2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
6 Desugaring arrow commands
9 module DsArrows ( dsProcExpr ) where
11 #include "HsVersions.h"
17 import HsSyn hiding (collectPatBinders, collectPatsBinders )
20 -- NB: The desugarer, which straddles the source and Core worlds, sometimes
21 -- needs to see source types (newtypes etc), and sometimes not
22 -- So WATCH OUT; check each use of split*Ty functions.
23 -- Sigh. This is a pain.
25 import {-# SOURCE #-} DsExpr ( dsExpr, dsLExpr, dsLocalBinds )
50 data DsCmdEnv = DsCmdEnv {
51 meth_binds :: [CoreBind],
52 arr_id, compose_id, first_id, app_id, choice_id, loop_id :: CoreExpr
55 mkCmdEnv :: SyntaxTable Id -> DsM DsCmdEnv
57 (meth_binds, ds_meths) <- dsSyntaxTable ids
59 meth_binds = meth_binds,
60 arr_id = Var (lookupEvidence ds_meths arrAName),
61 compose_id = Var (lookupEvidence ds_meths composeAName),
62 first_id = Var (lookupEvidence ds_meths firstAName),
63 app_id = Var (lookupEvidence ds_meths appAName),
64 choice_id = Var (lookupEvidence ds_meths choiceAName),
65 loop_id = Var (lookupEvidence ds_meths loopAName)
68 bindCmdEnv :: DsCmdEnv -> CoreExpr -> CoreExpr
69 bindCmdEnv ids body = foldr Let body (meth_binds ids)
71 -- arr :: forall b c. (b -> c) -> a b c
72 do_arr :: DsCmdEnv -> Type -> Type -> CoreExpr -> CoreExpr
73 do_arr ids b_ty c_ty f = mkApps (arr_id ids) [Type b_ty, Type c_ty, f]
75 -- (>>>) :: forall b c d. a b c -> a c d -> a b d
76 do_compose :: DsCmdEnv -> Type -> Type -> Type ->
77 CoreExpr -> CoreExpr -> CoreExpr
78 do_compose ids b_ty c_ty d_ty f g
79 = mkApps (compose_id ids) [Type b_ty, Type c_ty, Type d_ty, f, g]
81 -- first :: forall b c d. a b c -> a (b,d) (c,d)
82 do_first :: DsCmdEnv -> Type -> Type -> Type -> CoreExpr -> CoreExpr
83 do_first ids b_ty c_ty d_ty f
84 = mkApps (first_id ids) [Type b_ty, Type c_ty, Type d_ty, f]
86 -- app :: forall b c. a (a b c, b) c
87 do_app :: DsCmdEnv -> Type -> Type -> CoreExpr
88 do_app ids b_ty c_ty = mkApps (app_id ids) [Type b_ty, Type c_ty]
90 -- (|||) :: forall b d c. a b d -> a c d -> a (Either b c) d
91 -- note the swapping of d and c
92 do_choice :: DsCmdEnv -> Type -> Type -> Type ->
93 CoreExpr -> CoreExpr -> CoreExpr
94 do_choice ids b_ty c_ty d_ty f g
95 = mkApps (choice_id ids) [Type b_ty, Type d_ty, Type c_ty, f, g]
97 -- loop :: forall b d c. a (b,d) (c,d) -> a b c
98 -- note the swapping of d and c
99 do_loop :: DsCmdEnv -> Type -> Type -> Type -> CoreExpr -> CoreExpr
100 do_loop ids b_ty c_ty d_ty f
101 = mkApps (loop_id ids) [Type b_ty, Type d_ty, Type c_ty, f]
103 -- map_arrow (f :: b -> c) (g :: a c d) = arr f >>> g :: a b d
104 do_map_arrow :: DsCmdEnv -> Type -> Type -> Type ->
105 CoreExpr -> CoreExpr -> CoreExpr
106 do_map_arrow ids b_ty c_ty d_ty f c
107 = do_compose ids b_ty c_ty d_ty (do_arr ids b_ty c_ty f) c
109 mkFailExpr :: HsMatchContext Id -> Type -> DsM CoreExpr
111 = mkErrorAppDs pAT_ERROR_ID ty (matchContextErrString ctxt)
113 -- construct CoreExpr for \ (a :: a_ty, b :: b_ty) -> b
114 mkSndExpr :: Type -> Type -> DsM CoreExpr
115 mkSndExpr a_ty b_ty = do
116 a_var <- newSysLocalDs a_ty
117 b_var <- newSysLocalDs b_ty
118 pair_var <- newSysLocalDs (mkCorePairTy a_ty b_ty)
120 (coreCasePair pair_var a_var b_var (Var b_var)))
123 Build case analysis of a tuple. This cannot be done in the DsM monad,
124 because the list of variables is typically not yet defined.
127 -- coreCaseTuple [u1..] v [x1..xn] body
128 -- = case v of v { (x1, .., xn) -> body }
129 -- But the matching may be nested if the tuple is very big
131 coreCaseTuple :: UniqSupply -> Id -> [Id] -> CoreExpr -> CoreExpr
132 coreCaseTuple uniqs scrut_var vars body
133 = mkTupleCase uniqs vars body scrut_var (Var scrut_var)
135 coreCasePair :: Id -> Id -> Id -> CoreExpr -> CoreExpr
136 coreCasePair scrut_var var1 var2 body
137 = Case (Var scrut_var) scrut_var (exprType body)
138 [(DataAlt (tupleCon Boxed 2), [var1, var2], body)]
142 mkCorePairTy :: Type -> Type -> Type
143 mkCorePairTy t1 t2 = mkBoxedTupleTy [t1, t2]
145 mkCorePairExpr :: CoreExpr -> CoreExpr -> CoreExpr
146 mkCorePairExpr e1 e2 = mkCoreTup [e1, e2]
149 The input is divided into a local environment, which is a flat tuple
150 (unless it's too big), and a stack, each element of which is paired
151 with the environment in turn. In general, the input has the form
153 (...((x1,...,xn),s1),...sk)
155 where xi are the environment values, and si the ones on the stack,
156 with s1 being the "top", the first one to be matched with a lambda.
