2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[TcPat]{Typechecking patterns}
7 module TcPat ( tcPat, tcPatBndr_NoSigs, badFieldCon, polyPatSig ) where
9 #include "HsVersions.h"
11 import HsSyn ( InPat(..), OutPat(..), HsLit(..), HsExpr(..), Sig(..) )
12 import RnHsSyn ( RenamedPat )
13 import TcHsSyn ( TcPat, TcId )
16 import Inst ( Inst, OverloadedLit(..), InstOrigin(..),
17 emptyLIE, plusLIE, LIE,
18 newMethod, newOverloadedLit, newDicts, newClassDicts
20 import Name ( Name, getOccName, getSrcLoc )
21 import FieldLabel ( fieldLabelName )
22 import TcEnv ( tcLookupValue, tcLookupClassByKey,
23 tcLookupValueByKey, newLocalId, badCon
25 import TcType ( TcType, TcTyVar, tcInstTyVars, newTyVarTy )
26 import TcMonoType ( tcHsSigType )
27 import TcUnify ( unifyTauTy, unifyListTy, unifyTupleTy )
29 import CmdLineOpts ( opt_IrrefutableTuples )
30 import DataCon ( DataCon, dataConSig, dataConFieldLabels,
33 import Id ( Id, idType, isDataConWrapId_maybe )
34 import Type ( Type, isTauTy, mkTyConApp, mkClassPred, boxedTypeKind )
35 import Subst ( substTy, substClasses )
36 import TysPrim ( charPrimTy, intPrimTy, floatPrimTy,
37 doublePrimTy, addrPrimTy
39 import TysWiredIn ( charTy, stringTy, intTy )
40 import Unique ( eqClassOpKey, geClassOpKey, minusClassOpKey,
43 import BasicTypes ( isBoxed )
49 %************************************************************************
51 \subsection{Variable patterns}
53 %************************************************************************
56 -- This is the right function to pass to tcPat when there are no signatures
57 tcPatBndr_NoSigs binder_name pat_ty
58 = -- Need to make a new, monomorphic, Id
59 -- The binder_name is already being used for the polymorphic Id
60 newLocalId (getOccName binder_name) pat_ty loc `thenNF_Tc` \ bndr_id ->
63 loc = getSrcLoc binder_name
67 %************************************************************************
69 \subsection{Typechecking patterns}
71 %************************************************************************
74 tcPat :: (Name -> TcType -> TcM s TcId) -- How to construct a suitable (monomorphic)
75 -- Id for variables found in the pattern
76 -- The TcType is the expected type, see note below
79 -> TcType -- Expected type derived from the context
80 -- In the case of a function with a rank-2 signature,
81 -- this type might be a forall type.
82 -- INVARIANT: if it is, the foralls will always be visible,
83 -- not hidden inside a mutable type variable
86 LIE, -- Required by n+k and literal pats
87 Bag TcTyVar, -- TyVars bound by the pattern
88 -- These are just the existentially-bound ones.
89 -- Any tyvars bound by *type signatures* in the
90 -- patterns are brought into scope before we begin.
91 Bag (Name, TcId), -- Ids bound by the pattern, along with the Name under
92 -- which it occurs in the pattern
93 -- The two aren't the same because we conjure up a new
94 -- local name for each variable.
