2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[TcExpr]{Typecheck an expression}
7 module TcExpr ( tcApp, tcExpr, tcPolyExpr, tcId ) where
9 #include "HsVersions.h"
11 import HsSyn ( HsExpr(..), HsLit(..), ArithSeqInfo(..),
12 HsBinds(..), MonoBinds(..), Stmt(..), StmtCtxt(..),
13 mkMonoBind, nullMonoBinds
15 import RnHsSyn ( RenamedHsExpr, RenamedRecordBinds )
16 import TcHsSyn ( TcExpr, TcRecordBinds, mkHsConApp,
21 import BasicTypes ( RecFlag(..) )
23 import Inst ( Inst, InstOrigin(..), OverloadedLit(..),
24 LIE, emptyLIE, unitLIE, consLIE, plusLIE, plusLIEs,
26 newOverloadedLit, newMethod, newIPDict,
27 instOverloadedFun, newDicts, newClassDicts,
28 getIPsOfLIE, instToId, ipToId
30 import TcBinds ( tcBindsAndThen )
31 import TcEnv ( tcInstId,
32 tcLookupValue, tcLookupClassByKey,
34 tcExtendGlobalTyVars, tcLookupValueMaybe,
35 tcLookupTyCon, tcLookupDataCon
37 import TcMatches ( tcMatchesCase, tcMatchLambda, tcStmts )
38 import TcMonoType ( tcHsSigType, checkSigTyVars, sigCtxt )
39 import TcPat ( badFieldCon )
40 import TcSimplify ( tcSimplify, tcSimplifyAndCheck, partitionPredsOfLIE )
41 import TcType ( TcType, TcTauType,
43 tcInstTcType, tcSplitRhoTy,
44 newTyVarTy, newTyVarTy_OpenKind, zonkTcType )
46 import Class ( Class )
47 import FieldLabel ( FieldLabel, fieldLabelName, fieldLabelType
49 import Id ( idType, recordSelectorFieldLabel,
53 import DataCon ( dataConFieldLabels, dataConSig,
54 dataConStrictMarks, StrictnessMark(..)
56 import Name ( Name, getName )
57 import Type ( mkFunTy, mkAppTy, mkTyVarTy, mkTyVarTys,
59 splitFunTy_maybe, splitFunTys, isNotUsgTy,
61 splitForAllTys, splitRhoTy,
62 isTauTy, tyVarsOfType, tyVarsOfTypes,
63 isForAllTy, splitAlgTyConApp, splitAlgTyConApp_maybe,
64 boxedTypeKind, mkArrowKind,
67 import Subst ( mkTopTyVarSubst, substClasses )
68 import UsageSPUtils ( unannotTy )
69 import VarSet ( emptyVarSet, unionVarSet, elemVarSet, mkVarSet )
70 import TyCon ( tyConDataCons )
71 import TysPrim ( intPrimTy, charPrimTy, doublePrimTy,
72 floatPrimTy, addrPrimTy
74 import TysWiredIn ( boolTy, charTy, stringTy )
75 import PrelInfo ( ioTyCon_NAME )
76 import TcUnify ( unifyTauTy, unifyFunTy, unifyListTy, unifyTupleTy,
78 import Unique ( cCallableClassKey, cReturnableClassKey,
79 enumFromClassOpKey, enumFromThenClassOpKey,
80 enumFromToClassOpKey, enumFromThenToClassOpKey,
81 thenMClassOpKey, failMClassOpKey, returnMClassOpKey
84 import Maybes ( maybeToBool, mapMaybe )
85 import ListSetOps ( minusList )
87 import CmdLineOpts ( opt_WarnMissingFields )
91 %************************************************************************
93 \subsection{Main wrappers}
95 %************************************************************************
98 tcExpr :: RenamedHsExpr -- Expession to type check
99 -> TcType -- Expected type (could be a polytpye)
100 -> TcM s (TcExpr, LIE)
102 tcExpr expr ty | isForAllTy ty = -- Polymorphic case
103 tcPolyExpr expr ty `thenTc` \ (expr', lie, _, _, _) ->
104 returnTc (expr', lie)
106 | otherwise = -- Monomorphic case
111 %************************************************************************
113 \subsection{@tcPolyExpr@ typchecks an application}
115 %************************************************************************
118 -- tcPolyExpr is like tcMonoExpr, except that the expected type
119 -- can be a polymorphic one.
120 tcPolyExpr :: RenamedHsExpr
121 -> TcType -- Expected type
122 -> TcM s (TcExpr, LIE, -- Generalised expr with expected type, and LIE
123 TcExpr, TcTauType, LIE) -- Same thing, but instantiated; tau-type returned
125 tcPolyExpr arg expected_arg_ty
126 = -- Ha! The argument type of the function is a for-all type,
127 -- An example of rank-2 polymorphism.
129 -- To ensure that the forall'd type variables don't get unified with each
130 -- other or any other types, we make fresh copy of the alleged type
131 tcInstTcType expected_arg_ty `thenNF_Tc` \ (sig_tyvars, sig_rho) ->
133 (sig_theta, sig_tau) = splitRhoTy sig_rho
134 free_tyvars = tyVarsOfType expected_arg_ty
136 -- Type-check the arg and unify with expected type
137 tcMonoExpr arg sig_tau `thenTc` \ (arg', lie_arg) ->
139 -- Check that the sig_tyvars havn't been constrained
140 -- The interesting bit here is that we must include the free variables
141 -- of the expected arg ty. Here's an example:
142 -- runST (newVar True)
143 -- Here, if we don't make a check, we'll get a type (ST s (MutVar s Bool))
144 -- for (newVar True), with s fresh. Then we unify with the runST's arg type
145 -- forall s'. ST s' a. That unifies s' with s, and a with MutVar s Bool.
146 -- So now s' isn't unconstrained because it's linked to a.
147 -- Conclusion: include the free vars of the expected arg type in the
148 -- list of "free vars" for the signature check.
