2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[TcExpr]{Typecheck an expression}
7 module TcExpr ( tcExpr, tcMonoExpr, tcId ) where
9 #include "HsVersions.h"
11 import HsSyn ( HsExpr(..), HsLit(..), ArithSeqInfo(..),
12 HsMatchContext(..), HsDoContext(..), mkMonoBind
14 import RnHsSyn ( RenamedHsExpr, RenamedRecordBinds )
15 import TcHsSyn ( TcExpr, TcRecordBinds, simpleHsLitTy )
18 import TcUnify ( tcSub, tcGen, (<$>),
19 unifyTauTy, unifyFunTy, unifyListTy, unifyPArrTy,
21 import BasicTypes ( RecFlag(..), isMarkedStrict )
22 import Inst ( InstOrigin(..),
23 LIE, mkLIE, emptyLIE, unitLIE, plusLIE, plusLIEs,
24 newOverloadedLit, newMethod, newIPDict,
28 import TcBinds ( tcBindsAndThen )
29 import TcEnv ( tcLookupClass, tcLookupGlobalId, tcLookupGlobal_maybe,
30 tcLookupTyCon, tcLookupDataCon, tcLookupId
32 import TcMatches ( tcMatchesCase, tcMatchLambda, tcStmts )
33 import TcMonoType ( tcHsSigType, UserTypeCtxt(..) )
34 import TcPat ( badFieldCon )
35 import TcSimplify ( tcSimplifyIPs )
36 import TcMType ( tcInstTyVars, newTyVarTy, newTyVarTys, zonkTcType )
37 import TcType ( TcType, TcSigmaType, TcPhiType,
38 tcSplitFunTys, tcSplitTyConApp,
39 isSigmaTy, mkFunTy, mkAppTy, mkTyConTy,
40 mkTyConApp, mkClassPred, tcFunArgTy,
42 liftedTypeKind, openTypeKind, mkArrowKind,
43 tcSplitSigmaTy, tcTyConAppTyCon,
46 import FieldLabel ( FieldLabel, fieldLabelName, fieldLabelType, fieldLabelTyCon )
47 import Id ( idType, recordSelectorFieldLabel, isRecordSelector )
48 import DataCon ( dataConFieldLabels, dataConSig,
52 import TyCon ( TyCon, tyConTyVars, isAlgTyCon, tyConDataCons )
53 import Subst ( mkTopTyVarSubst, substTheta, substTy )
54 import VarSet ( elemVarSet )
55 import TysWiredIn ( boolTy, mkListTy, mkPArrTy, listTyCon, parrTyCon )
56 import PrelNames ( cCallableClassName,
58 enumFromName, enumFromThenName,
59 enumFromToName, enumFromThenToName,
60 enumFromToPName, enumFromThenToPName,
61 thenMName, failMName, returnMName, ioTyConName
64 import ListSetOps ( minusList )
67 import HscTypes ( TyThing(..) )
71 %************************************************************************
73 \subsection{Main wrappers}
75 %************************************************************************
78 tcExpr :: RenamedHsExpr -- Expession to type check
79 -> TcSigmaType -- Expected type (could be a polytpye)
80 -> TcM (TcExpr, LIE) -- Generalised expr with expected type, and LIE
82 tcExpr expr expected_ty
83 | not (isSigmaTy expected_ty) -- Monomorphic case
84 = tcMonoExpr expr expected_ty
87 = tcGen expected_ty (tcMonoExpr expr) `thenTc` \ (gen_fn, expr', lie) ->
88 returnTc (gen_fn <$> expr', lie)
92 %************************************************************************
94 \subsection{The TAUT rules for variables}
96 %************************************************************************
99 tcMonoExpr :: RenamedHsExpr -- Expession to type check
100 -> TcPhiType -- Expected type (could be a type variable)
101 -- Definitely no foralls at the top
105 tcMonoExpr (HsVar name) res_ty
106 = tcId name `thenNF_Tc` \ (expr', lie1, id_ty) ->
107 tcSub res_ty id_ty `thenTc` \ (co_fn, lie2) ->
108 returnTc (co_fn <$> expr', lie1 `plusLIE` lie2)
110 tcMonoExpr (HsIPVar ip) res_ty
111 = -- Implicit parameters must have a *tau-type* not a
112 -- type scheme. We enforce this by creating a fresh
113 -- type variable as its type. (Because res_ty may not
115 newTyVarTy openTypeKind `thenNF_Tc` \ ip_ty ->
116 newIPDict (IPOcc ip) ip ip_ty `thenNF_Tc` \ (ip', inst) ->
117 tcSub res_ty ip_ty `thenTc` \ (co_fn, lie) ->
118 returnNF_Tc (co_fn <$> HsIPVar ip', lie `plusLIE` unitLIE inst)
122 %************************************************************************
124 \subsection{Expressions type signatures}
126 %************************************************************************
129 tcMonoExpr in_expr@(ExprWithTySig expr poly_ty) res_ty
130 = tcHsSigType ExprSigCtxt poly_ty `thenTc` \ sig_tc_ty ->
131 tcAddErrCtxt (exprSigCtxt in_expr) $
132 tcExpr expr sig_tc_ty `thenTc` \ (expr', lie1) ->
133 tcSub res_ty sig_tc_ty `thenTc` \ (co_fn, lie2) ->
134 returnTc (co_fn <$> expr', lie1 `plusLIE` lie2)
138 %************************************************************************
140 \subsection{Other expression forms}
142 %************************************************************************
145 tcMonoExpr (HsLit lit) res_ty = tcLit lit res_ty
146 tcMonoExpr (HsOverLit lit) res_ty = newOverloadedLit (LiteralOrigin lit) lit res_ty
147 tcMonoExpr (HsPar expr) res_ty = tcMonoExpr expr res_ty
149 tcMonoExpr (NegApp expr neg_name) res_ty
150 = tcMonoExpr (HsApp (HsVar neg_name) expr) res_ty
152 tcMonoExpr (HsLam match) res_ty
153 = tcMatchLambda match res_ty `thenTc` \ (match',lie) ->
154 returnTc (HsLam match', lie)
156 tcMonoExpr (HsApp e1 e2) res_ty
157 = tcApp e1 [e2] res_ty
160 Note that the operators in sections are expected to be binary, and
161 a type error will occur if they aren't.
