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 )
45 import Util ( zipEqual )
50 %************************************************************************
52 \subsection{Variable patterns}
54 %************************************************************************
57 -- This is the right function to pass to tcPat when there are no signatures
58 tcPatBndr_NoSigs binder_name pat_ty
59 = -- Need to make a new, monomorphic, Id
60 -- The binder_name is already being used for the polymorphic Id
61 newLocalId (getOccName binder_name) pat_ty loc `thenNF_Tc` \ bndr_id ->
64 loc = getSrcLoc binder_name
68 %************************************************************************
70 \subsection{Typechecking patterns}
72 %************************************************************************
75 tcPat :: (Name -> TcType -> TcM s TcId) -- How to construct a suitable (monomorphic)
76 -- Id for variables found in the pattern
77 -- The TcType is the expected type, see note below
80 -> TcType -- Expected type derived from the context
81 -- In the case of a function with a rank-2 signature,
82 -- this type might be a forall type.
83 -- INVARIANT: if it is, the foralls will always be visible,
84 -- not hidden inside a mutable type variable
87 LIE, -- Required by n+k and literal pats
88 Bag TcTyVar, -- TyVars bound by the pattern
89 -- These are just the existentially-bound ones.
90 -- Any tyvars bound by *type signatures* in the
91 -- patterns are brought into scope before we begin.
92 Bag (Name, TcId), -- Ids bound by the pattern, along with the Name under
93 -- which it occurs in the pattern
94 -- The two aren't the same because we conjure up a new
95 -- local name for each variable.
96 LIE) -- Dicts or methods [see below] bound by the pattern
97 -- from existential constructor patterns
101 %************************************************************************
103 \subsection{Variables, wildcards, lazy pats, as-pats}
105 %************************************************************************
108 tcPat tc_bndr (VarPatIn name) pat_ty
109 = tc_bndr name pat_ty `thenTc` \ bndr_id ->
110 returnTc (VarPat bndr_id, emptyLIE, emptyBag, unitBag (name, bndr_id), emptyLIE)
112 tcPat tc_bndr (LazyPatIn pat) pat_ty
113 = tcPat tc_bndr pat pat_ty `thenTc` \ (pat', lie_req, tvs, ids, lie_avail) ->
114 returnTc (LazyPat pat', lie_req, tvs, ids, lie_avail)
116 tcPat tc_bndr pat_in@(AsPatIn name pat) pat_ty
117 = tc_bndr name pat_ty `thenTc` \ bndr_id ->
118 tcPat tc_bndr pat pat_ty `thenTc` \ (pat', lie_req, tvs, ids, lie_avail) ->
119 tcAddErrCtxt (patCtxt pat_in) $
120 returnTc (AsPat bndr_id pat', lie_req,
121 tvs, (name, bndr_id) `consBag` ids, lie_avail)
123 tcPat tc_bndr WildPatIn pat_ty
124 = returnTc (WildPat pat_ty, emptyLIE, emptyBag, emptyBag, emptyLIE)
126 tcPat tc_bndr (NegPatIn pat) pat_ty
127 = tcPat tc_bndr (negate_lit pat) pat_ty
129 negate_lit (LitPatIn (HsInt i)) = LitPatIn (HsInt (-i))
130 negate_lit (LitPatIn (HsIntPrim i)) = LitPatIn (HsIntPrim (-i))
131 negate_lit (LitPatIn (HsFrac f)) = LitPatIn (HsFrac (-f))
132 negate_lit (LitPatIn (HsFloatPrim f)) = LitPatIn (HsFloatPrim (-f))
133 negate_lit (LitPatIn (HsDoublePrim f)) = LitPatIn (HsDoublePrim (-f))
134 negate_lit _ = panic "TcPat:negate_pat"
136 tcPat tc_bndr (ParPatIn parend_pat) pat_ty
137 = tcPat tc_bndr parend_pat pat_ty
139 tcPat tc_bndr (SigPatIn pat sig) pat_ty
140 = tcHsSigType sig `thenTc` \ sig_ty ->
142 -- Check that the signature isn't a polymorphic one, which
143 -- we don't permit (at present, anyway)
144 checkTc (isTauTy sig_ty) (polyPatSig sig_ty) `thenTc_`
146 unifyTauTy pat_ty sig_ty `thenTc_`
147 tcPat tc_bndr pat sig_ty
150 %************************************************************************
152 \subsection{Explicit lists and tuples}
154 %************************************************************************
157 tcPat tc_bndr pat_in@(ListPatIn pats) pat_ty
158 = tcAddErrCtxt (patCtxt pat_in) $
159 unifyListTy pat_ty `thenTc` \ elem_ty ->
160 tcPats tc_bndr pats (repeat elem_ty) `thenTc` \ (pats', lie_req, tvs, ids, lie_avail) ->
161 returnTc (ListPat elem_ty pats', lie_req, tvs, ids, lie_avail)
163 tcPat tc_bndr pat_in@(TuplePatIn pats boxity) pat_ty
164 = tcAddErrCtxt (patCtxt pat_in) $
166 unifyTupleTy boxity arity pat_ty `thenTc` \ arg_tys ->
167 tcPats tc_bndr pats arg_tys `thenTc` \ (pats', lie_req, tvs, ids, lie_avail) ->
169 -- possibly do the "make all tuple-pats irrefutable" test:
171 unmangled_result = TuplePat pats' boxity
173 -- Under flag control turn a pattern (x,y,z) into ~(x,y,z)
174 -- so that we can experiment with lazy tuple-matching.
