2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
4 \section[TcBinds]{TcBinds}
7 #include "HsVersions.h"
9 module TcBinds ( tcBindsAndThen, tcPragmaSigs ) where
13 import HsSyn ( HsBinds(..), Bind(..), Sig(..), MonoBinds(..),
14 HsExpr, Match, PolyType, InPat, OutPat,
15 GRHSsAndBinds, ArithSeqInfo, HsLit, Fake,
17 import RnHsSyn ( RenamedHsBinds(..), RenamedBind(..), RenamedSig(..),
18 RenamedMonoBinds(..) )
19 import TcHsSyn ( TcHsBinds(..), TcBind(..), TcMonoBinds(..),
20 TcIdOcc(..), TcIdBndr(..) )
23 import GenSpecEtc ( checkSigTyVars, genBinds, TcSigInfo(..) )
24 import Inst ( Inst, LIE(..), emptyLIE, plusLIE, InstOrigin(..) )
25 import TcEnv ( tcExtendLocalValEnv, tcLookupLocalValueOK, newMonoIds )
26 import TcLoop ( tcGRHSsAndBinds )
27 import TcMatches ( tcMatchesFun )
28 import TcMonoType ( tcPolyType )
29 import TcPat ( tcPat )
30 import TcSimplify ( bindInstsOfLocalFuns )
31 import TcType ( newTcTyVar, tcInstType )
32 import Unify ( unifyTauTy )
34 import Kind ( mkBoxedTypeKind, mkTypeKind )
35 import Id ( GenId, idType, mkUserId )
36 import IdInfo ( noIdInfo )
37 import Name ( Name ) -- instances
38 import Maybes ( assocMaybe, catMaybes, Maybe(..) )
39 import Outputable ( pprNonOp )
40 import PragmaInfo ( PragmaInfo(..) )
42 import Type ( mkTyVarTy, mkTyVarTys, isTyVarTy,
43 mkSigmaTy, splitSigmaTy,
44 splitRhoTy, mkForAllTy, splitForAllTy )
48 %************************************************************************
50 \subsection{Type-checking bindings}
52 %************************************************************************
54 @tcBindsAndThen@ typechecks a @HsBinds@. The "and then" part is because
55 it needs to know something about the {\em usage} of the things bound,
56 so that it can create specialisations of them. So @tcBindsAndThen@
57 takes a function which, given an extended environment, E, typechecks
58 the scope of the bindings returning a typechecked thing and (most
59 important) an LIE. It is this LIE which is then used as the basis for
60 specialising the things bound.
62 @tcBindsAndThen@ also takes a "combiner" which glues together the
63 bindings and the "thing" to make a new "thing".
65 The real work is done by @tcBindAndThen@.
67 Recursive and non-recursive binds are handled in essentially the same
68 way: because of uniques there are no scoping issues left. The only
69 difference is that non-recursive bindings can bind primitive values.
71 Even for non-recursive binding groups we add typings for each binder
72 to the LVE for the following reason. When each individual binding is
73 checked the type of its LHS is unified with that of its RHS; and
74 type-checking the LHS of course requires that the binder is in scope.
76 At the top-level the LIE is sure to contain nothing but constant
77 dictionaries, which we resolve at the module level.