164 -- Left sections, equivalent to
171 tcMonoExpr in_expr@(SectionL arg1 op) res_ty
172 = tcExpr_id op `thenTc` \ (op', lie1, op_ty) ->
173 split_fun_ty op_ty 2 {- two args -} `thenTc` \ ([arg1_ty, arg2_ty], op_res_ty) ->
174 tcArg op (arg1, arg1_ty, 1) `thenTc` \ (arg1',lie2) ->
175 tcAddErrCtxt (exprCtxt in_expr) $
176 tcSub res_ty (mkFunTy arg2_ty op_res_ty) `thenTc` \ (co_fn, lie3) ->
177 returnTc (co_fn <$> SectionL arg1' op', lie1 `plusLIE` lie2 `plusLIE` lie3)
179 -- Right sections, equivalent to \ x -> x op expr, or
182 tcMonoExpr in_expr@(SectionR op arg2) res_ty
183 = tcExpr_id op `thenTc` \ (op', lie1, op_ty) ->
184 split_fun_ty op_ty 2 {- two args -} `thenTc` \ ([arg1_ty, arg2_ty], op_res_ty) ->
185 tcArg op (arg2, arg2_ty, 2) `thenTc` \ (arg2',lie2) ->
186 tcAddErrCtxt (exprCtxt in_expr) $
187 tcSub res_ty (mkFunTy arg1_ty op_res_ty) `thenTc` \ (co_fn, lie3) ->
188 returnTc (co_fn <$> SectionR op' arg2', lie1 `plusLIE` lie2 `plusLIE` lie3)
190 -- equivalent to (op e1) e2:
192 tcMonoExpr in_expr@(OpApp arg1 op fix arg2) res_ty
193 = tcExpr_id op `thenTc` \ (op', lie1, op_ty) ->
194 split_fun_ty op_ty 2 {- two args -} `thenTc` \ ([arg1_ty, arg2_ty], op_res_ty) ->
195 tcArg op (arg1, arg1_ty, 1) `thenTc` \ (arg1',lie2a) ->
196 tcArg op (arg2, arg2_ty, 2) `thenTc` \ (arg2',lie2b) ->
197 tcAddErrCtxt (exprCtxt in_expr) $
198 tcSub res_ty op_res_ty `thenTc` \ (co_fn, lie3) ->
199 returnTc (OpApp arg1' op' fix arg2',
200 lie1 `plusLIE` lie2a `plusLIE` lie2b `plusLIE` lie3)
203 The interesting thing about @ccall@ is that it is just a template
204 which we instantiate by filling in details about the types of its
205 argument and result (ie minimal typechecking is performed). So, the
206 basic story is that we allocate a load of type variables (to hold the
207 arg/result types); unify them with the args/result; and store them for
211 tcMonoExpr e0@(HsCCall lbl args may_gc is_casm ignored_fake_result_ty) res_ty
213 = getDOptsTc `thenNF_Tc` \ dflags ->
215 checkTc (not (is_casm && dopt_HscLang dflags /= HscC))
216 (vcat [text "_casm_ is only supported when compiling via C (-fvia-C).",
217 text "Either compile with -fvia-C, or, better, rewrite your code",
218 text "to use the foreign function interface. _casm_s are deprecated",
219 text "and support for them may one day disappear."])
222 -- Get the callable and returnable classes.
223 tcLookupClass cCallableClassName `thenNF_Tc` \ cCallableClass ->
224 tcLookupClass cReturnableClassName `thenNF_Tc` \ cReturnableClass ->
225 tcLookupTyCon ioTyConName `thenNF_Tc` \ ioTyCon ->
227 new_arg_dict (arg, arg_ty)
228 = newDicts (CCallOrigin (_UNPK_ lbl) (Just arg))
229 [mkClassPred cCallableClass [arg_ty]] `thenNF_Tc` \ arg_dicts ->
230 returnNF_Tc arg_dicts -- Actually a singleton bag
232 result_origin = CCallOrigin (_UNPK_ lbl) Nothing {- Not an arg -}
236 let tv_idxs | null args = []
237 | otherwise = [1..length args]
239 newTyVarTys (length tv_idxs) openTypeKind `thenNF_Tc` \ arg_tys ->
240 tcMonoExprs args arg_tys `thenTc` \ (args', args_lie) ->
242 -- The argument types can be unlifted or lifted; the result
243 -- type must, however, be lifted since it's an argument to the IO
245 newTyVarTy liftedTypeKind `thenNF_Tc` \ result_ty ->
247 io_result_ty = mkTyConApp ioTyCon [result_ty]
249 unifyTauTy res_ty io_result_ty `thenTc_`
251 -- Construct the extra insts, which encode the
252 -- constraints on the argument and result types.