150 tcExtendGlobalTyVars free_tyvars $
151 tcAddErrCtxtM (sigCtxt sig_msg sig_tyvars sig_theta sig_tau) $
153 checkSigTyVars sig_tyvars free_tyvars `thenTc` \ zonked_sig_tyvars ->
155 newDicts SignatureOrigin sig_theta `thenNF_Tc` \ (sig_dicts, dict_ids) ->
156 -- ToDo: better origin
158 (text "the type signature of an expression")
159 (mkVarSet zonked_sig_tyvars)
160 sig_dicts lie_arg `thenTc` \ (free_insts, inst_binds) ->
163 -- This HsLet binds any Insts which came out of the simplification.
164 -- It's a bit out of place here, but using AbsBind involves inventing
165 -- a couple of new names which seems worse.
166 generalised_arg = TyLam zonked_sig_tyvars $
171 returnTc ( generalised_arg, free_insts,
172 arg', sig_tau, lie_arg )
174 sig_msg = ptext SLIT("When checking an expression type signature")
177 %************************************************************************
179 \subsection{The TAUT rules for variables}
181 %************************************************************************
184 tcMonoExpr :: RenamedHsExpr -- Expession to type check
185 -> TcTauType -- Expected type (could be a type variable)
186 -> TcM s (TcExpr, LIE)
188 tcMonoExpr (HsVar name) res_ty
189 = tcId name `thenNF_Tc` \ (expr', lie, id_ty) ->
190 unifyTauTy res_ty id_ty `thenTc_`
192 -- Check that the result type doesn't have any nested for-alls.
193 -- For example, a "build" on its own is no good; it must be
194 -- applied to something.
195 checkTc (isTauTy id_ty)
196 (lurkingRank2Err name id_ty) `thenTc_`
198 returnTc (expr', lie)
202 tcMonoExpr (HsIPVar name) res_ty
203 -- ZZ What's the `id' used for here...
204 = let id = mkVanillaId name res_ty in
205 tcGetInstLoc (OccurrenceOf id) `thenNF_Tc` \ loc ->
206 newIPDict name res_ty loc `thenNF_Tc` \ ip ->
207 returnNF_Tc (HsIPVar (instToId ip), unitLIE ip)
210 %************************************************************************
212 \subsection{Literals}
214 %************************************************************************
219 tcMonoExpr (HsLit (HsInt i)) res_ty
220 = newOverloadedLit (LiteralOrigin (HsInt i))
221 (OverloadedIntegral i)
222 res_ty `thenNF_Tc` \ stuff ->
225 tcMonoExpr (HsLit (HsFrac f)) res_ty
226 = newOverloadedLit (LiteralOrigin (HsFrac f))
227 (OverloadedFractional f)
228 res_ty `thenNF_Tc` \ stuff ->
232 tcMonoExpr (HsLit lit@(HsLitLit s)) res_ty
233 = tcLookupClassByKey cCallableClassKey `thenNF_Tc` \ cCallableClass ->
234 newClassDicts (LitLitOrigin (_UNPK_ s))
235 [(cCallableClass,[res_ty])] `thenNF_Tc` \ (dicts, _) ->
236 returnTc (HsLitOut lit res_ty, dicts)
242 tcMonoExpr (HsLit lit@(HsCharPrim c)) res_ty
243 = unifyTauTy res_ty charPrimTy `thenTc_`
244 returnTc (HsLitOut lit charPrimTy, emptyLIE)
246 tcMonoExpr (HsLit lit@(HsStringPrim s)) res_ty
247 = unifyTauTy res_ty addrPrimTy `thenTc_`
248 returnTc (HsLitOut lit addrPrimTy, emptyLIE)
250 tcMonoExpr (HsLit lit@(HsIntPrim i)) res_ty
251 = unifyTauTy res_ty intPrimTy `thenTc_`
252 returnTc (HsLitOut lit intPrimTy, emptyLIE)
254 tcMonoExpr (HsLit lit@(HsFloatPrim f)) res_ty
255 = unifyTauTy res_ty floatPrimTy `thenTc_`
256 returnTc (HsLitOut lit floatPrimTy, emptyLIE)
258 tcMonoExpr (HsLit lit@(HsDoublePrim d)) res_ty
259 = unifyTauTy res_ty doublePrimTy `thenTc_`
260 returnTc (HsLitOut lit doublePrimTy, emptyLIE)
263 Unoverloaded literals:
266 tcMonoExpr (HsLit lit@(HsChar c)) res_ty
267 = unifyTauTy res_ty charTy `thenTc_`
268 returnTc (HsLitOut lit charTy, emptyLIE)
270 tcMonoExpr (HsLit lit@(HsString str)) res_ty
271 = unifyTauTy res_ty stringTy `thenTc_`
272 returnTc (HsLitOut lit stringTy, emptyLIE)
275 %************************************************************************
277 \subsection{Other expression forms}
279 %************************************************************************
282 tcMonoExpr (HsPar expr) res_ty -- preserve parens so printing needn't guess where they go
283 = tcMonoExpr expr res_ty
285 -- perform the negate *before* overloading the integer, since the case
286 -- of minBound on Ints fails otherwise. Could be done elsewhere, but
287 -- convenient to do it here.
289 tcMonoExpr (NegApp (HsLit (HsInt i)) neg) res_ty
290 = tcMonoExpr (HsLit (HsInt (-i))) res_ty
292 tcMonoExpr (NegApp expr neg) res_ty
293 = tcMonoExpr (HsApp neg expr) res_ty
295 tcMonoExpr (HsLam match) res_ty
296 = tcMatchLambda match res_ty `thenTc` \ (match',lie) ->
297 returnTc (HsLam match', lie)
299 tcMonoExpr (HsApp e1 e2) res_ty = accum e1 [e2]
301 accum (HsApp e1 e2) args = accum e1 (e2:args)
303 = tcApp fun args res_ty `thenTc` \ (fun', args', lie) ->
304 returnTc (foldl HsApp fun' args', lie)
306 -- equivalent to (op e1) e2:
307 tcMonoExpr (OpApp arg1 op fix arg2) res_ty
308 = tcApp op [arg1,arg2] res_ty `thenTc` \ (op', [arg1', arg2'], lie) ->
309 returnTc (OpApp arg1' op' fix arg2', lie)
312 Note that the operators in sections are expected to be binary, and
313 a type error will occur if they aren't.
