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 )
51 data DsCmdEnv = DsCmdEnv {
52 meth_binds :: [CoreBind],
53 arr_id, compose_id, first_id, app_id, choice_id, loop_id :: CoreExpr
56 mkCmdEnv :: SyntaxTable Id -> DsM DsCmdEnv
58 (meth_binds, ds_meths) <- dsSyntaxTable ids
60 meth_binds = meth_binds,
61 arr_id = Var (lookupEvidence ds_meths arrAName),
62 compose_id = Var (lookupEvidence ds_meths composeAName),
63 first_id = Var (lookupEvidence ds_meths firstAName),
64 app_id = Var (lookupEvidence ds_meths appAName),
65 choice_id = Var (lookupEvidence ds_meths choiceAName),
66 loop_id = Var (lookupEvidence ds_meths loopAName)
69 bindCmdEnv :: DsCmdEnv -> CoreExpr -> CoreExpr
70 bindCmdEnv ids body = foldr Let body (meth_binds ids)
72 -- arr :: forall b c. (b -> c) -> a b c
73 do_arr :: DsCmdEnv -> Type -> Type -> CoreExpr -> CoreExpr
74 do_arr ids b_ty c_ty f = mkApps (arr_id ids) [Type b_ty, Type c_ty, f]
76 -- (>>>) :: forall b c d. a b c -> a c d -> a b d
77 do_compose :: DsCmdEnv -> Type -> Type -> Type ->
78 CoreExpr -> CoreExpr -> CoreExpr
79 do_compose ids b_ty c_ty d_ty f g
80 = mkApps (compose_id ids) [Type b_ty, Type c_ty, Type d_ty, f, g]
82 -- first :: forall b c d. a b c -> a (b,d) (c,d)
83 do_first :: DsCmdEnv -> Type -> Type -> Type -> CoreExpr -> CoreExpr
84 do_first ids b_ty c_ty d_ty f
85 = mkApps (first_id ids) [Type b_ty, Type c_ty, Type d_ty, f]
87 -- app :: forall b c. a (a b c, b) c
88 do_app :: DsCmdEnv -> Type -> Type -> CoreExpr
89 do_app ids b_ty c_ty = mkApps (app_id ids) [Type b_ty, Type c_ty]
91 -- (|||) :: forall b d c. a b d -> a c d -> a (Either b c) d
92 -- note the swapping of d and c
93 do_choice :: DsCmdEnv -> Type -> Type -> Type ->
94 CoreExpr -> CoreExpr -> CoreExpr
95 do_choice ids b_ty c_ty d_ty f g
96 = mkApps (choice_id ids) [Type b_ty, Type d_ty, Type c_ty, f, g]
98 -- loop :: forall b d c. a (b,d) (c,d) -> a b c
99 -- note the swapping of d and c
100 do_loop :: DsCmdEnv -> Type -> Type -> Type -> CoreExpr -> CoreExpr
101 do_loop ids b_ty c_ty d_ty f
102 = mkApps (loop_id ids) [Type b_ty, Type d_ty, Type c_ty, f]
104 -- map_arrow (f :: b -> c) (g :: a c d) = arr f >>> g :: a b d
105 do_map_arrow :: DsCmdEnv -> Type -> Type -> Type ->
106 CoreExpr -> CoreExpr -> CoreExpr
107 do_map_arrow ids b_ty c_ty d_ty f c
108 = do_compose ids b_ty c_ty d_ty (do_arr ids b_ty c_ty f) c
110 mkFailExpr :: HsMatchContext Id -> Type -> DsM CoreExpr
112 = mkErrorAppDs pAT_ERROR_ID ty (matchContextErrString ctxt)
114 -- construct CoreExpr for \ (a :: a_ty, b :: b_ty) -> b
115 mkSndExpr :: Type -> Type -> DsM CoreExpr
116 mkSndExpr a_ty b_ty = do
117 a_var <- newSysLocalDs a_ty
118 b_var <- newSysLocalDs b_ty
119 pair_var <- newSysLocalDs (mkCorePairTy a_ty b_ty)
121 (coreCasePair pair_var a_var b_var (Var b_var)))
124 Build case analysis of a tuple. This cannot be done in the DsM monad,
125 because the list of variables is typically not yet defined.