253 mapNF_Tc new_arg_dict (zipEqual "tcMonoExpr:CCall" args arg_tys) `thenNF_Tc` \ ccarg_dicts_s ->
254 newDicts result_origin [mkClassPred cReturnableClass [result_ty]] `thenNF_Tc` \ ccres_dict ->
255 returnTc (HsCCall lbl args' may_gc is_casm io_result_ty,
256 mkLIE (ccres_dict ++ concat ccarg_dicts_s) `plusLIE` args_lie)
260 tcMonoExpr (HsSCC lbl expr) res_ty
261 = tcMonoExpr expr res_ty `thenTc` \ (expr', lie) ->
262 returnTc (HsSCC lbl expr', lie)
264 tcMonoExpr (HsLet binds expr) res_ty
267 binds -- Bindings to check
268 tc_expr `thenTc` \ (expr', lie) ->
269 returnTc (expr', lie)
271 tc_expr = tcMonoExpr expr res_ty `thenTc` \ (expr', lie) ->
272 returnTc (expr', lie)
273 combiner is_rec bind expr = HsLet (mkMonoBind bind [] is_rec) expr
275 tcMonoExpr in_expr@(HsCase scrut matches src_loc) res_ty
276 = tcAddSrcLoc src_loc $
277 tcAddErrCtxt (caseCtxt in_expr) $
279 -- Typecheck the case alternatives first.
280 -- The case patterns tend to give good type info to use
281 -- when typechecking the scrutinee. For example
284 -- will report that map is applied to too few arguments
286 -- Not only that, but it's better to check the matches on their
287 -- own, so that we get the expected results for scoped type variables.
289 -- (p::a, q::b) -> (q,p)
290 -- The above should work: the match (p,q) -> (q,p) is polymorphic as
291 -- claimed by the pattern signatures. But if we typechecked the
292 -- match with x in scope and x's type as the expected type, we'd be hosed.
294 tcMatchesCase matches res_ty `thenTc` \ (scrut_ty, matches', lie2) ->
296 tcAddErrCtxt (caseScrutCtxt scrut) (
297 tcMonoExpr scrut scrut_ty
298 ) `thenTc` \ (scrut',lie1) ->
300 returnTc (HsCase scrut' matches' src_loc, plusLIE lie1 lie2)
302 tcMonoExpr (HsIf pred b1 b2 src_loc) res_ty
303 = tcAddSrcLoc src_loc $
304 tcAddErrCtxt (predCtxt pred) (
305 tcMonoExpr pred boolTy ) `thenTc` \ (pred',lie1) ->
307 tcMonoExpr b1 res_ty `thenTc` \ (b1',lie2) ->
308 tcMonoExpr b2 res_ty `thenTc` \ (b2',lie3) ->
309 returnTc (HsIf pred' b1' b2' src_loc, plusLIE lie1 (plusLIE lie2 lie3))
313 tcMonoExpr expr@(HsDo do_or_lc stmts src_loc) res_ty
314 = tcDoStmts do_or_lc stmts src_loc res_ty
318 tcMonoExpr in_expr@(ExplicitList _ exprs) res_ty -- Non-empty list
319 = unifyListTy res_ty `thenTc` \ elt_ty ->
320 mapAndUnzipTc (tc_elt elt_ty) exprs `thenTc` \ (exprs', lies) ->
321 returnTc (ExplicitList elt_ty exprs', plusLIEs lies)
324 = tcAddErrCtxt (listCtxt expr) $
325 tcMonoExpr expr elt_ty
327 tcMonoExpr in_expr@(ExplicitPArr _ exprs) res_ty -- maybe empty
328 = unifyPArrTy res_ty `thenTc` \ elt_ty ->
329 mapAndUnzipTc (tc_elt elt_ty) exprs `thenTc` \ (exprs', lies) ->
330 returnTc (ExplicitPArr elt_ty exprs', plusLIEs lies)
333 = tcAddErrCtxt (parrCtxt expr) $
334 tcMonoExpr expr elt_ty
336 tcMonoExpr (ExplicitTuple exprs boxity) res_ty
337 = unifyTupleTy boxity (length exprs) res_ty `thenTc` \ arg_tys ->
338 mapAndUnzipTc (\ (expr, arg_ty) -> tcMonoExpr expr arg_ty)
339 (exprs `zip` arg_tys) -- we know they're of equal length.
