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 {-# SOURCE #-} TcExpr( tcExpr )
13 import HsSyn ( InPat(..), OutPat(..), HsLit(..), HsExpr(..), Sig(..) )
14 import RnHsSyn ( RenamedPat )
15 import TcHsSyn ( TcPat, TcId )
18 import Inst ( Inst, OverloadedLit(..), InstOrigin(..),
19 emptyLIE, plusLIE, LIE,
20 newMethod, newOverloadedLit,
21 newDicts, instToIdBndr
23 import Name ( Name, getOccName, getSrcLoc )
24 import FieldLabel ( fieldLabelName )
25 import TcEnv ( tcLookupValue,
26 tcLookupValueByKey, newLocalId, badCon
28 import TcType ( TcType, TcTyVar, tcInstTyVars, newTyVarTy )
29 import TcMonoType ( tcHsType )
30 import TcUnify ( unifyTauTy, unifyListTy,
31 unifyTupleTy, unifyUnboxedTupleTy
35 import CmdLineOpts ( opt_IrrefutableTuples )
36 import DataCon ( DataCon, dataConSig, dataConFieldLabels, dataConSourceArity )
37 import Id ( Id, idType, isDataConId_maybe )
38 import Type ( Type, isTauTy, mkTyConApp, boxedTypeKind )
39 import Subst ( substTy, substTheta )
40 import TysPrim ( charPrimTy, intPrimTy, floatPrimTy,
41 doublePrimTy, addrPrimTy
43 import TysWiredIn ( charTy, stringTy, intTy )
44 import SrcLoc ( SrcLoc )
45 import Unique ( eqClassOpKey, geClassOpKey, minusClassOpKey )
47 import Util ( zipEqual )
52 %************************************************************************
54 \subsection{Variable patterns}
56 %************************************************************************
59 -- This is the right function to pass to tcPat when there are no signatures
60 tcPatBndr_NoSigs binder_name pat_ty
61 = -- Need to make a new, monomorphic, Id
62 -- The binder_name is already being used for the polymorphic Id
63 newLocalId (getOccName binder_name) pat_ty loc `thenNF_Tc` \ bndr_id ->
66 loc = getSrcLoc binder_name
70 %************************************************************************
72 \subsection{Typechecking patterns}
74 %************************************************************************
77 tcPat :: (Name -> TcType -> TcM s TcId) -- How to construct a suitable (monomorphic)
78 -- Id for variables found in the pattern
79 -- The TcType is the expected type, see note below
82 -> TcType -- Expected type derived from the context
83 -- In the case of a function with a rank-2 signature,
84 -- this type might be a forall type.
85 -- INVARIANT: if it is, the foralls will always be visible,
86 -- not hidden inside a mutable type variable
89 LIE, -- Required by n+k and literal pats
90 Bag TcTyVar, -- TyVars bound by the pattern
91 -- These are just the existentially-bound ones.
92 -- Any tyvars bound by *type signatures* in the
93 -- patterns are brought into scope before we begin.
94 Bag (Name, TcId), -- Ids bound by the pattern, along with the Name under
95 -- which it occurs in the pattern
96 -- The two aren't the same because we conjure up a new
97 -- local name for each variable.
98 LIE) -- Dicts or methods [see below] bound by the pattern
99 -- from existential constructor patterns
103 %************************************************************************
105 \subsection{Variables, wildcards, lazy pats, as-pats}
107 %************************************************************************
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 (NegPatIn pat) pat_ty
129 = tcPat tc_bndr (negate_lit pat) pat_ty
131 negate_lit (LitPatIn (HsInt i)) = LitPatIn (HsInt (-i))
132 negate_lit (LitPatIn (HsIntPrim i)) = LitPatIn (HsIntPrim (-i))
133 negate_lit (LitPatIn (HsFrac f)) = LitPatIn (HsFrac (-f))
134 negate_lit (LitPatIn (HsFloatPrim f)) = LitPatIn (HsFloatPrim (-f))
135 negate_lit (LitPatIn (HsDoublePrim f)) = LitPatIn (HsDoublePrim (-f))
136 negate_lit _ = panic "TcPat:negate_pat"
138 tcPat tc_bndr (ParPatIn parend_pat) pat_ty
139 = tcPat tc_bndr parend_pat pat_ty
141 tcPat tc_bndr (SigPatIn pat sig) pat_ty
142 = tcHsType sig `thenTc` \ sig_ty ->
144 -- Check that the signature isn't a polymorphic one, which
145 -- we don't permit (at present, anyway)
146 checkTc (isTauTy sig_ty) (polyPatSig sig_ty) `thenTc_`
148 unifyTauTy pat_ty sig_ty `thenTc_`
149 tcPat tc_bndr pat sig_ty
152 %************************************************************************
154 \subsection{Explicit lists and tuples}
156 %************************************************************************
159 tcPat tc_bndr pat_in@(ListPatIn pats) pat_ty
160 = tcAddErrCtxt (patCtxt pat_in) $
161 unifyListTy pat_ty `thenTc` \ elem_ty ->
162 tcPats tc_bndr pats (repeat elem_ty) `thenTc` \ (pats', lie_req, tvs, ids, lie_avail) ->
163 returnTc (ListPat elem_ty pats', lie_req, tvs, ids, lie_avail)
165 tcPat tc_bndr pat_in@(TuplePatIn pats boxed) pat_ty
166 = tcAddErrCtxt (patCtxt pat_in) $
169 then unifyTupleTy arity pat_ty
170 else unifyUnboxedTupleTy arity pat_ty) `thenTc` \ arg_tys ->
172 tcPats tc_bndr pats arg_tys `thenTc` \ (pats', lie_req, tvs, ids, lie_avail) ->
174 -- possibly do the "make all tuple-pats irrefutable" test:
176 unmangled_result = TuplePat pats' boxed
178 -- Under flag control turn a pattern (x,y,z) into ~(x,y,z)
179 -- so that we can experiment with lazy tuple-matching.
