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 tcLookupTyConByKey, 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 TcImprove ( tcImprove )
42 import TcType ( TcType, TcTauType,
44 tcInstTcType, tcSplitRhoTy,
45 newTyVarTy, newTyVarTy_OpenKind, zonkTcType )
47 import Class ( Class )
48 import FieldLabel ( FieldLabel, fieldLabelName, fieldLabelType, fieldLabelTyCon )
49 import Id ( idType, recordSelectorFieldLabel, isRecordSelector,
52 import DataCon ( dataConFieldLabels, dataConSig,
53 dataConStrictMarks, StrictnessMark(..)
55 import Name ( Name, getName )
56 import Type ( mkFunTy, mkAppTy, mkTyVarTy, mkTyVarTys,
58 splitFunTy_maybe, splitFunTys, isNotUsgTy,
59 mkTyConApp, splitSigmaTy,
61 isTauTy, tyVarsOfType, tyVarsOfTypes,
62 isSigmaTy, splitAlgTyConApp, splitAlgTyConApp_maybe,
63 boxedTypeKind, mkArrowKind,
66 import TyCon ( TyCon, tyConTyVars )
67 import Subst ( mkTopTyVarSubst, substClasses, substTy )
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 TcUnify ( unifyTauTy, unifyFunTy, unifyListTy, unifyTupleTy )
76 import Unique ( cCallableClassKey, cReturnableClassKey,
77 enumFromClassOpKey, enumFromThenClassOpKey,
78 enumFromToClassOpKey, enumFromThenToClassOpKey,
79 thenMClassOpKey, failMClassOpKey, returnMClassOpKey, ioTyConKey
82 import Maybes ( maybeToBool, mapMaybe )
83 import ListSetOps ( minusList )
85 import CmdLineOpts ( opt_WarnMissingFields )
89 %************************************************************************
91 \subsection{Main wrappers}
93 %************************************************************************
96 tcExpr :: RenamedHsExpr -- Expession to type check
97 -> TcType -- Expected type (could be a polytpye)
98 -> TcM s (TcExpr, LIE)
100 tcExpr expr ty | isSigmaTy ty = -- Polymorphic case
101 tcPolyExpr expr ty `thenTc` \ (expr', lie, _, _, _) ->
102 returnTc (expr', lie)
104 | otherwise = -- Monomorphic case
109 %************************************************************************
111 \subsection{@tcPolyExpr@ typchecks an application}
113 %************************************************************************
116 -- tcPolyExpr is like tcMonoExpr, except that the expected type
117 -- can be a polymorphic one.
118 tcPolyExpr :: RenamedHsExpr
119 -> TcType -- Expected type
120 -> TcM s (TcExpr, LIE, -- Generalised expr with expected type, and LIE
121 TcExpr, TcTauType, LIE) -- Same thing, but instantiated; tau-type returned
123 tcPolyExpr arg expected_arg_ty
124 = -- Ha! The argument type of the function is a for-all type,
125 -- An example of rank-2 polymorphism.
127 -- To ensure that the forall'd type variables don't get unified with each
128 -- other or any other types, we make fresh copy of the alleged type
129 tcInstTcType expected_arg_ty `thenNF_Tc` \ (sig_tyvars, sig_rho) ->
131 (sig_theta, sig_tau) = splitRhoTy sig_rho
132 free_tyvars = tyVarsOfType expected_arg_ty
134 -- Type-check the arg and unify with expected type
135 tcMonoExpr arg sig_tau `thenTc` \ (arg', lie_arg) ->
137 -- Check that the sig_tyvars havn't been constrained
138 -- The interesting bit here is that we must include the free variables
139 -- of the expected arg ty. Here's an example:
140 -- runST (newVar True)
141 -- Here, if we don't make a check, we'll get a type (ST s (MutVar s Bool))
142 -- for (newVar True), with s fresh. Then we unify with the runST's arg type
143 -- forall s'. ST s' a. That unifies s' with s, and a with MutVar s Bool.
144 -- So now s' isn't unconstrained because it's linked to a.
145 -- Conclusion: include the free vars of the expected arg type in the
146 -- list of "free vars" for the signature check.
148 tcExtendGlobalTyVars free_tyvars $
149 tcAddErrCtxtM (sigCtxt sig_msg sig_tyvars sig_theta sig_tau) $
151 checkSigTyVars sig_tyvars free_tyvars `thenTc` \ zonked_sig_tyvars ->
153 newDicts SignatureOrigin sig_theta `thenNF_Tc` \ (sig_dicts, dict_ids) ->
154 tcImprove (sig_dicts `plusLIE` lie_arg) `thenTc_`
155 -- ToDo: better origin
157 (text "the type signature of an expression")
158 (mkVarSet zonked_sig_tyvars)
159 sig_dicts lie_arg `thenTc` \ (free_insts, inst_binds) ->
162 -- This HsLet binds any Insts which came out of the simplification.
163 -- It's a bit out of place here, but using AbsBind involves inventing
164 -- a couple of new names which seems worse.
165 generalised_arg = TyLam zonked_sig_tyvars $
170 returnTc ( generalised_arg, free_insts,
171 arg', sig_tau, lie_arg )
173 sig_msg = ptext SLIT("When checking an expression type signature")
176 %************************************************************************
178 \subsection{The TAUT rules for variables}
180 %************************************************************************
183 tcMonoExpr :: RenamedHsExpr -- Expession to type check
184 -> TcTauType -- Expected type (could be a type variable)
185 -> TcM s (TcExpr, LIE)
187 tcMonoExpr (HsVar name) res_ty
188 = tcId name `thenNF_Tc` \ (expr', lie, id_ty) ->
189 unifyTauTy res_ty id_ty `thenTc_`
191 -- Check that the result type doesn't have any nested for-alls.
192 -- For example, a "build" on its own is no good; it must be
193 -- applied to something.