128 -- coreCaseTuple [u1..] v [x1..xn] body
129 -- = case v of v { (x1, .., xn) -> body }
130 -- But the matching may be nested if the tuple is very big
132 coreCaseTuple :: UniqSupply -> Id -> [Id] -> CoreExpr -> CoreExpr
133 coreCaseTuple uniqs scrut_var vars body
134 = mkTupleCase uniqs vars body scrut_var (Var scrut_var)
136 coreCasePair :: Id -> Id -> Id -> CoreExpr -> CoreExpr
137 coreCasePair scrut_var var1 var2 body
138 = Case (Var scrut_var) scrut_var (exprType body)
139 [(DataAlt (tupleCon Boxed 2), [var1, var2], body)]
143 mkCorePairTy :: Type -> Type -> Type
144 mkCorePairTy t1 t2 = mkBoxedTupleTy [t1, t2]
146 mkCorePairExpr :: CoreExpr -> CoreExpr -> CoreExpr
147 mkCorePairExpr e1 e2 = mkCoreTup [e1, e2]
150 The input is divided into a local environment, which is a flat tuple
151 (unless it's too big), and a stack, each element of which is paired
152 with the stack in turn. In general, the input has the form
154 (...((x1,...,xn),s1),...sk)
156 where xi are the environment values, and si the ones on the stack,
157 with s1 being the "top", the first one to be matched with a lambda.
160 envStackType :: [Id] -> [Type] -> Type
161 envStackType ids stack_tys = foldl mkCorePairTy (mkBigCoreVarTupTy ids) stack_tys
163 ----------------------------------------------
166 -- (...((x1,...,xn),s1),...sk)
168 buildEnvStack :: [Id] -> [Id] -> CoreExpr
169 buildEnvStack env_ids stack_ids
170 = foldl mkCorePairExpr (mkBigCoreVarTup env_ids) (map Var stack_ids)
172 ----------------------------------------------
175 -- \ (...((x1,...,xn),s1),...sk) -> e
178 -- case zk of (zk-1,sk) ->
180 -- case z1 of (z0,s1) ->
181 -- case z0 of (x1,...,xn) ->
184 matchEnvStack :: [Id] -- x1..xn
188 matchEnvStack env_ids stack_ids body = do
189 uniqs <- newUniqueSupply
190 tup_var <- newSysLocalDs (mkBigCoreVarTupTy env_ids)
191 matchVarStack tup_var stack_ids
192 (coreCaseTuple uniqs tup_var env_ids body)
195 ----------------------------------------------
198 -- \ (...(z0,s1),...sk) -> e
201 -- case zk of (zk-1,sk) ->
203 -- case z1 of (z0,s1) ->
206 matchVarStack :: Id -- z0
210 matchVarStack env_id [] body
211 = return (Lam env_id body)
212 matchVarStack env_id (stack_id:stack_ids) body = do
213 pair_id <- newSysLocalDs (mkCorePairTy (idType env_id) (idType stack_id))
214 matchVarStack pair_id stack_ids
215 (coreCasePair pair_id env_id stack_id body)
219 mkHsEnvStackExpr :: [Id] -> [Id] -> LHsExpr Id
220 mkHsEnvStackExpr env_ids stack_ids
221 = foldl (\a b -> mkLHsTupleExpr [a,b])
222 (mkLHsVarTuple env_ids)
223 (map nlHsVar stack_ids)
226 Translation of arrow abstraction
230 -- A | xs |- c :: [] t' ---> c'
231 -- --------------------------
232 -- A |- proc p -> c :: a t t' ---> arr (\ p -> (xs)) >>> c'
234 -- where (xs) is the tuple of variables bound by p
240 dsProcExpr pat (L _ (HsCmdTop cmd [] cmd_ty ids)) = do
241 meth_ids <- mkCmdEnv ids
242 let locals = mkVarSet (collectPatBinders pat)
243 (core_cmd, _free_vars, env_ids) <- dsfixCmd meth_ids locals [] cmd_ty cmd
244 let env_ty = mkBigCoreVarTupTy env_ids
