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 FieldLabel ( FieldLabel, fieldLabelName, fieldLabelType, fieldLabelTyCon )
48 import Id ( idType, recordSelectorFieldLabel, isRecordSelector,
51 import DataCon ( dataConFieldLabels, dataConSig,
52 dataConStrictMarks, StrictnessMark(..)
54 import Name ( Name, getName )
55 import Type ( mkFunTy, mkAppTy, mkTyVarTy, mkTyVarTys,
57 splitFunTy_maybe, splitFunTys, isNotUsgTy,
58 mkTyConApp, splitSigmaTy,
60 isTauTy, tyVarsOfType, tyVarsOfTypes,
61 isSigmaTy, splitAlgTyConApp, splitAlgTyConApp_maybe,
62 boxedTypeKind, mkArrowKind,
65 import TyCon ( TyCon, tyConTyVars )
66 import Subst ( mkTopTyVarSubst, substClasses, substTy )
67 import UsageSPUtils ( unannotTy )
68 import VarSet ( emptyVarSet, unionVarSet, elemVarSet, mkVarSet )
69 import TyCon ( tyConDataCons )
70 import TysPrim ( intPrimTy, charPrimTy, doublePrimTy,
71 floatPrimTy, addrPrimTy
73 import TysWiredIn ( boolTy, charTy, stringTy )
74 import TcUnify ( unifyTauTy, unifyFunTy, unifyListTy, unifyTupleTy )
75 import Unique ( cCallableClassKey, cReturnableClassKey,
76 enumFromClassOpKey, enumFromThenClassOpKey,
77 enumFromToClassOpKey, enumFromThenToClassOpKey,
78 thenMClassOpKey, failMClassOpKey, returnMClassOpKey, ioTyConKey
81 import Maybes ( maybeToBool, mapMaybe )
82 import ListSetOps ( minusList )
84 import CmdLineOpts ( opt_WarnMissingFields )
88 %************************************************************************
90 \subsection{Main wrappers}
92 %************************************************************************
95 tcExpr :: RenamedHsExpr -- Expession to type check
96 -> TcType -- Expected type (could be a polytpye)
97 -> TcM s (TcExpr, LIE)
99 tcExpr expr ty | isSigmaTy ty = -- Polymorphic case
100 tcPolyExpr expr ty `thenTc` \ (expr', lie, _, _, _) ->
101 returnTc (expr', lie)
103 | otherwise = -- Monomorphic case
108 %************************************************************************
110 \subsection{@tcPolyExpr@ typchecks an application}
112 %************************************************************************
115 -- tcPolyExpr is like tcMonoExpr, except that the expected type
116 -- can be a polymorphic one.
117 tcPolyExpr :: RenamedHsExpr
118 -> TcType -- Expected type
119 -> TcM s (TcExpr, LIE, -- Generalised expr with expected type, and LIE
120 TcExpr, TcTauType, LIE) -- Same thing, but instantiated; tau-type returned
122 tcPolyExpr arg expected_arg_ty
123 = -- Ha! The argument type of the function is a for-all type,
124 -- An example of rank-2 polymorphism.
126 -- To ensure that the forall'd type variables don't get unified with each
127 -- other or any other types, we make fresh copy of the alleged type
128 tcInstTcType expected_arg_ty `thenNF_Tc` \ (sig_tyvars, sig_rho) ->
130 (sig_theta, sig_tau) = splitRhoTy sig_rho
131 free_tyvars = tyVarsOfType expected_arg_ty
133 -- Type-check the arg and unify with expected type
134 tcMonoExpr arg sig_tau `thenTc` \ (arg', lie_arg) ->
136 -- Check that the sig_tyvars havn't been constrained
137 -- The interesting bit here is that we must include the free variables
138 -- of the expected arg ty. Here's an example:
139 -- runST (newVar True)
140 -- Here, if we don't make a check, we'll get a type (ST s (MutVar s Bool))
141 -- for (newVar True), with s fresh. Then we unify with the runST's arg type
142 -- forall s'. ST s' a. That unifies s' with s, and a with MutVar s Bool.
143 -- So now s' isn't unconstrained because it's linked to a.
144 -- Conclusion: include the free vars of the expected arg type in the
145 -- list of "free vars" for the signature check.
147 tcExtendGlobalTyVars free_tyvars $
148 tcAddErrCtxtM (sigCtxt sig_msg sig_tyvars sig_theta sig_tau) $
150 checkSigTyVars sig_tyvars free_tyvars `thenTc` \ zonked_sig_tyvars ->
152 newDicts SignatureOrigin sig_theta `thenNF_Tc` \ (sig_dicts, dict_ids) ->
153 tcImprove (sig_dicts `plusLIE` lie_arg) `thenTc_`
154 -- ToDo: better origin
156 (text "the type signature of an expression")
157 (mkVarSet zonked_sig_tyvars)
158 sig_dicts lie_arg `thenTc` \ (free_insts, inst_binds) ->
161 -- This HsLet binds any Insts which came out of the simplification.
162 -- It's a bit out of place here, but using AbsBind involves inventing
163 -- a couple of new names which seems worse.
164 generalised_arg = TyLam zonked_sig_tyvars $
169 returnTc ( generalised_arg, free_insts,
170 arg', sig_tau, lie_arg )
172 sig_msg = ptext SLIT("When checking an expression type signature")
175 %************************************************************************
177 \subsection{The TAUT rules for variables}
179 %************************************************************************
182 tcMonoExpr :: RenamedHsExpr -- Expession to type check
183 -> TcTauType -- Expected type (could be a type variable)
184 -> TcM s (TcExpr, LIE)
186 tcMonoExpr (HsVar name) res_ty
187 = tcId name `thenNF_Tc` \ (expr', lie, id_ty) ->
188 unifyTauTy res_ty id_ty `thenTc_`
190 -- Check that the result type doesn't have any nested for-alls.
191 -- For example, a "build" on its own is no good; it must be
192 -- applied to something.
