2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
6 TcMatches: Typecheck some @Matches@
9 module TcMatches ( tcMatchesFun, tcGRHSsPat, tcMatchesCase, tcMatchLambda,
11 tcStmts, tcStmtsAndThen, tcDoStmts, tcBody,
12 tcDoStmt, tcMDoStmt, tcGuardStmt
15 import {-# SOURCE #-} TcExpr( tcSyntaxOp, tcInferRhoNC, tcInferRho, tcCheckId,
16 tcMonoExpr, tcMonoExprNC, tcPolyExpr )
32 import Coercion ( mkSymCoI )
38 -- Create chunkified tuple tybes for monad comprehensions
43 #include "HsVersions.h"
46 %************************************************************************
48 \subsection{tcMatchesFun, tcMatchesCase}
50 %************************************************************************
52 @tcMatchesFun@ typechecks a @[Match]@ list which occurs in a
53 @FunMonoBind@. The second argument is the name of the function, which
54 is used in error messages. It checks that all the equations have the
55 same number of arguments before using @tcMatches@ to do the work.
57 Note [Polymorphic expected type for tcMatchesFun]
58 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
59 tcMatchesFun may be given a *sigma* (polymorphic) type
60 so it must be prepared to use tcGen to skolemise it.
61 See Note [sig_tau may be polymorphic] in TcPat.
64 tcMatchesFun :: Name -> Bool
66 -> TcSigmaType -- Expected type of function
67 -> TcM (HsWrapper, MatchGroup TcId) -- Returns type of body
68 tcMatchesFun fun_name inf matches exp_ty
69 = do { -- Check that they all have the same no of arguments
70 -- Location is in the monad, set the caller so that
71 -- any inter-equation error messages get some vaguely
72 -- sensible location. Note: we have to do this odd
73 -- ann-grabbing, because we don't always have annotations in
74 -- hand when we call tcMatchesFun...
75 traceTc "tcMatchesFun" (ppr fun_name $$ ppr exp_ty)
76 ; checkArgs fun_name matches
78 ; (wrap_gen, (wrap_fun, group))
79 <- tcGen (FunSigCtxt fun_name) exp_ty $ \ _ exp_rho ->
80 -- Note [Polymorphic expected type for tcMatchesFun]
81 matchFunTys herald arity exp_rho $ \ pat_tys rhs_ty ->
82 tcMatches match_ctxt pat_tys rhs_ty matches
83 ; return (wrap_gen <.> wrap_fun, group) }
85 arity = matchGroupArity matches
86 herald = ptext (sLit "The equation(s) for")
87 <+> quotes (ppr fun_name) <+> ptext (sLit "have")
88 match_ctxt = MC { mc_what = FunRhs fun_name inf, mc_body = tcBody }
91 @tcMatchesCase@ doesn't do the argument-count check because the
92 parser guarantees that each equation has exactly one argument.
95 tcMatchesCase :: TcMatchCtxt -- Case context
96 -> TcRhoType -- Type of scrutinee
97 -> MatchGroup Name -- The case alternatives
98 -> TcRhoType -- Type of whole case expressions
99 -> TcM (MatchGroup TcId) -- Translated alternatives
101 tcMatchesCase ctxt scrut_ty matches res_ty
102 | isEmptyMatchGroup matches -- Allow empty case expressions
103 = return (MatchGroup [] (mkFunTys [scrut_ty] res_ty))
106 = tcMatches ctxt [scrut_ty] res_ty matches
108 tcMatchLambda :: MatchGroup Name -> TcRhoType -> TcM (HsWrapper, MatchGroup TcId)
109 tcMatchLambda match res_ty
110 = matchFunTys herald n_pats res_ty $ \ pat_tys rhs_ty ->
111 tcMatches match_ctxt pat_tys rhs_ty match
113 n_pats = matchGroupArity match
114 herald = sep [ ptext (sLit "The lambda expression")
115 <+> quotes (pprSetDepth (PartWay 1) $
116 pprMatches (LambdaExpr :: HsMatchContext Name) match),
117 -- The pprSetDepth makes the abstraction print briefly
119 match_ctxt = MC { mc_what = LambdaExpr,
123 @tcGRHSsPat@ typechecks @[GRHSs]@ that occur in a @PatMonoBind@.
126 tcGRHSsPat :: GRHSs Name -> TcRhoType -> TcM (GRHSs TcId)
127 -- Used for pattern bindings
128 tcGRHSsPat grhss res_ty = tcGRHSs match_ctxt grhss res_ty
130 match_ctxt = MC { mc_what = PatBindRhs,
137 :: SDoc -- See Note [Herald for matchExpecteFunTys] in TcUnify
140 -> ([TcSigmaType] -> TcRhoType -> TcM a)
141 -> TcM (HsWrapper, a)
143 -- Written in CPS style for historical reasons;
144 -- could probably be un-CPSd, like matchExpectedTyConApp
146 matchFunTys herald arity res_ty thing_inside
147 = do { (coi, pat_tys, res_ty) <- matchExpectedFunTys herald arity res_ty
148 ; res <- thing_inside pat_tys res_ty
149 ; return (coiToHsWrapper (mkSymCoI coi), res) }
152 %************************************************************************
156 %************************************************************************
159 tcMatches :: TcMatchCtxt
160 -> [TcSigmaType] -- Expected pattern types
161 -> TcRhoType -- Expected result-type of the Match.