175 -- This is a pretty odd place to make the switch, but
176 -- it was easy to do.
178 possibly_mangled_result
179 | opt_IrrefutableTuples && isBoxed boxity = LazyPat unmangled_result
180 | otherwise = unmangled_result
182 returnTc (possibly_mangled_result, lie_req, tvs, ids, lie_avail)
187 %************************************************************************
189 \subsection{Other constructors}
192 %************************************************************************
195 tcPat tc_bndr pat@(ConPatIn name arg_pats) pat_ty
196 = tcConPat tc_bndr pat name arg_pats pat_ty
198 tcPat tc_bndr pat@(ConOpPatIn pat1 op _ pat2) pat_ty
199 = tcConPat tc_bndr pat op [pat1, pat2] pat_ty
203 %************************************************************************
207 %************************************************************************
210 tcPat tc_bndr pat@(RecPatIn name rpats) pat_ty
211 = tcAddErrCtxt (patCtxt pat) $
213 -- Check the constructor itself
214 tcConstructor pat name pat_ty `thenTc` \ (data_con, ex_tvs, dicts, lie_avail1, arg_tys) ->
216 field_tys = zipEqual "tcPat"
217 (map fieldLabelName (dataConFieldLabels data_con))
222 tc_fields field_tys rpats `thenTc` \ (rpats', lie_req, tvs, ids, lie_avail2) ->
224 returnTc (RecPat data_con pat_ty ex_tvs dicts rpats',
226 listToBag ex_tvs `unionBags` tvs,
228 lie_avail1 `plusLIE` lie_avail2)
231 tc_fields field_tys []
232 = returnTc ([], emptyLIE, emptyBag, emptyBag, emptyLIE)
234 tc_fields field_tys ((field_label, rhs_pat, pun_flag) : rpats)
235 = tc_fields field_tys rpats `thenTc` \ (rpats', lie_req1, tvs1, ids1, lie_avail1) ->
237 (case [ty | (f,ty) <- field_tys, f == field_label] of
239 -- No matching field; chances are this field label comes from some
240 -- other record type (or maybe none). As well as reporting an
241 -- error we still want to typecheck the pattern, principally to
242 -- make sure that all the variables it binds are put into the
243 -- environment, else the type checker crashes later:
244 -- f (R { foo = (a,b) }) = a+b
245 -- If foo isn't one of R's fields, we don't want to crash when
246 -- typechecking the "a+b".