194 checkTc (isTauTy id_ty)
195 (lurkingRank2Err name id_ty) `thenTc_`
197 returnTc (expr', lie)
201 tcMonoExpr (HsIPVar name) res_ty
202 -- ZZ What's the `id' used for here...
203 = let id = mkVanillaId name res_ty in
204 tcGetInstLoc (OccurrenceOf id) `thenNF_Tc` \ loc ->
205 newIPDict name res_ty loc `thenNF_Tc` \ ip ->
206 returnNF_Tc (HsIPVar (instToId ip), unitLIE ip)
209 %************************************************************************
211 \subsection{Literals}
213 %************************************************************************
218 tcMonoExpr (HsLit (HsInt i)) res_ty
219 = newOverloadedLit (LiteralOrigin (HsInt i))
220 (OverloadedIntegral i)
221 res_ty `thenNF_Tc` \ stuff ->
224 tcMonoExpr (HsLit (HsFrac f)) res_ty
225 = newOverloadedLit (LiteralOrigin (HsFrac f))
226 (OverloadedFractional f)
227 res_ty `thenNF_Tc` \ stuff ->
231 tcMonoExpr (HsLit lit@(HsLitLit s)) res_ty
232 = tcLookupClassByKey cCallableClassKey `thenNF_Tc` \ cCallableClass ->
233 newClassDicts (LitLitOrigin (_UNPK_ s))
234 [(cCallableClass,[res_ty])] `thenNF_Tc` \ (dicts, _) ->
235 returnTc (HsLitOut lit res_ty, dicts)
241 tcMonoExpr (HsLit lit@(HsCharPrim c)) res_ty
242 = unifyTauTy res_ty charPrimTy `thenTc_`
243 returnTc (HsLitOut lit charPrimTy, emptyLIE)
245 tcMonoExpr (HsLit lit@(HsStringPrim s)) res_ty
246 = unifyTauTy res_ty addrPrimTy `thenTc_`
247 returnTc (HsLitOut lit addrPrimTy, emptyLIE)
249 tcMonoExpr (HsLit lit@(HsIntPrim i)) res_ty
250 = unifyTauTy res_ty intPrimTy `thenTc_`
251 returnTc (HsLitOut lit intPrimTy, emptyLIE)
253 tcMonoExpr (HsLit lit@(HsFloatPrim f)) res_ty
254 = unifyTauTy res_ty floatPrimTy `thenTc_`
255 returnTc (HsLitOut lit floatPrimTy, emptyLIE)
257 tcMonoExpr (HsLit lit@(HsDoublePrim d)) res_ty
258 = unifyTauTy res_ty doublePrimTy `thenTc_`
259 returnTc (HsLitOut lit doublePrimTy, emptyLIE)
262 Unoverloaded literals:
265 tcMonoExpr (HsLit lit@(HsChar c)) res_ty
266 = unifyTauTy res_ty charTy `thenTc_`
267 returnTc (HsLitOut lit charTy, emptyLIE)
269 tcMonoExpr (HsLit lit@(HsString str)) res_ty
270 = unifyTauTy res_ty stringTy `thenTc_`
271 returnTc (HsLitOut lit stringTy, emptyLIE)
274 %************************************************************************
276 \subsection{Other expression forms}
278 %************************************************************************
281 tcMonoExpr (HsPar expr) res_ty -- preserve parens so printing needn't guess where they go
282 = tcMonoExpr expr res_ty
284 -- perform the negate *before* overloading the integer, since the case
285 -- of minBound on Ints fails otherwise. Could be done elsewhere, but
286 -- convenient to do it here.
288 tcMonoExpr (NegApp (HsLit (HsInt i)) neg) res_ty
289 = tcMonoExpr (HsLit (HsInt (-i))) res_ty
291 tcMonoExpr (NegApp expr neg) res_ty
292 = tcMonoExpr (HsApp neg expr) res_ty
294 tcMonoExpr (HsLam match) res_ty
295 = tcMatchLambda match res_ty `thenTc` \ (match',lie) ->
296 returnTc (HsLam match', lie)
298 tcMonoExpr (HsApp e1 e2) res_ty = accum e1 [e2]
300 accum (HsApp e1 e2) args = accum e1 (e2:args)
302 = tcApp fun args res_ty `thenTc` \ (fun', args', lie) ->
303 returnTc (foldl HsApp fun' args', lie)
305 -- equivalent to (op e1) e2:
306 tcMonoExpr (OpApp arg1 op fix arg2) res_ty
307 = tcApp op [arg1,arg2] res_ty `thenTc` \ (op', [arg1', arg2'], lie) ->
308 returnTc (OpApp arg1' op' fix arg2', lie)
311 Note that the operators in sections are expected to be binary, and
312 a type error will occur if they aren't.
315 -- Left sections, equivalent to
322 tcMonoExpr in_expr@(SectionL arg op) res_ty
323 = tcApp op [arg] res_ty `thenTc` \ (op', [arg'], lie) ->
325 -- Check that res_ty is a function type
326 -- Without this check we barf in the desugarer on
328 -- because it tries to desugar to
329 -- f op = \r -> 3 op r
330 -- so (3 `op`) had better be a function!
331 tcAddErrCtxt (sectionLAppCtxt in_expr) $
332 unifyFunTy res_ty `thenTc_`
334 returnTc (SectionL arg' op', lie)
336 -- Right sections, equivalent to \ x -> x op expr, or
339 tcMonoExpr in_expr@(SectionR op expr) res_ty
340 = tcExpr_id op `thenTc` \ (op', lie1, op_ty) ->
341 tcAddErrCtxt (sectionRAppCtxt in_expr) $
342 split_fun_ty op_ty 2 {- two args -} `thenTc` \ ([arg1_ty, arg2_ty], op_res_ty) ->
343 tcMonoExpr expr arg2_ty `thenTc` \ (expr',lie2) ->
344 unifyTauTy res_ty (mkFunTy arg1_ty op_res_ty) `thenTc_`
345 returnTc (SectionR op' expr', lie1 `plusLIE` lie2)
348 The interesting thing about @ccall@ is that it is just a template
349 which we instantiate by filling in details about the types of its
350 argument and result (ie minimal typechecking is performed). So, the
351 basic story is that we allocate a load of type variables (to hold the
352 arg/result types); unify them with the args/result; and store them for
356 tcMonoExpr (HsCCall lbl args may_gc is_asm ignored_fake_result_ty) res_ty
357 = -- Get the callable and returnable classes.