159 envStackType :: [Id] -> [Type] -> Type
160 envStackType ids stack_tys = foldl mkCorePairTy (mkBigCoreVarTupTy ids) stack_tys
162 ----------------------------------------------
165 -- (...((x1,...,xn),s1),...sk)
167 buildEnvStack :: [Id] -> [Id] -> CoreExpr
168 buildEnvStack env_ids stack_ids
169 = foldl mkCorePairExpr (mkBigCoreVarTup env_ids) (map Var stack_ids)
171 ----------------------------------------------
174 -- \ (...((x1,...,xn),s1),...sk) -> e
177 -- case zk of (zk-1,sk) ->
179 -- case z1 of (z0,s1) ->
180 -- case z0 of (x1,...,xn) ->
183 matchEnvStack :: [Id] -- x1..xn
187 matchEnvStack env_ids stack_ids body = do
188 uniqs <- newUniqueSupply
189 tup_var <- newSysLocalDs (mkBigCoreVarTupTy env_ids)
190 matchVarStack tup_var stack_ids
191 (coreCaseTuple uniqs tup_var env_ids body)
194 ----------------------------------------------
197 -- \ (...(z0,s1),...sk) -> e
200 -- case zk of (zk-1,sk) ->
202 -- case z1 of (z0,s1) ->
205 matchVarStack :: Id -- z0
209 matchVarStack env_id [] body
210 = return (Lam env_id body)
211 matchVarStack env_id (stack_id:stack_ids) body = do
212 pair_id <- newSysLocalDs (mkCorePairTy (idType env_id) (idType stack_id))
213 matchVarStack pair_id stack_ids
214 (coreCasePair pair_id env_id stack_id body)
218 mkHsEnvStackExpr :: [Id] -> [Id] -> LHsExpr Id
219 mkHsEnvStackExpr env_ids stack_ids
220 = foldl (\a b -> mkLHsTupleExpr [a,b])
221 (mkLHsVarTuple env_ids)
222 (map nlHsVar stack_ids)
225 Translation of arrow abstraction
229 -- A | xs |- c :: [] t' ---> c'
230 -- --------------------------
231 -- A |- proc p -> c :: a t t' ---> arr (\ p -> (xs)) >>> c'
233 -- where (xs) is the tuple of variables bound by p
239 dsProcExpr pat (L _ (HsCmdTop cmd [] cmd_ty ids)) = do
240 meth_ids <- mkCmdEnv ids
241 let locals = mkVarSet (collectPatBinders pat)
242 (core_cmd, _free_vars, env_ids) <- dsfixCmd meth_ids locals [] cmd_ty cmd
243 let env_ty = mkBigCoreVarTupTy env_ids
244 fail_expr <- mkFailExpr ProcExpr env_ty
245 var <- selectSimpleMatchVarL pat
246 match_code <- matchSimply (Var var) ProcExpr pat (mkBigCoreVarTup env_ids) fail_expr
247 let pat_ty = hsLPatType pat
248 proc_code = do_map_arrow meth_ids pat_ty env_ty cmd_ty
251 return (bindCmdEnv meth_ids proc_code)
252 dsProcExpr _ c = pprPanic "dsProcExpr" (ppr c)
255 Translation of command judgements of the form
257 A | xs |- c :: [ts] t
260 dsLCmd :: DsCmdEnv -> IdSet -> [Id] -> [Type] -> Type -> LHsCmd Id
261 -> DsM (CoreExpr, IdSet)
262 dsLCmd ids local_vars env_ids stack res_ty cmd
263 = dsCmd ids local_vars env_ids stack res_ty (unLoc cmd)
265 dsCmd :: DsCmdEnv -- arrow combinators
266 -> IdSet -- set of local vars available to this command
267 -> [Id] -- list of vars in the input to this command
268 -- This is typically fed back,
269 -- so don't pull on it too early
270 -> [Type] -- type of the stack
271 -> Type -- return type of the command
272 -> HsCmd Id -- command to desugar
273 -> DsM (CoreExpr, -- desugared expression
274 IdSet) -- set of local vars that occur free
276 -- A |- f :: a (t*ts) t'
278 -- -----------------------------
279 -- A | xs |- f -< arg :: [ts] t'
281 -- ---> arr (\ ((xs)*ts) -> (arg*ts)) >>> f
283 dsCmd ids local_vars env_ids stack res_ty
284 (HsArrApp arrow arg arrow_ty HsFirstOrderApp _)= do
286 (a_arg_ty, _res_ty') = tcSplitAppTy arrow_ty
287 (_a_ty, arg_ty) = tcSplitAppTy a_arg_ty
288 core_arrow <- dsLExpr arrow
289 core_arg <- dsLExpr arg
290 stack_ids <- mapM newSysLocalDs stack
291 core_make_arg <- matchEnvStack env_ids stack_ids
292 (foldl mkCorePairExpr core_arg (map Var stack_ids))
293 return (do_map_arrow ids
294 (envStackType env_ids stack)
299 exprFreeVars core_arg `intersectVarSet` local_vars)
301 -- A, xs |- f :: a (t*ts) t'
303 -- ------------------------------
304 -- A | xs |- f -<< arg :: [ts] t'
306 -- ---> arr (\ ((xs)*ts) -> (f,(arg*ts))) >>> app
308 dsCmd ids local_vars env_ids stack res_ty
309 (HsArrApp arrow arg arrow_ty HsHigherOrderApp _) = do
311 (a_arg_ty, _res_ty') = tcSplitAppTy arrow_ty
312 (_a_ty, arg_ty) = tcSplitAppTy a_arg_ty
314 core_arrow <- dsLExpr arrow
315 core_arg <- dsLExpr arg
316 stack_ids <- mapM newSysLocalDs stack
317 core_make_pair <- matchEnvStack env_ids stack_ids
318 (mkCorePairExpr core_arrow
319 (foldl mkCorePairExpr core_arg (map Var stack_ids)))
321 return (do_map_arrow ids
322 (envStackType env_ids stack)
323 (mkCorePairTy arrow_ty arg_ty)
326 (do_app ids arg_ty res_ty),
327 (exprFreeVars core_arrow `unionVarSet` exprFreeVars core_arg)
328 `intersectVarSet` local_vars)
330 -- A | ys |- c :: [t:ts] t'
332 -- ------------------------
333 -- A | xs |- c e :: [ts] t'