247 [] -> addErrTc (badFieldCon name field_label) `thenNF_Tc_`
248 newTyVarTy boxedTypeKind `thenNF_Tc_`
249 returnTc (error "Bogus selector Id", pat_ty)
251 -- The normal case, when the field comes from the right constructor
253 ASSERT( null extras )
254 tcLookupValue field_label `thenNF_Tc` \ sel_id ->
255 returnTc (sel_id, pat_ty)
256 ) `thenTc` \ (sel_id, pat_ty) ->
258 tcPat tc_bndr rhs_pat pat_ty `thenTc` \ (rhs_pat', lie_req2, tvs2, ids2, lie_avail2) ->
260 returnTc ((sel_id, rhs_pat', pun_flag) : rpats',
261 lie_req1 `plusLIE` lie_req2,
262 tvs1 `unionBags` tvs2,
263 ids1 `unionBags` ids2,
264 lie_avail1 `plusLIE` lie_avail2)
267 %************************************************************************
269 \subsection{Non-overloaded literals}
271 %************************************************************************
274 tcPat tc_bndr (LitPatIn lit@(HsChar _)) pat_ty = tcSimpleLitPat lit charTy pat_ty
275 tcPat tc_bndr (LitPatIn lit@(HsIntPrim _)) pat_ty = tcSimpleLitPat lit intPrimTy pat_ty
276 tcPat tc_bndr (LitPatIn lit@(HsCharPrim _)) pat_ty = tcSimpleLitPat lit charPrimTy pat_ty
277 tcPat tc_bndr (LitPatIn lit@(HsStringPrim _)) pat_ty = tcSimpleLitPat lit addrPrimTy pat_ty
278 tcPat tc_bndr (LitPatIn lit@(HsFloatPrim _)) pat_ty = tcSimpleLitPat lit floatPrimTy pat_ty
279 tcPat tc_bndr (LitPatIn lit@(HsDoublePrim _)) pat_ty = tcSimpleLitPat lit doublePrimTy pat_ty
281 tcPat tc_bndr (LitPatIn lit@(HsLitLit s)) pat_ty
282 -- cf tcExpr on LitLits
283 = tcLookupClassByKey cCallableClassKey `thenNF_Tc` \ cCallableClass ->
284 newDicts (LitLitOrigin (_UNPK_ s))
285 [mkClassPred cCallableClass [pat_ty]] `thenNF_Tc` \ (dicts, _) ->
286 returnTc (LitPat lit pat_ty, dicts, emptyBag, emptyBag, emptyLIE)
289 %************************************************************************
291 \subsection{Overloaded patterns: int literals and \tr{n+k} patterns}
293 %************************************************************************
296 tcPat tc_bndr pat@(LitPatIn lit@(HsString str)) pat_ty
297 = unifyTauTy pat_ty stringTy `thenTc_`
298 tcLookupValueByKey eqClassOpKey `thenNF_Tc` \ sel_id ->
299 newMethod (PatOrigin pat) sel_id [stringTy] `thenNF_Tc` \ (lie, eq_id) ->
301 comp_op = HsApp (HsVar eq_id) (HsLitOut lit stringTy)
303 returnTc (NPat lit stringTy comp_op, lie, emptyBag, emptyBag, emptyLIE)
306 tcPat tc_bndr pat@(LitPatIn lit@(HsInt i)) pat_ty
307 = tcOverloadedLitPat pat lit (OverloadedIntegral i) pat_ty
309 tcPat tc_bndr pat@(LitPatIn lit@(HsFrac f)) pat_ty
310 = tcOverloadedLitPat pat lit (OverloadedFractional f) pat_ty
313 tcPat tc_bndr pat@(NPlusKPatIn name lit@(HsInt i)) pat_ty
314 = tc_bndr name pat_ty `thenTc` \ bndr_id ->
315 tcLookupValueByKey geClassOpKey `thenNF_Tc` \ ge_sel_id ->
316 tcLookupValueByKey minusClassOpKey `thenNF_Tc` \ minus_sel_id ->
318 newOverloadedLit origin
319 (OverloadedIntegral i) pat_ty `thenNF_Tc` \ (over_lit_expr, lie1) ->
321 newMethod origin ge_sel_id [pat_ty] `thenNF_Tc` \ (lie2, ge_id) ->
322 newMethod origin minus_sel_id [pat_ty] `thenNF_Tc` \ (lie3, minus_id) ->
324 returnTc (NPlusKPat bndr_id lit pat_ty
325 (SectionR (HsVar ge_id) over_lit_expr)
326 (SectionR (HsVar minus_id) over_lit_expr),
327 lie1 `plusLIE` lie2 `plusLIE` lie3,
328 emptyBag, unitBag (name, bndr_id), emptyLIE)
330 origin = PatOrigin pat
332 tcPat tc_bndr (NPlusKPatIn pat other) pat_ty
333 = panic "TcPat:NPlusKPat: not an HsInt literal"
336 %************************************************************************
338 \subsection{Lists of patterns}
340 %************************************************************************
345 tcPats :: (Name -> TcType -> TcM s TcId) -- How to deal with variables
346 -> [RenamedPat] -> [TcType] -- Excess 'expected types' discarded