358 tcLookupClassByKey cCallableClassKey `thenNF_Tc` \ cCallableClass ->
359 tcLookupClassByKey cReturnableClassKey `thenNF_Tc` \ cReturnableClass ->
360 tcLookupTyConByKey ioTyConKey `thenNF_Tc` \ ioTyCon ->
362 new_arg_dict (arg, arg_ty)
363 = newClassDicts (CCallOrigin (_UNPK_ lbl) (Just arg))
364 [(cCallableClass, [arg_ty])] `thenNF_Tc` \ (arg_dicts, _) ->
365 returnNF_Tc arg_dicts -- Actually a singleton bag
367 result_origin = CCallOrigin (_UNPK_ lbl) Nothing {- Not an arg -}
371 let n_args = length args
372 tv_idxs | n_args == 0 = []
373 | otherwise = [1..n_args]
375 mapNF_Tc (\ _ -> newTyVarTy_OpenKind) tv_idxs `thenNF_Tc` \ arg_tys ->
376 tcMonoExprs args arg_tys `thenTc` \ (args', args_lie) ->
378 -- The argument types can be unboxed or boxed; the result
379 -- type must, however, be boxed since it's an argument to the IO
381 newTyVarTy boxedTypeKind `thenNF_Tc` \ result_ty ->
383 io_result_ty = mkTyConApp ioTyCon [result_ty]
385 unifyTauTy res_ty io_result_ty `thenTc_`
387 -- Construct the extra insts, which encode the
388 -- constraints on the argument and result types.
389 mapNF_Tc new_arg_dict (zipEqual "tcMonoExpr:CCall" args arg_tys) `thenNF_Tc` \ ccarg_dicts_s ->
390 newClassDicts result_origin [(cReturnableClass, [result_ty])] `thenNF_Tc` \ (ccres_dict, _) ->
391 returnTc (HsCCall lbl args' may_gc is_asm io_result_ty,
392 foldr plusLIE ccres_dict ccarg_dicts_s `plusLIE` args_lie)
396 tcMonoExpr (HsSCC lbl expr) res_ty
397 = tcMonoExpr expr res_ty `thenTc` \ (expr', lie) ->
398 returnTc (HsSCC lbl expr', lie)
400 tcMonoExpr (HsLet binds expr) res_ty
403 binds -- Bindings to check
404 tc_expr `thenTc` \ (expr', lie) ->
405 returnTc (expr', lie)
407 tc_expr = tcMonoExpr expr res_ty `thenTc` \ (expr', lie) ->
408 returnTc (expr', lie)
409 combiner is_rec bind expr = HsLet (mkMonoBind bind [] is_rec) expr
411 tcMonoExpr in_expr@(HsCase scrut matches src_loc) res_ty
412 = tcAddSrcLoc src_loc $
413 tcAddErrCtxt (caseCtxt in_expr) $
415 -- Typecheck the case alternatives first.
416 -- The case patterns tend to give good type info to use
417 -- when typechecking the scrutinee. For example
420 -- will report that map is applied to too few arguments
422 -- Not only that, but it's better to check the matches on their
423 -- own, so that we get the expected results for scoped type variables.
425 -- (p::a, q::b) -> (q,p)
426 -- The above should work: the match (p,q) -> (q,p) is polymorphic as
427 -- claimed by the pattern signatures. But if we typechecked the
428 -- match with x in scope and x's type as the expected type, we'd be hosed.
430 tcMatchesCase matches res_ty `thenTc` \ (scrut_ty, matches', lie2) ->
432 tcAddErrCtxt (caseScrutCtxt scrut) (
433 tcMonoExpr scrut scrut_ty
434 ) `thenTc` \ (scrut',lie1) ->
436 returnTc (HsCase scrut' matches' src_loc, plusLIE lie1 lie2)
438 tcMonoExpr (HsIf pred b1 b2 src_loc) res_ty
439 = tcAddSrcLoc src_loc $
440 tcAddErrCtxt (predCtxt pred) (
441 tcMonoExpr pred boolTy ) `thenTc` \ (pred',lie1) ->
443 tcMonoExpr b1 res_ty `thenTc` \ (b1',lie2) ->
444 tcMonoExpr b2 res_ty `thenTc` \ (b2',lie3) ->
445 returnTc (HsIf pred' b1' b2' src_loc, plusLIE lie1 (plusLIE lie2 lie3))
449 tcMonoExpr expr@(HsDo do_or_lc stmts src_loc) res_ty
450 = tcDoStmts do_or_lc stmts src_loc res_ty
454 tcMonoExpr in_expr@(ExplicitList exprs) res_ty -- Non-empty list
455 = unifyListTy res_ty `thenTc` \ elt_ty ->
456 mapAndUnzipTc (tc_elt elt_ty) exprs `thenTc` \ (exprs', lies) ->
457 returnTc (ExplicitListOut elt_ty exprs', plusLIEs lies)
460 = tcAddErrCtxt (listCtxt expr) $
461 tcMonoExpr expr elt_ty
463 tcMonoExpr (ExplicitTuple exprs boxity) res_ty
464 = unifyTupleTy boxity (length exprs) res_ty `thenTc` \ arg_tys ->
465 mapAndUnzipTc (\ (expr, arg_ty) -> tcMonoExpr expr arg_ty)
466 (exprs `zip` arg_tys) -- we know they're of equal length.