81 :: (TcHsBinds s -> thing -> thing) -- Combinator
83 -> TcM s (thing, LIE s, thing_ty)
84 -> TcM s (thing, LIE s, thing_ty)
86 tcBindsAndThen combiner EmptyBinds do_next
87 = do_next `thenTc` \ (thing, lie, thing_ty) ->
88 returnTc (combiner EmptyBinds thing, lie, thing_ty)
90 tcBindsAndThen combiner (SingleBind bind) do_next
91 = tcBindAndThen combiner bind [] do_next
93 tcBindsAndThen combiner (BindWith bind sigs) do_next
94 = tcBindAndThen combiner bind sigs do_next
96 tcBindsAndThen combiner (ThenBinds binds1 binds2) do_next
97 = tcBindsAndThen combiner binds1 (tcBindsAndThen combiner binds2 do_next)
100 An aside. The original version of @tcBindsAndThen@ which lacks a
101 combiner function, appears below. Though it is perfectly well
102 behaved, it cannot be typed by Haskell, because the recursive call is
103 at a different type to the definition itself. There aren't too many
104 examples of this, which is why I thought it worth preserving! [SLPJ]
109 -> TcM s (thing, LIE s, thing_ty))
110 -> TcM s ((TcHsBinds s, thing), LIE s, thing_ty)
112 tcBindsAndThen EmptyBinds do_next
113 = do_next `thenTc` \ (thing, lie, thing_ty) ->
114 returnTc ((EmptyBinds, thing), lie, thing_ty)
116 tcBindsAndThen (SingleBind bind) do_next
117 = tcBindAndThen bind [] do_next
119 tcBindsAndThen (BindWith bind sigs) do_next
120 = tcBindAndThen bind sigs do_next
122 tcBindsAndThen (ThenBinds binds1 binds2) do_next
123 = tcBindsAndThen binds1 (tcBindsAndThen binds2 do_next)
124 `thenTc` \ ((binds1', (binds2', thing')), lie1, thing_ty) ->
126 returnTc ((binds1' `ThenBinds` binds2', thing'), lie1, thing_ty)
129 %************************************************************************
133 %************************************************************************
137 :: (TcHsBinds s -> thing -> thing) -- Combinator
138 -> RenamedBind -- The Bind to typecheck
139 -> [RenamedSig] -- ...and its signatures
140 -> TcM s (thing, LIE s, thing_ty) -- Thing to type check in
142 -> TcM s (thing, LIE s, thing_ty) -- Results, incl the
144 tcBindAndThen combiner bind sigs do_next
145 = fixTc (\ ~(prag_info_fn, _) ->
146 -- This is the usual prag_info fix; the PragmaInfo field of an Id
147 -- is not inspected till ages later in the compiler, so there
148 -- should be no black-hole problems here.
150 tcBindAndSigs binder_names bind
151 sigs prag_info_fn `thenTc` \ (poly_binds, poly_lie, poly_ids) ->
153 -- Extend the environment to bind the new polymorphic Ids
154 tcExtendLocalValEnv binder_names poly_ids $
156 -- Build bindings and IdInfos corresponding to user pragmas
157 tcPragmaSigs sigs `thenTc` \ (prag_info_fn, prag_binds, prag_lie) ->
159 -- Now do whatever happens next, in the augmented envt
160 do_next `thenTc` \ (thing, thing_lie, thing_ty) ->
162 -- Create specialisations of functions bound here
163 bindInstsOfLocalFuns (prag_lie `plusLIE` thing_lie)
164 poly_ids `thenTc` \ (lie2, inst_mbinds) ->
168 final_lie = lie2 `plusLIE` poly_lie
169 final_binds = poly_binds `ThenBinds`
170 SingleBind (NonRecBind inst_mbinds) `ThenBinds`
173 returnTc (prag_info_fn, (combiner final_binds thing, final_lie, thing_ty))
174 ) `thenTc` \ (_, result) ->
177 binder_names = collectBinders bind
180 tcBindAndSigs binder_names bind sigs prag_info_fn
182 -- If typechecking the binds fails, then return with each
183 -- binder given type (forall a.a), to minimise subsequent
185 newTcTyVar mkBoxedTypeKind `thenNF_Tc` \ alpha_tv ->
187 forall_a_a = mkForAllTy alpha_tv (mkTyVarTy alpha_tv)
188 poly_ids = [ mkUserId name forall_a_a (prag_info_fn name)
189 | name <- binder_names]
191 returnTc (EmptyBinds, emptyLIE, poly_ids)
194 -- Create a new identifier for each binder, with each being given
195 -- a type-variable type.
