tcPatBndr penv name pat_ty
; res <- tcExtendIdEnv1 name id thing_inside
; return (mkHsWrapPatCo co (VarPat id) pat_ty, res) }
tc_pat penv (ParPat pat) pat_ty thing_inside
= do { (pat', res) <- tc_lpat pat pat_ty penv thing_inside
; return (ParPat pat', res) }
tc_pat penv (BangPat pat) pat_ty thing_inside
= do { (pat', res) <- tc_lpat pat pat_ty penv thing_inside
; return (BangPat pat', res) }
tc_pat penv lpat@(LazyPat pat) pat_ty thing_inside
= do { (pat', (res, pat_ct))
<- tc_lpat pat pat_ty (makeLazy penv) $
captureConstraints thing_inside
; emitConstraints pat_ct
; when (any (isUnLiftedType . idType) $ collectPatBinders pat') $
lazyUnliftedPatErr lpat
; pat_ty' <- newFlexiTyVarTy liftedTypeKind
; _ <- unifyType pat_ty pat_ty'
; return (LazyPat pat', res) }
tc_pat _ p@(QuasiQuotePat _) _ _
= pprPanic "Should never see QuasiQuotePat in type checker" (ppr p)
tc_pat _ (WildPat _) pat_ty thing_inside
= do { res <- thing_inside
; return (WildPat pat_ty, res) }
tc_pat penv (AsPat (L nm_loc name) pat) pat_ty thing_inside
= do { (co, bndr_id) <- setSrcSpan nm_loc (tcPatBndr penv name pat_ty)
; (pat', res) <- tcExtendIdEnv1 name bndr_id $
tc_lpat pat (idType bndr_id) penv thing_inside
; return (mkHsWrapPatCo co (AsPat (L nm_loc bndr_id) pat') pat_ty, res) }
tc_pat penv (ViewPat expr pat _) overall_pat_ty thing_inside
= do {
; (expr',expr'_inferred) <- tcInferRho expr
; (expr_co, pat_ty) <- tcInfer $ \ pat_ty ->
unifyType expr'_inferred (mkFunTy overall_pat_ty pat_ty)
; (pat', res) <- tc_lpat pat pat_ty penv thing_inside
; return (ViewPat (mkLHsWrapCo expr_co expr') pat' overall_pat_ty, res) }
tc_pat penv (SigPatIn pat sig_ty) pat_ty thing_inside
= do { (inner_ty, tv_binds, nwc_binds, wrap) <- tcPatSig (inPatBind penv)
sig_ty pat_ty
; (pat', res) <- tcExtendTyVarEnv2 (tv_binds ++ nwc_binds) $
tc_lpat pat inner_ty penv thing_inside
; return (mkHsWrapPat wrap (SigPatOut pat' inner_ty) pat_ty, res) }
tc_pat penv (ListPat pats _ Nothing) pat_ty thing_inside
= do { (coi, elt_ty) <- matchExpectedPatTy matchExpectedListTy pat_ty
; (pats', res) <- tcMultiple (\p -> tc_lpat p elt_ty)
pats penv thing_inside
; return (mkHsWrapPat coi (ListPat pats' elt_ty Nothing) pat_ty, res)
}
tc_pat penv (ListPat pats _ (Just (_,e))) pat_ty thing_inside
= do { list_pat_ty <- newFlexiTyVarTy liftedTypeKind
; e' <- tcSyntaxOp ListOrigin e (mkFunTy pat_ty list_pat_ty)
; (coi, elt_ty) <- matchExpectedPatTy matchExpectedListTy list_pat_ty
; (pats', res) <- tcMultiple (\p -> tc_lpat p elt_ty)
pats penv thing_inside
; return (mkHsWrapPat coi (ListPat pats' elt_ty (Just (pat_ty,e'))) list_pat_ty, res)
}
tc_pat penv (PArrPat pats _) pat_ty thing_inside
= do { (coi, elt_ty) <- matchExpectedPatTy matchExpectedPArrTy pat_ty
; (pats', res) <- tcMultiple (\p -> tc_lpat p elt_ty)
pats penv thing_inside
; return (mkHsWrapPat coi (PArrPat pats' elt_ty) pat_ty, res)