193 checkTc (isTauTy id_ty)
194 (lurkingRank2Err name id_ty) `thenTc_`
196 returnTc (expr', lie)
200 tcMonoExpr (HsIPVar name) res_ty
201 -- ZZ What's the `id' used for here...
202 = let id = mkVanillaId name res_ty in
203 tcGetInstLoc (OccurrenceOf id) `thenNF_Tc` \ loc ->
204 newIPDict name res_ty loc `thenNF_Tc` \ ip ->
205 returnNF_Tc (HsIPVar (instToId ip), unitLIE ip)
208 %************************************************************************
210 \subsection{Literals}
212 %************************************************************************
217 tcMonoExpr (HsLit (HsInt i)) res_ty
218 = newOverloadedLit (LiteralOrigin (HsInt i))
219 (OverloadedIntegral i)
220 res_ty `thenNF_Tc` \ stuff ->
223 tcMonoExpr (HsLit (HsFrac f)) res_ty
224 = newOverloadedLit (LiteralOrigin (HsFrac f))
225 (OverloadedFractional f)
226 res_ty `thenNF_Tc` \ stuff ->
230 tcMonoExpr (HsLit lit@(HsLitLit s)) res_ty
231 = tcLookupClassByKey cCallableClassKey `thenNF_Tc` \ cCallableClass ->
232 newClassDicts (LitLitOrigin (_UNPK_ s))
233 [(cCallableClass,[res_ty])] `thenNF_Tc` \ (dicts, _) ->
234 returnTc (HsLitOut lit res_ty, dicts)
240 tcMonoExpr (HsLit lit@(HsCharPrim c)) res_ty
241 = unifyTauTy res_ty charPrimTy `thenTc_`
242 returnTc (HsLitOut lit charPrimTy, emptyLIE)
244 tcMonoExpr (HsLit lit@(HsStringPrim s)) res_ty
245 = unifyTauTy res_ty addrPrimTy `thenTc_`
246 returnTc (HsLitOut lit addrPrimTy, emptyLIE)
248 tcMonoExpr (HsLit lit@(HsIntPrim i)) res_ty
249 = unifyTauTy res_ty intPrimTy `thenTc_`
250 returnTc (HsLitOut lit intPrimTy, emptyLIE)
252 tcMonoExpr (HsLit lit@(HsFloatPrim f)) res_ty
253 = unifyTauTy res_ty floatPrimTy `thenTc_`
254 returnTc (HsLitOut lit floatPrimTy, emptyLIE)
256 tcMonoExpr (HsLit lit@(HsDoublePrim d)) res_ty
257 = unifyTauTy res_ty doublePrimTy `thenTc_`
258 returnTc (HsLitOut lit doublePrimTy, emptyLIE)
261 Unoverloaded literals:
264 tcMonoExpr (HsLit lit@(HsChar c)) res_ty
265 = unifyTauTy res_ty charTy `thenTc_`
266 returnTc (HsLitOut lit charTy, emptyLIE)
268 tcMonoExpr (HsLit lit@(HsString str)) res_ty
269 = unifyTauTy res_ty stringTy `thenTc_`
270 returnTc (HsLitOut lit stringTy, emptyLIE)
273 %************************************************************************
275 \subsection{Other expression forms}
277 %************************************************************************
280 tcMonoExpr (HsPar expr) res_ty -- preserve parens so printing needn't guess where they go
281 = tcMonoExpr expr res_ty
283 -- perform the negate *before* overloading the integer, since the case
284 -- of minBound on Ints fails otherwise. Could be done elsewhere, but
285 -- convenient to do it here.
287 tcMonoExpr (NegApp (HsLit (HsInt i)) neg) res_ty
288 = tcMonoExpr (HsLit (HsInt (-i))) res_ty
290 tcMonoExpr (NegApp expr neg) res_ty
291 = tcMonoExpr (HsApp neg expr) res_ty
293 tcMonoExpr (HsLam match) res_ty
294 = tcMatchLambda match res_ty `thenTc` \ (match',lie) ->
295 returnTc (HsLam match', lie)
297 tcMonoExpr (HsApp e1 e2) res_ty = accum e1 [e2]
299 accum (HsApp e1 e2) args = accum e1 (e2:args)
301 = tcApp fun args res_ty `thenTc` \ (fun', args', lie) ->
302 returnTc (foldl HsApp fun' args', lie)
304 -- equivalent to (op e1) e2:
305 tcMonoExpr (OpApp arg1 op fix arg2) res_ty
306 = tcApp op [arg1,arg2] res_ty `thenTc` \ (op', [arg1', arg2'], lie) ->
307 returnTc (OpApp arg1' op' fix arg2', lie)
310 Note that the operators in sections are expected to be binary, and
311 a type error will occur if they aren't.
314 -- Left sections, equivalent to
321 tcMonoExpr in_expr@(SectionL arg op) res_ty
322 = tcApp op [arg] res_ty `thenTc` \ (op', [arg'], lie) ->
324 -- Check that res_ty is a function type
325 -- Without this check we barf in the desugarer on
327 -- because it tries to desugar to
328 -- f op = \r -> 3 op r
329 -- so (3 `op`) had better be a function!
330 tcAddErrCtxt (sectionLAppCtxt in_expr) $
331 unifyFunTy res_ty `thenTc_`
333 returnTc (SectionL arg' op', lie)
335 -- Right sections, equivalent to \ x -> x op expr, or
338 tcMonoExpr in_expr@(SectionR op expr) res_ty
339 = tcExpr_id op `thenTc` \ (op', lie1, op_ty) ->
340 tcAddErrCtxt (sectionRAppCtxt in_expr) $
341 split_fun_ty op_ty 2 {- two args -} `thenTc` \ ([arg1_ty, arg2_ty], op_res_ty) ->
342 tcMonoExpr expr arg2_ty `thenTc` \ (expr',lie2) ->
343 unifyTauTy res_ty (mkFunTy arg1_ty op_res_ty) `thenTc_`
344 returnTc (SectionR op' expr', lie1 `plusLIE` lie2)
347 The interesting thing about @ccall@ is that it is just a template
348 which we instantiate by filling in details about the types of its
349 argument and result (ie minimal typechecking is performed). So, the
350 basic story is that we allocate a load of type variables (to hold the
351 arg/result types); unify them with the args/result; and store them for
355 tcMonoExpr (HsCCall lbl args may_gc is_asm ignored_fake_result_ty) res_ty
356 = -- Get the callable and returnable classes.