95 LIE) -- Dicts or methods [see below] bound by the pattern
96 -- from existential constructor patterns
100 %************************************************************************
102 \subsection{Variables, wildcards, lazy pats, as-pats}
104 %************************************************************************
107 tcPat tc_bndr (VarPatIn name) pat_ty
108 = tc_bndr name pat_ty `thenTc` \ bndr_id ->
109 returnTc (VarPat bndr_id, emptyLIE, emptyBag, unitBag (name, bndr_id), emptyLIE)
111 tcPat tc_bndr (LazyPatIn pat) pat_ty
112 = tcPat tc_bndr pat pat_ty `thenTc` \ (pat', lie_req, tvs, ids, lie_avail) ->
113 returnTc (LazyPat pat', lie_req, tvs, ids, lie_avail)
115 tcPat tc_bndr pat_in@(AsPatIn name pat) pat_ty
116 = tc_bndr name pat_ty `thenTc` \ bndr_id ->
117 tcPat tc_bndr pat pat_ty `thenTc` \ (pat', lie_req, tvs, ids, lie_avail) ->
118 tcAddErrCtxt (patCtxt pat_in) $
119 returnTc (AsPat bndr_id pat', lie_req,
120 tvs, (name, bndr_id) `consBag` ids, lie_avail)
122 tcPat tc_bndr WildPatIn pat_ty
123 = returnTc (WildPat pat_ty, emptyLIE, emptyBag, emptyBag, emptyLIE)
125 tcPat tc_bndr (NegPatIn pat) pat_ty
126 = tcPat tc_bndr (negate_lit pat) pat_ty
128 negate_lit (LitPatIn (HsInt i)) = LitPatIn (HsInt (-i))
129 negate_lit (LitPatIn (HsIntPrim i)) = LitPatIn (HsIntPrim (-i))
130 negate_lit (LitPatIn (HsFrac f)) = LitPatIn (HsFrac (-f))
131 negate_lit (LitPatIn (HsFloatPrim f)) = LitPatIn (HsFloatPrim (-f))
132 negate_lit (LitPatIn (HsDoublePrim f)) = LitPatIn (HsDoublePrim (-f))
133 negate_lit _ = panic "TcPat:negate_pat"
135 tcPat tc_bndr (ParPatIn parend_pat) pat_ty
136 = tcPat tc_bndr parend_pat pat_ty
138 tcPat tc_bndr (SigPatIn pat sig) pat_ty
139 = tcHsSigType sig `thenTc` \ sig_ty ->
141 -- Check that the signature isn't a polymorphic one, which
142 -- we don't permit (at present, anyway)
143 checkTc (isTauTy sig_ty) (polyPatSig sig_ty) `thenTc_`
145 unifyTauTy pat_ty sig_ty `thenTc_`
146 tcPat tc_bndr pat sig_ty
149 %************************************************************************
151 \subsection{Explicit lists and tuples}
153 %************************************************************************
156 tcPat tc_bndr pat_in@(ListPatIn pats) pat_ty
157 = tcAddErrCtxt (patCtxt pat_in) $
158 unifyListTy pat_ty `thenTc` \ elem_ty ->
159 tcPats tc_bndr pats (repeat elem_ty) `thenTc` \ (pats', lie_req, tvs, ids, lie_avail) ->
160 returnTc (ListPat elem_ty pats', lie_req, tvs, ids, lie_avail)
162 tcPat tc_bndr pat_in@(TuplePatIn pats boxity) pat_ty
163 = tcAddErrCtxt (patCtxt pat_in) $
165 unifyTupleTy boxity arity pat_ty `thenTc` \ arg_tys ->
166 tcPats tc_bndr pats arg_tys `thenTc` \ (pats', lie_req, tvs, ids, lie_avail) ->
168 -- possibly do the "make all tuple-pats irrefutable" test:
170 unmangled_result = TuplePat pats' boxity
172 -- Under flag control turn a pattern (x,y,z) into ~(x,y,z)
173 -- so that we can experiment with lazy tuple-matching.
174 -- This is a pretty odd place to make the switch, but
175 -- it was easy to do.