163 -> TcM (MatchGroup TcId)
165 data TcMatchCtxt -- c.f. TcStmtCtxt, also in this module
166 = MC { mc_what :: HsMatchContext Name, -- What kind of thing this is
167 mc_body :: LHsExpr Name -- Type checker for a body of
170 -> TcM (LHsExpr TcId) }
172 tcMatches ctxt pat_tys rhs_ty (MatchGroup matches _)
173 = ASSERT( not (null matches) ) -- Ensure that rhs_ty is filled in
174 do { matches' <- mapM (tcMatch ctxt pat_tys rhs_ty) matches
175 ; return (MatchGroup matches' (mkFunTys pat_tys rhs_ty)) }
178 tcMatch :: TcMatchCtxt
179 -> [TcSigmaType] -- Expected pattern types
180 -> TcRhoType -- Expected result-type of the Match.
184 tcMatch ctxt pat_tys rhs_ty match
185 = wrapLocM (tc_match ctxt pat_tys rhs_ty) match
187 tc_match ctxt pat_tys rhs_ty match@(Match pats maybe_rhs_sig grhss)
188 = add_match_ctxt match $
189 do { (pats', grhss') <- tcPats (mc_what ctxt) pats pat_tys $
190 tc_grhss ctxt maybe_rhs_sig grhss rhs_ty
191 ; return (Match pats' Nothing grhss') }
193 tc_grhss ctxt Nothing grhss rhs_ty
194 = tcGRHSs ctxt grhss rhs_ty -- No result signature
196 -- Result type sigs are no longer supported
197 tc_grhss _ (Just {}) _ _
198 = panic "tc_ghrss" -- Rejected by renamer
200 -- For (\x -> e), tcExpr has already said "In the expresssion \x->e"
201 -- so we don't want to add "In the lambda abstraction \x->e"
202 add_match_ctxt match thing_inside
203 = case mc_what ctxt of
204 LambdaExpr -> thing_inside
205 m_ctxt -> addErrCtxt (pprMatchInCtxt m_ctxt match) thing_inside
208 tcGRHSs :: TcMatchCtxt -> GRHSs Name -> TcRhoType
211 -- Notice that we pass in the full res_ty, so that we get
212 -- good inference from simple things like
213 -- f = \(x::forall a.a->a) -> <stuff>
214 -- We used to force it to be a monotype when there was more than one guard
215 -- but we don't need to do that any more
217 tcGRHSs ctxt (GRHSs grhss binds) res_ty
218 = do { (binds', grhss') <- tcLocalBinds binds $
219 mapM (wrapLocM (tcGRHS ctxt res_ty)) grhss
221 ; return (GRHSs grhss' binds') }
224 tcGRHS :: TcMatchCtxt -> TcRhoType -> GRHS Name -> TcM (GRHS TcId)
226 tcGRHS ctxt res_ty (GRHS guards rhs)
227 = do { (guards', rhs') <- tcStmtsAndThen stmt_ctxt tcGuardStmt guards res_ty $
229 ; return (GRHS guards' rhs') }
231 stmt_ctxt = PatGuard (mc_what ctxt)
235 %************************************************************************
237 \subsection{@tcDoStmts@ typechecks a {\em list} of do statements}
239 %************************************************************************
242 tcDoStmts :: HsStmtContext Name
245 -> TcM (HsExpr TcId) -- Returns a HsDo
246 tcDoStmts ListComp stmts res_ty
247 = do { (coi, elt_ty) <- matchExpectedListTy res_ty
248 ; stmts' <- tcStmts ListComp (tcLcStmt listTyCon) stmts elt_ty
249 ; return $ mkHsWrapCoI coi
250 (HsDo ListComp stmts' (mkListTy elt_ty)) }
252 tcDoStmts PArrComp stmts res_ty
253 = do { (coi, elt_ty) <- matchExpectedPArrTy res_ty
254 ; stmts' <- tcStmts PArrComp (tcLcStmt parrTyCon) stmts elt_ty
255 ; return $ mkHsWrapCoI coi
256 (HsDo PArrComp stmts' (mkPArrTy elt_ty)) }
258 tcDoStmts DoExpr stmts res_ty
259 = do { stmts' <- tcStmts DoExpr tcDoStmt stmts res_ty
260 ; return (HsDo DoExpr stmts' res_ty) }
262 tcDoStmts MDoExpr stmts res_ty
263 = do { stmts' <- tcStmts MDoExpr tcDoStmt stmts res_ty
264 ; return (HsDo MDoExpr stmts' res_ty) }
266 tcDoStmts MonadComp stmts res_ty
267 = do { stmts' <- tcStmts MonadComp tcMcStmt stmts res_ty
268 ; return (HsDo MonadComp stmts' res_ty) }
270 tcDoStmts ctxt _ _ = pprPanic "tcDoStmts" (pprStmtContext ctxt)
272 tcBody :: LHsExpr Name -> TcRhoType -> TcM (LHsExpr TcId)
274 = do { traceTc "tcBody" (ppr res_ty)
275 ; body' <- tcMonoExpr body res_ty
281 %************************************************************************
285 %************************************************************************