467 `thenTc` \ (exprs', lies) ->
468 returnTc (ExplicitTuple exprs' boxity, plusLIEs lies)
470 tcMonoExpr expr@(RecordCon con_name rbinds) res_ty
471 = tcAddErrCtxt (recordConCtxt expr) $
472 tcId con_name `thenNF_Tc` \ (con_expr, con_lie, con_tau) ->
474 (_, record_ty) = splitFunTys con_tau
475 (tycon, ty_args, _) = splitAlgTyConApp record_ty
477 ASSERT( maybeToBool (splitAlgTyConApp_maybe record_ty ) )
478 unifyTauTy res_ty record_ty `thenTc_`
480 -- Check that the record bindings match the constructor
481 -- con_name is syntactically constrained to be a data constructor
482 tcLookupDataCon con_name `thenTc` \ (data_con, _, _) ->
484 bad_fields = badFields rbinds data_con
486 if not (null bad_fields) then
487 mapNF_Tc (addErrTc . badFieldCon con_name) bad_fields `thenNF_Tc_`
488 failTc -- Fail now, because tcRecordBinds will crash on a bad field
491 -- Typecheck the record bindings
492 tcRecordBinds tycon ty_args rbinds `thenTc` \ (rbinds', rbinds_lie) ->
495 missing_s_fields = missingStrictFields rbinds data_con
497 checkTcM (null missing_s_fields)
498 (mapNF_Tc (addErrTc . missingStrictFieldCon con_name) missing_s_fields `thenNF_Tc_`
499 returnNF_Tc ()) `thenNF_Tc_`
501 missing_fields = missingFields rbinds data_con
503 checkTcM (not (opt_WarnMissingFields && not (null missing_fields)))
504 (mapNF_Tc ((warnTc True) . missingFieldCon con_name) missing_fields `thenNF_Tc_`
505 returnNF_Tc ()) `thenNF_Tc_`
507 returnTc (RecordConOut data_con con_expr rbinds', con_lie `plusLIE` rbinds_lie)
509 -- The main complication with RecordUpd is that we need to explicitly
510 -- handle the *non-updated* fields. Consider:
512 -- data T a b = MkT1 { fa :: a, fb :: b }
513 -- | MkT2 { fa :: a, fc :: Int -> Int }
514 -- | MkT3 { fd :: a }
516 -- upd :: T a b -> c -> T a c
517 -- upd t x = t { fb = x}
519 -- The type signature on upd is correct (i.e. the result should not be (T a b))
520 -- because upd should be equivalent to:
522 -- upd t x = case t of
523 -- MkT1 p q -> MkT1 p x
524 -- MkT2 a b -> MkT2 p b
525 -- MkT3 d -> error ...
527 -- So we need to give a completely fresh type to the result record,
528 -- and then constrain it by the fields that are *not* updated ("p" above).
530 -- Note that because MkT3 doesn't contain all the fields being updated,
531 -- its RHS is simply an error, so it doesn't impose any type constraints
533 -- All this is done in STEP 4 below.
535 tcMonoExpr expr@(RecordUpd record_expr rbinds) res_ty
536 = tcAddErrCtxt (recordUpdCtxt expr) $
539 -- Check that the field names are really field names
540 ASSERT( not (null rbinds) )
542 field_names = [field_name | (field_name, _, _) <- rbinds]
544 mapNF_Tc tcLookupValueMaybe field_names `thenNF_Tc` \ maybe_sel_ids ->
546 bad_guys = [field_name | (field_name, maybe_sel_id) <- field_names `zip` maybe_sel_ids,
549 Just sel_id -> not (isRecordSelector sel_id)
552 mapNF_Tc (addErrTc . notSelector) bad_guys `thenTc_`
553 if not (null bad_guys) then
558 -- Figure out the tycon and data cons from the first field name
560 (Just sel_id : _) = maybe_sel_ids
561 (_, _, tau) = ASSERT( isNotUsgTy (idType sel_id) )
562 splitSigmaTy (idType sel_id) -- Selectors can be overloaded
563 -- when the data type has a context
564 Just (data_ty, _) = splitFunTy_maybe tau -- Must succeed since sel_id is a selector
565 (tycon, _, data_cons) = splitAlgTyConApp data_ty
566 (con_tyvars, _, _, _, _, _) = dataConSig (head data_cons)
568 tcInstTyVars con_tyvars `thenNF_Tc` \ (_, result_inst_tys, _) ->
571 -- Check that at least one constructor has all the named fields
572 -- i.e. has an empty set of bad fields returned by badFields
573 checkTc (any (null . badFields rbinds) data_cons)
574 (badFieldsUpd rbinds) `thenTc_`
577 -- Typecheck the update bindings.
578 -- (Do this after checking for bad fields in case there's a field that
579 -- doesn't match the constructor.)
581 result_record_ty = mkTyConApp tycon result_inst_tys
583 unifyTauTy res_ty result_record_ty `thenTc_`
584 tcRecordBinds tycon result_inst_tys rbinds `thenTc` \ (rbinds', rbinds_lie) ->
587 -- Use the un-updated fields to find a vector of booleans saying
588 -- which type arguments must be the same in updatee and result.
590 -- WARNING: this code assumes that all data_cons in a common tycon
591 -- have FieldLabels abstracted over the same tyvars.