348 LIE, -- Required by n+k and literal pats
350 Bag (Name, TcId), -- Ids bound by the pattern
351 LIE) -- Dicts bound by the pattern
353 tcPats tc_bndr [] tys = returnTc ([], emptyLIE, emptyBag, emptyBag, emptyLIE)
355 tcPats tc_bndr (ty:tys) (pat:pats)
356 = tcPat tc_bndr ty pat `thenTc` \ (pat', lie_req1, tvs1, ids1, lie_avail1) ->
357 tcPats tc_bndr tys pats `thenTc` \ (pats', lie_req2, tvs2, ids2, lie_avail2) ->
359 returnTc (pat':pats', lie_req1 `plusLIE` lie_req2,
360 tvs1 `unionBags` tvs2, ids1 `unionBags` ids2,
361 lie_avail1 `plusLIE` lie_avail2)
364 ------------------------------------------------------
366 tcSimpleLitPat lit lit_ty pat_ty
367 = unifyTauTy pat_ty lit_ty `thenTc_`
368 returnTc (LitPat lit lit_ty, emptyLIE, emptyBag, emptyBag, emptyLIE)
371 tcOverloadedLitPat pat lit over_lit pat_ty
372 = newOverloadedLit (PatOrigin pat) over_lit pat_ty `thenNF_Tc` \ (over_lit_expr, lie1) ->
373 tcLookupValueByKey eqClassOpKey `thenNF_Tc` \ eq_sel_id ->
374 newMethod origin eq_sel_id [pat_ty] `thenNF_Tc` \ (lie2, eq_id) ->
376 returnTc (NPat lit pat_ty (HsApp (HsVar eq_id)
379 emptyBag, emptyBag, emptyLIE)
381 origin = PatOrigin pat
384 ------------------------------------------------------
386 tcConstructor pat con_name pat_ty
387 = -- Check that it's a constructor
388 tcLookupValue con_name `thenNF_Tc` \ con_id ->
389 case isDataConWrapId_maybe con_id of {
390 Nothing -> failWithTc (badCon con_id);
395 (tvs, _, ex_tvs, ex_theta, arg_tys, tycon) = dataConSig data_con
396 -- Ignore the theta; overloaded constructors only
397 -- behave differently when called, not when used for
400 tcInstTyVars (ex_tvs ++ tvs) `thenNF_Tc` \ (all_tvs', ty_args', tenv) ->
402 ex_theta' = substClasses tenv ex_theta
403 arg_tys' = map (substTy tenv) arg_tys
405 n_ex_tvs = length ex_tvs
406 ex_tvs' = take n_ex_tvs all_tvs'
407 result_ty = mkTyConApp tycon (drop n_ex_tvs ty_args')
409 newClassDicts (PatOrigin pat) ex_theta' `thenNF_Tc` \ (lie_avail, dicts) ->
411 -- Check overall type matches
412 unifyTauTy pat_ty result_ty `thenTc_`
414 returnTc (data_con, ex_tvs', dicts, lie_avail, arg_tys')
418 ------------------------------------------------------
420 tcConPat tc_bndr pat con_name arg_pats pat_ty
421 = tcAddErrCtxt (patCtxt pat) $
423 -- Check the constructor itself
424 tcConstructor pat con_name pat_ty `thenTc` \ (data_con, ex_tvs', dicts, lie_avail1, arg_tys') ->
426 -- Check correct arity
428 con_arity = dataConSourceArity data_con
429 no_of_args = length arg_pats
431 checkTc (con_arity == no_of_args)
432 (arityErr "Constructor" data_con con_arity no_of_args) `thenTc_`
435 tcPats tc_bndr arg_pats arg_tys' `thenTc` \ (arg_pats', lie_req, tvs, ids, lie_avail2) ->
437 returnTc (ConPat data_con pat_ty ex_tvs' dicts arg_pats',
439 listToBag ex_tvs' `unionBags` tvs,
441 lie_avail1 `plusLIE` lie_avail2)
445 %************************************************************************
447 \subsection{Errors and contexts}
449 %************************************************************************
452 patCtxt pat = hang (ptext SLIT("In the pattern:"))
455 recordLabel field_label
456 = hang (hcat [ptext SLIT("When matching record field"), ppr field_label])
457 4 (hcat [ptext SLIT("with its immediately enclosing constructor")])
459 recordRhs field_label pat
460 = hang (ptext SLIT("In the record field pattern"))
461 4 (sep [ppr field_label, char '=', ppr pat])
463 badFieldCon :: Name -> Name -> SDoc
464 badFieldCon con field
465 = hsep [ptext SLIT("Constructor") <+> quotes (ppr con),
466 ptext SLIT("does not have field"), quotes (ppr field)]
468 polyPatSig :: TcType -> SDoc
470 = hang (ptext SLIT("Illegal polymorphic type signature in pattern:"))