316 -- Left sections, equivalent to
323 tcMonoExpr in_expr@(SectionL arg op) res_ty
324 = tcApp op [arg] res_ty `thenTc` \ (op', [arg'], lie) ->
326 -- Check that res_ty is a function type
327 -- Without this check we barf in the desugarer on
329 -- because it tries to desugar to
330 -- f op = \r -> 3 op r
331 -- so (3 `op`) had better be a function!
332 tcAddErrCtxt (sectionLAppCtxt in_expr) $
333 unifyFunTy res_ty `thenTc_`
335 returnTc (SectionL arg' op', lie)
337 -- Right sections, equivalent to \ x -> x op expr, or
340 tcMonoExpr in_expr@(SectionR op expr) res_ty
341 = tcExpr_id op `thenTc` \ (op', lie1, op_ty) ->
342 tcAddErrCtxt (sectionRAppCtxt in_expr) $
343 split_fun_ty op_ty 2 {- two args -} `thenTc` \ ([arg1_ty, arg2_ty], op_res_ty) ->
344 tcMonoExpr expr arg2_ty `thenTc` \ (expr',lie2) ->
345 unifyTauTy res_ty (mkFunTy arg1_ty op_res_ty) `thenTc_`
346 returnTc (SectionR op' expr', lie1 `plusLIE` lie2)
349 The interesting thing about @ccall@ is that it is just a template
350 which we instantiate by filling in details about the types of its
351 argument and result (ie minimal typechecking is performed). So, the
352 basic story is that we allocate a load of type variables (to hold the
353 arg/result types); unify them with the args/result; and store them for
357 tcMonoExpr (HsCCall lbl args may_gc is_asm ignored_fake_result_ty) res_ty
358 = -- Get the callable and returnable classes.
359 tcLookupClassByKey cCallableClassKey `thenNF_Tc` \ cCallableClass ->
360 tcLookupClassByKey cReturnableClassKey `thenNF_Tc` \ cReturnableClass ->
361 tcLookupTyCon ioTyCon_NAME `thenNF_Tc` \ ioTyCon ->
363 new_arg_dict (arg, arg_ty)
364 = newClassDicts (CCallOrigin (_UNPK_ lbl) (Just arg))
365 [(cCallableClass, [arg_ty])] `thenNF_Tc` \ (arg_dicts, _) ->
366 returnNF_Tc arg_dicts -- Actually a singleton bag
368 result_origin = CCallOrigin (_UNPK_ lbl) Nothing {- Not an arg -}
372 let n_args = length args
373 tv_idxs | n_args == 0 = []
374 | otherwise = [1..n_args]
376 mapNF_Tc (\ _ -> newTyVarTy_OpenKind) tv_idxs `thenNF_Tc` \ arg_tys ->
377 tcMonoExprs args arg_tys `thenTc` \ (args', args_lie) ->
379 -- The argument types can be unboxed or boxed; the result
380 -- type must, however, be boxed since it's an argument to the IO
382 newTyVarTy boxedTypeKind `thenNF_Tc` \ result_ty ->
384 io_result_ty = mkTyConApp ioTyCon [result_ty]
385 [ioDataCon] = tyConDataCons ioTyCon
387 unifyTauTy res_ty io_result_ty `thenTc_`
389 -- Construct the extra insts, which encode the
390 -- constraints on the argument and result types.
391 mapNF_Tc new_arg_dict (zipEqual "tcMonoExpr:CCall" args arg_tys) `thenNF_Tc` \ ccarg_dicts_s ->
392 newClassDicts result_origin [(cReturnableClass, [result_ty])] `thenNF_Tc` \ (ccres_dict, _) ->
393 returnTc (HsCCall lbl args' may_gc is_asm io_result_ty,
394 foldr plusLIE ccres_dict ccarg_dicts_s `plusLIE` args_lie)
398 tcMonoExpr (HsSCC lbl expr) res_ty
399 = tcMonoExpr expr res_ty `thenTc` \ (expr', lie) ->
400 returnTc (HsSCC lbl expr', lie)
402 tcMonoExpr (HsLet binds expr) res_ty
405 binds -- Bindings to check
406 tc_expr `thenTc` \ (expr', lie) ->
407 returnTc (expr', lie)
409 tc_expr = tcMonoExpr expr res_ty `thenTc` \ (expr', lie) ->
410 returnTc (expr', lie)
411 combiner is_rec bind expr = HsLet (mkMonoBind bind [] is_rec) expr
413 tcMonoExpr in_expr@(HsCase scrut matches src_loc) res_ty
414 = tcAddSrcLoc src_loc $
415 tcAddErrCtxt (caseCtxt in_expr) $
417 -- Typecheck the case alternatives first.
418 -- The case patterns tend to give good type info to use
419 -- when typechecking the scrutinee. For example
422 -- will report that map is applied to too few arguments
424 -- Not only that, but it's better to check the matches on their
425 -- own, so that we get the expected results for scoped type variables.
427 -- (p::a, q::b) -> (q,p)
428 -- The above should work: the match (p,q) -> (q,p) is polymorphic as
429 -- claimed by the pattern signatures. But if we typechecked the
430 -- match with x in scope and x's type as the expected type, we'd be hosed.