357 tcLookupClassByKey cCallableClassKey `thenNF_Tc` \ cCallableClass ->
358 tcLookupClassByKey cReturnableClassKey `thenNF_Tc` \ cReturnableClass ->
359 tcLookupTyConByKey ioTyConKey `thenNF_Tc` \ ioTyCon ->
361 new_arg_dict (arg, arg_ty)
362 = newClassDicts (CCallOrigin (_UNPK_ lbl) (Just arg))
363 [(cCallableClass, [arg_ty])] `thenNF_Tc` \ (arg_dicts, _) ->
364 returnNF_Tc arg_dicts -- Actually a singleton bag
366 result_origin = CCallOrigin (_UNPK_ lbl) Nothing {- Not an arg -}
370 let n_args = length args
371 tv_idxs | n_args == 0 = []
372 | otherwise = [1..n_args]
374 mapNF_Tc (\ _ -> newTyVarTy_OpenKind) tv_idxs `thenNF_Tc` \ arg_tys ->
375 tcMonoExprs args arg_tys `thenTc` \ (args', args_lie) ->
377 -- The argument types can be unboxed or boxed; the result
378 -- type must, however, be boxed since it's an argument to the IO
380 newTyVarTy boxedTypeKind `thenNF_Tc` \ result_ty ->
382 io_result_ty = mkTyConApp ioTyCon [result_ty]
384 unifyTauTy res_ty io_result_ty `thenTc_`
386 -- Construct the extra insts, which encode the
387 -- constraints on the argument and result types.
388 mapNF_Tc new_arg_dict (zipEqual "tcMonoExpr:CCall" args arg_tys) `thenNF_Tc` \ ccarg_dicts_s ->
389 newClassDicts result_origin [(cReturnableClass, [result_ty])] `thenNF_Tc` \ (ccres_dict, _) ->
390 returnTc (HsCCall lbl args' may_gc is_asm io_result_ty,
391 foldr plusLIE ccres_dict ccarg_dicts_s `plusLIE` args_lie)
395 tcMonoExpr (HsSCC lbl expr) res_ty
396 = tcMonoExpr expr res_ty `thenTc` \ (expr', lie) ->
397 returnTc (HsSCC lbl expr', lie)
399 tcMonoExpr (HsLet binds expr) res_ty
402 binds -- Bindings to check
403 tc_expr `thenTc` \ (expr', lie) ->
404 returnTc (expr', lie)
406 tc_expr = tcMonoExpr expr res_ty `thenTc` \ (expr', lie) ->
407 returnTc (expr', lie)
408 combiner is_rec bind expr = HsLet (mkMonoBind bind [] is_rec) expr
410 tcMonoExpr in_expr@(HsCase scrut matches src_loc) res_ty
411 = tcAddSrcLoc src_loc $
412 tcAddErrCtxt (caseCtxt in_expr) $
414 -- Typecheck the case alternatives first.
415 -- The case patterns tend to give good type info to use
416 -- when typechecking the scrutinee. For example
419 -- will report that map is applied to too few arguments
421 -- Not only that, but it's better to check the matches on their
422 -- own, so that we get the expected results for scoped type variables.
424 -- (p::a, q::b) -> (q,p)
425 -- The above should work: the match (p,q) -> (q,p) is polymorphic as
426 -- claimed by the pattern signatures. But if we typechecked the
427 -- match with x in scope and x's type as the expected type, we'd be hosed.
429 tcMatchesCase matches res_ty `thenTc` \ (scrut_ty, matches', lie2) ->
431 tcAddErrCtxt (caseScrutCtxt scrut) (
432 tcMonoExpr scrut scrut_ty
433 ) `thenTc` \ (scrut',lie1) ->
435 returnTc (HsCase scrut' matches' src_loc, plusLIE lie1 lie2)
437 tcMonoExpr (HsIf pred b1 b2 src_loc) res_ty
438 = tcAddSrcLoc src_loc $
439 tcAddErrCtxt (predCtxt pred) (
440 tcMonoExpr pred boolTy ) `thenTc` \ (pred',lie1) ->
442 tcMonoExpr b1 res_ty `thenTc` \ (b1',lie2) ->
443 tcMonoExpr b2 res_ty `thenTc` \ (b2',lie3) ->
444 returnTc (HsIf pred' b1' b2' src_loc, plusLIE lie1 (plusLIE lie2 lie3))
448 tcMonoExpr expr@(HsDo do_or_lc stmts src_loc) res_ty
449 = tcDoStmts do_or_lc stmts src_loc res_ty
453 tcMonoExpr in_expr@(ExplicitList exprs) res_ty -- Non-empty list
454 = unifyListTy res_ty `thenTc` \ elt_ty ->
455 mapAndUnzipTc (tc_elt elt_ty) exprs `thenTc` \ (exprs', lies) ->
456 returnTc (ExplicitListOut elt_ty exprs', plusLIEs lies)
459 = tcAddErrCtxt (listCtxt expr) $
460 tcMonoExpr expr elt_ty
462 tcMonoExpr (ExplicitTuple exprs boxity) res_ty
463 = unifyTupleTy boxity (length exprs) res_ty `thenTc` \ arg_tys ->
464 mapAndUnzipTc (\ (expr, arg_ty) -> tcMonoExpr expr arg_ty)
465 (exprs `zip` arg_tys) -- we know they're of equal length.