340 `thenTc` \ (exprs', lies) ->
341 returnTc (ExplicitTuple exprs' boxity, plusLIEs lies)
343 tcMonoExpr expr@(RecordCon con_name rbinds) res_ty
344 = tcAddErrCtxt (recordConCtxt expr) $
345 tcId con_name `thenNF_Tc` \ (con_expr, con_lie, con_tau) ->
347 (_, record_ty) = tcSplitFunTys con_tau
348 (tycon, ty_args) = tcSplitTyConApp record_ty
350 ASSERT( isAlgTyCon tycon )
351 unifyTauTy res_ty record_ty `thenTc_`
353 -- Check that the record bindings match the constructor
354 -- con_name is syntactically constrained to be a data constructor
355 tcLookupDataCon con_name `thenTc` \ data_con ->
357 bad_fields = badFields rbinds data_con
359 if not (null bad_fields) then
360 mapNF_Tc (addErrTc . badFieldCon con_name) bad_fields `thenNF_Tc_`
361 failTc -- Fail now, because tcRecordBinds will crash on a bad field
364 -- Typecheck the record bindings
365 tcRecordBinds tycon ty_args rbinds `thenTc` \ (rbinds', rbinds_lie) ->
368 (missing_s_fields, missing_fields) = missingFields rbinds data_con
370 checkTcM (null missing_s_fields)
371 (mapNF_Tc (addErrTc . missingStrictFieldCon con_name) missing_s_fields `thenNF_Tc_`
372 returnNF_Tc ()) `thenNF_Tc_`
373 doptsTc Opt_WarnMissingFields `thenNF_Tc` \ warn ->
374 checkTcM (not (warn && not (null missing_fields)))
375 (mapNF_Tc ((warnTc True) . missingFieldCon con_name) missing_fields `thenNF_Tc_`
376 returnNF_Tc ()) `thenNF_Tc_`
378 returnTc (RecordConOut data_con con_expr rbinds', con_lie `plusLIE` rbinds_lie)
380 -- The main complication with RecordUpd is that we need to explicitly
381 -- handle the *non-updated* fields. Consider:
383 -- data T a b = MkT1 { fa :: a, fb :: b }
384 -- | MkT2 { fa :: a, fc :: Int -> Int }
385 -- | MkT3 { fd :: a }
387 -- upd :: T a b -> c -> T a c
388 -- upd t x = t { fb = x}
390 -- The type signature on upd is correct (i.e. the result should not be (T a b))
391 -- because upd should be equivalent to:
393 -- upd t x = case t of
394 -- MkT1 p q -> MkT1 p x
395 -- MkT2 a b -> MkT2 p b
396 -- MkT3 d -> error ...
398 -- So we need to give a completely fresh type to the result record,
399 -- and then constrain it by the fields that are *not* updated ("p" above).
401 -- Note that because MkT3 doesn't contain all the fields being updated,
402 -- its RHS is simply an error, so it doesn't impose any type constraints
404 -- All this is done in STEP 4 below.
406 tcMonoExpr expr@(RecordUpd record_expr rbinds) res_ty
407 = tcAddErrCtxt (recordUpdCtxt expr) $
410 -- Check that the field names are really field names
411 ASSERT( not (null rbinds) )
413 field_names = [field_name | (field_name, _, _) <- rbinds]
415 mapNF_Tc tcLookupGlobal_maybe field_names `thenNF_Tc` \ maybe_sel_ids ->
417 bad_guys = [ addErrTc (notSelector field_name)
418 | (field_name, maybe_sel_id) <- field_names `zip` maybe_sel_ids,
420 Just (AnId sel_id) -> not (isRecordSelector sel_id)
424 checkTcM (null bad_guys) (listNF_Tc bad_guys `thenNF_Tc_` failTc) `thenTc_`
427 -- Figure out the tycon and data cons from the first field name
429 -- It's OK to use the non-tc splitters here (for a selector)
430 (Just (AnId sel_id) : _) = maybe_sel_ids
431 (_, _, tau) = tcSplitSigmaTy (idType sel_id) -- Selectors can be overloaded
432 -- when the data type has a context
433 data_ty = tcFunArgTy tau -- Must succeed since sel_id is a selector
434 tycon = tcTyConAppTyCon data_ty
435 data_cons = tyConDataCons tycon
436 (con_tyvars, _, _, _, _, _) = dataConSig (head data_cons)
438 tcInstTyVars con_tyvars `thenNF_Tc` \ (_, result_inst_tys, _) ->
441 -- Check that at least one constructor has all the named fields
442 -- i.e. has an empty set of bad fields returned by badFields
443 checkTc (any (null . badFields rbinds) data_cons)
444 (badFieldsUpd rbinds) `thenTc_`
447 -- Typecheck the update bindings.
448 -- (Do this after checking for bad fields in case there's a field that
449 -- doesn't match the constructor.)
451 result_record_ty = mkTyConApp tycon result_inst_tys
453 unifyTauTy res_ty result_record_ty `thenTc_`
454 tcRecordBinds tycon result_inst_tys rbinds `thenTc` \ (rbinds', rbinds_lie) ->
457 -- Use the un-updated fields to find a vector of booleans saying
458 -- which type arguments must be the same in updatee and result.
460 -- WARNING: this code assumes that all data_cons in a common tycon
461 -- have FieldLabels abstracted over the same tyvars.
463 upd_field_lbls = [recordSelectorFieldLabel sel_id | (sel_id, _, _) <- rbinds']
464 con_field_lbls_s = map dataConFieldLabels data_cons
466 -- A constructor is only relevant to this process if
467 -- it contains all the fields that are being updated
468 relevant_field_lbls_s = filter is_relevant con_field_lbls_s
469 is_relevant con_field_lbls = all (`elem` con_field_lbls) upd_field_lbls
471 non_upd_field_lbls = concat relevant_field_lbls_s `minusList` upd_field_lbls
472 common_tyvars = tyVarsOfTypes (map fieldLabelType non_upd_field_lbls)
474 mk_inst_ty (tyvar, result_inst_ty)
475 | tyvar `elemVarSet` common_tyvars = returnNF_Tc result_inst_ty -- Same as result type
476 | otherwise = newTyVarTy liftedTypeKind -- Fresh type
478 mapNF_Tc mk_inst_ty (zip con_tyvars result_inst_tys) `thenNF_Tc` \ inst_tys ->
481 -- Typecheck the expression to be updated
483 record_ty = mkTyConApp tycon inst_tys
485 tcMonoExpr record_expr record_ty `thenTc` \ (record_expr', record_lie) ->
488 -- Figure out the LIE we need. We have to generate some
489 -- dictionaries for the data type context, since we are going to
490 -- do some construction.