335 -- ---> arr (\ ((xs)*ts) -> let z = e in (((ys),z)*ts)) >>> c
337 dsCmd ids local_vars env_ids stack res_ty (HsApp cmd arg) = do
338 core_arg <- dsLExpr arg
340 arg_ty = exprType core_arg
341 stack' = arg_ty:stack
342 (core_cmd, free_vars, env_ids')
343 <- dsfixCmd ids local_vars stack' res_ty cmd
344 stack_ids <- mapM newSysLocalDs stack
345 arg_id <- newSysLocalDs arg_ty
346 -- push the argument expression onto the stack
348 core_body = bindNonRec arg_id core_arg
349 (buildEnvStack env_ids' (arg_id:stack_ids))
350 -- match the environment and stack against the input
351 core_map <- matchEnvStack env_ids stack_ids core_body
352 return (do_map_arrow ids
353 (envStackType env_ids stack)
354 (envStackType env_ids' stack')
358 (exprFreeVars core_arg `intersectVarSet` local_vars)
359 `unionVarSet` free_vars)
361 -- A | ys |- c :: [ts] t'
362 -- -----------------------------------------------
363 -- A | xs |- \ p1 ... pk -> c :: [t1:...:tk:ts] t'
365 -- ---> arr (\ ((((xs), p1), ... pk)*ts) -> ((ys)*ts)) >>> c
367 dsCmd ids local_vars env_ids stack res_ty
368 (HsLam (MatchGroup [L _ (Match pats _ (GRHSs [L _ (GRHS [] body)] _ ))] _)) = do
370 pat_vars = mkVarSet (collectPatsBinders pats)
371 local_vars' = local_vars `unionVarSet` pat_vars
372 stack' = drop (length pats) stack
373 (core_body, free_vars, env_ids') <- dsfixCmd ids local_vars' stack' res_ty body
374 stack_ids <- mapM newSysLocalDs stack
376 -- the expression is built from the inside out, so the actions
377 -- are presented in reverse order
380 (actual_ids, stack_ids') = splitAt (length pats) stack_ids
381 -- build a new environment, plus what's left of the stack
382 core_expr = buildEnvStack env_ids' stack_ids'
383 in_ty = envStackType env_ids stack
384 in_ty' = envStackType env_ids' stack'
386 fail_expr <- mkFailExpr LambdaExpr in_ty'
387 -- match the patterns against the top of the old stack
388 match_code <- matchSimplys (map Var actual_ids) LambdaExpr pats core_expr fail_expr
389 -- match the old environment and stack against the input
390 select_code <- matchEnvStack env_ids stack_ids match_code
391 return (do_map_arrow ids in_ty in_ty' res_ty select_code core_body,
392 free_vars `minusVarSet` pat_vars)
394 dsCmd ids local_vars env_ids stack res_ty (HsPar cmd)
395 = dsLCmd ids local_vars env_ids stack res_ty cmd
397 -- A, xs |- e :: Bool
398 -- A | xs1 |- c1 :: [ts] t
399 -- A | xs2 |- c2 :: [ts] t
400 -- ----------------------------------------
401 -- A | xs |- if e then c1 else c2 :: [ts] t
403 -- ---> arr (\ ((xs)*ts) ->
404 -- if e then Left ((xs1)*ts) else Right ((xs2)*ts)) >>>
407 dsCmd ids local_vars env_ids stack res_ty (HsIf mb_fun cond then_cmd else_cmd) = do
408 core_cond <- dsLExpr cond
409 (core_then, fvs_then, then_ids) <- dsfixCmd ids local_vars stack res_ty then_cmd
410 (core_else, fvs_else, else_ids) <- dsfixCmd ids local_vars stack res_ty else_cmd
411 stack_ids <- mapM newSysLocalDs stack
412 either_con <- dsLookupTyCon eitherTyConName
413 left_con <- dsLookupDataCon leftDataConName
414 right_con <- dsLookupDataCon rightDataConName
416 let mk_left_expr ty1 ty2 e = mkConApp left_con [Type ty1, Type ty2, e]
417 mk_right_expr ty1 ty2 e = mkConApp right_con [Type ty1, Type ty2, e]
419 in_ty = envStackType env_ids stack
420 then_ty = envStackType then_ids stack
421 else_ty = envStackType else_ids stack
422 sum_ty = mkTyConApp either_con [then_ty, else_ty]
423 fvs_cond = exprFreeVars core_cond `intersectVarSet` local_vars
425 core_left = mk_left_expr then_ty else_ty (buildEnvStack then_ids stack_ids)
426 core_right = mk_right_expr then_ty else_ty (buildEnvStack else_ids stack_ids)
428 core_if <- case mb_fun of
429 Just fun -> do { core_fun <- dsExpr fun
430 ; matchEnvStack env_ids stack_ids $
431 mkCoreApps core_fun [core_cond, core_left, core_right] }
432 Nothing -> matchEnvStack env_ids stack_ids $
433 mkIfThenElse core_cond core_left core_right
435 return (do_map_arrow ids in_ty sum_ty res_ty
437 (do_choice ids then_ty else_ty res_ty core_then core_else),
438 fvs_cond `unionVarSet` fvs_then `unionVarSet` fvs_else)
441 Case commands are treated in much the same way as if commands
442 (see above) except that there are more alternatives. For example
444 case e of { p1 -> c1; p2 -> c2; p3 -> c3 }
448 arr (\ ((xs)*ts) -> case e of
449 p1 -> (Left (Left (xs1)*ts))
450 p2 -> Left ((Right (xs2)*ts))
451 p3 -> Right ((xs3)*ts)) >>>
454 The idea is to extract the commands from the case, build a balanced tree
455 of choices, and replace the commands with expressions that build tagged
456 tuples, obtaining a case expression that can be desugared normally.