}
tc_pat penv (TuplePat pats boxity _) pat_ty thing_inside
= do { let tc = tupleTyCon (boxityNormalTupleSort boxity) (length pats)
; (coi, arg_tys) <- matchExpectedPatTy (matchExpectedTyConApp tc) pat_ty
; (pats', res) <- tc_lpats penv pats arg_tys thing_inside
; dflags <- getDynFlags
; let
unmangled_result = TuplePat pats' boxity arg_tys
possibly_mangled_result
| gopt Opt_IrrefutableTuples dflags &&
isBoxed boxity = LazyPat (noLoc unmangled_result)
| otherwise = unmangled_result
; ASSERT( length arg_tys == length pats )
return (mkHsWrapPat coi possibly_mangled_result pat_ty, res)
}
tc_pat penv (ConPatIn con arg_pats) pat_ty thing_inside
= tcConPat penv con pat_ty arg_pats thing_inside
tc_pat _ (LitPat simple_lit) pat_ty thing_inside
= do { let lit_ty = hsLitType simple_lit
; co <- unifyPatType lit_ty pat_ty
; res <- thing_inside
; return ( mkHsWrapPatCo co (LitPat simple_lit) pat_ty
, res) }
tc_pat _ (NPat (L l over_lit) mb_neg eq) pat_ty thing_inside
= do { let orig = LiteralOrigin over_lit
; lit' <- newOverloadedLit orig over_lit pat_ty
; eq' <- tcSyntaxOp orig eq (mkFunTys [pat_ty, pat_ty] boolTy)
; mb_neg' <- case mb_neg of
Nothing -> return Nothing
Just neg ->
do { neg' <- tcSyntaxOp orig neg (mkFunTy pat_ty pat_ty)
; return (Just neg') }
; res <- thing_inside
; return (NPat (L l lit') mb_neg' eq', res) }
tc_pat penv (NPlusKPat (L nm_loc name) (L loc lit) ge minus) pat_ty thing_inside
= do { (co, bndr_id) <- setSrcSpan nm_loc (tcPatBndr penv name pat_ty)
; let pat_ty' = idType bndr_id
orig = LiteralOrigin lit
; lit' <- newOverloadedLit orig lit pat_ty'
; ge' <- tcSyntaxOp orig ge (mkFunTys [pat_ty', pat_ty'] boolTy)
; minus' <- tcSyntaxOp orig minus (mkFunTys [pat_ty', pat_ty'] pat_ty')
; let pat' = NPlusKPat (L nm_loc bndr_id) (L loc lit') ge' minus'
; icls <- tcLookupClass integralClassName
; instStupidTheta orig [mkClassPred icls [pat_ty']]
; res <- tcExtendIdEnv1 name bndr_id thing_inside
; return (mkHsWrapPatCo co pat' pat_ty, res) }
tc_pat _ _other_pat _ _ = panic "tc_pat"
unifyPatType :: TcType -> TcType -> TcM TcCoercion
unifyPatType actual_ty expected_ty
= do { coi <- unifyType actual_ty expected_ty
; return (mkTcSymCo coi) }
tcConPat :: PatEnv -> Located Name
-> TcRhoType
-> HsConPatDetails Name -> TcM a
-> TcM (Pat TcId, a)
tcConPat penv con_lname@(L _ con_name) pat_ty arg_pats thing_inside
= do { con_like <- tcLookupConLike con_name
; case con_like of
RealDataCon data_con -> tcDataConPat penv con_lname data_con
pat_ty arg_pats thing_inside
PatSynCon pat_syn -> tcPatSynPat penv con_lname pat_syn
pat_ty arg_pats thing_inside
}
tcDataConPat :: PatEnv -> Located Name -> DataCon
-> TcRhoType
-> HsConPatDetails Name -> TcM a
-> TcM (Pat TcId, a)
tcDataConPat penv (L con_span con_name) data_con pat_ty arg_pats thing_inside
= do { let tycon = dataConTyCon data_con
(univ_tvs, ex_tvs, eq_spec, theta, arg_tys, _)