492 -- What dictionaries do we need? For the moment we assume that all
493 -- data constructors have the same context, and grab it from the first
494 -- constructor. If they have varying contexts then we'd have to
495 -- union the ones that could participate in the update.
497 (tyvars, theta, _, _, _, _) = dataConSig (head data_cons)
498 inst_env = mkTopTyVarSubst tyvars result_inst_tys
499 theta' = substTheta inst_env theta
501 newDicts RecordUpdOrigin theta' `thenNF_Tc` \ dicts ->
504 returnTc (RecordUpdOut record_expr' record_ty result_record_ty (map instToId dicts) rbinds',
505 mkLIE dicts `plusLIE` record_lie `plusLIE` rbinds_lie)
507 tcMonoExpr (ArithSeqIn seq@(From expr)) res_ty
508 = unifyListTy res_ty `thenTc` \ elt_ty ->
509 tcMonoExpr expr elt_ty `thenTc` \ (expr', lie1) ->
511 tcLookupGlobalId enumFromName `thenNF_Tc` \ sel_id ->
512 newMethod (ArithSeqOrigin seq)
513 sel_id [elt_ty] `thenNF_Tc` \ enum_from ->
515 returnTc (ArithSeqOut (HsVar (instToId enum_from)) (From expr'),
516 lie1 `plusLIE` unitLIE enum_from)
518 tcMonoExpr in_expr@(ArithSeqIn seq@(FromThen expr1 expr2)) res_ty
519 = tcAddErrCtxt (arithSeqCtxt in_expr) $
520 unifyListTy res_ty `thenTc` \ elt_ty ->
521 tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) ->
522 tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) ->
523 tcLookupGlobalId enumFromThenName `thenNF_Tc` \ sel_id ->
524 newMethod (ArithSeqOrigin seq) sel_id [elt_ty] `thenNF_Tc` \ enum_from_then ->
526 returnTc (ArithSeqOut (HsVar (instToId enum_from_then))
527 (FromThen expr1' expr2'),
528 lie1 `plusLIE` lie2 `plusLIE` unitLIE enum_from_then)
530 tcMonoExpr in_expr@(ArithSeqIn seq@(FromTo expr1 expr2)) res_ty
531 = tcAddErrCtxt (arithSeqCtxt in_expr) $
532 unifyListTy res_ty `thenTc` \ elt_ty ->
533 tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) ->
534 tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) ->
535 tcLookupGlobalId enumFromToName `thenNF_Tc` \ sel_id ->
536 newMethod (ArithSeqOrigin seq) sel_id [elt_ty] `thenNF_Tc` \ enum_from_to ->
538 returnTc (ArithSeqOut (HsVar (instToId enum_from_to))
539 (FromTo expr1' expr2'),
540 lie1 `plusLIE` lie2 `plusLIE` unitLIE enum_from_to)
542 tcMonoExpr in_expr@(ArithSeqIn seq@(FromThenTo expr1 expr2 expr3)) res_ty
543 = tcAddErrCtxt (arithSeqCtxt in_expr) $
544 unifyListTy res_ty `thenTc` \ elt_ty ->
545 tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) ->
546 tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) ->
547 tcMonoExpr expr3 elt_ty `thenTc` \ (expr3',lie3) ->
548 tcLookupGlobalId enumFromThenToName `thenNF_Tc` \ sel_id ->
549 newMethod (ArithSeqOrigin seq) sel_id [elt_ty] `thenNF_Tc` \ eft ->
551 returnTc (ArithSeqOut (HsVar (instToId eft))
552 (FromThenTo expr1' expr2' expr3'),
553 lie1 `plusLIE` lie2 `plusLIE` lie3 `plusLIE` unitLIE eft)
555 tcMonoExpr in_expr@(PArrSeqIn seq@(FromTo expr1 expr2)) res_ty
556 = tcAddErrCtxt (parrSeqCtxt in_expr) $
557 unifyPArrTy res_ty `thenTc` \ elt_ty ->
558 tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) ->
559 tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) ->
560 tcLookupGlobalId enumFromToPName `thenNF_Tc` \ sel_id ->
561 newMethod (PArrSeqOrigin seq) sel_id [elt_ty] `thenNF_Tc` \ enum_from_to ->
563 returnTc (PArrSeqOut (HsVar (instToId enum_from_to))
564 (FromTo expr1' expr2'),
565 lie1 `plusLIE` lie2 `plusLIE` unitLIE enum_from_to)
567 tcMonoExpr in_expr@(PArrSeqIn seq@(FromThenTo expr1 expr2 expr3)) res_ty
568 = tcAddErrCtxt (parrSeqCtxt in_expr) $
569 unifyPArrTy res_ty `thenTc` \ elt_ty ->
570 tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) ->
571 tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) ->
572 tcMonoExpr expr3 elt_ty `thenTc` \ (expr3',lie3) ->
573 tcLookupGlobalId enumFromThenToPName `thenNF_Tc` \ sel_id ->
574 newMethod (PArrSeqOrigin seq) sel_id [elt_ty] `thenNF_Tc` \ eft ->
576 returnTc (PArrSeqOut (HsVar (instToId eft))
577 (FromThenTo expr1' expr2' expr3'),
578 lie1 `plusLIE` lie2 `plusLIE` lie3 `plusLIE` unitLIE eft)
580 tcMonoExpr (PArrSeqIn _) _
581 = panic "TcExpr.tcMonoExpr: Infinite parallel array!"