457 To build all this, we use triples describing segments of the list of
458 case bodies, containing the following fields:
459 * a list of expressions of the form (Left|Right)* ((xs)*ts), to be put
460 into the case replacing the commands
461 * a sum type that is the common type of these expressions, and also the
462 input type of the arrow
463 * a CoreExpr for an arrow built by combining the translated command
467 dsCmd ids local_vars env_ids stack res_ty (HsCase exp (MatchGroup matches match_ty)) = do
468 stack_ids <- mapM newSysLocalDs stack
470 -- Extract and desugar the leaf commands in the case, building tuple
471 -- expressions that will (after tagging) replace these leaves
474 leaves = concatMap leavesMatch matches
475 make_branch (leaf, bound_vars) = do
476 (core_leaf, _fvs, leaf_ids) <-
477 dsfixCmd ids (local_vars `unionVarSet` bound_vars) stack res_ty leaf
478 return ([mkHsEnvStackExpr leaf_ids stack_ids],
479 envStackType leaf_ids stack,
482 branches <- mapM make_branch leaves
483 either_con <- dsLookupTyCon eitherTyConName
484 left_con <- dsLookupDataCon leftDataConName
485 right_con <- dsLookupDataCon rightDataConName
487 left_id = HsVar (dataConWrapId left_con)
488 right_id = HsVar (dataConWrapId right_con)
489 left_expr ty1 ty2 e = noLoc $ HsApp (noLoc $ HsWrap (mkWpTyApps [ty1, ty2]) left_id ) e
490 right_expr ty1 ty2 e = noLoc $ HsApp (noLoc $ HsWrap (mkWpTyApps [ty1, ty2]) right_id) e
492 -- Prefix each tuple with a distinct series of Left's and Right's,
493 -- in a balanced way, keeping track of the types.
495 merge_branches (builds1, in_ty1, core_exp1)
496 (builds2, in_ty2, core_exp2)
497 = (map (left_expr in_ty1 in_ty2) builds1 ++
498 map (right_expr in_ty1 in_ty2) builds2,
499 mkTyConApp either_con [in_ty1, in_ty2],
500 do_choice ids in_ty1 in_ty2 res_ty core_exp1 core_exp2)
501 (leaves', sum_ty, core_choices) = foldb merge_branches branches
503 -- Replace the commands in the case with these tagged tuples,
504 -- yielding a HsExpr Id we can feed to dsExpr.
506 (_, matches') = mapAccumL (replaceLeavesMatch res_ty) leaves' matches
507 in_ty = envStackType env_ids stack
509 pat_ty = funArgTy match_ty
510 match_ty' = mkFunTy pat_ty sum_ty
511 -- Note that we replace the HsCase result type by sum_ty,
512 -- which is the type of matches'
514 core_body <- dsExpr (HsCase exp (MatchGroup matches' match_ty'))
515 core_matches <- matchEnvStack env_ids stack_ids core_body
516 return (do_map_arrow ids in_ty sum_ty res_ty core_matches core_choices,
517 exprFreeVars core_body `intersectVarSet` local_vars)
519 -- A | ys |- c :: [ts] t
520 -- ----------------------------------
521 -- A | xs |- let binds in c :: [ts] t
523 -- ---> arr (\ ((xs)*ts) -> let binds in ((ys)*ts)) >>> c
525 dsCmd ids local_vars env_ids stack res_ty (HsLet binds body) = do
527 defined_vars = mkVarSet (collectLocalBinders binds)
528 local_vars' = local_vars `unionVarSet` defined_vars
530 (core_body, _free_vars, env_ids') <- dsfixCmd ids local_vars' stack res_ty body
531 stack_ids <- mapM newSysLocalDs stack
532 -- build a new environment, plus the stack, using the let bindings
533 core_binds <- dsLocalBinds binds (buildEnvStack env_ids' stack_ids)
534 -- match the old environment and stack against the input
535 core_map <- matchEnvStack env_ids stack_ids core_binds
536 return (do_map_arrow ids
537 (envStackType env_ids stack)
538 (envStackType env_ids' stack)
542 exprFreeVars core_binds `intersectVarSet` local_vars)
544 dsCmd ids local_vars env_ids [] res_ty (HsDo _ctxt stmts body _)
545 = dsCmdDo ids local_vars env_ids res_ty stmts body
547 -- A |- e :: forall e. a1 (e*ts1) t1 -> ... an (e*tsn) tn -> a (e*ts) t
548 -- A | xs |- ci :: [tsi] ti
549 -- -----------------------------------
550 -- A | xs |- (|e c1 ... cn|) :: [ts] t ---> e [t_xs] c1 ... cn
552 dsCmd _ids local_vars env_ids _stack _res_ty (HsArrForm op _ args) = do
553 let env_ty = mkBigCoreVarTupTy env_ids
554 core_op <- dsLExpr op
555 (core_args, fv_sets) <- mapAndUnzipM (dsTrimCmdArg local_vars env_ids) args
556 return (mkApps (App core_op (Type env_ty)) core_args,
557 unionVarSets fv_sets)
560 dsCmd ids local_vars env_ids stack res_ty (HsTick ix vars expr) = do
561 (expr1,id_set) <- dsLCmd ids local_vars env_ids stack res_ty expr
562 expr2 <- mkTickBox ix vars expr1
563 return (expr2,id_set)
565 dsCmd _ _ _ _ _ c = pprPanic "dsCmd" (ppr c)
567 -- A | ys |- c :: [ts] t (ys <= xs)
568 -- ---------------------
569 -- A | xs |- c :: [ts] t ---> arr_ts (\ (xs) -> (ys)) >>> c
572 :: IdSet -- set of local vars available to this command
573 -> [Id] -- list of vars in the input to this command
574 -> LHsCmdTop Id -- command argument to desugar
575 -> DsM (CoreExpr, -- desugared expression
576 IdSet) -- set of local vars that occur free
577 dsTrimCmdArg local_vars env_ids (L _ (HsCmdTop cmd stack cmd_ty ids)) = do
578 meth_ids <- mkCmdEnv ids
579 (core_cmd, free_vars, env_ids') <- dsfixCmd meth_ids local_vars stack cmd_ty cmd
580 stack_ids <- mapM newSysLocalDs stack
581 trim_code <- matchEnvStack env_ids stack_ids (buildEnvStack env_ids' stack_ids)
583 in_ty = envStackType env_ids stack
584 in_ty' = envStackType env_ids' stack
585 arg_code = if env_ids' == env_ids then core_cmd else
586 do_map_arrow meth_ids in_ty in_ty' cmd_ty trim_code core_cmd
587 return (bindCmdEnv meth_ids arg_code, free_vars)
589 -- Given A | xs |- c :: [ts] t, builds c with xs fed back.