177 possibly_mangled_result
178 | opt_IrrefutableTuples && isBoxed boxity = LazyPat unmangled_result
179 | otherwise = unmangled_result
181 returnTc (possibly_mangled_result, lie_req, tvs, ids, lie_avail)
186 %************************************************************************
188 \subsection{Other constructors}
191 %************************************************************************
194 tcPat tc_bndr pat@(ConPatIn name arg_pats) pat_ty
195 = tcConPat tc_bndr pat name arg_pats pat_ty
197 tcPat tc_bndr pat@(ConOpPatIn pat1 op _ pat2) pat_ty
198 = tcConPat tc_bndr pat op [pat1, pat2] pat_ty
202 %************************************************************************
206 %************************************************************************
209 tcPat tc_bndr pat@(RecPatIn name rpats) pat_ty
210 = tcAddErrCtxt (patCtxt pat) $
212 -- Check the constructor itself
213 tcConstructor pat name pat_ty `thenTc` \ (data_con, ex_tvs, dicts, lie_avail1, arg_tys) ->
215 -- Don't use zipEqual! If the constructor isn't really a record, then
216 -- dataConFieldLabels will be empty (and each field in the pattern
217 -- will generate an error below).
218 field_tys = zip (map fieldLabelName (dataConFieldLabels data_con))
223 tc_fields field_tys rpats `thenTc` \ (rpats', lie_req, tvs, ids, lie_avail2) ->
225 returnTc (RecPat data_con pat_ty ex_tvs dicts rpats',
227 listToBag ex_tvs `unionBags` tvs,
229 lie_avail1 `plusLIE` lie_avail2)
232 tc_fields field_tys []
233 = returnTc ([], emptyLIE, emptyBag, emptyBag, emptyLIE)
235 tc_fields field_tys ((field_label, rhs_pat, pun_flag) : rpats)
236 = tc_fields field_tys rpats `thenTc` \ (rpats', lie_req1, tvs1, ids1, lie_avail1) ->
238 (case [ty | (f,ty) <- field_tys, f == field_label] of
240 -- No matching field; chances are this field label comes from some
241 -- other record type (or maybe none). As well as reporting an
242 -- error we still want to typecheck the pattern, principally to
243 -- make sure that all the variables it binds are put into the
244 -- environment, else the type checker crashes later:
245 -- f (R { foo = (a,b) }) = a+b
246 -- If foo isn't one of R's fields, we don't want to crash when
247 -- typechecking the "a+b".
248 [] -> addErrTc (badFieldCon name field_label) `thenNF_Tc_`
249 newTyVarTy boxedTypeKind `thenNF_Tc_`
250 returnTc (error "Bogus selector Id", pat_ty)
252 -- The normal case, when the field comes from the right constructor
254 ASSERT( null extras )
255 tcLookupValue field_label `thenNF_Tc` \ sel_id ->
256 returnTc (sel_id, pat_ty)
257 ) `thenTc` \ (sel_id, pat_ty) ->
259 tcPat tc_bndr rhs_pat pat_ty `thenTc` \ (rhs_pat', lie_req2, tvs2, ids2, lie_avail2) ->
261 returnTc ((sel_id, rhs_pat', pun_flag) : rpats',
262 lie_req1 `plusLIE` lie_req2,
263 tvs1 `unionBags` tvs2,
264 ids1 `unionBags` ids2,
265 lie_avail1 `plusLIE` lie_avail2)
268 %************************************************************************
270 \subsection{Non-overloaded literals}
272 %************************************************************************
275 tcPat tc_bndr (LitPatIn lit@(HsChar _)) pat_ty = tcSimpleLitPat lit charTy pat_ty
276 tcPat tc_bndr (LitPatIn lit@(HsIntPrim _)) pat_ty = tcSimpleLitPat lit intPrimTy pat_ty