289 = forall thing. HsStmtContext Name
291 -> TcRhoType -- Result type for comprehension
292 -> (TcRhoType -> TcM thing) -- Checker for what follows the stmt
293 -> TcM (Stmt TcId, thing)
295 tcStmts :: HsStmtContext Name
296 -> TcStmtChecker -- NB: higher-rank type
300 tcStmts ctxt stmt_chk stmts res_ty
301 = do { (stmts', _) <- tcStmtsAndThen ctxt stmt_chk stmts res_ty $
305 tcStmtsAndThen :: HsStmtContext Name
306 -> TcStmtChecker -- NB: higher-rank type
309 -> (TcRhoType -> TcM thing)
310 -> TcM ([LStmt TcId], thing)
312 -- Note the higher-rank type. stmt_chk is applied at different
313 -- types in the equations for tcStmts
315 tcStmtsAndThen _ _ [] res_ty thing_inside
316 = do { thing <- thing_inside res_ty
317 ; return ([], thing) }
319 -- LetStmts are handled uniformly, regardless of context
320 tcStmtsAndThen ctxt stmt_chk (L loc (LetStmt binds) : stmts) res_ty thing_inside
321 = do { (binds', (stmts',thing)) <- tcLocalBinds binds $
322 tcStmtsAndThen ctxt stmt_chk stmts res_ty thing_inside
323 ; return (L loc (LetStmt binds') : stmts', thing) }
325 -- For the vanilla case, handle the location-setting part
326 tcStmtsAndThen ctxt stmt_chk (L loc stmt : stmts) res_ty thing_inside
327 = do { (stmt', (stmts', thing)) <-
329 addErrCtxt (pprStmtInCtxt ctxt stmt) $
330 stmt_chk ctxt stmt res_ty $ \ res_ty' ->
332 tcStmtsAndThen ctxt stmt_chk stmts res_ty' $
334 ; return (L loc stmt' : stmts', thing) }
336 --------------------------------
338 tcGuardStmt :: TcStmtChecker
339 tcGuardStmt _ (ExprStmt guard _ _ _) res_ty thing_inside
340 = do { guard' <- tcMonoExpr guard boolTy
341 ; thing <- thing_inside res_ty
342 ; return (ExprStmt guard' noSyntaxExpr noSyntaxExpr boolTy, thing) }
344 tcGuardStmt ctxt (BindStmt pat rhs _ _) res_ty thing_inside
345 = do { (rhs', rhs_ty) <- tcInferRhoNC rhs -- Stmt has a context already
346 ; (pat', thing) <- tcPat (StmtCtxt ctxt) pat rhs_ty $
348 ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) }
350 tcGuardStmt _ stmt _ _
351 = pprPanic "tcGuardStmt: unexpected Stmt" (ppr stmt)
354 --------------------------------
355 -- List comprehensions and PArrays
357 tcLcStmt :: TyCon -- The list/Parray type constructor ([] or PArray)
360 tcLcStmt _ _ (LastStmt body _) elt_ty thing_inside
361 = do { body' <- tcMonoExprNC body elt_ty
362 ; thing <- thing_inside (panic "tcLcStmt: thing_inside")
363 ; return (LastStmt body' noSyntaxExpr, thing) }
365 -- A generator, pat <- rhs
366 tcLcStmt m_tc ctxt (BindStmt pat rhs _ _) elt_ty thing_inside
367 = do { pat_ty <- newFlexiTyVarTy liftedTypeKind
368 ; rhs' <- tcMonoExpr rhs (mkTyConApp m_tc [pat_ty])
369 ; (pat', thing) <- tcPat (StmtCtxt ctxt) pat pat_ty $
371 ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) }
374 tcLcStmt _ _ (ExprStmt rhs _ _ _) elt_ty thing_inside
375 = do { rhs' <- tcMonoExpr rhs boolTy
376 ; thing <- thing_inside elt_ty
377 ; return (ExprStmt rhs' noSyntaxExpr noSyntaxExpr boolTy, thing) }
379 -- A parallel set of comprehensions
380 -- [ (g x, h x) | ... ; let g v = ...
381 -- | ... ; let h v = ... ]
383 -- It's possible that g,h are overloaded, so we need to feed the LIE from the
384 -- (g x, h x) up through both lots of bindings (so we get the bindLocalMethods).
385 -- Similarly if we had an existential pattern match:
387 -- data T = forall a. Show a => C a
389 -- [ (show x, show y) | ... ; C x <- ...
390 -- | ... ; C y <- ... ]
392 -- Then we need the LIE from (show x, show y) to be simplified against
393 -- the bindings for x and y.
395 -- It's difficult to do this in parallel, so we rely on the renamer to
396 -- ensure that g,h and x,y don't duplicate, and simply grow the environment.
397 -- So the binders of the first parallel group will be in scope in the second
398 -- group. But that's fine; there's no shadowing to worry about.