466 `thenTc` \ (exprs', lies) ->
467 returnTc (ExplicitTuple exprs' boxity, plusLIEs lies)
469 tcMonoExpr expr@(RecordCon con_name rbinds) res_ty
470 = tcAddErrCtxt (recordConCtxt expr) $
471 tcId con_name `thenNF_Tc` \ (con_expr, con_lie, con_tau) ->
473 (_, record_ty) = splitFunTys con_tau
474 (tycon, ty_args, _) = splitAlgTyConApp record_ty
476 ASSERT( maybeToBool (splitAlgTyConApp_maybe record_ty ) )
477 unifyTauTy res_ty record_ty `thenTc_`
479 -- Check that the record bindings match the constructor
480 -- con_name is syntactically constrained to be a data constructor
481 tcLookupDataCon con_name `thenTc` \ (data_con, _, _) ->
483 bad_fields = badFields rbinds data_con
485 if not (null bad_fields) then
486 mapNF_Tc (addErrTc . badFieldCon con_name) bad_fields `thenNF_Tc_`
487 failTc -- Fail now, because tcRecordBinds will crash on a bad field
490 -- Typecheck the record bindings
491 tcRecordBinds tycon ty_args rbinds `thenTc` \ (rbinds', rbinds_lie) ->
494 missing_s_fields = missingStrictFields rbinds data_con
496 checkTcM (null missing_s_fields)
497 (mapNF_Tc (addErrTc . missingStrictFieldCon con_name) missing_s_fields `thenNF_Tc_`
498 returnNF_Tc ()) `thenNF_Tc_`
500 missing_fields = missingFields rbinds data_con
502 checkTcM (not (opt_WarnMissingFields && not (null missing_fields)))
503 (mapNF_Tc ((warnTc True) . missingFieldCon con_name) missing_fields `thenNF_Tc_`
504 returnNF_Tc ()) `thenNF_Tc_`
506 returnTc (RecordConOut data_con con_expr rbinds', con_lie `plusLIE` rbinds_lie)
508 -- The main complication with RecordUpd is that we need to explicitly
509 -- handle the *non-updated* fields. Consider:
511 -- data T a b = MkT1 { fa :: a, fb :: b }
512 -- | MkT2 { fa :: a, fc :: Int -> Int }
513 -- | MkT3 { fd :: a }
515 -- upd :: T a b -> c -> T a c
516 -- upd t x = t { fb = x}
518 -- The type signature on upd is correct (i.e. the result should not be (T a b))
519 -- because upd should be equivalent to:
521 -- upd t x = case t of
522 -- MkT1 p q -> MkT1 p x
523 -- MkT2 a b -> MkT2 p b
524 -- MkT3 d -> error ...
526 -- So we need to give a completely fresh type to the result record,
527 -- and then constrain it by the fields that are *not* updated ("p" above).
529 -- Note that because MkT3 doesn't contain all the fields being updated,
530 -- its RHS is simply an error, so it doesn't impose any type constraints
532 -- All this is done in STEP 4 below.
534 tcMonoExpr expr@(RecordUpd record_expr rbinds) res_ty
535 = tcAddErrCtxt (recordUpdCtxt expr) $
538 -- Check that the field names are really field names
539 ASSERT( not (null rbinds) )
541 field_names = [field_name | (field_name, _, _) <- rbinds]
543 mapNF_Tc tcLookupValueMaybe field_names `thenNF_Tc` \ maybe_sel_ids ->
545 bad_guys = [field_name | (field_name, maybe_sel_id) <- field_names `zip` maybe_sel_ids,
548 Just sel_id -> not (isRecordSelector sel_id)
551 mapNF_Tc (addErrTc . notSelector) bad_guys `thenTc_`
552 if not (null bad_guys) then
557 -- Figure out the tycon and data cons from the first field name
559 (Just sel_id : _) = maybe_sel_ids
560 (_, _, tau) = ASSERT( isNotUsgTy (idType sel_id) )
561 splitSigmaTy (idType sel_id) -- Selectors can be overloaded
562 -- when the data type has a context
563 Just (data_ty, _) = splitFunTy_maybe tau -- Must succeed since sel_id is a selector
564 (tycon, _, data_cons) = splitAlgTyConApp data_ty
565 (con_tyvars, _, _, _, _, _) = dataConSig (head data_cons)
567 tcInstTyVars con_tyvars `thenNF_Tc` \ (_, result_inst_tys, _) ->
570 -- Check that at least one constructor has all the named fields
571 -- i.e. has an empty set of bad fields returned by badFields
572 checkTc (any (null . badFields rbinds) data_cons)
573 (badFieldsUpd rbinds) `thenTc_`
576 -- Typecheck the update bindings.
577 -- (Do this after checking for bad fields in case there's a field that
578 -- doesn't match the constructor.)
580 result_record_ty = mkTyConApp tycon result_inst_tys
582 unifyTauTy res_ty result_record_ty `thenTc_`
583 tcRecordBinds tycon result_inst_tys rbinds `thenTc` \ (rbinds', rbinds_lie) ->
586 -- Use the un-updated fields to find a vector of booleans saying
587 -- which type arguments must be the same in updatee and result.
589 -- WARNING: this code assumes that all data_cons in a common tycon
590 -- have FieldLabels abstracted over the same tyvars.