432 tcMatchesCase matches res_ty `thenTc` \ (scrut_ty, matches', lie2) ->
434 tcAddErrCtxt (caseScrutCtxt scrut) (
435 tcMonoExpr scrut scrut_ty
436 ) `thenTc` \ (scrut',lie1) ->
438 returnTc (HsCase scrut' matches' src_loc, plusLIE lie1 lie2)
440 tcMonoExpr (HsIf pred b1 b2 src_loc) res_ty
441 = tcAddSrcLoc src_loc $
442 tcAddErrCtxt (predCtxt pred) (
443 tcMonoExpr pred boolTy ) `thenTc` \ (pred',lie1) ->
445 tcMonoExpr b1 res_ty `thenTc` \ (b1',lie2) ->
446 tcMonoExpr b2 res_ty `thenTc` \ (b2',lie3) ->
447 returnTc (HsIf pred' b1' b2' src_loc, plusLIE lie1 (plusLIE lie2 lie3))
451 tcMonoExpr expr@(HsDo do_or_lc stmts src_loc) res_ty
452 = tcDoStmts do_or_lc stmts src_loc res_ty
456 tcMonoExpr in_expr@(ExplicitList exprs) res_ty -- Non-empty list
457 = unifyListTy res_ty `thenTc` \ elt_ty ->
458 mapAndUnzipTc (tc_elt elt_ty) exprs `thenTc` \ (exprs', lies) ->
459 returnTc (ExplicitListOut elt_ty exprs', plusLIEs lies)
462 = tcAddErrCtxt (listCtxt expr) $
463 tcMonoExpr expr elt_ty
465 tcMonoExpr (ExplicitTuple exprs boxed) res_ty
467 then unifyTupleTy (length exprs) res_ty
468 else unifyUnboxedTupleTy (length exprs) res_ty
469 ) `thenTc` \ arg_tys ->
470 mapAndUnzipTc (\ (expr, arg_ty) -> tcMonoExpr expr arg_ty)
471 (exprs `zip` arg_tys) -- we know they're of equal length.
472 `thenTc` \ (exprs', lies) ->
473 returnTc (ExplicitTuple exprs' boxed, plusLIEs lies)
475 tcMonoExpr expr@(RecordCon con_name rbinds) res_ty
476 = tcAddErrCtxt (recordConCtxt expr) $
477 tcId con_name `thenNF_Tc` \ (con_expr, con_lie, con_tau) ->
479 (_, record_ty) = splitFunTys con_tau
481 ASSERT( maybeToBool (splitAlgTyConApp_maybe record_ty ) )
482 unifyTauTy res_ty record_ty `thenTc_`
484 -- Check that the record bindings match the constructor
485 -- con_name is syntactically constrained to be a data constructor
486 tcLookupDataCon con_name `thenTc` \ (data_con, _, _) ->
488 bad_fields = badFields rbinds data_con
490 if not (null bad_fields) then
491 mapNF_Tc (addErrTc . badFieldCon con_name) bad_fields `thenNF_Tc_`
492 failTc -- Fail now, because tcRecordBinds will crash on a bad field
495 -- Typecheck the record bindings
496 tcRecordBinds record_ty rbinds `thenTc` \ (rbinds', rbinds_lie) ->
499 missing_s_fields = missingStrictFields rbinds data_con
501 checkTcM (null missing_s_fields)
502 (mapNF_Tc (addErrTc . missingStrictFieldCon con_name) missing_s_fields `thenNF_Tc_`
503 returnNF_Tc ()) `thenNF_Tc_`
505 missing_fields = missingFields rbinds data_con
507 checkTcM (not (opt_WarnMissingFields && not (null missing_fields)))
508 (mapNF_Tc ((warnTc True) . missingFieldCon con_name) missing_fields `thenNF_Tc_`
509 returnNF_Tc ()) `thenNF_Tc_`
511 returnTc (RecordConOut data_con con_expr rbinds', con_lie `plusLIE` rbinds_lie)
513 -- The main complication with RecordUpd is that we need to explicitly
514 -- handle the *non-updated* fields. Consider:
516 -- data T a b = MkT1 { fa :: a, fb :: b }
517 -- | MkT2 { fa :: a, fc :: Int -> Int }
518 -- | MkT3 { fd :: a }
520 -- upd :: T a b -> c -> T a c
521 -- upd t x = t { fb = x}
523 -- The type signature on upd is correct (i.e. the result should not be (T a b))
524 -- because upd should be equivalent to:
526 -- upd t x = case t of
527 -- MkT1 p q -> MkT1 p x
528 -- MkT2 a b -> MkT2 p b
529 -- MkT3 d -> error ...
531 -- So we need to give a completely fresh type to the result record,
532 -- and then constrain it by the fields that are *not* updated ("p" above).
534 -- Note that because MkT3 doesn't contain all the fields being updated,
535 -- its RHS is simply an error, so it doesn't impose any type constraints
537 -- All this is done in STEP 4 below.
539 tcMonoExpr expr@(RecordUpd record_expr rbinds) res_ty
540 = tcAddErrCtxt (recordUpdCtxt expr) $
543 -- Check that the field names are really field names
544 ASSERT( not (null rbinds) )
546 field_names = [field_name | (field_name, _, _) <- rbinds]
548 mapNF_Tc tcLookupValueMaybe field_names `thenNF_Tc` \ maybe_sel_ids ->
550 bad_guys = [field_name | (field_name, maybe_sel_id) <- field_names `zip` maybe_sel_ids,
553 Just sel_id -> not (isRecordSelector sel_id)
556 mapNF_Tc (addErrTc . notSelector) bad_guys `thenTc_`
557 if not (null bad_guys) then
562 -- Figure out the tycon and data cons from the first field name
564 (Just sel_id : _) = maybe_sel_ids
565 (_, tau) = ASSERT( isNotUsgTy (idType sel_id) )
566 splitForAllTys (idType sel_id)
567 Just (data_ty, _) = splitFunTy_maybe tau -- Must succeed since sel_id is a selector
568 (tycon, _, data_cons) = splitAlgTyConApp data_ty
569 (con_tyvars, theta, _, _, _, _) = dataConSig (head data_cons)
571 tcInstTyVars con_tyvars `thenNF_Tc` \ (_, result_inst_tys, _) ->
574 -- Check that at least one constructor has all the named fields
575 -- i.e. has an empty set of bad fields returned by badFields
576 checkTc (any (null . badFields rbinds) data_cons)
577 (badFieldsUpd rbinds) `thenTc_`
580 -- Typecheck the update bindings.
581 -- (Do this after checking for bad fields in case there's a field that
582 -- doesn't match the constructor.)
584 result_record_ty = mkTyConApp tycon result_inst_tys
586 unifyTauTy res_ty result_record_ty `thenTc_`
587 tcRecordBinds result_record_ty rbinds `thenTc` \ (rbinds', rbinds_lie) ->
590 -- Use the un-updated fields to find a vector of booleans saying
591 -- which type arguments must be the same in updatee and result.