245 fail_expr <- mkFailExpr ProcExpr env_ty
246 var <- selectSimpleMatchVarL pat
247 match_code <- matchSimply (Var var) ProcExpr pat (mkBigCoreVarTup env_ids) fail_expr
248 let pat_ty = hsLPatType pat
249 proc_code = do_map_arrow meth_ids pat_ty env_ty cmd_ty
252 return (bindCmdEnv meth_ids proc_code)
253 dsProcExpr _ c = pprPanic "dsProcExpr" (ppr c)
256 Translation of command judgements of the form
258 A | xs |- c :: [ts] t
261 dsLCmd :: DsCmdEnv -> IdSet -> [Id] -> [Type] -> Type -> LHsCmd Id
262 -> DsM (CoreExpr, IdSet)
263 dsLCmd ids local_vars env_ids stack res_ty cmd
264 = dsCmd ids local_vars env_ids stack res_ty (unLoc cmd)
266 dsCmd :: DsCmdEnv -- arrow combinators
267 -> IdSet -- set of local vars available to this command
268 -> [Id] -- list of vars in the input to this command
269 -- This is typically fed back,
270 -- so don't pull on it too early
271 -> [Type] -- type of the stack
272 -> Type -- return type of the command
273 -> HsCmd Id -- command to desugar
274 -> DsM (CoreExpr, -- desugared expression
275 IdSet) -- set of local vars that occur free
277 -- A |- f :: a (t*ts) t'
279 -- -----------------------------
280 -- A | xs |- f -< arg :: [ts] t'
282 -- ---> arr (\ ((xs)*ts) -> (arg*ts)) >>> f
284 dsCmd ids local_vars env_ids stack res_ty
285 (HsArrApp arrow arg arrow_ty HsFirstOrderApp _)= do
287 (a_arg_ty, _res_ty') = tcSplitAppTy arrow_ty
288 (_a_ty, arg_ty) = tcSplitAppTy a_arg_ty
289 core_arrow <- dsLExpr arrow
290 core_arg <- dsLExpr arg
291 stack_ids <- mapM newSysLocalDs stack
292 core_make_arg <- matchEnvStack env_ids stack_ids
293 (foldl mkCorePairExpr core_arg (map Var stack_ids))
294 return (do_map_arrow ids
295 (envStackType env_ids stack)
300 exprFreeVars core_arg `intersectVarSet` local_vars)
302 -- A, xs |- f :: a (t*ts) t'
304 -- ------------------------------
305 -- A | xs |- f -<< arg :: [ts] t'
307 -- ---> arr (\ ((xs)*ts) -> (f,(arg*ts))) >>> app
309 dsCmd ids local_vars env_ids stack res_ty
310 (HsArrApp arrow arg arrow_ty HsHigherOrderApp _) = do
312 (a_arg_ty, _res_ty') = tcSplitAppTy arrow_ty
313 (_a_ty, arg_ty) = tcSplitAppTy a_arg_ty
315 core_arrow <- dsLExpr arrow
316 core_arg <- dsLExpr arg
317 stack_ids <- mapM newSysLocalDs stack
318 core_make_pair <- matchEnvStack env_ids stack_ids
319 (mkCorePairExpr core_arrow
320 (foldl mkCorePairExpr core_arg (map Var stack_ids)))
322 return (do_map_arrow ids
323 (envStackType env_ids stack)
324 (mkCorePairTy arrow_ty arg_ty)
327 (do_app ids arg_ty res_ty),
328 (exprFreeVars core_arrow `unionVarSet` exprFreeVars core_arg)
329 `intersectVarSet` local_vars)
331 -- A | ys |- c :: [t:ts] t'
333 -- ------------------------
334 -- A | xs |- c e :: [ts] t'
336 -- ---> arr (\ ((xs)*ts) -> let z = e in (((ys),z)*ts)) >>> c
338 dsCmd ids local_vars env_ids stack res_ty (HsApp cmd arg) = do
339 core_arg <- dsLExpr arg
341 arg_ty = exprType core_arg
342 stack' = arg_ty:stack
343 (core_cmd, free_vars, env_ids')
344 <- dsfixCmd ids local_vars stack' res_ty cmd
345 stack_ids <- mapM newSysLocalDs stack
