2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[TcPat]{Typechecking patterns}
7 module TcPat ( tcPat, tcPatBndr_NoSigs, simpleHsLitTy, badFieldCon, polyPatSig ) where
9 #include "HsVersions.h"
11 import HsSyn ( InPat(..), OutPat(..), HsLit(..), HsOverLit(..), HsExpr(..) )
12 import RnHsSyn ( RenamedPat )
13 import TcHsSyn ( TcPat, TcId )
16 import Inst ( 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 ( dataConSig, dataConFieldLabels,
33 import Id ( isDataConWrapId_maybe )
34 import 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, integerTy )
40 import PrelNames ( eqClassOpKey, geClassOpKey,
41 cCallableClassKey, eqStringIdKey,
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 pat@(TypePatIn ty) pat_ty
108 = failWithTc (badTypePat pat)
110 tcPat tc_bndr (VarPatIn name) pat_ty
111 = tc_bndr name pat_ty `thenTc` \ bndr_id ->
112 returnTc (VarPat bndr_id, emptyLIE, emptyBag, unitBag (name, bndr_id), emptyLIE)
114 tcPat tc_bndr (LazyPatIn pat) pat_ty
115 = tcPat tc_bndr pat pat_ty `thenTc` \ (pat', lie_req, tvs, ids, lie_avail) ->
116 returnTc (LazyPat pat', lie_req, tvs, ids, lie_avail)
118 tcPat tc_bndr pat_in@(AsPatIn name pat) pat_ty
119 = tc_bndr name pat_ty `thenTc` \ bndr_id ->
120 tcPat tc_bndr pat pat_ty `thenTc` \ (pat', lie_req, tvs, ids, lie_avail) ->
121 tcAddErrCtxt (patCtxt pat_in) $
122 returnTc (AsPat bndr_id pat', lie_req,
123 tvs, (name, bndr_id) `consBag` ids, lie_avail)
125 tcPat tc_bndr WildPatIn pat_ty
126 = returnTc (WildPat pat_ty, emptyLIE, emptyBag, emptyBag, emptyLIE)
128 tcPat tc_bndr (ParPatIn parend_pat) pat_ty
129 = tcPat tc_bndr parend_pat pat_ty
131 tcPat tc_bndr (SigPatIn pat sig) pat_ty
132 = tcHsSigType sig `thenTc` \ sig_ty ->
134 -- Check that the signature isn't a polymorphic one, which
135 -- we don't permit (at present, anyway)
136 checkTc (isTauTy sig_ty) (polyPatSig sig_ty) `thenTc_`
138 unifyTauTy pat_ty sig_ty `thenTc_`
139 tcPat tc_bndr pat sig_ty
142 %************************************************************************
144 \subsection{Explicit lists and tuples}
146 %************************************************************************
149 tcPat tc_bndr pat_in@(ListPatIn pats) pat_ty
150 = tcAddErrCtxt (patCtxt pat_in) $
151 unifyListTy pat_ty `thenTc` \ elem_ty ->
152 tcPats tc_bndr pats (repeat elem_ty) `thenTc` \ (pats', lie_req, tvs, ids, lie_avail) ->
153 returnTc (ListPat elem_ty pats', lie_req, tvs, ids, lie_avail)
155 tcPat tc_bndr pat_in@(TuplePatIn pats boxity) pat_ty
156 = tcAddErrCtxt (patCtxt pat_in) $
158 unifyTupleTy boxity arity pat_ty `thenTc` \ arg_tys ->
159 tcPats tc_bndr pats arg_tys `thenTc` \ (pats', lie_req, tvs, ids, lie_avail) ->
161 -- possibly do the "make all tuple-pats irrefutable" test:
163 unmangled_result = TuplePat pats' boxity
165 -- Under flag control turn a pattern (x,y,z) into ~(x,y,z)
166 -- so that we can experiment with lazy tuple-matching.
167 -- This is a pretty odd place to make the switch, but
168 -- it was easy to do.
170 possibly_mangled_result
171 | opt_IrrefutableTuples && isBoxed boxity = LazyPat unmangled_result
172 | otherwise = unmangled_result
174 returnTc (possibly_mangled_result, lie_req, tvs, ids, lie_avail)
179 %************************************************************************
181 \subsection{Other constructors}
184 %************************************************************************
187 tcPat tc_bndr pat@(ConPatIn name arg_pats) pat_ty
188 = tcConPat tc_bndr pat name arg_pats pat_ty
190 tcPat tc_bndr pat@(ConOpPatIn pat1 op _ pat2) pat_ty
191 = tcConPat tc_bndr pat op [pat1, pat2] pat_ty
195 %************************************************************************
199 %************************************************************************
202 tcPat tc_bndr pat@(RecPatIn name rpats) pat_ty
203 = tcAddErrCtxt (patCtxt pat) $
205 -- Check the constructor itself
206 tcConstructor pat name pat_ty `thenTc` \ (data_con, ex_tvs, dicts, lie_avail1, arg_tys) ->
208 -- Don't use zipEqual! If the constructor isn't really a record, then
209 -- dataConFieldLabels will be empty (and each field in the pattern
210 -- will generate an error below).