593 -- WARNING: this code assumes that all data_cons in a common tycon
594 -- have FieldLabels abstracted over the same tyvars.
596 upd_field_lbls = [recordSelectorFieldLabel sel_id | (sel_id, _, _) <- rbinds']
597 con_field_lbls_s = map dataConFieldLabels data_cons
599 -- A constructor is only relevant to this process if
600 -- it contains all the fields that are being updated
601 relevant_field_lbls_s = filter is_relevant con_field_lbls_s
602 is_relevant con_field_lbls = all (`elem` con_field_lbls) upd_field_lbls
604 non_upd_field_lbls = concat relevant_field_lbls_s `minusList` upd_field_lbls
605 common_tyvars = tyVarsOfTypes (map fieldLabelType non_upd_field_lbls)
607 mk_inst_ty (tyvar, result_inst_ty)
608 | tyvar `elemVarSet` common_tyvars = returnNF_Tc result_inst_ty -- Same as result type
609 | otherwise = newTyVarTy boxedTypeKind -- Fresh type
611 mapNF_Tc mk_inst_ty (zip con_tyvars result_inst_tys) `thenNF_Tc` \ inst_tys ->
614 -- Typecheck the expression to be updated
616 record_ty = mkTyConApp tycon inst_tys
618 tcMonoExpr record_expr record_ty `thenTc` \ (record_expr', record_lie) ->
621 -- Figure out the LIE we need. We have to generate some
622 -- dictionaries for the data type context, since we are going to
623 -- do some construction.
625 -- What dictionaries do we need? For the moment we assume that all
626 -- data constructors have the same context, and grab it from the first
627 -- constructor. If they have varying contexts then we'd have to
628 -- union the ones that could participate in the update.
630 (tyvars, theta, _, _, _, _) = dataConSig (head data_cons)
631 inst_env = mkTopTyVarSubst tyvars result_inst_tys
632 theta' = substClasses inst_env theta
634 newClassDicts RecordUpdOrigin theta' `thenNF_Tc` \ (con_lie, dicts) ->
637 returnTc (RecordUpdOut record_expr' result_record_ty dicts rbinds',
638 con_lie `plusLIE` record_lie `plusLIE` rbinds_lie)
640 tcMonoExpr (ArithSeqIn seq@(From expr)) res_ty
641 = unifyListTy res_ty `thenTc` \ elt_ty ->
642 tcMonoExpr expr elt_ty `thenTc` \ (expr', lie1) ->
644 tcLookupValueByKey enumFromClassOpKey `thenNF_Tc` \ sel_id ->
645 newMethod (ArithSeqOrigin seq)
646 sel_id [elt_ty] `thenNF_Tc` \ (lie2, enum_from_id) ->
648 returnTc (ArithSeqOut (HsVar enum_from_id) (From expr'),
651 tcMonoExpr in_expr@(ArithSeqIn seq@(FromThen expr1 expr2)) res_ty
652 = tcAddErrCtxt (arithSeqCtxt in_expr) $
653 unifyListTy res_ty `thenTc` \ elt_ty ->
654 tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) ->
655 tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) ->
656 tcLookupValueByKey enumFromThenClassOpKey `thenNF_Tc` \ sel_id ->
657 newMethod (ArithSeqOrigin seq)
658 sel_id [elt_ty] `thenNF_Tc` \ (lie3, enum_from_then_id) ->
660 returnTc (ArithSeqOut (HsVar enum_from_then_id)
661 (FromThen expr1' expr2'),
662 lie1 `plusLIE` lie2 `plusLIE` lie3)
664 tcMonoExpr in_expr@(ArithSeqIn seq@(FromTo expr1 expr2)) res_ty
665 = tcAddErrCtxt (arithSeqCtxt in_expr) $
666 unifyListTy res_ty `thenTc` \ elt_ty ->
667 tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) ->
668 tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) ->
669 tcLookupValueByKey enumFromToClassOpKey `thenNF_Tc` \ sel_id ->
670 newMethod (ArithSeqOrigin seq)
671 sel_id [elt_ty] `thenNF_Tc` \ (lie3, enum_from_to_id) ->
673 returnTc (ArithSeqOut (HsVar enum_from_to_id)
674 (FromTo expr1' expr2'),
675 lie1 `plusLIE` lie2 `plusLIE` lie3)
677 tcMonoExpr in_expr@(ArithSeqIn seq@(FromThenTo expr1 expr2 expr3)) res_ty
678 = tcAddErrCtxt (arithSeqCtxt in_expr) $
679 unifyListTy res_ty `thenTc` \ elt_ty ->
680 tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) ->
681 tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) ->
682 tcMonoExpr expr3 elt_ty `thenTc` \ (expr3',lie3) ->
683 tcLookupValueByKey enumFromThenToClassOpKey `thenNF_Tc` \ sel_id ->
684 newMethod (ArithSeqOrigin seq)
685 sel_id [elt_ty] `thenNF_Tc` \ (lie4, eft_id) ->
687 returnTc (ArithSeqOut (HsVar eft_id)
688 (FromThenTo expr1' expr2' expr3'),
689 lie1 `plusLIE` lie2 `plusLIE` lie3 `plusLIE` lie4)
692 %************************************************************************
694 \subsection{Expressions type signatures}
696 %************************************************************************
699 tcMonoExpr in_expr@(ExprWithTySig expr poly_ty) res_ty
700 = tcSetErrCtxt (exprSigCtxt in_expr) $
701 tcHsSigType poly_ty `thenTc` \ sig_tc_ty ->
703 if not (isForAllTy sig_tc_ty) then
705 unifyTauTy sig_tc_ty res_ty `thenTc_`
706 tcMonoExpr expr sig_tc_ty
708 else -- Signature is polymorphic
709 tcPolyExpr expr sig_tc_ty `thenTc` \ (_, _, expr, expr_ty, lie) ->
711 -- Now match the signature type with res_ty.