593 upd_field_lbls = [recordSelectorFieldLabel sel_id | (sel_id, _, _) <- rbinds']
594 con_field_lbls_s = map dataConFieldLabels data_cons
596 -- A constructor is only relevant to this process if
597 -- it contains all the fields that are being updated
598 relevant_field_lbls_s = filter is_relevant con_field_lbls_s
599 is_relevant con_field_lbls = all (`elem` con_field_lbls) upd_field_lbls
601 non_upd_field_lbls = concat relevant_field_lbls_s `minusList` upd_field_lbls
602 common_tyvars = tyVarsOfTypes (map fieldLabelType non_upd_field_lbls)
604 mk_inst_ty (tyvar, result_inst_ty)
605 | tyvar `elemVarSet` common_tyvars = returnNF_Tc result_inst_ty -- Same as result type
606 | otherwise = newTyVarTy boxedTypeKind -- Fresh type
608 mapNF_Tc mk_inst_ty (zip con_tyvars result_inst_tys) `thenNF_Tc` \ inst_tys ->
611 -- Typecheck the expression to be updated
613 record_ty = mkTyConApp tycon inst_tys
615 tcMonoExpr record_expr record_ty `thenTc` \ (record_expr', record_lie) ->
618 -- Figure out the LIE we need. We have to generate some
619 -- dictionaries for the data type context, since we are going to
620 -- do some construction.
622 -- What dictionaries do we need? For the moment we assume that all
623 -- data constructors have the same context, and grab it from the first
624 -- constructor. If they have varying contexts then we'd have to
625 -- union the ones that could participate in the update.
627 (tyvars, theta, _, _, _, _) = dataConSig (head data_cons)
628 inst_env = mkTopTyVarSubst tyvars result_inst_tys
629 theta' = substClasses inst_env theta
631 newClassDicts RecordUpdOrigin theta' `thenNF_Tc` \ (con_lie, dicts) ->
634 returnTc (RecordUpdOut record_expr' result_record_ty dicts rbinds',
635 con_lie `plusLIE` record_lie `plusLIE` rbinds_lie)
637 tcMonoExpr (ArithSeqIn seq@(From expr)) res_ty
638 = unifyListTy res_ty `thenTc` \ elt_ty ->
639 tcMonoExpr expr elt_ty `thenTc` \ (expr', lie1) ->
641 tcLookupValueByKey enumFromClassOpKey `thenNF_Tc` \ sel_id ->
642 newMethod (ArithSeqOrigin seq)
643 sel_id [elt_ty] `thenNF_Tc` \ (lie2, enum_from_id) ->
645 returnTc (ArithSeqOut (HsVar enum_from_id) (From expr'),
648 tcMonoExpr in_expr@(ArithSeqIn seq@(FromThen expr1 expr2)) res_ty
649 = tcAddErrCtxt (arithSeqCtxt in_expr) $
650 unifyListTy res_ty `thenTc` \ elt_ty ->
651 tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) ->
652 tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) ->
653 tcLookupValueByKey enumFromThenClassOpKey `thenNF_Tc` \ sel_id ->
654 newMethod (ArithSeqOrigin seq)
655 sel_id [elt_ty] `thenNF_Tc` \ (lie3, enum_from_then_id) ->
657 returnTc (ArithSeqOut (HsVar enum_from_then_id)
658 (FromThen expr1' expr2'),
659 lie1 `plusLIE` lie2 `plusLIE` lie3)
661 tcMonoExpr in_expr@(ArithSeqIn seq@(FromTo expr1 expr2)) res_ty
662 = tcAddErrCtxt (arithSeqCtxt in_expr) $
663 unifyListTy res_ty `thenTc` \ elt_ty ->
664 tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) ->
665 tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) ->
666 tcLookupValueByKey enumFromToClassOpKey `thenNF_Tc` \ sel_id ->
667 newMethod (ArithSeqOrigin seq)
668 sel_id [elt_ty] `thenNF_Tc` \ (lie3, enum_from_to_id) ->
670 returnTc (ArithSeqOut (HsVar enum_from_to_id)
671 (FromTo expr1' expr2'),
672 lie1 `plusLIE` lie2 `plusLIE` lie3)
674 tcMonoExpr in_expr@(ArithSeqIn seq@(FromThenTo expr1 expr2 expr3)) res_ty
675 = tcAddErrCtxt (arithSeqCtxt in_expr) $
676 unifyListTy res_ty `thenTc` \ elt_ty ->
677 tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) ->
678 tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) ->
679 tcMonoExpr expr3 elt_ty `thenTc` \ (expr3',lie3) ->
680 tcLookupValueByKey enumFromThenToClassOpKey `thenNF_Tc` \ sel_id ->
681 newMethod (ArithSeqOrigin seq)
682 sel_id [elt_ty] `thenNF_Tc` \ (lie4, eft_id) ->
684 returnTc (ArithSeqOut (HsVar eft_id)
685 (FromThenTo expr1' expr2' expr3'),
686 lie1 `plusLIE` lie2 `plusLIE` lie3 `plusLIE` lie4)
689 %************************************************************************
691 \subsection{Expressions type signatures}
693 %************************************************************************
696 tcMonoExpr in_expr@(ExprWithTySig expr poly_ty) res_ty
697 = tcSetErrCtxt (exprSigCtxt in_expr) $
698 tcHsSigType poly_ty `thenTc` \ sig_tc_ty ->
700 if not (isSigmaTy sig_tc_ty) then
702 unifyTauTy sig_tc_ty res_ty `thenTc_`
703 tcMonoExpr expr sig_tc_ty
705 else -- Signature is polymorphic
706 tcPolyExpr expr sig_tc_ty `thenTc` \ (_, _, expr, expr_ty, lie) ->
708 -- Now match the signature type with res_ty.