582 -- the parser shouldn't have generated it and the renamer shouldn't have
586 %************************************************************************
588 \subsection{Implicit Parameter bindings}
590 %************************************************************************
593 tcMonoExpr (HsWith expr binds) res_ty
594 = tcMonoExpr expr res_ty `thenTc` \ (expr', expr_lie) ->
595 mapAndUnzip3Tc tcIPBind binds `thenTc` \ (avail_ips, binds', bind_lies) ->
597 -- If the binding binds ?x = E, we must now
598 -- discharge any ?x constraints in expr_lie
599 tcSimplifyIPs avail_ips expr_lie `thenTc` \ (expr_lie', dict_binds) ->
601 expr'' = HsLet (mkMonoBind dict_binds [] Recursive) expr'
603 returnTc (HsWith expr'' binds', expr_lie' `plusLIE` plusLIEs bind_lies)
606 = newTyVarTy openTypeKind `thenTc` \ ty ->
607 tcGetSrcLoc `thenTc` \ loc ->
608 newIPDict (IPBind ip) ip ty `thenNF_Tc` \ (ip', ip_inst) ->
609 tcMonoExpr expr ty `thenTc` \ (expr', lie) ->
610 returnTc (ip_inst, (ip', expr'), lie)
613 %************************************************************************
615 \subsection{@tcApp@ typchecks an application}
617 %************************************************************************
621 tcApp :: RenamedHsExpr -> [RenamedHsExpr] -- Function and args
622 -> TcType -- Expected result type of application
623 -> TcM (TcExpr, LIE) -- Translated fun and args
625 tcApp (HsApp e1 e2) args res_ty
626 = tcApp e1 (e2:args) res_ty -- Accumulate the arguments
628 tcApp fun args res_ty
629 = -- First type-check the function
630 tcExpr_id fun `thenTc` \ (fun', lie_fun, fun_ty) ->
632 tcAddErrCtxt (wrongArgsCtxt "too many" fun args) (
633 split_fun_ty fun_ty (length args)
634 ) `thenTc` \ (expected_arg_tys, actual_result_ty) ->
636 -- Now typecheck the args
637 mapAndUnzipTc (tcArg fun)
638 (zip3 args expected_arg_tys [1..]) `thenTc` \ (args', lie_args_s) ->
640 -- Unify with expected result after type-checking the args
641 -- so that the info from args percolates to actual_result_ty.
642 -- This is when we might detect a too-few args situation.
643 -- (One can think of cases when the opposite order would give
644 -- a better error message.)
645 tcAddErrCtxtM (checkArgsCtxt fun args res_ty actual_result_ty)
646 (tcSub res_ty actual_result_ty) `thenTc` \ (co_fn, lie_res) ->
648 returnTc (co_fn <$> foldl HsApp fun' args',
649 lie_res `plusLIE` lie_fun `plusLIE` plusLIEs lie_args_s)
652 -- If an error happens we try to figure out whether the
653 -- function has been given too many or too few arguments,
655 checkArgsCtxt fun args expected_res_ty actual_res_ty tidy_env
656 = zonkTcType expected_res_ty `thenNF_Tc` \ exp_ty' ->
657 zonkTcType actual_res_ty `thenNF_Tc` \ act_ty' ->
659 (env1, exp_ty'') = tidyOpenType tidy_env exp_ty'
660 (env2, act_ty'') = tidyOpenType env1 act_ty'
661 (exp_args, _) = tcSplitFunTys exp_ty''
662 (act_args, _) = tcSplitFunTys act_ty''
664 len_act_args = length act_args
665 len_exp_args = length exp_args
667 message | len_exp_args < len_act_args = wrongArgsCtxt "too few" fun args
668 | len_exp_args > len_act_args = wrongArgsCtxt "too many" fun args
669 | otherwise = appCtxt fun args
671 returnNF_Tc (env2, message)
674 split_fun_ty :: TcType -- The type of the function
675 -> Int -- Number of arguments
676 -> TcM ([TcType], -- Function argument types
677 TcType) -- Function result types
679 split_fun_ty fun_ty 0
680 = returnTc ([], fun_ty)
682 split_fun_ty fun_ty n
683 = -- Expect the function to have type A->B
684 unifyFunTy fun_ty `thenTc` \ (arg_ty, res_ty) ->
685 split_fun_ty res_ty (n-1) `thenTc` \ (arg_tys, final_res_ty) ->
686 returnTc (arg_ty:arg_tys, final_res_ty)
690 tcArg :: RenamedHsExpr -- The function (for error messages)
691 -> (RenamedHsExpr, TcSigmaType, Int) -- Actual argument and expected arg type
692 -> TcM (TcExpr, LIE) -- Resulting argument and LIE
694 tcArg the_fun (arg, expected_arg_ty, arg_no)
695 = tcAddErrCtxt (funAppCtxt the_fun arg arg_no) $
696 tcExpr arg expected_arg_ty
700 %************************************************************************
702 \subsection{@tcId@ typchecks an identifier occurrence}
704 %************************************************************************
707 tcId :: Name -> NF_TcM (TcExpr, LIE, TcType)