211 field_tys = zip (map fieldLabelName (dataConFieldLabels data_con))
216 tc_fields field_tys rpats `thenTc` \ (rpats', lie_req, tvs, ids, lie_avail2) ->
218 returnTc (RecPat data_con pat_ty ex_tvs dicts rpats',
220 listToBag ex_tvs `unionBags` tvs,
222 lie_avail1 `plusLIE` lie_avail2)
225 tc_fields field_tys []
226 = returnTc ([], emptyLIE, emptyBag, emptyBag, emptyLIE)
228 tc_fields field_tys ((field_label, rhs_pat, pun_flag) : rpats)
229 = tc_fields field_tys rpats `thenTc` \ (rpats', lie_req1, tvs1, ids1, lie_avail1) ->
231 (case [ty | (f,ty) <- field_tys, f == field_label] of
233 -- No matching field; chances are this field label comes from some
234 -- other record type (or maybe none). As well as reporting an
235 -- error we still want to typecheck the pattern, principally to
236 -- make sure that all the variables it binds are put into the
237 -- environment, else the type checker crashes later:
238 -- f (R { foo = (a,b) }) = a+b
239 -- If foo isn't one of R's fields, we don't want to crash when
240 -- typechecking the "a+b".
241 [] -> addErrTc (badFieldCon name field_label) `thenNF_Tc_`
242 newTyVarTy boxedTypeKind `thenNF_Tc_`
243 returnTc (error "Bogus selector Id", pat_ty)
245 -- The normal case, when the field comes from the right constructor
247 ASSERT( null extras )
248 tcLookupValue field_label `thenNF_Tc` \ sel_id ->
249 returnTc (sel_id, pat_ty)
250 ) `thenTc` \ (sel_id, pat_ty) ->
252 tcPat tc_bndr rhs_pat pat_ty `thenTc` \ (rhs_pat', lie_req2, tvs2, ids2, lie_avail2) ->
254 returnTc ((sel_id, rhs_pat', pun_flag) : rpats',
255 lie_req1 `plusLIE` lie_req2,
256 tvs1 `unionBags` tvs2,
257 ids1 `unionBags` ids2,
258 lie_avail1 `plusLIE` lie_avail2)
261 %************************************************************************
263 \subsection{Literals}
265 %************************************************************************
268 tcPat tc_bndr (LitPatIn lit@(HsLitLit s _)) pat_ty
269 -- cf tcExpr on LitLits
270 = tcLookupClassByKey cCallableClassKey `thenNF_Tc` \ cCallableClass ->
271 newDicts (LitLitOrigin (_UNPK_ s))
272 [mkClassPred cCallableClass [pat_ty]] `thenNF_Tc` \ (dicts, _) ->
273 returnTc (LitPat (HsLitLit s pat_ty) pat_ty, dicts, emptyBag, emptyBag, emptyLIE)
275 tcPat tc_bndr pat@(LitPatIn lit@(HsString _)) pat_ty
276 = unifyTauTy pat_ty stringTy `thenTc_`
277 tcLookupValueByKey eqStringIdKey `thenNF_Tc` \ eq_id ->
278 returnTc (NPat lit stringTy (HsVar eq_id `HsApp` HsLit lit),
279 emptyLIE, emptyBag, emptyBag, emptyLIE)
281 tcPat tc_bndr (LitPatIn simple_lit) pat_ty
282 = unifyTauTy pat_ty (simpleHsLitTy simple_lit) `thenTc_`
283 returnTc (LitPat simple_lit pat_ty, emptyLIE, emptyBag, emptyBag, emptyLIE)
285 tcPat tc_bndr pat@(NPatIn over_lit) pat_ty
286 = newOverloadedLit (PatOrigin pat) over_lit pat_ty `thenNF_Tc` \ (over_lit_expr, lie1) ->
287 tcLookupValueByKey eqClassOpKey `thenNF_Tc` \ eq_sel_id ->
288 newMethod origin eq_sel_id [pat_ty] `thenNF_Tc` \ (lie2, eq_id) ->
290 returnTc (NPat lit' pat_ty (HsApp (HsVar eq_id) over_lit_expr),
292 emptyBag, emptyBag, emptyLIE)
294 origin = PatOrigin pat
295 lit' = case over_lit of
296 HsIntegral i _ -> HsInteger i
297 HsFractional f _ -> HsRat f pat_ty
300 %************************************************************************
302 \subsection{n+k patterns}
304 %************************************************************************
307 tcPat tc_bndr pat@(NPlusKPatIn name lit@(HsIntegral i _) minus) pat_ty
308 = tc_bndr name pat_ty `thenTc` \ bndr_id ->
309 tcLookupValue minus `thenNF_Tc` \ minus_sel_id ->
310 tcLookupValueByKey geClassOpKey `thenNF_Tc` \ ge_sel_id ->
311 newOverloadedLit origin lit pat_ty `thenNF_Tc` \ (over_lit_expr, lie1) ->
312 newMethod origin ge_sel_id [pat_ty] `thenNF_Tc` \ (lie2, ge_id) ->
313 newMethod origin minus_sel_id [pat_ty] `thenNF_Tc` \ (lie3, minus_id) ->
315 returnTc (NPlusKPat bndr_id i pat_ty