709 -- We must not do this earlier, because res_ty might well
710 -- mention variables free in the environment, and we'd get
711 -- bogus complaints about not being able to for-all the
713 unifyTauTy res_ty expr_ty `thenTc_`
715 -- If everything is ok, return the stuff unchanged, except for
716 -- the effect of any substutions etc. We simply discard the
717 -- result of the tcSimplifyAndCheck (inside tcPolyExpr), except for any default
718 -- resolution it may have done, which is recorded in the
723 Implicit Parameter bindings.
726 tcMonoExpr (HsWith expr binds) res_ty
727 = tcMonoExpr expr res_ty `thenTc` \ (expr', lie) ->
728 tcIPBinds binds `thenTc` \ (binds', types, lie2) ->
729 partitionPredsOfLIE isBound lie `thenTc` \ (ips, lie', dict_binds) ->
730 let expr'' = if nullMonoBinds dict_binds
732 else HsLet (mkMonoBind (revBinds dict_binds) [] NonRecursive)
735 tcCheckIPBinds binds' types ips `thenTc_`
736 returnTc (HsWith expr'' binds', lie' `plusLIE` lie2)
738 = case ipName_maybe p of
739 Just n -> n `elem` names
741 names = map fst binds
742 -- revBinds is used because tcSimplify outputs the bindings
743 -- out-of-order. it's not a problem elsewhere because these
744 -- bindings are normally used in a recursive let
745 -- ZZ probably need to find a better solution
746 revBinds (b1 `AndMonoBinds` b2) =
747 (revBinds b2) `AndMonoBinds` (revBinds b1)
750 tcIPBinds ((name, expr) : binds)
751 = newTyVarTy_OpenKind `thenTc` \ ty ->
752 tcGetSrcLoc `thenTc` \ loc ->
753 let id = ipToId name ty loc in
754 tcMonoExpr expr ty `thenTc` \ (expr', lie) ->
755 zonkTcType ty `thenTc` \ ty' ->
756 tcIPBinds binds `thenTc` \ (binds', types, lie2) ->
757 returnTc ((id, expr') : binds', ty : types, lie `plusLIE` lie2)
758 tcIPBinds [] = returnTc ([], [], emptyLIE)
760 tcCheckIPBinds binds types ips
761 = foldrTc tcCheckIPBind (getIPsOfLIE ips) (zip binds types)
763 -- ZZ how do we use the loc?
764 tcCheckIPBind bt@((v, _), t1) ((n, t2) : ips) | getName v == n
765 = unifyTauTy t1 t2 `thenTc_`
766 tcCheckIPBind bt ips `thenTc` \ ips' ->
768 tcCheckIPBind bt (ip : ips)
769 = tcCheckIPBind bt ips `thenTc` \ ips' ->
775 Typecheck expression which in most cases will be an Id.
778 tcExpr_id :: RenamedHsExpr
784 HsVar name -> tcId name `thenNF_Tc` \ stuff ->
786 other -> newTyVarTy_OpenKind `thenNF_Tc` \ id_ty ->
787 tcMonoExpr id_expr id_ty `thenTc` \ (id_expr', lie_id) ->
788 returnTc (id_expr', lie_id, id_ty)
791 %************************************************************************
793 \subsection{@tcApp@ typchecks an application}
795 %************************************************************************
799 tcApp :: RenamedHsExpr -> [RenamedHsExpr] -- Function and args
800 -> TcType -- Expected result type of application
801 -> TcM s (TcExpr, [TcExpr], -- Translated fun and args
804 tcApp fun args res_ty
805 = -- First type-check the function
806 tcExpr_id fun `thenTc` \ (fun', lie_fun, fun_ty) ->
808 tcAddErrCtxt (wrongArgsCtxt "too many" fun args) (
809 split_fun_ty fun_ty (length args)
810 ) `thenTc` \ (expected_arg_tys, actual_result_ty) ->
812 -- Unify with expected result before type-checking the args
813 -- This is when we might detect a too-few args situation
814 tcAddErrCtxtM (checkArgsCtxt fun args res_ty actual_result_ty) (
815 unifyTauTy res_ty actual_result_ty
818 -- Now typecheck the args
819 mapAndUnzipTc (tcArg fun)
820 (zip3 args expected_arg_tys [1..]) `thenTc` \ (args', lie_args_s) ->
822 -- Check that the result type doesn't have any nested for-alls.
823 -- For example, a "build" on its own is no good; it must be applied to something.
824 checkTc (isTauTy actual_result_ty)
825 (lurkingRank2Err fun fun_ty) `thenTc_`
827 returnTc (fun', args', lie_fun `plusLIE` plusLIEs lie_args_s)
830 -- If an error happens we try to figure out whether the
831 -- function has been given too many or too few arguments,
833 checkArgsCtxt fun args expected_res_ty actual_res_ty tidy_env
834 = zonkTcType expected_res_ty `thenNF_Tc` \ exp_ty' ->
835 zonkTcType actual_res_ty `thenNF_Tc` \ act_ty' ->
837 (env1, exp_ty'') = tidyOpenType tidy_env exp_ty'
838 (env2, act_ty'') = tidyOpenType env1 act_ty'
839 (exp_args, _) = splitFunTys exp_ty''
840 (act_args, _) = splitFunTys act_ty''
842 message | length exp_args < length act_args = wrongArgsCtxt "too few" fun args
843 | length exp_args > length act_args = wrongArgsCtxt "too many" fun args
844 | otherwise = appCtxt fun args
846 returnNF_Tc (env2, message)
849 split_fun_ty :: TcType -- The type of the function
850 -> Int -- Number of arguments
851 -> TcM s ([TcType], -- Function argument types
852 TcType) -- Function result types
854 split_fun_ty fun_ty 0
855 = returnTc ([], fun_ty)
857 split_fun_ty fun_ty n
858 = -- Expect the function to have type A->B
859 unifyFunTy fun_ty `thenTc` \ (arg_ty, res_ty) ->
860 split_fun_ty res_ty (n-1) `thenTc` \ (arg_tys, final_res_ty) ->
861 returnTc (arg_ty:arg_tys, final_res_ty)
865 tcArg :: RenamedHsExpr -- The function (for error messages)
866 -> (RenamedHsExpr, TcType, Int) -- Actual argument and expected arg type
867 -> TcM s (TcExpr, LIE) -- Resulting argument and LIE
869 tcArg the_fun (arg, expected_arg_ty, arg_no)
870 = tcAddErrCtxt (funAppCtxt the_fun arg arg_no) $
871 tcExpr arg expected_arg_ty
875 %************************************************************************
877 \subsection{@tcId@ typchecks an identifier occurrence}
879 %************************************************************************
881 Between the renamer and the first invocation of the UsageSP inference,
882 identifiers read from interface files will have usage information in
883 their types, whereas other identifiers will not. The unannotTy here
884 in @tcId@ prevents this information from pointlessly propagating
885 further prior to the first usage inference.