708 tcId name -- Look up the Id and instantiate its type
709 = tcLookupId name `thenNF_Tc` \ id ->
713 Typecheck expression which in most cases will be an Id.
716 tcExpr_id :: RenamedHsExpr -> TcM (TcExpr, LIE, TcType)
717 tcExpr_id (HsVar name) = tcId name
718 tcExpr_id expr = newTyVarTy openTypeKind `thenNF_Tc` \ id_ty ->
719 tcMonoExpr expr id_ty `thenTc` \ (expr', lie_id) ->
720 returnTc (expr', lie_id, id_ty)
724 %************************************************************************
726 \subsection{@tcDoStmts@ typechecks a {\em list} of do statements}
728 %************************************************************************
731 -- I don't like this lumping together of do expression and list/array
732 -- comprehensions; creating the monad instances is entirely pointless in the
733 -- latter case; I'll leave the list case as it is for the moment, but handle
734 -- arrays extra (would be better to handle arrays and lists together, though)
737 tcDoStmts PArrComp stmts src_loc res_ty
739 ASSERT( not (null stmts) )
740 tcAddSrcLoc src_loc $
742 unifyPArrTy res_ty `thenTc` \elt_ty ->
743 let tc_ty = mkTyConTy parrTyCon
744 m_ty = (mkPArrTy, elt_ty)
746 tcStmts (DoCtxt PArrComp) m_ty stmts `thenTc` \(stmts', stmts_lie) ->
747 returnTc (HsDoOut PArrComp stmts'
748 undefined undefined undefined -- don't touch!
752 tcDoStmts do_or_lc stmts src_loc res_ty
753 = -- get the Monad and MonadZero classes
754 -- create type consisting of a fresh monad tyvar
755 ASSERT( not (null stmts) )
756 tcAddSrcLoc src_loc $
758 -- If it's a comprehension we're dealing with,
759 -- force it to be a list comprehension.
760 -- (as of Haskell 98, monad comprehensions are no more.)
761 -- Similarily, array comprehensions must involve parallel arrays types
764 ListComp -> unifyListTy res_ty `thenTc` \ elt_ty ->
765 returnNF_Tc (mkTyConTy listTyCon, (mkListTy, elt_ty))
767 PArrComp -> panic "TcExpr.tcDoStmts: How did we get here?!?"
769 _ -> newTyVarTy (mkArrowKind liftedTypeKind liftedTypeKind) `thenNF_Tc` \ m_ty ->
770 newTyVarTy liftedTypeKind `thenNF_Tc` \ elt_ty ->
771 unifyTauTy res_ty (mkAppTy m_ty elt_ty) `thenTc_`
772 returnNF_Tc (m_ty, (mkAppTy m_ty, elt_ty))
773 ) `thenNF_Tc` \ (tc_ty, m_ty) ->
775 tcStmts (DoCtxt do_or_lc) m_ty stmts `thenTc` \ (stmts', stmts_lie) ->
777 -- Build the then and zero methods in case we need them
778 -- It's important that "then" and "return" appear just once in the final LIE,
779 -- not only for typechecker efficiency, but also because otherwise during
780 -- simplification we end up with silly stuff like
781 -- then = case d of (t,r) -> t
783 -- where the second "then" sees that it already exists in the "available" stuff.
785 tcLookupGlobalId returnMName `thenNF_Tc` \ return_sel_id ->
786 tcLookupGlobalId thenMName `thenNF_Tc` \ then_sel_id ->
787 tcLookupGlobalId failMName `thenNF_Tc` \ fail_sel_id ->
788 newMethod DoOrigin return_sel_id [tc_ty] `thenNF_Tc` \ return_inst ->
789 newMethod DoOrigin then_sel_id [tc_ty] `thenNF_Tc` \ then_inst ->
790 newMethod DoOrigin fail_sel_id [tc_ty] `thenNF_Tc` \ fail_inst ->
792 monad_lie = mkLIE [return_inst, then_inst, fail_inst]
794 returnTc (HsDoOut do_or_lc stmts'
795 (instToId return_inst) (instToId then_inst) (instToId fail_inst)
797 stmts_lie `plusLIE` monad_lie)
801 %************************************************************************
803 \subsection{Record bindings}
805 %************************************************************************
807 Game plan for record bindings
808 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
809 1. Find the TyCon for the bindings, from the first field label.
811 2. Instantiate its tyvars and unify (T a1 .. an) with expected_ty.
813 For each binding field = value
815 3. Instantiate the field type (from the field label) using the type
818 4 Type check the value using tcArg, passing the field type as
819 the expected argument type.