346 arg_id <- newSysLocalDs arg_ty
347 -- push the argument expression onto the stack
349 core_body = bindNonRec arg_id core_arg
350 (buildEnvStack env_ids' (arg_id:stack_ids))
351 -- match the environment and stack against the input
352 core_map <- matchEnvStack env_ids stack_ids core_body
353 return (do_map_arrow ids
354 (envStackType env_ids stack)
355 (envStackType env_ids' stack')
359 (exprFreeVars core_arg `intersectVarSet` local_vars)
360 `unionVarSet` free_vars)
362 -- A | ys |- c :: [ts] t'
363 -- -----------------------------------------------
364 -- A | xs |- \ p1 ... pk -> c :: [t1:...:tk:ts] t'
366 -- ---> arr (\ ((((xs), p1), ... pk)*ts) -> ((ys)*ts)) >>> c
368 dsCmd ids local_vars env_ids stack res_ty
369 (HsLam (MatchGroup [L _ (Match pats _ (GRHSs [L _ (GRHS [] body)] _ ))] _)) = do
371 pat_vars = mkVarSet (collectPatsBinders pats)
372 local_vars' = local_vars `unionVarSet` pat_vars
373 stack' = drop (length pats) stack
374 (core_body, free_vars, env_ids') <- dsfixCmd ids local_vars' stack' res_ty body
375 stack_ids <- mapM newSysLocalDs stack
377 -- the expression is built from the inside out, so the actions
378 -- are presented in reverse order
381 (actual_ids, stack_ids') = splitAt (length pats) stack_ids
382 -- build a new environment, plus what's left of the stack
383 core_expr = buildEnvStack env_ids' stack_ids'
384 in_ty = envStackType env_ids stack
385 in_ty' = envStackType env_ids' stack'
387 fail_expr <- mkFailExpr LambdaExpr in_ty'
388 -- match the patterns against the top of the old stack
389 match_code <- matchSimplys (map Var actual_ids) LambdaExpr pats core_expr fail_expr
390 -- match the old environment and stack against the input
391 select_code <- matchEnvStack env_ids stack_ids match_code
392 return (do_map_arrow ids in_ty in_ty' res_ty select_code core_body,
393 free_vars `minusVarSet` pat_vars)
395 dsCmd ids local_vars env_ids stack res_ty (HsPar cmd)
396 = dsLCmd ids local_vars env_ids stack res_ty cmd
398 -- A, xs |- e :: Bool
399 -- A | xs1 |- c1 :: [ts] t
400 -- A | xs2 |- c2 :: [ts] t
401 -- ----------------------------------------
402 -- A | xs |- if e then c1 else c2 :: [ts] t
404 -- ---> arr (\ ((xs)*ts) ->
405 -- if e then Left ((xs1)*ts) else Right ((xs2)*ts)) >>>
408 dsCmd ids local_vars env_ids stack res_ty (HsIf cond then_cmd else_cmd) = do
409 core_cond <- dsLExpr cond
410 (core_then, fvs_then, then_ids) <- dsfixCmd ids local_vars stack res_ty then_cmd
411 (core_else, fvs_else, else_ids) <- dsfixCmd ids local_vars stack res_ty else_cmd
412 stack_ids <- mapM newSysLocalDs stack
413 either_con <- dsLookupTyCon eitherTyConName
414 left_con <- dsLookupDataCon leftDataConName
415 right_con <- dsLookupDataCon rightDataConName
417 left_expr ty1 ty2 e = mkConApp left_con [Type ty1, Type ty2, e]
418 right_expr ty1 ty2 e = mkConApp right_con [Type ty1, Type ty2, e]
420 in_ty = envStackType env_ids stack
421 then_ty = envStackType then_ids stack
422 else_ty = envStackType else_ids stack
423 sum_ty = mkTyConApp either_con [then_ty, else_ty]