592 upd_field_lbls = [recordSelectorFieldLabel sel_id | (sel_id, _, _) <- rbinds']
593 con_field_lbls_s = map dataConFieldLabels data_cons
595 -- A constructor is only relevant to this process if
596 -- it contains all the fields that are being updated
597 relevant_field_lbls_s = filter is_relevant con_field_lbls_s
598 is_relevant con_field_lbls = all (`elem` con_field_lbls) upd_field_lbls
600 non_upd_field_lbls = concat relevant_field_lbls_s `minusList` upd_field_lbls
601 common_tyvars = tyVarsOfTypes (map fieldLabelType non_upd_field_lbls)
603 mk_inst_ty (tyvar, result_inst_ty)
604 | tyvar `elemVarSet` common_tyvars = returnNF_Tc result_inst_ty -- Same as result type
605 | otherwise = newTyVarTy boxedTypeKind -- Fresh type
607 mapNF_Tc mk_inst_ty (zip con_tyvars result_inst_tys) `thenNF_Tc` \ inst_tys ->
610 -- Typecheck the expression to be updated
612 record_ty = mkTyConApp tycon inst_tys
614 tcMonoExpr record_expr record_ty `thenTc` \ (record_expr', record_lie) ->
617 -- Figure out the LIE we need. We have to generate some
618 -- dictionaries for the data type context, since we are going to
619 -- do some construction.
621 -- What dictionaries do we need? For the moment we assume that all
622 -- data constructors have the same context, and grab it from the first
623 -- constructor. If they have varying contexts then we'd have to
624 -- union the ones that could participate in the update.
626 (tyvars, theta, _, _, _, _) = dataConSig (head data_cons)
627 inst_env = mkTopTyVarSubst tyvars result_inst_tys
628 theta' = substClasses inst_env theta
630 newClassDicts RecordUpdOrigin theta' `thenNF_Tc` \ (con_lie, dicts) ->
633 returnTc (RecordUpdOut record_expr' result_record_ty dicts rbinds',
634 con_lie `plusLIE` record_lie `plusLIE` rbinds_lie)
636 tcMonoExpr (ArithSeqIn seq@(From expr)) res_ty
637 = unifyListTy res_ty `thenTc` \ elt_ty ->
638 tcMonoExpr expr elt_ty `thenTc` \ (expr', lie1) ->
640 tcLookupValueByKey enumFromClassOpKey `thenNF_Tc` \ sel_id ->
641 newMethod (ArithSeqOrigin seq)
642 sel_id [elt_ty] `thenNF_Tc` \ (lie2, enum_from_id) ->
644 returnTc (ArithSeqOut (HsVar enum_from_id) (From expr'),
647 tcMonoExpr in_expr@(ArithSeqIn seq@(FromThen expr1 expr2)) res_ty
648 = tcAddErrCtxt (arithSeqCtxt in_expr) $
649 unifyListTy res_ty `thenTc` \ elt_ty ->
650 tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) ->
651 tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) ->
652 tcLookupValueByKey enumFromThenClassOpKey `thenNF_Tc` \ sel_id ->
653 newMethod (ArithSeqOrigin seq)
654 sel_id [elt_ty] `thenNF_Tc` \ (lie3, enum_from_then_id) ->
656 returnTc (ArithSeqOut (HsVar enum_from_then_id)
657 (FromThen expr1' expr2'),
658 lie1 `plusLIE` lie2 `plusLIE` lie3)
660 tcMonoExpr in_expr@(ArithSeqIn seq@(FromTo expr1 expr2)) res_ty
661 = tcAddErrCtxt (arithSeqCtxt in_expr) $
662 unifyListTy res_ty `thenTc` \ elt_ty ->
663 tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) ->
664 tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) ->
665 tcLookupValueByKey enumFromToClassOpKey `thenNF_Tc` \ sel_id ->
666 newMethod (ArithSeqOrigin seq)
667 sel_id [elt_ty] `thenNF_Tc` \ (lie3, enum_from_to_id) ->
669 returnTc (ArithSeqOut (HsVar enum_from_to_id)
670 (FromTo expr1' expr2'),
671 lie1 `plusLIE` lie2 `plusLIE` lie3)
673 tcMonoExpr in_expr@(ArithSeqIn seq@(FromThenTo expr1 expr2 expr3)) res_ty
674 = tcAddErrCtxt (arithSeqCtxt in_expr) $
675 unifyListTy res_ty `thenTc` \ elt_ty ->
676 tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) ->
677 tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) ->
678 tcMonoExpr expr3 elt_ty `thenTc` \ (expr3',lie3) ->
679 tcLookupValueByKey enumFromThenToClassOpKey `thenNF_Tc` \ sel_id ->
680 newMethod (ArithSeqOrigin seq)
681 sel_id [elt_ty] `thenNF_Tc` \ (lie4, eft_id) ->
683 returnTc (ArithSeqOut (HsVar eft_id)
684 (FromThenTo expr1' expr2' expr3'),
685 lie1 `plusLIE` lie2 `plusLIE` lie3 `plusLIE` lie4)
688 %************************************************************************
690 \subsection{Expressions type signatures}
692 %************************************************************************
695 tcMonoExpr in_expr@(ExprWithTySig expr poly_ty) res_ty
696 = tcSetErrCtxt (exprSigCtxt in_expr) $
697 tcHsSigType poly_ty `thenTc` \ sig_tc_ty ->
699 if not (isSigmaTy sig_tc_ty) then
701 unifyTauTy sig_tc_ty res_ty `thenTc_`
702 tcMonoExpr expr sig_tc_ty
704 else -- Signature is polymorphic
705 tcPolyExpr expr sig_tc_ty `thenTc` \ (_, _, expr, expr_ty, lie) ->
707 -- Now match the signature type with res_ty.