590 -- Typically needs to be prefixed with arr (\p -> ((xs)*ts))
593 :: DsCmdEnv -- arrow combinators
594 -> IdSet -- set of local vars available to this command
595 -> [Type] -- type of the stack
596 -> Type -- return type of the command
597 -> LHsCmd Id -- command to desugar
598 -> DsM (CoreExpr, -- desugared expression
599 IdSet, -- set of local vars that occur free
600 [Id]) -- set as a list, fed back
601 dsfixCmd ids local_vars stack cmd_ty cmd
602 = fixDs (\ ~(_,_,env_ids') -> do
603 (core_cmd, free_vars) <- dsLCmd ids local_vars env_ids' stack cmd_ty cmd
604 return (core_cmd, free_vars, varSetElems free_vars))
608 Translation of command judgements of the form
610 A | xs |- do { ss } :: [] t
614 dsCmdDo :: DsCmdEnv -- arrow combinators
615 -> IdSet -- set of local vars available to this statement
616 -> [Id] -- list of vars in the input to this statement
617 -- This is typically fed back,
618 -- so don't pull on it too early
619 -> Type -- return type of the statement
620 -> [LStmt Id] -- statements to desugar
621 -> LHsExpr Id -- body
622 -> DsM (CoreExpr, -- desugared expression
623 IdSet) -- set of local vars that occur free
625 -- A | xs |- c :: [] t
626 -- --------------------------
627 -- A | xs |- do { c } :: [] t
629 dsCmdDo ids local_vars env_ids res_ty [] body
630 = dsLCmd ids local_vars env_ids [] res_ty body
632 dsCmdDo ids local_vars env_ids res_ty (stmt:stmts) body = do
634 bound_vars = mkVarSet (collectLStmtBinders stmt)
635 local_vars' = local_vars `unionVarSet` bound_vars
636 (core_stmts, _, env_ids') <- fixDs (\ ~(_,_,env_ids') -> do
637 (core_stmts, fv_stmts) <- dsCmdDo ids local_vars' env_ids' res_ty stmts body
638 return (core_stmts, fv_stmts, varSetElems fv_stmts))
639 (core_stmt, fv_stmt) <- dsCmdLStmt ids local_vars env_ids env_ids' stmt
640 return (do_compose ids
641 (mkBigCoreVarTupTy env_ids)
642 (mkBigCoreVarTupTy env_ids')
649 A statement maps one local environment to another, and is represented
650 as an arrow from one tuple type to another. A statement sequence is
651 translated to a composition of such arrows.
653 dsCmdLStmt :: DsCmdEnv -> IdSet -> [Id] -> [Id] -> LStmt Id
654 -> DsM (CoreExpr, IdSet)
655 dsCmdLStmt ids local_vars env_ids out_ids cmd
656 = dsCmdStmt ids local_vars env_ids out_ids (unLoc cmd)
659 :: DsCmdEnv -- arrow combinators
660 -> IdSet -- set of local vars available to this statement
661 -> [Id] -- list of vars in the input to this statement
662 -- This is typically fed back,
663 -- so don't pull on it too early
664 -> [Id] -- list of vars in the output of this statement
665 -> Stmt Id -- statement to desugar
666 -> DsM (CoreExpr, -- desugared expression
667 IdSet) -- set of local vars that occur free
669 -- A | xs1 |- c :: [] t
670 -- A | xs' |- do { ss } :: [] t'
671 -- ------------------------------
672 -- A | xs |- do { c; ss } :: [] t'
674 -- ---> arr (\ (xs) -> ((xs1),(xs'))) >>> first c >>>
677 dsCmdStmt ids local_vars env_ids out_ids (ExprStmt cmd _ c_ty) = do
678 (core_cmd, fv_cmd, env_ids1) <- dsfixCmd ids local_vars [] c_ty cmd
679 core_mux <- matchEnvStack env_ids []
680 (mkCorePairExpr (mkBigCoreVarTup env_ids1) (mkBigCoreVarTup out_ids))
682 in_ty = mkBigCoreVarTupTy env_ids
683 in_ty1 = mkBigCoreVarTupTy env_ids1
684 out_ty = mkBigCoreVarTupTy out_ids
685 before_c_ty = mkCorePairTy in_ty1 out_ty
686 after_c_ty = mkCorePairTy c_ty out_ty
687 snd_fn <- mkSndExpr c_ty out_ty
688 return (do_map_arrow ids in_ty before_c_ty out_ty core_mux $
689 do_compose ids before_c_ty after_c_ty out_ty
690 (do_first ids in_ty1 c_ty out_ty core_cmd) $
691 do_arr ids after_c_ty out_ty snd_fn,
692 extendVarSetList fv_cmd out_ids)
695 -- A | xs1 |- c :: [] t
696 -- A | xs' |- do { ss } :: [] t' xs2 = xs' - defs(p)
697 -- -----------------------------------
698 -- A | xs |- do { p <- c; ss } :: [] t'
700 -- ---> arr (\ (xs) -> ((xs1),(xs2))) >>> first c >>>
701 -- arr (\ (p, (xs2)) -> (xs')) >>> ss
703 -- It would be simpler and more consistent to do this using second,
704 -- but that's likely to be defined in terms of first.