277 tcPat tc_bndr (LitPatIn lit@(HsCharPrim _)) pat_ty = tcSimpleLitPat lit charPrimTy pat_ty
278 tcPat tc_bndr (LitPatIn lit@(HsStringPrim _)) pat_ty = tcSimpleLitPat lit addrPrimTy pat_ty
279 tcPat tc_bndr (LitPatIn lit@(HsFloatPrim _)) pat_ty = tcSimpleLitPat lit floatPrimTy pat_ty
280 tcPat tc_bndr (LitPatIn lit@(HsDoublePrim _)) pat_ty = tcSimpleLitPat lit doublePrimTy pat_ty
282 tcPat tc_bndr (LitPatIn lit@(HsLitLit s)) pat_ty
283 -- cf tcExpr on LitLits
284 = tcLookupClassByKey cCallableClassKey `thenNF_Tc` \ cCallableClass ->
285 newDicts (LitLitOrigin (_UNPK_ s))
286 [mkClassPred cCallableClass [pat_ty]] `thenNF_Tc` \ (dicts, _) ->
287 returnTc (LitPat lit pat_ty, dicts, emptyBag, emptyBag, emptyLIE)
290 %************************************************************************
292 \subsection{Overloaded patterns: int literals and \tr{n+k} patterns}
294 %************************************************************************
297 tcPat tc_bndr pat@(LitPatIn lit@(HsString str)) pat_ty
298 = unifyTauTy pat_ty stringTy `thenTc_`
299 tcLookupValueByKey eqClassOpKey `thenNF_Tc` \ sel_id ->
300 newMethod (PatOrigin pat) sel_id [stringTy] `thenNF_Tc` \ (lie, eq_id) ->
302 comp_op = HsApp (HsVar eq_id) (HsLitOut lit stringTy)
304 returnTc (NPat lit stringTy comp_op, lie, emptyBag, emptyBag, emptyLIE)
307 tcPat tc_bndr pat@(LitPatIn lit@(HsInt i)) pat_ty
308 = tcOverloadedLitPat pat lit (OverloadedIntegral i) pat_ty
310 tcPat tc_bndr pat@(LitPatIn lit@(HsFrac f)) pat_ty
311 = tcOverloadedLitPat pat lit (OverloadedFractional f) pat_ty
314 tcPat tc_bndr pat@(NPlusKPatIn name lit@(HsInt i)) pat_ty
315 = tc_bndr name pat_ty `thenTc` \ bndr_id ->
316 tcLookupValueByKey geClassOpKey `thenNF_Tc` \ ge_sel_id ->
317 tcLookupValueByKey minusClassOpKey `thenNF_Tc` \ minus_sel_id ->
319 newOverloadedLit origin
320 (OverloadedIntegral i) pat_ty `thenNF_Tc` \ (over_lit_expr, lie1) ->
322 newMethod origin ge_sel_id [pat_ty] `thenNF_Tc` \ (lie2, ge_id) ->
323 newMethod origin minus_sel_id [pat_ty] `thenNF_Tc` \ (lie3, minus_id) ->
325 returnTc (NPlusKPat bndr_id lit pat_ty
326 (SectionR (HsVar ge_id) over_lit_expr)
327 (SectionR (HsVar minus_id) over_lit_expr),
328 lie1 `plusLIE` lie2 `plusLIE` lie3,
329 emptyBag, unitBag (name, bndr_id), emptyLIE)
331 origin = PatOrigin pat
333 tcPat tc_bndr (NPlusKPatIn pat other) pat_ty
334 = panic "TcPat:NPlusKPat: not an HsInt literal"
337 %************************************************************************
339 \subsection{Lists of patterns}
341 %************************************************************************
346 tcPats :: (Name -> TcType -> TcM s TcId) -- How to deal with variables
347 -> [RenamedPat] -> [TcType] -- Excess 'expected types' discarded
349 LIE, -- Required by n+k and literal pats
351 Bag (Name, TcId), -- Ids bound by the pattern
352 LIE) -- Dicts bound by the pattern
354 tcPats tc_bndr [] tys = returnTc ([], emptyLIE, emptyBag, emptyBag, emptyLIE)
356 tcPats tc_bndr (ty:tys) (pat:pats)
357 = tcPat tc_bndr ty pat `thenTc` \ (pat', lie_req1, tvs1, ids1, lie_avail1) ->
358 tcPats tc_bndr tys pats `thenTc` \ (pats', lie_req2, tvs2, ids2, lie_avail2) ->
360 returnTc (pat':pats', lie_req1 `plusLIE` lie_req2,