196 newMonoIds binder_names kind (\ mono_ids ->
197 tcTySigs sigs `thenTc` \ sig_info ->
198 tc_bind bind `thenTc` \ (bind', lie) ->
199 returnTc (mono_ids, bind', lie, sig_info)
201 `thenTc` \ (mono_ids, bind', lie, sig_info) ->
203 -- Notice that genBinds gets the old (non-extended) environment
204 genBinds binder_names mono_ids bind' lie sig_info prag_info_fn
207 NonRecBind _ -> mkBoxedTypeKind -- Recursive, so no unboxed types
208 RecBind _ -> mkTypeKind -- Non-recursive, so we permit unboxed types
212 tc_bind :: RenamedBind -> TcM s (TcBind s, LIE s)
214 tc_bind (NonRecBind mono_binds)
215 = tcMonoBinds mono_binds `thenTc` \ (mono_binds2, lie) ->
216 returnTc (NonRecBind mono_binds2, lie)
218 tc_bind (RecBind mono_binds)
219 = tcMonoBinds mono_binds `thenTc` \ (mono_binds2, lie) ->
220 returnTc (RecBind mono_binds2, lie)
224 tcMonoBinds :: RenamedMonoBinds -> TcM s (TcMonoBinds s, LIE s)
226 tcMonoBinds EmptyMonoBinds = returnTc (EmptyMonoBinds, emptyLIE)
228 tcMonoBinds (AndMonoBinds mb1 mb2)
229 = tcMonoBinds mb1 `thenTc` \ (mb1a, lie1) ->
230 tcMonoBinds mb2 `thenTc` \ (mb2a, lie2) ->
231 returnTc (AndMonoBinds mb1a mb2a, lie1 `plusLIE` lie2)
233 tcMonoBinds bind@(PatMonoBind pat grhss_and_binds locn)
237 tcPat pat `thenTc` \ (pat2, lie_pat, pat_ty) ->
239 -- BINDINGS AND GRHSS
240 tcGRHSsAndBinds grhss_and_binds `thenTc` \ (grhss_and_binds2, lie, grhss_ty) ->
242 -- Unify the two sides
243 tcAddErrCtxt (patMonoBindsCtxt bind) $
244 unifyTauTy pat_ty grhss_ty `thenTc_`
247 returnTc (PatMonoBind pat2 grhss_and_binds2 locn,
250 tcMonoBinds (FunMonoBind name matches locn)
252 tcLookupLocalValueOK "tcMonoBinds" name `thenNF_Tc` \ id ->
253 tcMatchesFun name (idType id) matches `thenTc` \ (matches', lie) ->
254 returnTc (FunMonoBind (TcId id) matches' locn, lie)
257 %************************************************************************
259 \subsection{Signatures}
261 %************************************************************************
263 @tcSigs@ checks the signatures for validity, and returns a list of
264 {\em freshly-instantiated} signatures. That is, the types are already
265 split up, and have fresh type variables installed. All non-type-signature
266 "RenamedSigs" are ignored.
269 tcTySigs :: [RenamedSig] -> TcM s [TcSigInfo s]
271 tcTySigs (Sig v ty _ src_loc : other_sigs)
272 = tcAddSrcLoc src_loc (
273 tcPolyType ty `thenTc` \ sigma_ty ->
274 tcInstType [] sigma_ty `thenNF_Tc` \ sigma_ty' ->
276 (tyvars', theta', tau') = splitSigmaTy sigma_ty'
279 tcLookupLocalValueOK "tcSig1" v `thenNF_Tc` \ val ->
280 unifyTauTy (idType val) tau' `thenTc_`
282 returnTc (TySigInfo val tyvars' theta' tau' src_loc)
283 ) `thenTc` \ sig_info1 ->
285 tcTySigs other_sigs `thenTc` \ sig_infos ->
286 returnTc (sig_info1 : sig_infos)
288 tcTySigs (other : sigs) = tcTySigs sigs
289 tcTySigs [] = returnTc []
293 %************************************************************************
295 \subsection{SPECIALIZE pragmas}
297 %************************************************************************
300 @tcPragmaSigs@ munches up the "signatures" that arise through *user*
301 pragmas. It is convenient for them to appear in the @[RenamedSig]@
302 part of a binding because then the same machinery can be used for
303 moving them into place as is done for type signatures.