708 -- We must not do this earlier, because res_ty might well
709 -- mention variables free in the environment, and we'd get
710 -- bogus complaints about not being able to for-all the
712 unifyTauTy res_ty expr_ty `thenTc_`
714 -- If everything is ok, return the stuff unchanged, except for
715 -- the effect of any substutions etc. We simply discard the
716 -- result of the tcSimplifyAndCheck (inside tcPolyExpr), except for any default
717 -- resolution it may have done, which is recorded in the
722 Implicit Parameter bindings.
725 tcMonoExpr (HsWith expr binds) res_ty
726 = tcMonoExpr expr res_ty `thenTc` \ (expr', lie) ->
727 tcIPBinds binds `thenTc` \ (binds', types, lie2) ->
728 partitionPredsOfLIE isBound lie `thenTc` \ (ips, lie', dict_binds) ->
729 let expr'' = if nullMonoBinds dict_binds
731 else HsLet (mkMonoBind (revBinds dict_binds) [] NonRecursive)
734 tcCheckIPBinds binds' types ips `thenTc_`
735 returnTc (HsWith expr'' binds', lie' `plusLIE` lie2)
737 = case ipName_maybe p of
738 Just n -> n `elem` names
740 names = map fst binds
741 -- revBinds is used because tcSimplify outputs the bindings
742 -- out-of-order. it's not a problem elsewhere because these
743 -- bindings are normally used in a recursive let
744 -- ZZ probably need to find a better solution
745 revBinds (b1 `AndMonoBinds` b2) =
746 (revBinds b2) `AndMonoBinds` (revBinds b1)
749 tcIPBinds ((name, expr) : binds)
750 = newTyVarTy_OpenKind `thenTc` \ ty ->
751 tcGetSrcLoc `thenTc` \ loc ->
752 let id = ipToId name ty loc in
753 tcMonoExpr expr ty `thenTc` \ (expr', lie) ->
754 zonkTcType ty `thenTc` \ ty' ->
755 tcIPBinds binds `thenTc` \ (binds', types, lie2) ->
756 returnTc ((id, expr') : binds', ty : types, lie `plusLIE` lie2)
757 tcIPBinds [] = returnTc ([], [], emptyLIE)
759 tcCheckIPBinds binds types ips
760 = foldrTc tcCheckIPBind (getIPsOfLIE ips) (zip binds types)
762 -- ZZ how do we use the loc?
763 tcCheckIPBind bt@((v, _), t1) ((n, t2) : ips) | getName v == n
764 = unifyTauTy t1 t2 `thenTc_`
765 tcCheckIPBind bt ips `thenTc` \ ips' ->
767 tcCheckIPBind bt (ip : ips)
768 = tcCheckIPBind bt ips `thenTc` \ ips' ->
774 Typecheck expression which in most cases will be an Id.
777 tcExpr_id :: RenamedHsExpr
783 HsVar name -> tcId name `thenNF_Tc` \ stuff ->
785 other -> newTyVarTy_OpenKind `thenNF_Tc` \ id_ty ->
786 tcMonoExpr id_expr id_ty `thenTc` \ (id_expr', lie_id) ->
787 returnTc (id_expr', lie_id, id_ty)
790 %************************************************************************
792 \subsection{@tcApp@ typchecks an application}
794 %************************************************************************
798 tcApp :: RenamedHsExpr -> [RenamedHsExpr] -- Function and args
799 -> TcType -- Expected result type of application
800 -> TcM s (TcExpr, [TcExpr], -- Translated fun and args
803 tcApp fun args res_ty
804 = -- First type-check the function
805 tcExpr_id fun `thenTc` \ (fun', lie_fun, fun_ty) ->
807 tcAddErrCtxt (wrongArgsCtxt "too many" fun args) (
808 split_fun_ty fun_ty (length args)
809 ) `thenTc` \ (expected_arg_tys, actual_result_ty) ->
811 -- Unify with expected result before type-checking the args
812 -- This is when we might detect a too-few args situation
813 tcAddErrCtxtM (checkArgsCtxt fun args res_ty actual_result_ty) (
814 unifyTauTy res_ty actual_result_ty
817 -- Now typecheck the args
818 mapAndUnzipTc (tcArg fun)
819 (zip3 args expected_arg_tys [1..]) `thenTc` \ (args', lie_args_s) ->
821 -- Check that the result type doesn't have any nested for-alls.
822 -- For example, a "build" on its own is no good; it must be applied to something.
823 checkTc (isTauTy actual_result_ty)
824 (lurkingRank2Err fun fun_ty) `thenTc_`
826 returnTc (fun', args', lie_fun `plusLIE` plusLIEs lie_args_s)
829 -- If an error happens we try to figure out whether the
830 -- function has been given too many or too few arguments,
832 checkArgsCtxt fun args expected_res_ty actual_res_ty tidy_env
833 = zonkTcType expected_res_ty `thenNF_Tc` \ exp_ty' ->
834 zonkTcType actual_res_ty `thenNF_Tc` \ act_ty' ->
836 (env1, exp_ty'') = tidyOpenType tidy_env exp_ty'
837 (env2, act_ty'') = tidyOpenType env1 act_ty'
838 (exp_args, _) = splitFunTys exp_ty''
839 (act_args, _) = splitFunTys act_ty''
841 message | length exp_args < length act_args = wrongArgsCtxt "too few" fun args
842 | length exp_args > length act_args = wrongArgsCtxt "too many" fun args
843 | otherwise = appCtxt fun args
845 returnNF_Tc (env2, message)
848 split_fun_ty :: TcType -- The type of the function
849 -> Int -- Number of arguments
850 -> TcM s ([TcType], -- Function argument types
851 TcType) -- Function result types
853 split_fun_ty fun_ty 0
854 = returnTc ([], fun_ty)
856 split_fun_ty fun_ty n
857 = -- Expect the function to have type A->B
858 unifyFunTy fun_ty `thenTc` \ (arg_ty, res_ty) ->
859 split_fun_ty res_ty (n-1) `thenTc` \ (arg_tys, final_res_ty) ->
860 returnTc (arg_ty:arg_tys, final_res_ty)
864 tcArg :: RenamedHsExpr -- The function (for error messages)
865 -> (RenamedHsExpr, TcType, Int) -- Actual argument and expected arg type
866 -> TcM s (TcExpr, LIE) -- Resulting argument and LIE
868 tcArg the_fun (arg, expected_arg_ty, arg_no)
869 = tcAddErrCtxt (funAppCtxt the_fun arg arg_no) $
870 tcExpr arg expected_arg_ty
874 %************************************************************************
876 \subsection{@tcId@ typchecks an identifier occurrence}
878 %************************************************************************
880 Between the renamer and the first invocation of the UsageSP inference,
881 identifiers read from interface files will have usage information in
882 their types, whereas other identifiers will not. The unannotTy here
883 in @tcId@ prevents this information from pointlessly propagating
884 further prior to the first usage inference.