361 tvs1 `unionBags` tvs2, ids1 `unionBags` ids2,
362 lie_avail1 `plusLIE` lie_avail2)
365 ------------------------------------------------------
367 tcSimpleLitPat lit lit_ty pat_ty
368 = unifyTauTy pat_ty lit_ty `thenTc_`
369 returnTc (LitPat lit lit_ty, emptyLIE, emptyBag, emptyBag, emptyLIE)
372 tcOverloadedLitPat pat lit over_lit pat_ty
373 = newOverloadedLit (PatOrigin pat) over_lit pat_ty `thenNF_Tc` \ (over_lit_expr, lie1) ->
374 tcLookupValueByKey eqClassOpKey `thenNF_Tc` \ eq_sel_id ->
375 newMethod origin eq_sel_id [pat_ty] `thenNF_Tc` \ (lie2, eq_id) ->
377 returnTc (NPat lit pat_ty (HsApp (HsVar eq_id)
380 emptyBag, emptyBag, emptyLIE)
382 origin = PatOrigin pat
385 ------------------------------------------------------
387 tcConstructor pat con_name pat_ty
388 = -- Check that it's a constructor
389 tcLookupValue con_name `thenNF_Tc` \ con_id ->
390 case isDataConWrapId_maybe con_id of {
391 Nothing -> failWithTc (badCon con_id);
396 (tvs, _, ex_tvs, ex_theta, arg_tys, tycon) = dataConSig data_con
397 -- Ignore the theta; overloaded constructors only
398 -- behave differently when called, not when used for
401 tcInstTyVars (ex_tvs ++ tvs) `thenNF_Tc` \ (all_tvs', ty_args', tenv) ->
403 ex_theta' = substClasses tenv ex_theta
404 arg_tys' = map (substTy tenv) arg_tys
406 n_ex_tvs = length ex_tvs
407 ex_tvs' = take n_ex_tvs all_tvs'
408 result_ty = mkTyConApp tycon (drop n_ex_tvs ty_args')
410 newClassDicts (PatOrigin pat) ex_theta' `thenNF_Tc` \ (lie_avail, dicts) ->
412 -- Check overall type matches
413 unifyTauTy pat_ty result_ty `thenTc_`
415 returnTc (data_con, ex_tvs', dicts, lie_avail, arg_tys')
419 ------------------------------------------------------
421 tcConPat tc_bndr pat con_name arg_pats pat_ty
422 = tcAddErrCtxt (patCtxt pat) $
424 -- Check the constructor itself
425 tcConstructor pat con_name pat_ty `thenTc` \ (data_con, ex_tvs', dicts, lie_avail1, arg_tys') ->
427 -- Check correct arity
429 con_arity = dataConSourceArity data_con
430 no_of_args = length arg_pats
432 checkTc (con_arity == no_of_args)
433 (arityErr "Constructor" data_con con_arity no_of_args) `thenTc_`
436 tcPats tc_bndr arg_pats arg_tys' `thenTc` \ (arg_pats', lie_req, tvs, ids, lie_avail2) ->
438 returnTc (ConPat data_con pat_ty ex_tvs' dicts arg_pats',
440 listToBag ex_tvs' `unionBags` tvs,
442 lie_avail1 `plusLIE` lie_avail2)
446 %************************************************************************
448 \subsection{Errors and contexts}
450 %************************************************************************
453 patCtxt pat = hang (ptext SLIT("In the pattern:"))
456 recordLabel field_label
457 = hang (hcat [ptext SLIT("When matching record field"), ppr field_label])
458 4 (hcat [ptext SLIT("with its immediately enclosing constructor")])
460 recordRhs field_label pat
461 = hang (ptext SLIT("In the record field pattern"))
462 4 (sep [ppr field_label, char '=', ppr pat])
464 badFieldCon :: Name -> Name -> SDoc
465 badFieldCon con field
466 = hsep [ptext SLIT("Constructor") <+> quotes (ppr con),
467 ptext SLIT("does not have field"), quotes (ppr field)]
469 polyPatSig :: TcType -> SDoc
471 = hang (ptext SLIT("Illegal polymorphic type signature in pattern:"))