306 tcPragmaSigs :: [RenamedSig] -- The pragma signatures
307 -> TcM s (Name -> PragmaInfo, -- Maps name to the appropriate PragmaInfo
311 tcPragmaSigs sigs = returnTc ( \name -> NoPragmaInfo, EmptyBinds, emptyLIE )
315 = mapAndUnzip3Tc tcPragmaSig sigs `thenTc` \ (names_w_id_infos, binds, lies) ->
317 name_to_info name = foldr ($) noIdInfo
318 [info_fn | (n,info_fn) <- names_w_id_infos, n==name]
320 returnTc (name_to_info,
321 foldr ThenBinds EmptyBinds binds,
322 foldr plusLIE emptyLIE lies)
325 Here are the easy cases for tcPragmaSigs
328 tcPragmaSig (DeforestSig name loc)
329 = returnTc ((name, addInfo DoDeforest),EmptyBinds,emptyLIE)
330 tcPragmaSig (InlineSig name loc)
331 = returnTc ((name, addInfo_UF (iWantToBeINLINEd UnfoldAlways)), EmptyBinds, emptyLIE)
332 tcPragmaSig (MagicUnfoldingSig name string loc)
333 = returnTc ((name, addInfo_UF (mkMagicUnfolding string)), EmptyBinds, emptyLIE)
336 The interesting case is for SPECIALISE pragmas. There are two forms.
337 Here's the first form:
339 f :: Ord a => [a] -> b -> b
340 {-# SPECIALIZE f :: [Int] -> b -> b #-}
343 For this we generate:
345 f* = /\ b -> let d1 = ...
349 where f* is a SpecPragmaId. The **sole** purpose of SpecPragmaIds is to
350 retain a right-hand-side that the simplifier will otherwise discard as
351 dead code... the simplifier has a flag that tells it not to discard
352 SpecPragmaId bindings.
354 In this case the f* retains a call-instance of the overloaded
355 function, f, (including appropriate dictionaries) so that the
356 specialiser will subsequently discover that there's a call of @f@ at
357 Int, and will create a specialisation for @f@. After that, the
358 binding for @f*@ can be discarded.
360 The second form is this:
362 f :: Ord a => [a] -> b -> b
363 {-# SPECIALIZE f :: [Int] -> b -> b = g #-}
366 Here @g@ is specified as a function that implements the specialised
367 version of @f@. Suppose that g has type (a->b->b); that is, g's type
368 is more general than that required. For this we generate
370 f@Int = /\b -> g Int b
374 Here @f@@Int@ is a SpecId, the specialised version of @f@. It inherits
375 f's export status etc. @f*@ is a SpecPragmaId, as before, which just serves
376 to prevent @f@@Int@ from being discarded prematurely. After specialisation,
377 if @f@@Int@ is going to be used at all it will be used explicitly, so the simplifier can
378 discard the f* binding.
380 Actually, there is really only point in giving a SPECIALISE pragma on exported things,
381 and the simplifer won't discard SpecIds for exporte things anyway, so maybe this is
385 tcPragmaSig (SpecSig name poly_ty maybe_spec_name src_loc)
386 = tcAddSrcLoc src_loc $
387 tcAddErrCtxt (valSpecSigCtxt name spec_ty) $
389 -- Get and instantiate its alleged specialised type
390 tcPolyType poly_ty `thenTc` \ sig_sigma ->
391 tcInstType [] sig_sigma `thenNF_Tc` \ sig_ty ->
393 (sig_tyvars, sig_theta, sig_tau) = splitSigmaTy sig_ty
394 origin = ValSpecOrigin name
397 -- Check that the SPECIALIZE pragma had an empty context
398 checkTc (null sig_theta)
399 (panic "SPECIALIZE non-empty context (ToDo: msg)") `thenTc_`
401 -- Get and instantiate the type of the id mentioned
402 tcLookupLocalValueOK "tcPragmaSig" name `thenNF_Tc` \ main_id ->
403 tcInstType [] (idType main_id) `thenNF_Tc` \ main_ty ->
405 (main_tyvars, main_rho) = splitForAllTy main_ty
406 (main_theta,main_tau) = splitRhoTy main_rho
407 main_arg_tys = mkTyVarTys main_tyvars
410 -- Check that the specialised type is indeed an instance of
411 -- the type of the main function.
412 unifyTauTy sig_tau main_tau `thenTc_`
413 checkSigTyVars sig_tyvars sig_tau `thenTc_`
415 -- Check that the type variables of the polymorphic function are
416 -- either left polymorphic, or instantiate to ground type.