712 -- We must not do this earlier, because res_ty might well
713 -- mention variables free in the environment, and we'd get
714 -- bogus complaints about not being able to for-all the
716 unifyTauTy res_ty expr_ty `thenTc_`
718 -- If everything is ok, return the stuff unchanged, except for
719 -- the effect of any substutions etc. We simply discard the
720 -- result of the tcSimplifyAndCheck (inside tcPolyExpr), except for any default
721 -- resolution it may have done, which is recorded in the
726 Implicit Parameter bindings.
729 tcMonoExpr (HsWith expr binds) res_ty
730 = tcMonoExpr expr res_ty `thenTc` \ (expr', lie) ->
731 tcIPBinds binds `thenTc` \ (binds', types, lie2) ->
732 partitionPredsOfLIE isBound lie `thenTc` \ (ips, lie', dict_binds) ->
733 pprTrace "tcMonoExpr With" (ppr (ips, lie', dict_binds)) $
734 let expr'' = if nullMonoBinds dict_binds
736 else HsLet (mkMonoBind (revBinds dict_binds) [] NonRecursive)
739 tcCheckIPBinds binds' types ips `thenTc_`
740 returnTc (HsWith expr'' binds', lie' `plusLIE` lie2)
742 = case ipName_maybe p of
743 Just n -> n `elem` names
745 names = map fst binds
746 -- revBinds is used because tcSimplify outputs the bindings
747 -- out-of-order. it's not a problem elsewhere because these
748 -- bindings are normally used in a recursive let
749 -- ZZ probably need to find a better solution
750 revBinds (b1 `AndMonoBinds` b2) =
751 (revBinds b2) `AndMonoBinds` (revBinds b1)
754 tcIPBinds ((name, expr) : binds)
755 = newTyVarTy_OpenKind `thenTc` \ ty ->
756 tcGetSrcLoc `thenTc` \ loc ->
757 let id = ipToId name ty loc in
758 tcMonoExpr expr ty `thenTc` \ (expr', lie) ->
759 zonkTcType ty `thenTc` \ ty' ->
760 tcIPBinds binds `thenTc` \ (binds', types, lie2) ->
761 returnTc ((id, expr') : binds', ty : types, lie `plusLIE` lie2)
762 tcIPBinds [] = returnTc ([], [], emptyLIE)
764 tcCheckIPBinds binds types ips
765 = foldrTc tcCheckIPBind (getIPsOfLIE ips) (zip binds types)
767 -- ZZ how do we use the loc?
768 tcCheckIPBind bt@((v, _), t1) ((n, t2) : ips) | getName v == n
769 = unifyTauTy t1 t2 `thenTc_`
770 tcCheckIPBind bt ips `thenTc` \ ips' ->
772 tcCheckIPBind bt (ip : ips)
773 = tcCheckIPBind bt ips `thenTc` \ ips' ->
779 Typecheck expression which in most cases will be an Id.
782 tcExpr_id :: RenamedHsExpr
788 HsVar name -> tcId name `thenNF_Tc` \ stuff ->
790 other -> newTyVarTy_OpenKind `thenNF_Tc` \ id_ty ->
791 tcMonoExpr id_expr id_ty `thenTc` \ (id_expr', lie_id) ->
792 returnTc (id_expr', lie_id, id_ty)
795 %************************************************************************
797 \subsection{@tcApp@ typchecks an application}
799 %************************************************************************
803 tcApp :: RenamedHsExpr -> [RenamedHsExpr] -- Function and args
804 -> TcType -- Expected result type of application
805 -> TcM s (TcExpr, [TcExpr], -- Translated fun and args
808 tcApp fun args res_ty
809 = -- First type-check the function
810 tcExpr_id fun `thenTc` \ (fun', lie_fun, fun_ty) ->
812 tcAddErrCtxt (wrongArgsCtxt "too many" fun args) (
813 split_fun_ty fun_ty (length args)
814 ) `thenTc` \ (expected_arg_tys, actual_result_ty) ->
816 -- Unify with expected result before type-checking the args
817 -- This is when we might detect a too-few args situation
818 tcAddErrCtxtM (checkArgsCtxt fun args res_ty actual_result_ty) (
819 unifyTauTy res_ty actual_result_ty
822 -- Now typecheck the args
823 mapAndUnzipTc (tcArg fun)
824 (zip3 args expected_arg_tys [1..]) `thenTc` \ (args', lie_args_s) ->
826 -- Check that the result type doesn't have any nested for-alls.
827 -- For example, a "build" on its own is no good; it must be applied to something.
828 checkTc (isTauTy actual_result_ty)
829 (lurkingRank2Err fun fun_ty) `thenTc_`
831 returnTc (fun', args', lie_fun `plusLIE` plusLIEs lie_args_s)
834 -- If an error happens we try to figure out whether the
835 -- function has been given too many or too few arguments,
837 checkArgsCtxt fun args expected_res_ty actual_res_ty tidy_env
838 = zonkTcType expected_res_ty `thenNF_Tc` \ exp_ty' ->
839 zonkTcType actual_res_ty `thenNF_Tc` \ act_ty' ->
841 (env1, exp_ty'') = tidyOpenType tidy_env exp_ty'
842 (env2, act_ty'') = tidyOpenType env1 act_ty'
843 (exp_args, _) = splitFunTys exp_ty''
844 (act_args, _) = splitFunTys act_ty''
846 message | length exp_args < length act_args = wrongArgsCtxt "too few" fun args
847 | length exp_args > length act_args = wrongArgsCtxt "too many" fun args
848 | otherwise = appCtxt fun args
850 returnNF_Tc (env2, message)
853 split_fun_ty :: TcType -- The type of the function
854 -> Int -- Number of arguments
855 -> TcM s ([TcType], -- Function argument types
856 TcType) -- Function result types
858 split_fun_ty fun_ty 0
859 = returnTc ([], fun_ty)
861 split_fun_ty fun_ty n
862 = -- Expect the function to have type A->B
863 unifyFunTy fun_ty `thenTc` \ (arg_ty, res_ty) ->
864 split_fun_ty res_ty (n-1) `thenTc` \ (arg_tys, final_res_ty) ->
865 returnTc (arg_ty:arg_tys, final_res_ty)
869 tcArg :: RenamedHsExpr -- The function (for error messages)
870 -> (RenamedHsExpr, TcType, Int) -- Actual argument and expected arg type
871 -> TcM s (TcExpr, LIE) -- Resulting argument and LIE
873 tcArg the_fun (arg, expected_arg_ty, arg_no)
874 = tcAddErrCtxt (funAppCtxt the_fun arg arg_no) $
875 tcExpr arg expected_arg_ty
879 %************************************************************************
881 \subsection{@tcId@ typchecks an identifier occurrence}
883 %************************************************************************
885 Between the renamer and the first invocation of the UsageSP inference,
886 identifiers read from interface files will have usage information in
887 their types, whereas other identifiers will not. The unannotTy here
888 in @tcId@ prevents this information from pointlessly propagating
889 further prior to the first usage inference.