706 dsCmdStmt ids local_vars env_ids out_ids (BindStmt pat cmd _ _) = do
707 (core_cmd, fv_cmd, env_ids1) <- dsfixCmd ids local_vars [] (hsLPatType pat) cmd
709 pat_ty = hsLPatType pat
710 pat_vars = mkVarSet (collectPatBinders pat)
711 env_ids2 = varSetElems (mkVarSet out_ids `minusVarSet` pat_vars)
712 env_ty2 = mkBigCoreVarTupTy env_ids2
714 -- multiplexing function
715 -- \ (xs) -> ((xs1),(xs2))
717 core_mux <- matchEnvStack env_ids []
718 (mkCorePairExpr (mkBigCoreVarTup env_ids1) (mkBigCoreVarTup env_ids2))
720 -- projection function
721 -- \ (p, (xs2)) -> (zs)
723 env_id <- newSysLocalDs env_ty2
724 uniqs <- newUniqueSupply
726 after_c_ty = mkCorePairTy pat_ty env_ty2
727 out_ty = mkBigCoreVarTupTy out_ids
728 body_expr = coreCaseTuple uniqs env_id env_ids2 (mkBigCoreVarTup out_ids)
730 fail_expr <- mkFailExpr (StmtCtxt DoExpr) out_ty
731 pat_id <- selectSimpleMatchVarL pat
732 match_code <- matchSimply (Var pat_id) (StmtCtxt DoExpr) pat body_expr fail_expr
733 pair_id <- newSysLocalDs after_c_ty
735 proj_expr = Lam pair_id (coreCasePair pair_id pat_id env_id match_code)
737 -- put it all together
739 in_ty = mkBigCoreVarTupTy env_ids
740 in_ty1 = mkBigCoreVarTupTy env_ids1
741 in_ty2 = mkBigCoreVarTupTy env_ids2
742 before_c_ty = mkCorePairTy in_ty1 in_ty2
743 return (do_map_arrow ids in_ty before_c_ty out_ty core_mux $
744 do_compose ids before_c_ty after_c_ty out_ty
745 (do_first ids in_ty1 pat_ty in_ty2 core_cmd) $
746 do_arr ids after_c_ty out_ty proj_expr,
747 fv_cmd `unionVarSet` (mkVarSet out_ids `minusVarSet` pat_vars))
749 -- A | xs' |- do { ss } :: [] t
750 -- --------------------------------------
751 -- A | xs |- do { let binds; ss } :: [] t
753 -- ---> arr (\ (xs) -> let binds in (xs')) >>> ss
755 dsCmdStmt ids local_vars env_ids out_ids (LetStmt binds) = do
756 -- build a new environment using the let bindings
757 core_binds <- dsLocalBinds binds (mkBigCoreVarTup out_ids)
758 -- match the old environment against the input
759 core_map <- matchEnvStack env_ids [] core_binds
761 (mkBigCoreVarTupTy env_ids)
762 (mkBigCoreVarTupTy out_ids)
764 exprFreeVars core_binds `intersectVarSet` local_vars)
766 -- A | ys |- do { ss; returnA -< ((xs1), (ys2)) } :: [] ...