= dataConFullSig data_con
header = L con_span (RealDataCon data_con)
; (wrap, ctxt_res_tys) <- matchExpectedPatTy (matchExpectedConTy tycon) pat_ty
; setSrcSpan con_span $ addDataConStupidTheta data_con ctxt_res_tys
; checkExistentials ex_tvs penv
; (tenv, ex_tvs') <- tcInstSuperSkolTyVarsX
(zipTopTvSubst univ_tvs ctxt_res_tys) ex_tvs
; let
arg_tys' = substTys tenv arg_tys
; traceTc "tcConPat" (vcat [ ppr con_name, ppr univ_tvs, ppr ex_tvs, ppr eq_spec
, ppr ex_tvs', ppr ctxt_res_tys, ppr arg_tys' ])
; if null ex_tvs && null eq_spec && null theta
then do {
(arg_pats', res) <- tcConArgs (RealDataCon data_con) arg_tys'
arg_pats penv thing_inside
; let res_pat = ConPatOut { pat_con = header,
pat_tvs = [], pat_dicts = [],
pat_binds = emptyTcEvBinds,
pat_args = arg_pats',
pat_arg_tys = ctxt_res_tys,
pat_wrap = idHsWrapper }
; return (mkHsWrapPat wrap res_pat pat_ty, res) }
else do
{ let theta' = substTheta tenv (eqSpecPreds eq_spec ++ theta)
no_equalities = not (any isEqPred theta')
skol_info = case pe_ctxt penv of
LamPat mc -> PatSkol (RealDataCon data_con) mc
LetPat {} -> UnkSkol
; gadts_on <- xoptM Opt_GADTs
; families_on <- xoptM Opt_TypeFamilies
; checkTc (no_equalities || gadts_on || families_on)
(text "A pattern match on a GADT requires the" <+>
text "GADTs or TypeFamilies language extension")
; given <- newEvVars theta'
; (ev_binds, (arg_pats', res))
<- checkConstraints skol_info ex_tvs' given $
tcConArgs (RealDataCon data_con) arg_tys' arg_pats penv thing_inside
; let res_pat = ConPatOut { pat_con = header,
pat_tvs = ex_tvs',
pat_dicts = given,
pat_binds = ev_binds,
pat_args = arg_pats',
pat_arg_tys = ctxt_res_tys,
pat_wrap = idHsWrapper }
; return (mkHsWrapPat wrap res_pat pat_ty, res)
} }
tcPatSynPat :: PatEnv -> Located Name -> PatSyn
-> TcRhoType
-> HsConPatDetails Name -> TcM a
-> TcM (Pat TcId, a)
tcPatSynPat penv (L con_span _) pat_syn pat_ty arg_pats thing_inside
= do { let (univ_tvs, ex_tvs, prov_theta, req_theta, arg_tys, ty) = patSynSig pat_syn
; (subst, univ_tvs') <- tcInstTyVars univ_tvs
; checkExistentials ex_tvs penv
; (tenv, ex_tvs') <- tcInstSuperSkolTyVarsX subst ex_tvs
; let ty' = substTy tenv ty
arg_tys' = substTys tenv arg_tys
prov_theta' = substTheta tenv prov_theta
req_theta' = substTheta tenv req_theta
; wrap <- coToHsWrapper <$> unifyType ty' pat_ty
; traceTc "tcPatSynPat" (ppr pat_syn $$
ppr pat_ty $$
ppr ty' $$
ppr ex_tvs' $$
ppr prov_theta' $$
ppr req_theta' $$
ppr arg_tys')
; prov_dicts' <- newEvVars prov_theta'
; let skol_info = case pe_ctxt penv of
LamPat mc -> PatSkol (PatSynCon pat_syn) mc
LetPat {} -> UnkSkol
; req_wrap <- instCall PatOrigin (mkTyVarTys univ_tvs') req_theta'
; traceTc "instCall" (ppr req_wrap)
; traceTc "checkConstraints {" Outputable.empty
; (ev_binds, (arg_pats', res))
<- checkConstraints skol_info ex_tvs' prov_dicts' $