887 tcId :: Name -> NF_TcM s (TcExpr, LIE, TcType)
890 = -- Look up the Id and instantiate its type
891 tcLookupValueMaybe name `thenNF_Tc` \ maybe_local ->
894 Just tc_id -> instantiate_it (OccurrenceOf tc_id) tc_id (unannotTy (idType tc_id))
896 Nothing -> tcLookupValue name `thenNF_Tc` \ id ->
897 tcInstId id `thenNF_Tc` \ (tyvars, theta, tau) ->
898 instantiate_it2 (OccurrenceOf id) id tyvars theta tau
901 -- The instantiate_it loop runs round instantiating the Id.
902 -- It has to be a loop because we are now prepared to entertain
904 -- f:: forall a. Eq a => forall b. Baz b => tau
905 -- We want to instantiate this to
906 -- f2::tau {f2 = f1 b (Baz b), f1 = f a (Eq a)}
907 instantiate_it orig fun ty
908 = tcInstTcType ty `thenNF_Tc` \ (tyvars, rho) ->
909 tcSplitRhoTy rho `thenNF_Tc` \ (theta, tau) ->
910 instantiate_it2 orig fun tyvars theta tau
912 instantiate_it2 orig fun tyvars theta tau
913 = if null theta then -- Is it overloaded?
914 returnNF_Tc (mkHsTyApp (HsVar fun) arg_tys, emptyLIE, tau)
916 -- Yes, it's overloaded
917 instOverloadedFun orig fun arg_tys theta tau `thenNF_Tc` \ (fun', lie1) ->
918 instantiate_it orig fun' tau `thenNF_Tc` \ (expr, lie2, final_tau) ->
919 returnNF_Tc (expr, lie1 `plusLIE` lie2, final_tau)
922 arg_tys = mkTyVarTys tyvars
925 %************************************************************************
927 \subsection{@tcDoStmts@ typechecks a {\em list} of do statements}
929 %************************************************************************
932 tcDoStmts do_or_lc stmts src_loc res_ty
933 = -- get the Monad and MonadZero classes
934 -- create type consisting of a fresh monad tyvar
935 ASSERT( not (null stmts) )
936 tcAddSrcLoc src_loc $
938 newTyVarTy (mkArrowKind boxedTypeKind boxedTypeKind) `thenNF_Tc` \ m ->
939 newTyVarTy boxedTypeKind `thenNF_Tc` \ elt_ty ->
940 unifyTauTy res_ty (mkAppTy m elt_ty) `thenTc_`
942 -- If it's a comprehension we're dealing with,
943 -- force it to be a list comprehension.
944 -- (as of Haskell 98, monad comprehensions are no more.)
946 ListComp -> unifyListTy res_ty `thenTc_` returnTc ()
947 _ -> returnTc ()) `thenTc_`
949 tcStmts do_or_lc (mkAppTy m) stmts elt_ty `thenTc` \ (stmts', stmts_lie) ->
951 -- Build the then and zero methods in case we need them
952 -- It's important that "then" and "return" appear just once in the final LIE,
953 -- not only for typechecker efficiency, but also because otherwise during
954 -- simplification we end up with silly stuff like
955 -- then = case d of (t,r) -> t
957 -- where the second "then" sees that it already exists in the "available" stuff.
959 tcLookupValueByKey returnMClassOpKey `thenNF_Tc` \ return_sel_id ->
960 tcLookupValueByKey thenMClassOpKey `thenNF_Tc` \ then_sel_id ->
961 tcLookupValueByKey failMClassOpKey `thenNF_Tc` \ fail_sel_id ->
962 newMethod DoOrigin return_sel_id [m] `thenNF_Tc` \ (return_lie, return_id) ->
963 newMethod DoOrigin then_sel_id [m] `thenNF_Tc` \ (then_lie, then_id) ->
964 newMethod DoOrigin fail_sel_id [m] `thenNF_Tc` \ (fail_lie, fail_id) ->
966 monad_lie = then_lie `plusLIE` return_lie `plusLIE` fail_lie
968 returnTc (HsDoOut do_or_lc stmts' return_id then_id fail_id res_ty src_loc,
969 stmts_lie `plusLIE` monad_lie)
973 %************************************************************************
975 \subsection{Record bindings}
977 %************************************************************************
979 Game plan for record bindings
980 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
981 1. Find the TyCon for the bindings, from the first field label.
983 2. Instantiate its tyvars and unify (T a1 .. an) with expected_ty.
985 For each binding field = value
987 3. Instantiate the field type (from the field label) using the type
990 4 Type check the value using tcArg, passing the field type as
991 the expected argument type.