892 tcId :: Name -> NF_TcM s (TcExpr, LIE, TcType)
895 = -- Look up the Id and instantiate its type
896 tcLookupValueMaybe name `thenNF_Tc` \ maybe_local ->
899 Just tc_id -> instantiate_it (OccurrenceOf tc_id) (HsVar tc_id) (unannotTy (idType tc_id))
901 Nothing -> tcLookupValue name `thenNF_Tc` \ id ->
902 tcInstId id `thenNF_Tc` \ (tyvars, theta, tau) ->
903 instantiate_it2 (OccurrenceOf id) (HsVar id) tyvars theta tau
906 -- The instantiate_it loop runs round instantiating the Id.
907 -- It has to be a loop because we are now prepared to entertain
909 -- f:: forall a. Eq a => forall b. Baz b => tau
910 -- We want to instantiate this to
911 -- f2::tau {f2 = f1 b (Baz b), f1 = f a (Eq a)}
912 instantiate_it orig fun ty
913 = tcInstTcType ty `thenNF_Tc` \ (tyvars, rho) ->
914 tcSplitRhoTy rho `thenNF_Tc` \ (theta, tau) ->
915 instantiate_it2 orig fun tyvars theta tau
917 instantiate_it2 orig fun tyvars theta tau
918 = if null theta then -- Is it overloaded?
919 returnNF_Tc (mkHsTyApp fun arg_tys, emptyLIE, tau)
921 -- Yes, it's overloaded
922 instOverloadedFun orig fun arg_tys theta tau `thenNF_Tc` \ (fun', lie1) ->
923 instantiate_it orig fun' tau `thenNF_Tc` \ (expr, lie2, final_tau) ->
924 returnNF_Tc (expr, lie1 `plusLIE` lie2, final_tau)
927 arg_tys = mkTyVarTys tyvars
930 %************************************************************************
932 \subsection{@tcDoStmts@ typechecks a {\em list} of do statements}
934 %************************************************************************
937 tcDoStmts do_or_lc stmts src_loc res_ty
938 = -- get the Monad and MonadZero classes
939 -- create type consisting of a fresh monad tyvar
940 ASSERT( not (null stmts) )
941 tcAddSrcLoc src_loc $
943 newTyVarTy (mkArrowKind boxedTypeKind boxedTypeKind) `thenNF_Tc` \ m ->
944 newTyVarTy boxedTypeKind `thenNF_Tc` \ elt_ty ->
945 unifyTauTy res_ty (mkAppTy m elt_ty) `thenTc_`
947 -- If it's a comprehension we're dealing with,
948 -- force it to be a list comprehension.
949 -- (as of Haskell 98, monad comprehensions are no more.)
951 ListComp -> unifyListTy res_ty `thenTc_` returnTc ()
952 _ -> returnTc ()) `thenTc_`
954 tcStmts do_or_lc (mkAppTy m) stmts elt_ty `thenTc` \ (stmts', stmts_lie) ->
956 -- Build the then and zero methods in case we need them
957 -- It's important that "then" and "return" appear just once in the final LIE,
958 -- not only for typechecker efficiency, but also because otherwise during
959 -- simplification we end up with silly stuff like
960 -- then = case d of (t,r) -> t
962 -- where the second "then" sees that it already exists in the "available" stuff.
964 tcLookupValueByKey returnMClassOpKey `thenNF_Tc` \ return_sel_id ->
965 tcLookupValueByKey thenMClassOpKey `thenNF_Tc` \ then_sel_id ->
966 tcLookupValueByKey failMClassOpKey `thenNF_Tc` \ fail_sel_id ->
967 newMethod DoOrigin return_sel_id [m] `thenNF_Tc` \ (return_lie, return_id) ->
968 newMethod DoOrigin then_sel_id [m] `thenNF_Tc` \ (then_lie, then_id) ->
969 newMethod DoOrigin fail_sel_id [m] `thenNF_Tc` \ (fail_lie, fail_id) ->
971 monad_lie = then_lie `plusLIE` return_lie `plusLIE` fail_lie
973 returnTc (HsDoOut do_or_lc stmts' return_id then_id fail_id res_ty src_loc,
974 stmts_lie `plusLIE` monad_lie)
978 %************************************************************************
980 \subsection{Record bindings}
982 %************************************************************************
984 Game plan for record bindings
985 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
988 1. look up "field", to find its selector Id, which must have type
989 forall a1..an. T a1 .. an -> tau
990 where tau is the type of the field.