424 fvs_cond = exprFreeVars core_cond `intersectVarSet` local_vars
426 core_if <- matchEnvStack env_ids stack_ids
427 (mkIfThenElse core_cond
428 (left_expr then_ty else_ty (buildEnvStack then_ids stack_ids))
429 (right_expr then_ty else_ty (buildEnvStack else_ids stack_ids)))
430 return (do_map_arrow ids in_ty sum_ty res_ty
432 (do_choice ids then_ty else_ty res_ty core_then core_else),
433 fvs_cond `unionVarSet` fvs_then `unionVarSet` fvs_else)
436 Case commands are treated in much the same way as if commands
437 (see above) except that there are more alternatives. For example
439 case e of { p1 -> c1; p2 -> c2; p3 -> c3 }
443 arr (\ ((xs)*ts) -> case e of
444 p1 -> (Left (Left (xs1)*ts))
445 p2 -> Left ((Right (xs2)*ts))
446 p3 -> Right ((xs3)*ts)) >>>
449 The idea is to extract the commands from the case, build a balanced tree
450 of choices, and replace the commands with expressions that build tagged
451 tuples, obtaining a case expression that can be desugared normally.
452 To build all this, we use triples describing segments of the list of
453 case bodies, containing the following fields:
454 * a list of expressions of the form (Left|Right)* ((xs)*ts), to be put
455 into the case replacing the commands
456 * a sum type that is the common type of these expressions, and also the
457 input type of the arrow
458 * a CoreExpr for an arrow built by combining the translated command
462 dsCmd ids local_vars env_ids stack res_ty (HsCase exp (MatchGroup matches match_ty)) = do
463 stack_ids <- mapM newSysLocalDs stack
465 -- Extract and desugar the leaf commands in the case, building tuple
466 -- expressions that will (after tagging) replace these leaves
469 leaves = concatMap leavesMatch matches
470 make_branch (leaf, bound_vars) = do
471 (core_leaf, _fvs, leaf_ids) <-
472 dsfixCmd ids (local_vars `unionVarSet` bound_vars) stack res_ty leaf
473 return ([mkHsEnvStackExpr leaf_ids stack_ids],
474 envStackType leaf_ids stack,
477 branches <- mapM make_branch leaves
478 either_con <- dsLookupTyCon eitherTyConName
479 left_con <- dsLookupDataCon leftDataConName
480 right_con <- dsLookupDataCon rightDataConName
482 left_id = HsVar (dataConWrapId left_con)
483 right_id = HsVar (dataConWrapId right_con)
484 left_expr ty1 ty2 e = noLoc $ HsApp (noLoc $ HsWrap (mkWpTyApps [ty1, ty2]) left_id ) e
485 right_expr ty1 ty2 e = noLoc $ HsApp (noLoc $ HsWrap (mkWpTyApps [ty1, ty2]) right_id) e
487 -- Prefix each tuple with a distinct series of Left's and Right's,
488 -- in a balanced way, keeping track of the types.
490 merge_branches (builds1, in_ty1, core_exp1)
491 (builds2, in_ty2, core_exp2)
492 = (map (left_expr in_ty1 in_ty2) builds1 ++
493 map (right_expr in_ty1 in_ty2) builds2,
494 mkTyConApp either_con [in_ty1, in_ty2],
495 do_choice ids in_ty1 in_ty2 res_ty core_exp1 core_exp2)
496 (leaves', sum_ty, core_choices) = foldb merge_branches branches
498 -- Replace the commands in the case with these tagged tuples,
499 -- yielding a HsExpr Id we can feed to dsExpr.