400 tcLcStmt m_tc ctxt (ParStmt bndr_stmts_s _ _ _) elt_ty thing_inside
401 = do { (pairs', thing) <- loop bndr_stmts_s
402 ; return (ParStmt pairs' noSyntaxExpr noSyntaxExpr noSyntaxExpr, thing) }
404 -- loop :: [([LStmt Name], [Name])] -> TcM ([([LStmt TcId], [TcId])], thing)
405 loop [] = do { thing <- thing_inside elt_ty
406 ; return ([], thing) } -- matching in the branches
408 loop ((stmts, names) : pairs)
409 = do { (stmts', (ids, pairs', thing))
410 <- tcStmtsAndThen ctxt (tcLcStmt m_tc) stmts elt_ty $ \ _elt_ty' ->
411 do { ids <- tcLookupLocalIds names
412 ; (pairs', thing) <- loop pairs
413 ; return (ids, pairs', thing) }
414 ; return ( (stmts', ids) : pairs', thing ) }
416 tcLcStmt m_tc ctxt (TransStmt { trS_form = form, trS_stmts = stmts
417 , trS_bndrs = bindersMap
418 , trS_by = by, trS_using = using }) elt_ty thing_inside
419 = do { let (bndr_names, n_bndr_names) = unzip bindersMap
420 unused_ty = pprPanic "tcLcStmt: inner ty" (ppr bindersMap)
421 -- The inner 'stmts' lack a LastStmt, so the element type
422 -- passed in to tcStmtsAndThen is never looked at
423 ; (stmts', (bndr_ids, by'))
424 <- tcStmtsAndThen (TransformStmtCtxt ctxt) (tcLcStmt m_tc) stmts unused_ty $ \_ -> do
426 Nothing -> return Nothing
427 Just e -> do { e_ty <- tcInferRho e; return (Just e_ty) }
428 ; bndr_ids <- tcLookupLocalIds bndr_names
429 ; return (bndr_ids, by') }
431 ; let m_app ty = mkTyConApp m_tc [ty]
433 --------------- Typecheck the 'using' function -------------
434 -- using :: ((a,b,c)->t) -> m (a,b,c) -> m (a,b,c)m (ThenForm)
435 -- :: ((a,b,c)->t) -> m (a,b,c) -> m (m (a,b,c))) (GroupForm)
437 -- n_app :: Type -> Type -- Wraps a 'ty' into '[ty]' for GroupForm
438 ; let n_app = case form of
439 ThenForm -> (\ty -> ty)
442 by_arrow :: Type -> Type -- Wraps 'ty' to '(a->t) -> ty' if the By is present
443 by_arrow = case by' of
445 Just (_,e_ty) -> \ty -> e_ty `mkFunTy` ty
447 tup_ty = mkBigCoreVarTupTy bndr_ids
448 poly_arg_ty = m_app alphaTy
449 poly_res_ty = m_app (n_app alphaTy)
450 using_poly_ty = mkForAllTy alphaTyVar $ by_arrow $
451 poly_arg_ty `mkFunTy` poly_res_ty
453 ; using' <- tcPolyExpr using using_poly_ty
454 ; let final_using = fmap (HsWrap (WpTyApp tup_ty)) using'
456 -- 'stmts' returns a result of type (m1_ty tuple_ty),
457 -- typically something like [(Int,Bool,Int)]
458 -- We don't know what tuple_ty is yet, so we use a variable
459 ; let mk_n_bndr :: Name -> TcId -> TcId
460 mk_n_bndr n_bndr_name bndr_id = mkLocalId n_bndr_name (n_app (idType bndr_id))
462 -- Ensure that every old binder of type `b` is linked up with its
463 -- new binder which should have type `n b`
464 -- See Note [GroupStmt binder map] in HsExpr
465 n_bndr_ids = zipWith mk_n_bndr n_bndr_names bndr_ids
466 bindersMap' = bndr_ids `zip` n_bndr_ids
468 -- Type check the thing in the environment with
469 -- these new binders and return the result
470 ; thing <- tcExtendIdEnv n_bndr_ids (thing_inside elt_ty)
472 ; return (emptyTransStmt { trS_stmts = stmts', trS_bndrs = bindersMap'
473 , trS_by = fmap fst by', trS_using = final_using
474 , trS_form = form }, thing) }
476 tcLcStmt _ _ stmt _ _
477 = pprPanic "tcLcStmt: unexpected Stmt" (ppr stmt)
480 --------------------------------
481 -- Monad comprehensions
483 tcMcStmt :: TcStmtChecker
485 tcMcStmt _ (LastStmt body return_op) res_ty thing_inside
486 = do { a_ty <- newFlexiTyVarTy liftedTypeKind
487 ; return_op' <- tcSyntaxOp MCompOrigin return_op
488 (a_ty `mkFunTy` res_ty)
489 ; body' <- tcMonoExprNC body a_ty
490 ; thing <- thing_inside (panic "tcMcStmt: thing_inside")
491 ; return (LastStmt body' return_op', thing) }
493 -- Generators for monad comprehensions ( pat <- rhs )
495 -- [ body | q <- gen ] -> gen :: m a
499 tcMcStmt ctxt (BindStmt pat rhs bind_op fail_op) res_ty thing_inside
500 = do { rhs_ty <- newFlexiTyVarTy liftedTypeKind
501 ; pat_ty <- newFlexiTyVarTy liftedTypeKind
502 ; new_res_ty <- newFlexiTyVarTy liftedTypeKind
504 -- (>>=) :: rhs_ty -> (pat_ty -> new_res_ty) -> res_ty
505 ; bind_op' <- tcSyntaxOp MCompOrigin bind_op
506 (mkFunTys [rhs_ty, mkFunTy pat_ty new_res_ty] res_ty)
508 -- If (but only if) the pattern can fail, typecheck the 'fail' operator
509 ; fail_op' <- if isIrrefutableHsPat pat
510 then return noSyntaxExpr
511 else tcSyntaxOp MCompOrigin fail_op (mkFunTy stringTy new_res_ty)
513 ; rhs' <- tcMonoExprNC rhs rhs_ty
514 ; (pat', thing) <- tcPat (StmtCtxt ctxt) pat pat_ty $
515 thing_inside new_res_ty
517 ; return (BindStmt pat' rhs' bind_op' fail_op', thing) }
519 -- Boolean expressions.