tcConArgs (PatSynCon pat_syn) arg_tys' arg_pats penv thing_inside
; traceTc "checkConstraints }" (ppr ev_binds)
; let res_pat = ConPatOut { pat_con = L con_span $ PatSynCon pat_syn,
pat_tvs = ex_tvs',
pat_dicts = prov_dicts',
pat_binds = ev_binds,
pat_args = arg_pats',
pat_arg_tys = mkTyVarTys univ_tvs',
pat_wrap = req_wrap }
; return (mkHsWrapPat wrap res_pat pat_ty, res) }
matchExpectedPatTy :: (TcRhoType -> TcM (TcCoercion, a))
-> TcRhoType -> TcM (HsWrapper, a)
matchExpectedPatTy inner_match pat_ty
| null tvs && null theta
= do { (co, res) <- inner_match pat_ty
; return (coToHsWrapper (mkTcSymCo co), res) }
| otherwise
= do { (subst, tvs') <- tcInstTyVars tvs
; wrap1 <- instCall PatOrigin (mkTyVarTys tvs') (substTheta subst theta)
; (wrap2, arg_tys) <- matchExpectedPatTy inner_match (TcType.substTy subst tau)
; return (wrap2 <.> wrap1, arg_tys) }
where
(tvs, theta, tau) = tcSplitSigmaTy pat_ty
matchExpectedConTy :: TyCon
-> TcRhoType
-> TcM (TcCoercion, [TcSigmaType])
matchExpectedConTy data_tc pat_ty
| Just (fam_tc, fam_args, co_tc) <- tyConFamInstSig_maybe data_tc
= do { (subst, tvs') <- tcInstTyVars (tyConTyVars data_tc)
; traceTc "matchExpectedConTy" (vcat [ppr data_tc,
ppr (tyConTyVars data_tc),
ppr fam_tc, ppr fam_args])
; co1 <- unifyType (mkTyConApp fam_tc (substTys subst fam_args)) pat_ty
; let tys' = mkTyVarTys tvs'
co2 = mkTcUnbranchedAxInstCo Nominal co_tc tys'
; return (mkTcSymCo co2 `mkTcTransCo` co1, tys') }
| otherwise
= matchExpectedTyConApp data_tc pat_ty
tcConArgs :: ConLike -> [TcSigmaType]
-> Checker (HsConPatDetails Name) (HsConPatDetails Id)
tcConArgs con_like arg_tys (PrefixCon arg_pats) penv thing_inside
= do { checkTc (con_arity == no_of_args)
(arityErr "Constructor" con_like con_arity no_of_args)
; let pats_w_tys = zipEqual "tcConArgs" arg_pats arg_tys
; (arg_pats', res) <- tcMultiple tcConArg pats_w_tys
penv thing_inside
; return (PrefixCon arg_pats', res) }
where
con_arity = conLikeArity con_like
no_of_args = length arg_pats
tcConArgs con_like arg_tys (InfixCon p1 p2) penv thing_inside
= do { checkTc (con_arity == 2)
(arityErr "Constructor" con_like con_arity 2)
; let [arg_ty1,arg_ty2] = arg_tys
; ([p1',p2'], res) <- tcMultiple tcConArg [(p1,arg_ty1),(p2,arg_ty2)]
penv thing_inside
; return (InfixCon p1' p2', res) }
where
con_arity = conLikeArity con_like
tcConArgs con_like arg_tys (RecCon (HsRecFields rpats dd)) penv thing_inside
= do { (rpats', res) <- tcMultiple tc_field rpats penv thing_inside
; return (RecCon (HsRecFields rpats' dd), res) }
where
tc_field :: Checker (LHsRecField FieldLabel (LPat Name))
(LHsRecField TcId (LPat TcId))
tc_field (L l (HsRecField field_lbl pat pun)) penv thing_inside
= do { (sel_id, pat_ty) <- wrapLocFstM find_field_ty field_lbl
; (pat', res) <- tcConArg (pat, pat_ty) penv thing_inside
; return (L l (HsRecField sel_id pat' pun), res) }
find_field_ty :: FieldLabel -> TcM (Id, TcType)