417 -- Also check that the overloaded type variables are instantiated to
418 -- ground type; or equivalently that all dictionaries have ground type
419 mapTc zonkTcType main_arg_tys `thenNF_Tc` \ main_arg_tys' ->
420 zonkTcThetaType main_theta `thenNF_Tc` \ main_theta' ->
421 tcAddErrCtxt (specGroundnessCtxt main_arg_tys')
422 (checkTc (all isGroundOrTyVarTy main_arg_tys')) `thenTc_`
423 tcAddErrCtxt (specContextGroundnessCtxt main_theta')
424 (checkTc (and [isGroundTy ty | (_,ty) <- theta'])) `thenTc_`
426 -- Build the SpecPragmaId; it is the thing that makes sure we
427 -- don't prematurely dead-code-eliminate the binding we are really interested in.
428 newSpecPragmaId name sig_ty `thenNF_Tc` \ spec_pragma_id ->
430 -- Build a suitable binding; depending on whether we were given
431 -- a value (Maybe Name) to be used as the specialisation.
433 Nothing -> -- No implementation function specified
435 -- Make a Method inst for the occurrence of the overloaded function
436 newMethodWithGivenTy (OccurrenceOf name)
437 (TcId main_id) main_arg_tys main_rho `thenNF_Tc` \ (lie, meth_id) ->
440 pseudo_bind = VarMonoBind spec_pragma_id pseudo_rhs
441 pseudo_rhs = mkHsTyLam sig_tyvars (HsVar (TcId meth_id))
443 returnTc (pseudo_bind, lie, \ info -> info)
445 Just spec_name -> -- Use spec_name as the specialisation value ...
447 -- Type check a simple occurrence of the specialised Id
448 tcId spec_name `thenTc` \ (spec_body, spec_lie, spec_tau) ->
450 -- Check that it has the correct type, and doesn't constrain the
451 -- signature variables at all
452 unifyTauTy sig_tau spec_tau `thenTc_`
453 checkSigTyVars sig_tyvars sig_tau `thenTc_`
455 -- Make a local SpecId to bind to applied spec_id
456 newSpecId main_id main_arg_tys sig_ty `thenNF_Tc` \ local_spec_id ->
459 spec_rhs = mkHsTyLam sig_tyvars spec_body
460 spec_binds = VarMonoBind local_spec_id spec_rhs
462 VarMonoBind spec_pragma_id (HsVar (TcId local_spec_id))
463 spec_info = SpecInfo spec_tys (length main_theta) local_spec_id
465 returnTc ((name, addInfo spec_info), spec_binds, spec_lie)
470 Error contexts and messages
471 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
473 patMonoBindsCtxt bind sty
474 = ppHang (ppPStr SLIT("In a pattern binding:")) 4 (ppr sty bind)
476 --------------------------------------------
477 specContextGroundnessCtxt -- err_ctxt dicts sty
478 = panic "specContextGroundnessCtxt"
481 ppSep [ppBesides [ppStr "In the SPECIALIZE pragma for `", ppr sty name, ppStr "'"],
482 ppBesides [ppStr " specialised to the type `", ppr sty spec_ty, ppStr "'"],
484 ppStr "... not all overloaded type variables were instantiated",
485 ppStr "to ground types:"])
486 4 (ppAboves [ppCat [ppr sty c, ppr sty t]
487 | (c,t) <- map getDictClassAndType dicts])
489 (name, spec_ty, locn, pp_spec_id)
491 ValSpecSigCtxt n ty loc -> (n, ty, loc, \ x -> ppNil)
492 ValSpecSpecIdCtxt n ty spec loc ->
494 \ sty -> ppBesides [ppStr "... type of explicit id `", ppr sty spec, ppStr "'"])
497 -----------------------------------------------
499 = panic "specGroundnessCtxt"
502 valSpecSigCtxt v ty sty
503 = ppHang (ppPStr SLIT("In a SPECIALIZE pragma for a value:"))
504 4 (ppSep [ppBeside (pprNonOp sty v) (ppPStr SLIT(" ::")),