316 (SectionR (HsVar ge_id) over_lit_expr)
317 (SectionR (HsVar minus_id) over_lit_expr),
318 lie1 `plusLIE` lie2 `plusLIE` lie3,
319 emptyBag, unitBag (name, bndr_id), emptyLIE)
321 origin = PatOrigin pat
324 %************************************************************************
326 \subsection{Lists of patterns}
328 %************************************************************************
333 tcPats :: (Name -> TcType -> TcM s TcId) -- How to deal with variables
334 -> [RenamedPat] -> [TcType] -- Excess 'expected types' discarded
336 LIE, -- Required by n+k and literal pats
338 Bag (Name, TcId), -- Ids bound by the pattern
339 LIE) -- Dicts bound by the pattern
341 tcPats tc_bndr [] tys = returnTc ([], emptyLIE, emptyBag, emptyBag, emptyLIE)
343 tcPats tc_bndr (ty:tys) (pat:pats)
344 = tcPat tc_bndr ty pat `thenTc` \ (pat', lie_req1, tvs1, ids1, lie_avail1) ->
345 tcPats tc_bndr tys pats `thenTc` \ (pats', lie_req2, tvs2, ids2, lie_avail2) ->
347 returnTc (pat':pats', lie_req1 `plusLIE` lie_req2,
348 tvs1 `unionBags` tvs2, ids1 `unionBags` ids2,
349 lie_avail1 `plusLIE` lie_avail2)
352 ------------------------------------------------------
354 simpleHsLitTy :: HsLit -> TcType
355 simpleHsLitTy (HsCharPrim c) = charPrimTy
356 simpleHsLitTy (HsStringPrim s) = addrPrimTy
357 simpleHsLitTy (HsInt i) = intTy
358 simpleHsLitTy (HsInteger i) = integerTy
359 simpleHsLitTy (HsIntPrim i) = intPrimTy
360 simpleHsLitTy (HsFloatPrim f) = floatPrimTy
361 simpleHsLitTy (HsDoublePrim d) = doublePrimTy
362 simpleHsLitTy (HsChar c) = charTy
363 simpleHsLitTy (HsString str) = stringTy
367 ------------------------------------------------------
369 tcConstructor pat con_name pat_ty
370 = -- Check that it's a constructor
371 tcLookupValue con_name `thenNF_Tc` \ con_id ->
372 case isDataConWrapId_maybe con_id of {
373 Nothing -> failWithTc (badCon con_id);
378 (tvs, _, ex_tvs, ex_theta, arg_tys, tycon) = dataConSig data_con
379 -- Ignore the theta; overloaded constructors only
380 -- behave differently when called, not when used for
383 tcInstTyVars (ex_tvs ++ tvs) `thenNF_Tc` \ (all_tvs', ty_args', tenv) ->
385 ex_theta' = substClasses tenv ex_theta
386 arg_tys' = map (substTy tenv) arg_tys
388 n_ex_tvs = length ex_tvs
389 ex_tvs' = take n_ex_tvs all_tvs'
390 result_ty = mkTyConApp tycon (drop n_ex_tvs ty_args')
392 newClassDicts (PatOrigin pat) ex_theta' `thenNF_Tc` \ (lie_avail, dicts) ->
394 -- Check overall type matches
395 unifyTauTy pat_ty result_ty `thenTc_`
397 returnTc (data_con, ex_tvs', dicts, lie_avail, arg_tys')
401 ------------------------------------------------------
403 tcConPat tc_bndr pat con_name arg_pats pat_ty
404 = tcAddErrCtxt (patCtxt pat) $
406 -- Check the constructor itself
407 tcConstructor pat con_name pat_ty `thenTc` \ (data_con, ex_tvs', dicts, lie_avail1, arg_tys') ->
409 -- Check correct arity
411 con_arity = dataConSourceArity data_con
412 no_of_args = length arg_pats
414 checkTc (con_arity == no_of_args)
415 (arityErr "Constructor" data_con con_arity no_of_args) `thenTc_`
418 tcPats tc_bndr arg_pats arg_tys' `thenTc` \ (arg_pats', lie_req, tvs, ids, lie_avail2) ->
420 returnTc (ConPat data_con pat_ty ex_tvs' dicts arg_pats',
422 listToBag ex_tvs' `unionBags` tvs,
424 lie_avail1 `plusLIE` lie_avail2)
428 %************************************************************************
430 \subsection{Errors and contexts}
432 %************************************************************************
435 patCtxt pat = hang (ptext SLIT("In the pattern:"))
438 badFieldCon :: Name -> Name -> SDoc
439 badFieldCon con field
440 = hsep [ptext SLIT("Constructor") <+> quotes (ppr con),
441 ptext SLIT("does not have field"), quotes (ppr field)]
443 polyPatSig :: TcType -> SDoc
445 = hang (ptext SLIT("Illegal polymorphic type signature in pattern:"))
448 badTypePat pat = ptext SLIT("Illegal type pattern") <+> ppr pat