888 tcId :: Name -> NF_TcM s (TcExpr, LIE, TcType)
891 = -- Look up the Id and instantiate its type
892 tcLookupValueMaybe name `thenNF_Tc` \ maybe_local ->
895 Just tc_id -> instantiate_it (OccurrenceOf tc_id) tc_id (unannotTy (idType tc_id))
897 Nothing -> tcLookupValue name `thenNF_Tc` \ id ->
898 tcInstId id `thenNF_Tc` \ (tyvars, theta, tau) ->
899 instantiate_it2 (OccurrenceOf id) id tyvars theta tau
902 -- The instantiate_it loop runs round instantiating the Id.
903 -- It has to be a loop because we are now prepared to entertain
905 -- f:: forall a. Eq a => forall b. Baz b => tau
906 -- We want to instantiate this to
907 -- f2::tau {f2 = f1 b (Baz b), f1 = f a (Eq a)}
908 instantiate_it orig fun ty
909 = tcInstTcType ty `thenNF_Tc` \ (tyvars, rho) ->
910 tcSplitRhoTy rho `thenNF_Tc` \ (theta, tau) ->
911 instantiate_it2 orig fun tyvars theta tau
913 instantiate_it2 orig fun tyvars theta tau
914 = if null theta then -- Is it overloaded?
915 returnNF_Tc (mkHsTyApp (HsVar fun) arg_tys, emptyLIE, tau)
917 -- Yes, it's overloaded
918 instOverloadedFun orig fun arg_tys theta tau `thenNF_Tc` \ (fun', lie1) ->
919 instantiate_it orig fun' tau `thenNF_Tc` \ (expr, lie2, final_tau) ->
920 returnNF_Tc (expr, lie1 `plusLIE` lie2, final_tau)
923 arg_tys = mkTyVarTys tyvars
926 %************************************************************************
928 \subsection{@tcDoStmts@ typechecks a {\em list} of do statements}
930 %************************************************************************
933 tcDoStmts do_or_lc stmts src_loc res_ty
934 = -- get the Monad and MonadZero classes
935 -- create type consisting of a fresh monad tyvar
936 ASSERT( not (null stmts) )
937 tcAddSrcLoc src_loc $
939 newTyVarTy (mkArrowKind boxedTypeKind boxedTypeKind) `thenNF_Tc` \ m ->
940 newTyVarTy boxedTypeKind `thenNF_Tc` \ elt_ty ->
941 unifyTauTy res_ty (mkAppTy m elt_ty) `thenTc_`
943 -- If it's a comprehension we're dealing with,
944 -- force it to be a list comprehension.
945 -- (as of Haskell 98, monad comprehensions are no more.)
947 ListComp -> unifyListTy res_ty `thenTc_` returnTc ()
948 _ -> returnTc ()) `thenTc_`
950 tcStmts do_or_lc (mkAppTy m) stmts elt_ty `thenTc` \ (stmts', stmts_lie) ->
952 -- Build the then and zero methods in case we need them
953 -- It's important that "then" and "return" appear just once in the final LIE,
954 -- not only for typechecker efficiency, but also because otherwise during
955 -- simplification we end up with silly stuff like
956 -- then = case d of (t,r) -> t
958 -- where the second "then" sees that it already exists in the "available" stuff.
960 tcLookupValueByKey returnMClassOpKey `thenNF_Tc` \ return_sel_id ->
961 tcLookupValueByKey thenMClassOpKey `thenNF_Tc` \ then_sel_id ->
962 tcLookupValueByKey failMClassOpKey `thenNF_Tc` \ fail_sel_id ->
963 newMethod DoOrigin return_sel_id [m] `thenNF_Tc` \ (return_lie, return_id) ->
964 newMethod DoOrigin then_sel_id [m] `thenNF_Tc` \ (then_lie, then_id) ->
965 newMethod DoOrigin fail_sel_id [m] `thenNF_Tc` \ (fail_lie, fail_id) ->
967 monad_lie = then_lie `plusLIE` return_lie `plusLIE` fail_lie
969 returnTc (HsDoOut do_or_lc stmts' return_id then_id fail_id res_ty src_loc,
970 stmts_lie `plusLIE` monad_lie)
974 %************************************************************************
976 \subsection{Record bindings}
978 %************************************************************************
980 Game plan for record bindings
981 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
982 1. Find the TyCon for the bindings, from the first field label.
984 2. Instantiate its tyvars and unify (T a1 .. an) with expected_ty.
986 For each binding field = value
988 3. Instantiate the field type (from the field label) using the type
991 4 Type check the value using tcArg, passing the field type as
992 the expected argument type.