find_field_ty field_lbl
= case [ty | (f,ty) <- field_tys, f == field_lbl] of
[] -> failWith (badFieldCon con_like field_lbl)
(pat_ty : extras) ->
ASSERT( null extras )
do { sel_id <- tcLookupField field_lbl
; return (sel_id, pat_ty) }
field_tys :: [(FieldLabel, TcType)]
field_tys = case con_like of
RealDataCon data_con -> zip (dataConFieldLabels data_con) arg_tys
PatSynCon{} -> []
conLikeArity :: ConLike -> Arity
conLikeArity (RealDataCon data_con) = dataConSourceArity data_con
conLikeArity (PatSynCon pat_syn) = patSynArity pat_syn
tcConArg :: Checker (LPat Name, TcSigmaType) (LPat Id)
tcConArg (arg_pat, arg_ty) penv thing_inside
= tc_lpat arg_pat arg_ty penv thing_inside
addDataConStupidTheta :: DataCon -> [TcType] -> TcM ()
addDataConStupidTheta data_con inst_tys
| null stupid_theta = return ()
| otherwise = instStupidTheta origin inst_theta
where
origin = OccurrenceOf (dataConName data_con)
stupid_theta = dataConStupidTheta data_con
tenv = mkTopTvSubst (dataConUnivTyVars data_con `zip` inst_tys)
inst_theta = substTheta tenv stupid_theta
maybeWrapPatCtxt :: Pat Name -> (TcM a -> TcM b) -> TcM a -> TcM b
maybeWrapPatCtxt pat tcm thing_inside
| not (worth_wrapping pat) = tcm thing_inside
| otherwise = addErrCtxt msg $ tcm $ popErrCtxt thing_inside
where
worth_wrapping (VarPat {}) = False
worth_wrapping (ParPat {}) = False
worth_wrapping (AsPat {}) = False
worth_wrapping _ = True
msg = hang (ptext (sLit "In the pattern:")) 2 (ppr pat)
checkExistentials :: [TyVar] -> PatEnv -> TcM ()
checkExistentials [] _ = return ()
checkExistentials _ (PE { pe_ctxt = LetPat {}}) = failWithTc existentialLetPat
checkExistentials _ (PE { pe_ctxt = LamPat ProcExpr }) = failWithTc existentialProcPat
checkExistentials _ (PE { pe_lazy = True }) = failWithTc existentialLazyPat
checkExistentials _ _ = return ()
existentialLazyPat :: SDoc
existentialLazyPat
= hang (ptext (sLit "An existential or GADT data constructor cannot be used"))
2 (ptext (sLit "inside a lazy (~) pattern"))
existentialProcPat :: SDoc
existentialProcPat
= ptext (sLit "Proc patterns cannot use existential or GADT data constructors")
existentialLetPat :: SDoc
existentialLetPat
= vcat [text "My brain just exploded",
text "I can't handle pattern bindings for existential or GADT data constructors.",
text "Instead, use a case-expression, or do-notation, to unpack the constructor."]
badFieldCon :: ConLike -> Name -> SDoc
badFieldCon con field
= hsep [ptext (sLit "Constructor") <+> quotes (ppr con),
ptext (sLit "does not have field"), quotes (ppr field)]
polyPatSig :: TcType -> SDoc
polyPatSig sig_ty
= hang (ptext (sLit "Illegal polymorphic type signature in pattern:"))
2 (ppr sig_ty)
lazyUnliftedPatErr :: OutputableBndr name => Pat name -> TcM ()
lazyUnliftedPatErr pat
= failWithTc $
hang (ptext (sLit "A lazy (~) pattern cannot contain unlifted types:"))
2 (ppr pat)