521 -- [ body | stmts, expr ] -> expr :: m Bool
523 tcMcStmt _ (ExprStmt rhs then_op guard_op _) res_ty thing_inside
524 = do { -- Deal with rebindable syntax:
525 -- guard_op :: test_ty -> rhs_ty
526 -- then_op :: rhs_ty -> new_res_ty -> res_ty
527 -- Where test_ty is, for example, Bool
528 test_ty <- newFlexiTyVarTy liftedTypeKind
529 ; rhs_ty <- newFlexiTyVarTy liftedTypeKind
530 ; new_res_ty <- newFlexiTyVarTy liftedTypeKind
531 ; rhs' <- tcMonoExpr rhs test_ty
532 ; guard_op' <- tcSyntaxOp MCompOrigin guard_op
533 (mkFunTy test_ty rhs_ty)
534 ; then_op' <- tcSyntaxOp MCompOrigin then_op
535 (mkFunTys [rhs_ty, new_res_ty] res_ty)
536 ; thing <- thing_inside new_res_ty
537 ; return (ExprStmt rhs' then_op' guard_op' rhs_ty, thing) }
539 -- Grouping statements
541 -- [ body | stmts, then group by e ]
543 -- [ body | stmts, then group by e using f ]
545 -- f :: forall a. (a -> t) -> m a -> m (m a)
546 -- [ body | stmts, then group using f ]
547 -- -> f :: forall a. m a -> m (m a)
549 -- We type [ body | (stmts, group by e using f), ... ]
550 -- f <optional by> [ (a,b,c) | stmts ] >>= \(a,b,c) -> ...body....
552 -- We type the functions as follows:
553 -- f <optional by> :: m1 (a,b,c) -> m2 (a,b,c) (ThenForm)
554 -- :: m1 (a,b,c) -> m2 (n (a,b,c)) (GroupForm)
555 -- (>>=) :: m2 (a,b,c) -> ((a,b,c) -> res) -> res (ThenForm)
556 -- :: m2 (n (a,b,c)) -> (n (a,b,c) -> res) -> res (GroupForm)
558 tcMcStmt ctxt (TransStmt { trS_stmts = stmts, trS_bndrs = bindersMap
559 , trS_by = by, trS_using = using, trS_form = form
560 , trS_ret = return_op, trS_bind = bind_op
561 , trS_fmap = fmap_op }) res_ty thing_inside
562 = do { let star_star_kind = liftedTypeKind `mkArrowKind` liftedTypeKind
563 ; m1_ty <- newFlexiTyVarTy star_star_kind
564 ; m2_ty <- newFlexiTyVarTy star_star_kind
565 ; tup_ty <- newFlexiTyVarTy liftedTypeKind
566 ; by_e_ty <- newFlexiTyVarTy liftedTypeKind -- The type of the 'by' expression (if any)
568 --------------- Typecheck the 'using' function -------------
569 -- using :: ((a,b,c)->t) -> m1 (a,b,c) -> m2 (n (a,b,c))
571 -- n_app :: Type -> Type -- Wraps a 'ty' into '(n ty)' for GroupForm
572 ; n_app <- case form of
573 ThenForm -> return (\ty -> ty)
574 _ -> do { n_ty <- newFlexiTyVarTy star_star_kind
575 ; return (n_ty `mkAppTy`) }
576 ; let by_arrow :: Type -> Type -- Wraps 'ty' to '(a->t) -> ty' if the By is present
577 by_arrow = case by of
579 Just {} -> \ty -> by_e_ty `mkFunTy` ty
581 poly_arg_ty = m1_ty `mkAppTy` alphaTy
582 using_arg_ty = m1_ty `mkAppTy` tup_ty
583 poly_res_ty = m2_ty `mkAppTy` n_app alphaTy
584 using_res_ty = m2_ty `mkAppTy` n_app tup_ty
585 using_poly_ty = mkForAllTy alphaTyVar $ by_arrow $
586 poly_arg_ty `mkFunTy` poly_res_ty
588 ; using' <- tcPolyExpr using using_poly_ty