993 This extends OK when the field types are universally quantified.
998 :: TyCon -- Type constructor for the record
999 -> [TcType] -- Args of this type constructor
1000 -> RenamedRecordBinds
1001 -> TcM s (TcRecordBinds, LIE)
1003 tcRecordBinds tycon ty_args rbinds
1004 = mapAndUnzipTc do_bind rbinds `thenTc` \ (rbinds', lies) ->
1005 returnTc (rbinds', plusLIEs lies)
1007 tenv = mkTopTyVarSubst (tyConTyVars tycon) ty_args
1009 do_bind (field_lbl_name, rhs, pun_flag)
1010 = tcLookupValue field_lbl_name `thenNF_Tc` \ sel_id ->
1012 field_lbl = recordSelectorFieldLabel sel_id
1013 field_ty = substTy tenv (fieldLabelType field_lbl)
1015 ASSERT( isRecordSelector sel_id )
1016 -- This lookup and assertion will surely succeed, because
1017 -- we check that the fields are indeed record selectors
1018 -- before calling tcRecordBinds
1019 ASSERT2( fieldLabelTyCon field_lbl == tycon, ppr field_lbl )
1020 -- The caller of tcRecordBinds has already checked
1021 -- that all the fields come from the same type
1023 tcPolyExpr rhs field_ty `thenTc` \ (rhs', lie, _, _, _) ->
1025 returnTc ((sel_id, rhs', pun_flag), lie)
1027 badFields rbinds data_con
1028 = [field_name | (field_name, _, _) <- rbinds,
1029 not (field_name `elem` field_names)
1032 field_names = map fieldLabelName (dataConFieldLabels data_con)
1034 missingStrictFields rbinds data_con
1035 = [ fn | fn <- strict_field_names,
1036 not (fn `elem` field_names_used)
1039 field_names_used = [ field_name | (field_name, _, _) <- rbinds ]
1040 strict_field_names = mapMaybe isStrict field_info
1042 isStrict (fl, MarkedStrict) = Just (fieldLabelName fl)
1043 isStrict _ = Nothing
1045 field_info = zip (dataConFieldLabels data_con)
1046 (dataConStrictMarks data_con)
1048 missingFields rbinds data_con
1049 = [ fn | fn <- non_strict_field_names, not (fn `elem` field_names_used) ]
1051 field_names_used = [ field_name | (field_name, _, _) <- rbinds ]
1053 -- missing strict fields have already been flagged as
1054 -- being so, so leave them out here.
1055 non_strict_field_names = mapMaybe isn'tStrict field_info
1057 isn'tStrict (fl, MarkedStrict) = Nothing
1058 isn'tStrict (fl, _) = Just (fieldLabelName fl)
1060 field_info = zip (dataConFieldLabels data_con)
1061 (dataConStrictMarks data_con)
1065 %************************************************************************
1067 \subsection{@tcMonoExprs@ typechecks a {\em list} of expressions}
1069 %************************************************************************
1072 tcMonoExprs :: [RenamedHsExpr] -> [TcType] -> TcM s ([TcExpr], LIE)
1074 tcMonoExprs [] [] = returnTc ([], emptyLIE)
1075 tcMonoExprs (expr:exprs) (ty:tys)
1076 = tcMonoExpr expr ty `thenTc` \ (expr', lie1) ->
1077 tcMonoExprs exprs tys `thenTc` \ (exprs', lie2) ->
1078 returnTc (expr':exprs', lie1 `plusLIE` lie2)
1082 % =================================================
1089 pp_nest_hang :: String -> SDoc -> SDoc
1090 pp_nest_hang lbl stuff = nest 2 (hang (text lbl) 4 stuff)
1093 Boring and alphabetical:
1096 = hang (ptext SLIT("In an arithmetic sequence:")) 4 (ppr expr)
1099 = hang (ptext SLIT("In the case expression:")) 4 (ppr expr)
1102 = hang (ptext SLIT("In the scrutinee of a case expression:")) 4 (ppr expr)
1105 = hang (ptext SLIT("In an expression with a type signature:"))
1109 = hang (ptext SLIT("In the list element:")) 4 (ppr expr)
1112 = hang (ptext SLIT("In the predicate expression:")) 4 (ppr expr)
1114 sectionRAppCtxt expr
1115 = hang (ptext SLIT("In the right section:")) 4 (ppr expr)
1117 sectionLAppCtxt expr
1118 = hang (ptext SLIT("In the left section:")) 4 (ppr expr)
1120 funAppCtxt fun arg arg_no
1121 = hang (hsep [ ptext SLIT("In the"), speakNth arg_no, ptext SLIT("argument of"),
1122 quotes (ppr fun) <> text ", namely"])
1123 4 (quotes (ppr arg))
1125 wrongArgsCtxt too_many_or_few fun args
1126 = hang (ptext SLIT("Probable cause:") <+> quotes (ppr fun)
1127 <+> ptext SLIT("is applied to") <+> text too_many_or_few
1128 <+> ptext SLIT("arguments in the call"))
1129 4 (parens (ppr the_app))
1131 the_app = foldl HsApp fun args -- Used in error messages
1134 = ptext SLIT("In the application") <+> quotes (ppr the_app)
1136 the_app = foldl HsApp fun args -- Used in error messages
1138 lurkingRank2Err fun fun_ty
1139 = hang (hsep [ptext SLIT("Illegal use of"), quotes (ppr fun)])
1140 4 (vcat [ptext SLIT("It is applied to too few arguments"),
1141 ptext SLIT("so that the result type has for-alls in it")])
1143 rank2ArgCtxt arg expected_arg_ty
1144 = ptext SLIT("In a polymorphic function argument:") <+> ppr arg
1147 = hang (ptext SLIT("No constructor has all these fields:"))
1148 4 (pprQuotedList fields)
1150 fields = [field | (field, _, _) <- rbinds]
1152 recordUpdCtxt expr = ptext SLIT("In the record update:") <+> ppr expr
1153 recordConCtxt expr = ptext SLIT("In the record construction:") <+> ppr expr
1156 = hsep [quotes (ppr field), ptext SLIT("is not a record selector")]
1158 illegalCcallTyErr isArg ty
1159 = hang (hsep [ptext SLIT("Unacceptable"), arg_or_res, ptext SLIT("type in _ccall_ or _casm_:")])
1163 | isArg = ptext SLIT("argument")
1164 | otherwise = ptext SLIT("result")
1167 missingStrictFieldCon :: Name -> Name -> SDoc
1168 missingStrictFieldCon con field
1169 = hsep [ptext SLIT("Constructor") <+> quotes (ppr con),
1170 ptext SLIT("does not have the required strict field"), quotes (ppr field)]
1172 missingFieldCon :: Name -> Name -> SDoc
1173 missingFieldCon con field
1174 = hsep [ptext SLIT("Field") <+> quotes (ppr field),
1175 ptext SLIT("is not initialised")]