767 -- A | xs' |- do { ss' } :: [] t
768 -- ------------------------------------
769 -- A | xs |- do { rec ss; ss' } :: [] t
771 -- xs1 = xs' /\ defs(ss)
772 -- xs2 = xs' - defs(ss)
773 -- ys1 = ys - defs(ss)
774 -- ys2 = ys /\ defs(ss)
776 -- ---> arr (\(xs) -> ((ys1),(xs2))) >>>
777 -- first (loop (arr (\((ys1),~(ys2)) -> (ys)) >>> ss)) >>>
778 -- arr (\((xs1),(xs2)) -> (xs')) >>> ss'
780 dsCmdStmt ids local_vars env_ids out_ids
781 (RecStmt { recS_stmts = stmts, recS_later_ids = later_ids, recS_rec_ids = rec_ids
782 , recS_rec_rets = rhss, recS_dicts = _binds }) = do
783 let -- ToDo: ****** binds not desugared; ROSS PLEASE FIX ********
784 env2_id_set = mkVarSet out_ids `minusVarSet` mkVarSet later_ids
785 env2_ids = varSetElems env2_id_set
786 env2_ty = mkBigCoreVarTupTy env2_ids
788 -- post_loop_fn = \((later_ids),(env2_ids)) -> (out_ids)
790 uniqs <- newUniqueSupply
791 env2_id <- newSysLocalDs env2_ty
793 later_ty = mkBigCoreVarTupTy later_ids
794 post_pair_ty = mkCorePairTy later_ty env2_ty
795 post_loop_body = coreCaseTuple uniqs env2_id env2_ids (mkBigCoreVarTup out_ids)
797 post_loop_fn <- matchEnvStack later_ids [env2_id] post_loop_body
801 (core_loop, env1_id_set, env1_ids)
802 <- dsRecCmd ids local_vars stmts later_ids rec_ids rhss
804 -- pre_loop_fn = \(env_ids) -> ((env1_ids),(env2_ids))
807 env1_ty = mkBigCoreVarTupTy env1_ids
808 pre_pair_ty = mkCorePairTy env1_ty env2_ty
809 pre_loop_body = mkCorePairExpr (mkBigCoreVarTup env1_ids)
810 (mkBigCoreVarTup env2_ids)
812 pre_loop_fn <- matchEnvStack env_ids [] pre_loop_body
814 -- arr pre_loop_fn >>> first (loop (...)) >>> arr post_loop_fn
817 env_ty = mkBigCoreVarTupTy env_ids
818 out_ty = mkBigCoreVarTupTy out_ids
819 core_body = do_map_arrow ids env_ty pre_pair_ty out_ty
821 (do_compose ids pre_pair_ty post_pair_ty out_ty
822 (do_first ids env1_ty later_ty env2_ty
824 (do_arr ids post_pair_ty out_ty
827 return (core_body, env1_id_set `unionVarSet` env2_id_set)
829 dsCmdStmt _ _ _ _ s = pprPanic "dsCmdStmt" (ppr s)
831 -- loop (arr (\ ((env1_ids), ~(rec_ids)) -> (env_ids)) >>>
833 -- arr (\ (out_ids) -> ((later_ids),(rhss))) >>>
835 dsRecCmd :: DsCmdEnv -> VarSet -> [LStmt Id] -> [Var] -> [Var] -> [HsExpr Id]
836 -> DsM (CoreExpr, VarSet, [Var])
837 dsRecCmd ids local_vars stmts later_ids rec_ids rhss = do
839 rec_id_set = mkVarSet rec_ids
840 out_ids = varSetElems (mkVarSet later_ids `unionVarSet` rec_id_set)
841 out_ty = mkBigCoreVarTupTy out_ids
842 local_vars' = local_vars `unionVarSet` rec_id_set
844 -- mk_pair_fn = \ (out_ids) -> ((later_ids),(rhss))
846 core_rhss <- mapM dsExpr rhss
848 later_tuple = mkBigCoreVarTup later_ids
849 later_ty = mkBigCoreVarTupTy later_ids
850 rec_tuple = mkBigCoreTup core_rhss
851 rec_ty = mkBigCoreVarTupTy rec_ids
852 out_pair = mkCorePairExpr later_tuple rec_tuple
853 out_pair_ty = mkCorePairTy later_ty rec_ty
855 mk_pair_fn <- matchEnvStack out_ids [] out_pair
859 (core_stmts, fv_stmts, env_ids) <- dsfixCmdStmts ids local_vars' out_ids stmts
861 -- squash_pair_fn = \ ((env1_ids), ~(rec_ids)) -> (env_ids)
863 rec_id <- newSysLocalDs rec_ty
865 env1_id_set = fv_stmts `minusVarSet` rec_id_set
866 env1_ids = varSetElems env1_id_set
867 env1_ty = mkBigCoreVarTupTy env1_ids
868 in_pair_ty = mkCorePairTy env1_ty rec_ty
869 core_body = mkBigCoreTup (map selectVar env_ids)
872 | v `elemVarSet` rec_id_set
873 = mkTupleSelector rec_ids v rec_id (Var rec_id)
876 squash_pair_fn <- matchEnvStack env1_ids [rec_id] core_body
878 -- loop (arr squash_pair_fn >>> ss >>> arr mk_pair_fn)
881 env_ty = mkBigCoreVarTupTy env_ids
882 core_loop = do_loop ids env1_ty later_ty rec_ty
883 (do_map_arrow ids in_pair_ty env_ty out_pair_ty
885 (do_compose ids env_ty out_ty out_pair_ty
887 (do_arr ids out_ty out_pair_ty mk_pair_fn)))
889 return (core_loop, env1_id_set, env1_ids)
892 A sequence of statements (as in a rec) is desugared to an arrow between
897 :: DsCmdEnv -- arrow combinators
898 -> IdSet -- set of local vars available to this statement
899 -> [Id] -- output vars of these statements
900 -> [LStmt Id] -- statements to desugar
901 -> DsM (CoreExpr, -- desugared expression
902 IdSet, -- set of local vars that occur free
905 dsfixCmdStmts ids local_vars out_ids stmts
906 = fixDs (\ ~(_,_,env_ids) -> do
907 (core_stmts, fv_stmts) <- dsCmdStmts ids local_vars env_ids out_ids stmts
908 return (core_stmts, fv_stmts, varSetElems fv_stmts))
911 :: DsCmdEnv -- arrow combinators
912 -> IdSet -- set of local vars available to this statement
913 -> [Id] -- list of vars in the input to these statements
914 -> [Id] -- output vars of these statements
915 -> [LStmt Id] -- statements to desugar
916 -> DsM (CoreExpr, -- desugared expression
917 IdSet) -- set of local vars that occur free
919 dsCmdStmts ids local_vars env_ids out_ids [stmt]
920 = dsCmdLStmt ids local_vars env_ids out_ids stmt
922 dsCmdStmts ids local_vars env_ids out_ids (stmt:stmts) = do
924 bound_vars = mkVarSet (collectLStmtBinders stmt)
925 local_vars' = local_vars `unionVarSet` bound_vars
926 (core_stmts, _fv_stmts, env_ids') <- dsfixCmdStmts ids local_vars' out_ids stmts
927 (core_stmt, fv_stmt) <- dsCmdLStmt ids local_vars env_ids env_ids' stmt
928 return (do_compose ids
929 (mkBigCoreVarTupTy env_ids)
930 (mkBigCoreVarTupTy env_ids')
931 (mkBigCoreVarTupTy out_ids)
936 dsCmdStmts _ _ _ _ [] = panic "dsCmdStmts []"