589 ; let final_using = fmap (HsWrap (WpTyApp tup_ty)) using'
591 --------------- Typecheck the 'bind' function -------------
592 -- (>>=) :: m2 (n (a,b,c)) -> ( n (a,b,c) -> new_res_ty ) -> res_ty
593 ; new_res_ty <- newFlexiTyVarTy liftedTypeKind
594 ; let n_tup_ty = n_app tup_ty -- n (a,b,c)
595 ; bind_op' <- tcSyntaxOp MCompOrigin bind_op $
596 using_res_ty `mkFunTy` (n_tup_ty `mkFunTy` new_res_ty)
599 --------------- Typecheck the 'fmap' function -------------
600 ; fmap_op' <- case form of
601 ThenForm -> return noSyntaxExpr
602 _ -> fmap unLoc . tcPolyExpr (noLoc fmap_op) $
603 mkForAllTy alphaTyVar $ mkForAllTy betaTyVar $
604 (alphaTy `mkFunTy` betaTy)
605 `mkFunTy` (n_app alphaTy)
606 `mkFunTy` (n_app betaTy)
608 -- 'stmts' returns a result of type (m1_ty tuple_ty),
609 -- typically something like [(Int,Bool,Int)]
610 -- We don't know what tuple_ty is yet, so we use a variable
611 ; let (bndr_names, n_bndr_names) = unzip bindersMap
612 ; (stmts', (bndr_ids, by', return_op')) <-
613 tcStmtsAndThen (TransformStmtCtxt ctxt) tcMcStmt stmts using_arg_ty $ \res_ty' -> do
615 Nothing -> return Nothing
616 Just e -> do { e' <- tcMonoExpr e by_e_ty; return (Just e') }
618 -- Find the Ids (and hence types) of all old binders
619 ; bndr_ids <- tcLookupLocalIds bndr_names
621 -- 'return' is only used for the binders, so we know its type.
622 -- return :: (a,b,c,..) -> m (a,b,c,..)
623 ; return_op' <- tcSyntaxOp MCompOrigin return_op $
624 (mkBigCoreVarTupTy bndr_ids) `mkFunTy` res_ty'
626 ; return (bndr_ids, by', return_op') }
628 ; let mk_n_bndr :: Name -> TcId -> TcId
629 mk_n_bndr n_bndr_name bndr_id = mkLocalId n_bndr_name (n_app (idType bndr_id))
631 -- Ensure that every old binder of type `b` is linked up with its
632 -- new binder which should have type `n b`
633 -- See Note [GroupStmt binder map] in HsExpr
634 n_bndr_ids = zipWith mk_n_bndr n_bndr_names bndr_ids
635 bindersMap' = bndr_ids `zip` n_bndr_ids
637 -- Type check the thing in the environment with
638 -- these new binders and return the result
639 ; thing <- tcExtendIdEnv n_bndr_ids (thing_inside res_ty)
641 ; return (TransStmt { trS_stmts = stmts', trS_bndrs = bindersMap'
642 , trS_by = by', trS_using = final_using
643 , trS_ret = return_op', trS_bind = bind_op'
644 , trS_fmap = fmap_op', trS_form = form }, thing) }
646 -- Typecheck `ParStmt`. See `tcLcStmt` for more informations about typechecking
649 -- Note: The `mzip` function will get typechecked via:
651 -- ParStmt [st1::t1, st2::t2, st3::t3]
654 -- -> (m st2 -> m st3 -> m (st2, st3)) -- recursive call
655 -- -> m (st1, (st2, st3))
657 tcMcStmt ctxt (ParStmt bndr_stmts_s mzip_op bind_op return_op) res_ty thing_inside
658 = do { (_,(m_ty,_)) <- matchExpectedAppTy res_ty
659 -- ToDo: what if the coercion isn't the identity?