994 This extends OK when the field types are universally quantified.
999 :: TyCon -- Type constructor for the record
1000 -> [TcType] -- Args of this type constructor
1001 -> RenamedRecordBinds
1002 -> TcM s (TcRecordBinds, LIE)
1004 tcRecordBinds tycon ty_args rbinds
1005 = mapAndUnzipTc do_bind rbinds `thenTc` \ (rbinds', lies) ->
1006 returnTc (rbinds', plusLIEs lies)
1008 tenv = mkTopTyVarSubst (tyConTyVars tycon) ty_args
1010 do_bind (field_lbl_name, rhs, pun_flag)
1011 = tcLookupValue field_lbl_name `thenNF_Tc` \ sel_id ->
1013 field_lbl = recordSelectorFieldLabel sel_id
1014 field_ty = substTy tenv (fieldLabelType field_lbl)
1016 ASSERT( isRecordSelector sel_id )
1017 -- This lookup and assertion will surely succeed, because
1018 -- we check that the fields are indeed record selectors
1019 -- before calling tcRecordBinds
1020 ASSERT2( fieldLabelTyCon field_lbl == tycon, ppr field_lbl )
1021 -- The caller of tcRecordBinds has already checked
1022 -- that all the fields come from the same type
1024 tcPolyExpr rhs field_ty `thenTc` \ (rhs', lie, _, _, _) ->
1026 returnTc ((sel_id, rhs', pun_flag), lie)
1028 badFields rbinds data_con
1029 = [field_name | (field_name, _, _) <- rbinds,
1030 not (field_name `elem` field_names)
1033 field_names = map fieldLabelName (dataConFieldLabels data_con)
1035 missingStrictFields rbinds data_con
1036 = [ fn | fn <- strict_field_names,
1037 not (fn `elem` field_names_used)
1040 field_names_used = [ field_name | (field_name, _, _) <- rbinds ]
1041 strict_field_names = mapMaybe isStrict field_info
1043 isStrict (fl, MarkedStrict) = Just (fieldLabelName fl)
1044 isStrict _ = Nothing
1046 field_info = zip (dataConFieldLabels data_con)
1047 (dataConStrictMarks data_con)
1049 missingFields rbinds data_con
1050 = [ fn | fn <- non_strict_field_names, not (fn `elem` field_names_used) ]
1052 field_names_used = [ field_name | (field_name, _, _) <- rbinds ]
1054 -- missing strict fields have already been flagged as
1055 -- being so, so leave them out here.
1056 non_strict_field_names = mapMaybe isn'tStrict field_info
1058 isn'tStrict (fl, MarkedStrict) = Nothing
1059 isn'tStrict (fl, _) = Just (fieldLabelName fl)
1061 field_info = zip (dataConFieldLabels data_con)
1062 (dataConStrictMarks data_con)
1066 %************************************************************************
1068 \subsection{@tcMonoExprs@ typechecks a {\em list} of expressions}
1070 %************************************************************************
1073 tcMonoExprs :: [RenamedHsExpr] -> [TcType] -> TcM s ([TcExpr], LIE)
1075 tcMonoExprs [] [] = returnTc ([], emptyLIE)
1076 tcMonoExprs (expr:exprs) (ty:tys)
1077 = tcMonoExpr expr ty `thenTc` \ (expr', lie1) ->
1078 tcMonoExprs exprs tys `thenTc` \ (exprs', lie2) ->
1079 returnTc (expr':exprs', lie1 `plusLIE` lie2)
1083 % =================================================
1090 pp_nest_hang :: String -> SDoc -> SDoc
1091 pp_nest_hang lbl stuff = nest 2 (hang (text lbl) 4 stuff)
1094 Boring and alphabetical:
1097 = hang (ptext SLIT("In an arithmetic sequence:")) 4 (ppr expr)
1100 = hang (ptext SLIT("In the case expression:")) 4 (ppr expr)
1103 = hang (ptext SLIT("In the scrutinee of a case expression:")) 4 (ppr expr)
1106 = hang (ptext SLIT("In an expression with a type signature:"))
1110 = hang (ptext SLIT("In the list element:")) 4 (ppr expr)
1113 = hang (ptext SLIT("In the predicate expression:")) 4 (ppr expr)
1115 sectionRAppCtxt expr
1116 = hang (ptext SLIT("In the right section:")) 4 (ppr expr)
1118 sectionLAppCtxt expr
1119 = hang (ptext SLIT("In the left section:")) 4 (ppr expr)
1121 funAppCtxt fun arg arg_no
1122 = hang (hsep [ ptext SLIT("In the"), speakNth arg_no, ptext SLIT("argument of"),
1123 quotes (ppr fun) <> text ", namely"])
1124 4 (quotes (ppr arg))
1126 wrongArgsCtxt too_many_or_few fun args
1127 = hang (ptext SLIT("Probable cause:") <+> quotes (ppr fun)
1128 <+> ptext SLIT("is applied to") <+> text too_many_or_few
1129 <+> ptext SLIT("arguments in the call"))
1130 4 (parens (ppr the_app))
1132 the_app = foldl HsApp fun args -- Used in error messages
1135 = ptext SLIT("In the application") <+> quotes (ppr the_app)
1137 the_app = foldl HsApp fun args -- Used in error messages
1139 lurkingRank2Err fun fun_ty
1140 = hang (hsep [ptext SLIT("Illegal use of"), quotes (ppr fun)])
1141 4 (vcat [ptext SLIT("It is applied to too few arguments"),
1142 ptext SLIT("so that the result type has for-alls in it")])
1144 rank2ArgCtxt arg expected_arg_ty
1145 = ptext SLIT("In a polymorphic function argument:") <+> ppr arg
1148 = hang (ptext SLIT("No constructor has all these fields:"))
1149 4 (pprQuotedList fields)
1151 fields = [field | (field, _, _) <- rbinds]
1153 recordUpdCtxt expr = ptext SLIT("In the record update:") <+> ppr expr
1154 recordConCtxt expr = ptext SLIT("In the record construction:") <+> ppr expr
1157 = hsep [quotes (ppr field), ptext SLIT("is not a record selector")]
1159 illegalCcallTyErr isArg ty
1160 = hang (hsep [ptext SLIT("Unacceptable"), arg_or_res, ptext SLIT("type in _ccall_ or _casm_:")])
1164 | isArg = ptext SLIT("argument")
1165 | otherwise = ptext SLIT("result")
1168 missingStrictFieldCon :: Name -> Name -> SDoc
1169 missingStrictFieldCon con field
1170 = hsep [ptext SLIT("Constructor") <+> quotes (ppr con),
1171 ptext SLIT("does not have the required strict field"), quotes (ppr field)]
1173 missingFieldCon :: Name -> Name -> SDoc
1174 missingFieldCon con field
1175 = hsep [ptext SLIT("Field") <+> quotes (ppr field),
1176 ptext SLIT("is not initialised")]