940 Match a list of expressions against a list of patterns, left-to-right.
943 matchSimplys :: [CoreExpr] -- Scrutinees
944 -> HsMatchContext Name -- Match kind
945 -> [LPat Id] -- Patterns they should match
946 -> CoreExpr -- Return this if they all match
947 -> CoreExpr -- Return this if they don't
949 matchSimplys [] _ctxt [] result_expr _fail_expr = return result_expr
950 matchSimplys (exp:exps) ctxt (pat:pats) result_expr fail_expr = do
951 match_code <- matchSimplys exps ctxt pats result_expr fail_expr
952 matchSimply exp ctxt pat match_code fail_expr
953 matchSimplys _ _ _ _ _ = panic "matchSimplys"
956 List of leaf expressions, with set of variables bound in each
959 leavesMatch :: LMatch Id -> [(LHsExpr Id, IdSet)]
960 leavesMatch (L _ (Match pats _ (GRHSs grhss binds)))
962 defined_vars = mkVarSet (collectPatsBinders pats)
964 mkVarSet (collectLocalBinders binds)
967 mkVarSet (collectLStmtsBinders stmts)
968 `unionVarSet` defined_vars)
969 | L _ (GRHS stmts expr) <- grhss]
972 Replace the leaf commands in a match
976 :: Type -- new result type
977 -> [LHsExpr Id] -- replacement leaf expressions of that type
978 -> LMatch Id -- the matches of a case command
979 -> ([LHsExpr Id],-- remaining leaf expressions
980 LMatch Id) -- updated match
981 replaceLeavesMatch _res_ty leaves (L loc (Match pat mt (GRHSs grhss binds)))
983 (leaves', grhss') = mapAccumL replaceLeavesGRHS leaves grhss
985 (leaves', L loc (Match pat mt (GRHSs grhss' binds)))
988 :: [LHsExpr Id] -- replacement leaf expressions of that type
989 -> LGRHS Id -- rhss of a case command
990 -> ([LHsExpr Id],-- remaining leaf expressions
991 LGRHS Id) -- updated GRHS
992 replaceLeavesGRHS (leaf:leaves) (L loc (GRHS stmts _))
993 = (leaves, L loc (GRHS stmts leaf))
994 replaceLeavesGRHS [] _ = panic "replaceLeavesGRHS []"
997 Balanced fold of a non-empty list.
1000 foldb :: (a -> a -> a) -> [a] -> a
1001 foldb _ [] = error "foldb of empty list"
1003 foldb f xs = foldb f (fold_pairs xs)
1006 fold_pairs [x] = [x]
1007 fold_pairs (x1:x2:xs) = f x1 x2:fold_pairs xs
1010 Note [Dictionary binders in ConPatOut] See also same Note in HsUtils
1011 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1012 The following functions to collect value variables from patterns are
1013 copied from HsUtils, with one change: we also collect the dictionary
1014 bindings (pat_binds) from ConPatOut. We need them for cases like
1016 h :: Arrow a => Int -> a (Int,Int) Int
1017 h x = proc (y,z) -> case compare x y of
1018 GT -> returnA -< z+x
1020 The type checker turns the case into
1023 GT { p77 = plusInt } -> returnA -< p77 z x
1025 Here p77 is a local binding for the (+) operation.
1027 See comments in HsUtils for why the other version does not include
1031 collectPatBinders :: LPat Id -> [Id]
1032 collectPatBinders pat = collectl pat []
1034 collectPatsBinders :: [LPat Id] -> [Id]
1035 collectPatsBinders pats = foldr collectl [] pats
1037 ---------------------
1038 collectl :: LPat Id -> [Id] -> [Id]
1039 -- See Note [Dictionary binders in ConPatOut]
1040 collectl (L _ pat) bndrs
1043 go (VarPat var) = var : bndrs
1044 go (VarPatOut var bs) = var : collectEvBinders bs
1046 go (WildPat _) = bndrs
1047 go (LazyPat pat) = collectl pat bndrs
1048 go (BangPat pat) = collectl pat bndrs
1049 go (AsPat (L _ a) pat) = a : collectl pat bndrs
1050 go (ParPat pat) = collectl pat bndrs
1052 go (ListPat pats _) = foldr collectl bndrs pats
1053 go (PArrPat pats _) = foldr collectl bndrs pats
1054 go (TuplePat pats _ _) = foldr collectl bndrs pats
1056 go (ConPatIn _ ps) = foldr collectl bndrs (hsConPatArgs ps)
1057 go (ConPatOut {pat_args=ps, pat_binds=ds}) =
1059 ++ foldr collectl bndrs (hsConPatArgs ps)
1060 go (LitPat _) = bndrs
1061 go (NPat _ _ _) = bndrs
1062 go (NPlusKPat (L _ n) _ _ _) = n : bndrs
1064 go (SigPatIn pat _) = collectl pat bndrs
1065 go (SigPatOut pat _) = collectl pat bndrs
1066 go (TypePat _) = bndrs
1067 go (CoPat _ pat _) = collectl (noLoc pat) bndrs
1068 go (ViewPat _ pat _) = collectl pat bndrs
1069 go p@(QuasiQuotePat {}) = pprPanic "collectl/go" (ppr p)
1071 collectEvBinders :: TcEvBinds -> [Id]
1072 collectEvBinders (EvBinds bs) = foldrBag add_ev_bndr [] bs
1073 collectEvBinders (TcEvBinds {}) = panic "ToDo: collectEvBinders"
1075 add_ev_bndr :: EvBind -> [Id] -> [Id]
1076 add_ev_bndr (EvBind b _) bs | isId b = b:bs
1078 -- A worry: what about coercion variable binders??