180 -- This is a pretty odd place to make the switch, but
181 -- it was easy to do.
183 possibly_mangled_result
184 | opt_IrrefutableTuples && boxed = LazyPat unmangled_result
185 | otherwise = unmangled_result
187 returnTc (possibly_mangled_result, lie_req, tvs, ids, lie_avail)
192 %************************************************************************
194 \subsection{Other constructors}
197 %************************************************************************
200 tcPat tc_bndr pat@(ConPatIn name arg_pats) pat_ty
201 = tcConPat tc_bndr pat name arg_pats pat_ty
203 tcPat tc_bndr pat@(ConOpPatIn pat1 op _ pat2) pat_ty
204 = tcConPat tc_bndr pat op [pat1, pat2] pat_ty
208 %************************************************************************
212 %************************************************************************
215 tcPat tc_bndr pat@(RecPatIn name rpats) pat_ty
216 = tcAddErrCtxt (patCtxt pat) $
218 -- Check the constructor itself
219 tcConstructor pat name pat_ty `thenTc` \ (data_con, ex_tvs, dicts, lie_avail1, arg_tys) ->
221 field_tys = zipEqual "tcPat"
222 (map fieldLabelName (dataConFieldLabels data_con))
227 tc_fields field_tys rpats `thenTc` \ (rpats', lie_req, tvs, ids, lie_avail2) ->
229 returnTc (RecPat data_con pat_ty ex_tvs dicts rpats',
231 listToBag ex_tvs `unionBags` tvs,
233 lie_avail1 `plusLIE` lie_avail2)
236 tc_fields field_tys []
237 = returnTc ([], emptyLIE, emptyBag, emptyBag, emptyLIE)
239 tc_fields field_tys ((field_label, rhs_pat, pun_flag) : rpats)
240 = tc_fields field_tys rpats `thenTc` \ (rpats', lie_req1, tvs1, ids1, lie_avail1) ->
242 (case [ty | (f,ty) <- field_tys, f == field_label] of
244 -- No matching field; chances are this field label comes from some
245 -- other record type (or maybe none). As well as reporting an
246 -- error we still want to typecheck the pattern, principally to
247 -- make sure that all the variables it binds are put into the
248 -- environment, else the type checker crashes later:
249 -- f (R { foo = (a,b) }) = a+b
250 -- If foo isn't one of R's fields, we don't want to crash when
251 -- typechecking the "a+b".
252 [] -> addErrTc (badFieldCon name field_label) `thenNF_Tc_`
253 newTyVarTy boxedTypeKind `thenNF_Tc_`
254 returnTc (error "Bogus selector Id", pat_ty)
256 -- The normal case, when the field comes from the right constructor
258 ASSERT( null extras )
259 tcLookupValue field_label `thenNF_Tc` \ sel_id ->
260 returnTc (sel_id, pat_ty)
261 ) `thenTc` \ (sel_id, pat_ty) ->
263 tcPat tc_bndr rhs_pat pat_ty `thenTc` \ (rhs_pat', lie_req2, tvs2, ids2, lie_avail2) ->
265 returnTc ((sel_id, rhs_pat', pun_flag) : rpats',
266 lie_req1 `plusLIE` lie_req2,
267 tvs1 `unionBags` tvs2,
268 ids1 `unionBags` ids2,
269 lie_avail1 `plusLIE` lie_avail2)
272 %************************************************************************
274 \subsection{Non-overloaded literals}
276 %************************************************************************
279 tcPat tc_bndr (LitPatIn lit@(HsChar _)) pat_ty = tcSimpleLitPat lit charTy pat_ty
280 tcPat tc_bndr (LitPatIn lit@(HsIntPrim _)) pat_ty = tcSimpleLitPat lit intPrimTy pat_ty
281 tcPat tc_bndr (LitPatIn lit@(HsCharPrim _)) pat_ty = tcSimpleLitPat lit charPrimTy pat_ty
282 tcPat tc_bndr (LitPatIn lit@(HsStringPrim _)) pat_ty = tcSimpleLitPat lit addrPrimTy pat_ty
283 tcPat tc_bndr (LitPatIn lit@(HsFloatPrim _)) pat_ty = tcSimpleLitPat lit floatPrimTy pat_ty
284 tcPat tc_bndr (LitPatIn lit@(HsDoublePrim _)) pat_ty = tcSimpleLitPat lit doublePrimTy pat_ty
286 tcPat tc_bndr (LitPatIn lit@(HsLitLit s)) pat_ty = tcSimpleLitPat lit intTy pat_ty
287 -- This one looks weird!
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 isDataConId_maybe con_id of {
391 Nothing -> failWithTc (badCon con_id);
396 (tvs, theta, 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' = substTheta 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 newDicts (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("Polymorphic type signature in pattern"))