661 ; (pairs', thing) <- loop m_ty bndr_stmts_s
663 ; let mzip_ty = mkForAllTys [alphaTyVar, betaTyVar] $
664 (m_ty `mkAppTy` alphaTy)
666 (m_ty `mkAppTy` betaTy)
668 (m_ty `mkAppTy` mkBoxedTupleTy [alphaTy, betaTy])
669 ; mzip_op' <- unLoc `fmap` tcPolyExpr (noLoc mzip_op) mzip_ty
672 ; let tys = map (mkBigCoreVarTupTy . snd) pairs'
673 tuple_ty = mk_tuple_ty tys
675 ; bind_op' <- tcSyntaxOp MCompOrigin bind_op $
676 (m_ty `mkAppTy` tuple_ty)
678 (tuple_ty `mkFunTy` res_ty)
682 ; return_op' <- fmap unLoc . tcPolyExpr (noLoc return_op) $
683 mkForAllTy alphaTyVar $
684 alphaTy `mkFunTy` (m_ty `mkAppTy` alphaTy)
686 ; return (ParStmt pairs' mzip_op' bind_op' return_op', thing) }
688 where mk_tuple_ty tys = foldr1 (\tn tm -> mkBoxedTupleTy [tn, tm]) tys
690 -- loop :: Type -- m_ty
691 -- -> [([LStmt Name], [Name])]
692 -- -> TcM ([([LStmt TcId], [TcId])], thing)
693 loop _ [] = do { thing <- thing_inside res_ty
694 ; return ([], thing) } -- matching in the branches
696 loop m_ty ((stmts, names) : pairs)
697 = do { -- type dummy since we don't know all binder types yet
698 ty_dummy <- newFlexiTyVarTy liftedTypeKind
699 ; (stmts', (ids, pairs', thing))
700 <- tcStmtsAndThen ctxt tcMcStmt stmts ty_dummy $ \res_ty' ->
701 do { ids <- tcLookupLocalIds names
702 ; _ <- unifyType res_ty' (m_ty `mkAppTy` mkBigCoreVarTupTy ids)
703 ; (pairs', thing) <- loop m_ty pairs
704 ; return (ids, pairs', thing) }
705 ; return ( (stmts', ids) : pairs', thing ) }
708 = pprPanic "tcMcStmt: unexpected Stmt" (ppr stmt)
710 --------------------------------
712 -- The main excitement here is dealing with rebindable syntax
714 tcDoStmt :: TcStmtChecker
716 tcDoStmt _ (LastStmt body _) res_ty thing_inside
717 = do { body' <- tcMonoExprNC body res_ty
718 ; thing <- thing_inside (panic "tcDoStmt: thing_inside")
719 ; return (LastStmt body' noSyntaxExpr, thing) }
721 tcDoStmt ctxt (BindStmt pat rhs bind_op fail_op) res_ty thing_inside
722 = do { -- Deal with rebindable syntax:
723 -- (>>=) :: rhs_ty -> (pat_ty -> new_res_ty) -> res_ty
724 -- This level of generality is needed for using do-notation
725 -- in full generality; see Trac #1537
727 -- I'd like to put this *after* the tcSyntaxOp
728 -- (see Note [Treat rebindable syntax first], but that breaks
729 -- the rigidity info for GADTs. When we move to the new story
730 -- for GADTs, we can move this after tcSyntaxOp
731 rhs_ty <- newFlexiTyVarTy liftedTypeKind
732 ; pat_ty <- newFlexiTyVarTy liftedTypeKind
733 ; new_res_ty <- newFlexiTyVarTy liftedTypeKind
734 ; bind_op' <- tcSyntaxOp DoOrigin bind_op
735 (mkFunTys [rhs_ty, mkFunTy pat_ty new_res_ty] res_ty)
737 -- If (but only if) the pattern can fail,
738 -- typecheck the 'fail' operator
739 ; fail_op' <- if isIrrefutableHsPat pat
740 then return noSyntaxExpr
741 else tcSyntaxOp DoOrigin fail_op (mkFunTy stringTy new_res_ty)
743 ; rhs' <- tcMonoExprNC rhs rhs_ty
744 ; (pat', thing) <- tcPat (StmtCtxt ctxt) pat pat_ty $
745 thing_inside new_res_ty
747 ; return (BindStmt pat' rhs' bind_op' fail_op', thing) }
750 tcDoStmt _ (ExprStmt rhs then_op _ _) res_ty thing_inside
751 = do { -- Deal with rebindable syntax;
752 -- (>>) :: rhs_ty -> new_res_ty -> res_ty
753 -- See also Note [Treat rebindable syntax first]
754 rhs_ty <- newFlexiTyVarTy liftedTypeKind
755 ; new_res_ty <- newFlexiTyVarTy liftedTypeKind
756 ; then_op' <- tcSyntaxOp DoOrigin then_op
757 (mkFunTys [rhs_ty, new_res_ty] res_ty)
759 ; rhs' <- tcMonoExprNC rhs rhs_ty
760 ; thing <- thing_inside new_res_ty
761 ; return (ExprStmt rhs' then_op' noSyntaxExpr rhs_ty, thing) }
763 tcDoStmt ctxt (RecStmt { recS_stmts = stmts, recS_later_ids = later_names
764 , recS_rec_ids = rec_names, recS_ret_fn = ret_op
765 , recS_mfix_fn = mfix_op, recS_bind_fn = bind_op })
767 = do { let tup_names = rec_names ++ filterOut (`elem` rec_names) later_names
768 ; tup_elt_tys <- newFlexiTyVarTys (length tup_names) liftedTypeKind
769 ; let tup_ids = zipWith mkLocalId tup_names tup_elt_tys
770 tup_ty = mkBoxedTupleTy tup_elt_tys
772 ; tcExtendIdEnv tup_ids $ do
773 { stmts_ty <- newFlexiTyVarTy liftedTypeKind
774 ; (stmts', (ret_op', tup_rets))
775 <- tcStmtsAndThen ctxt tcDoStmt stmts stmts_ty $ \ inner_res_ty ->
776 do { tup_rets <- zipWithM tcCheckId tup_names tup_elt_tys
777 -- Unify the types of the "final" Ids (which may