821 This extends OK when the field types are universally quantified.
826 :: TyCon -- Type constructor for the record
827 -> [TcType] -- Args of this type constructor
828 -> RenamedRecordBinds
829 -> TcM (TcRecordBinds, LIE)
831 tcRecordBinds tycon ty_args rbinds
832 = mapAndUnzipTc do_bind rbinds `thenTc` \ (rbinds', lies) ->
833 returnTc (rbinds', plusLIEs lies)
835 tenv = mkTopTyVarSubst (tyConTyVars tycon) ty_args
837 do_bind (field_lbl_name, rhs, pun_flag)
838 = tcLookupGlobalId field_lbl_name `thenNF_Tc` \ sel_id ->
840 field_lbl = recordSelectorFieldLabel sel_id
841 field_ty = substTy tenv (fieldLabelType field_lbl)
843 ASSERT( isRecordSelector sel_id )
844 -- This lookup and assertion will surely succeed, because
845 -- we check that the fields are indeed record selectors
846 -- before calling tcRecordBinds
847 ASSERT2( fieldLabelTyCon field_lbl == tycon, ppr field_lbl )
848 -- The caller of tcRecordBinds has already checked
849 -- that all the fields come from the same type
851 tcExpr rhs field_ty `thenTc` \ (rhs', lie) ->
853 returnTc ((sel_id, rhs', pun_flag), lie)
855 badFields rbinds data_con
856 = [field_name | (field_name, _, _) <- rbinds,
857 not (field_name `elem` field_names)
860 field_names = map fieldLabelName (dataConFieldLabels data_con)
862 missingFields rbinds data_con
863 | null field_labels = ([], []) -- Not declared as a record;
864 -- But C{} is still valid
866 = (missing_strict_fields, other_missing_fields)
868 missing_strict_fields
869 = [ fl | (fl, str) <- field_info,
871 not (fieldLabelName fl `elem` field_names_used)
874 = [ fl | (fl, str) <- field_info,
875 not (isMarkedStrict str),
876 not (fieldLabelName fl `elem` field_names_used)
879 field_names_used = [ field_name | (field_name, _, _) <- rbinds ]
880 field_labels = dataConFieldLabels data_con
882 field_info = zipEqual "missingFields"
884 (dropList ex_theta (dataConStrictMarks data_con))
885 -- The 'drop' is because dataConStrictMarks
886 -- includes the existential dictionaries
887 (_, _, _, ex_theta, _, _) = dataConSig data_con
890 %************************************************************************
892 \subsection{@tcMonoExprs@ typechecks a {\em list} of expressions}
894 %************************************************************************
897 tcMonoExprs :: [RenamedHsExpr] -> [TcType] -> TcM ([TcExpr], LIE)
899 tcMonoExprs [] [] = returnTc ([], emptyLIE)
900 tcMonoExprs (expr:exprs) (ty:tys)
901 = tcMonoExpr expr ty `thenTc` \ (expr', lie1) ->
902 tcMonoExprs exprs tys `thenTc` \ (exprs', lie2) ->
903 returnTc (expr':exprs', lie1 `plusLIE` lie2)
907 %************************************************************************
909 \subsection{Literals}
911 %************************************************************************
916 tcLit :: HsLit -> TcType -> TcM (TcExpr, LIE)
917 tcLit (HsLitLit s _) res_ty
918 = tcLookupClass cCallableClassName `thenNF_Tc` \ cCallableClass ->
919 newDicts (LitLitOrigin (_UNPK_ s))
920 [mkClassPred cCallableClass [res_ty]] `thenNF_Tc` \ dicts ->
921 returnTc (HsLit (HsLitLit s res_ty), mkLIE dicts)
924 = unifyTauTy res_ty (simpleHsLitTy lit) `thenTc_`
925 returnTc (HsLit lit, emptyLIE)
929 %************************************************************************
931 \subsection{Errors and contexts}
933 %************************************************************************
937 Boring and alphabetical:
940 = hang (ptext SLIT("In an arithmetic sequence:")) 4 (ppr expr)
943 = hang (ptext SLIT("In a parallel array sequence:")) 4 (ppr expr)
946 = hang (ptext SLIT("In the case expression:")) 4 (ppr expr)
949 = hang (ptext SLIT("In the scrutinee of a case expression:")) 4 (ppr expr)
952 = hang (ptext SLIT("In an expression with a type signature:"))
956 = hang (ptext SLIT("In the list element:")) 4 (ppr expr)
959 = hang (ptext SLIT("In the parallel array element:")) 4 (ppr expr)
962 = hang (ptext SLIT("In the predicate expression:")) 4 (ppr expr)
965 = hang (ptext SLIT("In the expression:")) 4 (ppr expr)
967 funAppCtxt fun arg arg_no
968 = hang (hsep [ ptext SLIT("In the"), speakNth arg_no, ptext SLIT("argument of"),
969 quotes (ppr fun) <> text ", namely"])
972 wrongArgsCtxt too_many_or_few fun args
973 = hang (ptext SLIT("Probable cause:") <+> quotes (ppr fun)
974 <+> ptext SLIT("is applied to") <+> text too_many_or_few
975 <+> ptext SLIT("arguments in the call"))
976 4 (parens (ppr the_app))
978 the_app = foldl HsApp fun args -- Used in error messages
981 = ptext SLIT("In the application") <+> quotes (ppr the_app)
983 the_app = foldl HsApp fun args -- Used in error messages
985 lurkingRank2Err fun fun_ty
986 = hang (hsep [ptext SLIT("Illegal use of"), quotes (ppr fun)])
987 4 (vcat [ptext SLIT("It is applied to too few arguments"),
988 ptext SLIT("so that the result type has for-alls in it:") <+> ppr fun_ty])
991 = hang (ptext SLIT("No constructor has all these fields:"))
992 4 (pprQuotedList fields)
994 fields = [field | (field, _, _) <- rbinds]
996 recordUpdCtxt expr = ptext SLIT("In the record update:") <+> ppr expr
997 recordConCtxt expr = ptext SLIT("In the record construction:") <+> ppr expr
1000 = hsep [quotes (ppr field), ptext SLIT("is not a record selector")]
1002 missingStrictFieldCon :: Name -> FieldLabel -> SDoc
1003 missingStrictFieldCon con field
1004 = hsep [ptext SLIT("Constructor") <+> quotes (ppr con),
1005 ptext SLIT("does not have the required strict field"), quotes (ppr field)]
1007 missingFieldCon :: Name -> FieldLabel -> SDoc
1008 missingFieldCon con field
1009 = hsep [ptext SLIT("Field") <+> quotes (ppr field),
1010 ptext SLIT("is not initialised")]