992 2. Instantiate this type
994 3. Unify the (T a1 .. an) part with the "expected result type", which
995 is passed in. This checks that all the field labels come from the
998 4. Type check the value using tcArg, passing tau as the expected
1001 This extends OK when the field types are universally quantified.
1003 Actually, to save excessive creation of fresh type variables,
1008 :: TcType -- Expected type of whole record
1009 -> RenamedRecordBinds
1010 -> TcM s (TcRecordBinds, LIE)
1012 tcRecordBinds expected_record_ty rbinds
1013 = mapAndUnzipTc do_bind rbinds `thenTc` \ (rbinds', lies) ->
1014 returnTc (rbinds', plusLIEs lies)
1016 do_bind (field_label, rhs, pun_flag)
1017 = tcLookupValue field_label `thenNF_Tc` \ sel_id ->
1018 ASSERT( isRecordSelector sel_id )
1019 -- This lookup and assertion will surely succeed, because
1020 -- we check that the fields are indeed record selectors
1021 -- before calling tcRecordBinds
1023 tcInstId sel_id `thenNF_Tc` \ (_, _, tau) ->
1025 -- Record selectors all have type
1026 -- forall a1..an. T a1 .. an -> tau
1027 ASSERT( maybeToBool (splitFunTy_maybe tau) )
1029 -- Selector must have type RecordType -> FieldType
1030 Just (record_ty, field_ty) = splitFunTy_maybe tau
1032 unifyTauTy expected_record_ty record_ty `thenTc_`
1033 tcPolyExpr rhs field_ty `thenTc` \ (rhs', lie, _, _, _) ->
1034 returnTc ((sel_id, rhs', pun_flag), lie)
1036 badFields rbinds data_con
1037 = [field_name | (field_name, _, _) <- rbinds,
1038 not (field_name `elem` field_names)
1041 field_names = map fieldLabelName (dataConFieldLabels data_con)
1043 missingStrictFields rbinds data_con
1044 = [ fn | fn <- strict_field_names,
1045 not (fn `elem` field_names_used)
1048 field_names_used = [ field_name | (field_name, _, _) <- rbinds ]
1049 strict_field_names = mapMaybe isStrict field_info
1051 isStrict (fl, MarkedStrict) = Just (fieldLabelName fl)
1052 isStrict _ = Nothing
1054 field_info = zip (dataConFieldLabels data_con)
1055 (dataConStrictMarks data_con)
1057 missingFields rbinds data_con
1058 = [ fn | fn <- non_strict_field_names, not (fn `elem` field_names_used) ]
1060 field_names_used = [ field_name | (field_name, _, _) <- rbinds ]
1062 -- missing strict fields have already been flagged as
1063 -- being so, so leave them out here.
1064 non_strict_field_names = mapMaybe isn'tStrict field_info
1066 isn'tStrict (fl, MarkedStrict) = Nothing
1067 isn'tStrict (fl, _) = Just (fieldLabelName fl)
1069 field_info = zip (dataConFieldLabels data_con)
1070 (dataConStrictMarks data_con)
1074 %************************************************************************
1076 \subsection{@tcMonoExprs@ typechecks a {\em list} of expressions}
1078 %************************************************************************
1081 tcMonoExprs :: [RenamedHsExpr] -> [TcType] -> TcM s ([TcExpr], LIE)
1083 tcMonoExprs [] [] = returnTc ([], emptyLIE)
1084 tcMonoExprs (expr:exprs) (ty:tys)
1085 = tcMonoExpr expr ty `thenTc` \ (expr', lie1) ->
1086 tcMonoExprs exprs tys `thenTc` \ (exprs', lie2) ->
1087 returnTc (expr':exprs', lie1 `plusLIE` lie2)
1091 % =================================================
1098 pp_nest_hang :: String -> SDoc -> SDoc
1099 pp_nest_hang lbl stuff = nest 2 (hang (text lbl) 4 stuff)
1102 Boring and alphabetical:
1105 = hang (ptext SLIT("In an arithmetic sequence:")) 4 (ppr expr)
1108 = hang (ptext SLIT("In the case expression:")) 4 (ppr expr)
1111 = hang (ptext SLIT("In the scrutinee of a case expression:")) 4 (ppr expr)
1114 = hang (ptext SLIT("In an expression with a type signature:"))
1118 = hang (ptext SLIT("In the list element:")) 4 (ppr expr)
1121 = hang (ptext SLIT("In the predicate expression:")) 4 (ppr expr)
1123 sectionRAppCtxt expr
1124 = hang (ptext SLIT("In the right section:")) 4 (ppr expr)
1126 sectionLAppCtxt expr
1127 = hang (ptext SLIT("In the left section:")) 4 (ppr expr)
1129 funAppCtxt fun arg arg_no
1130 = hang (hsep [ ptext SLIT("In the"), speakNth arg_no, ptext SLIT("argument of"),
1131 quotes (ppr fun) <> text ", namely"])
1132 4 (quotes (ppr arg))
1134 wrongArgsCtxt too_many_or_few fun args
1135 = hang (ptext SLIT("Probable cause:") <+> quotes (ppr fun)
1136 <+> ptext SLIT("is applied to") <+> text too_many_or_few
1137 <+> ptext SLIT("arguments in the call"))
1138 4 (parens (ppr the_app))
1140 the_app = foldl HsApp fun args -- Used in error messages
1143 = ptext SLIT("In the application") <+> quotes (ppr the_app)
1145 the_app = foldl HsApp fun args -- Used in error messages
1147 lurkingRank2Err fun fun_ty
1148 = hang (hsep [ptext SLIT("Illegal use of"), quotes (ppr fun)])
1149 4 (vcat [ptext SLIT("It is applied to too few arguments"),
1150 ptext SLIT("so that the result type has for-alls in it")])
1152 rank2ArgCtxt arg expected_arg_ty
1153 = ptext SLIT("In a polymorphic function argument:") <+> ppr arg
1156 = hang (ptext SLIT("No constructor has all these fields:"))
1157 4 (pprQuotedList fields)
1159 fields = [field | (field, _, _) <- rbinds]
1161 recordUpdCtxt expr = ptext SLIT("In the record update:") <+> ppr expr
1162 recordConCtxt expr = ptext SLIT("In the record construction:") <+> ppr expr
1165 = hsep [quotes (ppr field), ptext SLIT("is not a record selector")]
1167 illegalCcallTyErr isArg ty
1168 = hang (hsep [ptext SLIT("Unacceptable"), arg_or_res, ptext SLIT("type in _ccall_ or _casm_:")])
1172 | isArg = ptext SLIT("argument")
1173 | otherwise = ptext SLIT("result")
1176 missingStrictFieldCon :: Name -> Name -> SDoc
1177 missingStrictFieldCon con field
1178 = hsep [ptext SLIT("Constructor") <+> quotes (ppr con),
1179 ptext SLIT("does not have the required strict field"), quotes (ppr field)]
1181 missingFieldCon :: Name -> Name -> SDoc
1182 missingFieldCon con field
1183 = hsep [ptext SLIT("Field") <+> quotes (ppr field),
1184 ptext SLIT("is not initialised")]