778 -- be polymorphic) with those of "knot-tied" Ids
779 ; ret_op' <- tcSyntaxOp DoOrigin ret_op (mkFunTy tup_ty inner_res_ty)
780 ; return (ret_op', tup_rets) }
782 ; mfix_res_ty <- newFlexiTyVarTy liftedTypeKind
783 ; mfix_op' <- tcSyntaxOp DoOrigin mfix_op
784 (mkFunTy (mkFunTy tup_ty stmts_ty) mfix_res_ty)
786 ; new_res_ty <- newFlexiTyVarTy liftedTypeKind
787 ; bind_op' <- tcSyntaxOp DoOrigin bind_op
788 (mkFunTys [mfix_res_ty, mkFunTy tup_ty new_res_ty] res_ty)
790 ; thing <- thing_inside new_res_ty
791 -- ; lie_binds <- bindLocalMethods lie tup_ids
793 ; let rec_ids = takeList rec_names tup_ids
794 ; later_ids <- tcLookupLocalIds later_names
795 ; traceTc "tcdo" $ vcat [ppr rec_ids <+> ppr (map idType rec_ids),
796 ppr later_ids <+> ppr (map idType later_ids)]
797 ; return (RecStmt { recS_stmts = stmts', recS_later_ids = later_ids
798 , recS_rec_ids = rec_ids, recS_ret_fn = ret_op'
799 , recS_mfix_fn = mfix_op', recS_bind_fn = bind_op'
800 , recS_rec_rets = tup_rets, recS_ret_ty = stmts_ty }, thing)
804 = pprPanic "tcDoStmt: unexpected Stmt" (ppr stmt)
807 Note [Treat rebindable syntax first]
808 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
810 do { bar; ... } :: IO ()
811 we want to typecheck 'bar' in the knowledge that it should be an IO thing,
812 pushing info from the context into the RHS. To do this, we check the
813 rebindable syntax first, and push that information into (tcMonoExprNC rhs).
814 Otherwise the error shows up when cheking the rebindable syntax, and
815 the expected/inferred stuff is back to front (see Trac #3613).
818 --------------------------------
820 -- The distinctive features here are
822 -- (b) no rebindable syntax
824 tcMDoStmt :: (LHsExpr Name -> TcM (LHsExpr TcId, TcType)) -- RHS inference
826 -- Used only by TcArrows... should be gotten rid of
827 tcMDoStmt tc_rhs ctxt (BindStmt pat rhs _ _) res_ty thing_inside
828 = do { (rhs', pat_ty) <- tc_rhs rhs
829 ; (pat', thing) <- tcPat (StmtCtxt ctxt) pat pat_ty $
831 ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) }
833 tcMDoStmt tc_rhs _ (ExprStmt rhs _ _ _) res_ty thing_inside
834 = do { (rhs', elt_ty) <- tc_rhs rhs
835 ; thing <- thing_inside res_ty
836 ; return (ExprStmt rhs' noSyntaxExpr noSyntaxExpr elt_ty, thing) }
838 tcMDoStmt tc_rhs ctxt (RecStmt { recS_stmts = stmts, recS_later_ids = laterNames
839 , recS_rec_ids = recNames }) res_ty thing_inside
840 = do { rec_tys <- newFlexiTyVarTys (length recNames) liftedTypeKind
841 ; let rec_ids = zipWith mkLocalId recNames rec_tys
842 ; tcExtendIdEnv rec_ids $ do
843 { (stmts', (later_ids, rec_rets))
844 <- tcStmtsAndThen ctxt (tcMDoStmt tc_rhs) stmts res_ty $ \ _res_ty' ->
845 -- ToDo: res_ty not really right
846 do { rec_rets <- zipWithM tcCheckId recNames rec_tys
847 ; later_ids <- tcLookupLocalIds laterNames
848 ; return (later_ids, rec_rets) }
850 ; thing <- tcExtendIdEnv later_ids (thing_inside res_ty)
851 -- NB: The rec_ids for the recursive things
852 -- already scope over this part. This binding may shadow
853 -- some of them with polymorphic things with the same Name
854 -- (see note [RecStmt] in HsExpr)
856 ; return (emptyRecStmt { recS_stmts = stmts', recS_later_ids = later_ids
857 , recS_rec_ids = rec_ids, recS_rec_rets = rec_rets
858 , recS_ret_ty = res_ty }, thing)
861 tcMDoStmt _ _ stmt _ _
862 = pprPanic "tcMDoStmt: unexpected Stmt" (ppr stmt)
866 %************************************************************************
868 \subsection{Errors and contexts}
870 %************************************************************************
872 @sameNoOfArgs@ takes a @[RenamedMatch]@ and decides whether the same
873 number of args are used in each equation.
876 checkArgs :: Name -> MatchGroup Name -> TcM ()
877 checkArgs fun (MatchGroup (match1:matches) _)
878 | null bad_matches = return ()
880 = failWithTc (vcat [ptext (sLit "Equations for") <+> quotes (ppr fun) <+>
881 ptext (sLit "have different numbers of arguments"),
882 nest 2 (ppr (getLoc match1)),
883 nest 2 (ppr (getLoc (head bad_matches)))])
885 n_args1 = args_in_match match1
886 bad_matches = [m | m <- matches, args_in_match m /= n_args1]
888 args_in_match :: LMatch Name -> Int
889 args_in_match (L _ (Match pats _ _)) = length pats
890 checkArgs fun _ = pprPanic "TcPat.checkArgs" (ppr fun) -- Matches always non-empty