501 (_, matches') = mapAccumL (replaceLeavesMatch res_ty) leaves' matches
502 in_ty = envStackType env_ids stack
504 pat_ty = funArgTy match_ty
505 match_ty' = mkFunTy pat_ty sum_ty
506 -- Note that we replace the HsCase result type by sum_ty,
507 -- which is the type of matches'
509 core_body <- dsExpr (HsCase exp (MatchGroup matches' match_ty'))
510 core_matches <- matchEnvStack env_ids stack_ids core_body
511 return (do_map_arrow ids in_ty sum_ty res_ty core_matches core_choices,
512 exprFreeVars core_body `intersectVarSet` local_vars)
514 -- A | ys |- c :: [ts] t
515 -- ----------------------------------
516 -- A | xs |- let binds in c :: [ts] t
518 -- ---> arr (\ ((xs)*ts) -> let binds in ((ys)*ts)) >>> c
520 dsCmd ids local_vars env_ids stack res_ty (HsLet binds body) = do
522 defined_vars = mkVarSet (collectLocalBinders binds)
523 local_vars' = local_vars `unionVarSet` defined_vars
525 (core_body, _free_vars, env_ids') <- dsfixCmd ids local_vars' stack res_ty body
526 stack_ids <- mapM newSysLocalDs stack
527 -- build a new environment, plus the stack, using the let bindings
528 core_binds <- dsLocalBinds binds (buildEnvStack env_ids' stack_ids)
529 -- match the old environment and stack against the input
530 core_map <- matchEnvStack env_ids stack_ids core_binds
531 return (do_map_arrow ids
532 (envStackType env_ids stack)
533 (envStackType env_ids' stack)
537 exprFreeVars core_binds `intersectVarSet` local_vars)
539 dsCmd ids local_vars env_ids [] res_ty (HsDo _ctxt stmts body _)
540 = dsCmdDo ids local_vars env_ids res_ty stmts body
542 -- A |- e :: forall e. a1 (e*ts1) t1 -> ... an (e*tsn) tn -> a (e*ts) t
543 -- A | xs |- ci :: [tsi] ti
544 -- -----------------------------------
545 -- A | xs |- (|e c1 ... cn|) :: [ts] t ---> e [t_xs] c1 ... cn
547 dsCmd _ids local_vars env_ids _stack _res_ty (HsArrForm op _ args) = do
548 let env_ty = mkBigCoreVarTupTy env_ids
549 core_op <- dsLExpr op
550 (core_args, fv_sets) <- mapAndUnzipM (dsTrimCmdArg local_vars env_ids) args
551 return (mkApps (App core_op (Type env_ty)) core_args,
552 unionVarSets fv_sets)
555 dsCmd ids local_vars env_ids stack res_ty (HsTick ix vars expr) = do
556 (expr1,id_set) <- dsLCmd ids local_vars env_ids stack res_ty expr
557 expr2 <- mkTickBox ix vars expr1
558 return (expr2,id_set)
560 dsCmd _ _ _ _ _ c = pprPanic "dsCmd" (ppr c)
562 -- A | ys |- c :: [ts] t (ys <= xs)
563 -- ---------------------
564 -- A | xs |- c :: [ts] t ---> arr_ts (\ (xs) -> (ys)) >>> c
567 :: IdSet -- set of local vars available to this command
568 -> [Id] -- list of vars in the input to this command
569 -> LHsCmdTop Id -- command argument to desugar
570 -> DsM (CoreExpr, -- desugared expression
571 IdSet) -- set of local vars that occur free
572 dsTrimCmdArg local_vars env_ids (L _ (HsCmdTop cmd stack cmd_ty ids)) = do
573 meth_ids <- mkCmdEnv ids
574 (core_cmd, free_vars, env_ids') <- dsfixCmd meth_ids local_vars stack cmd_ty cmd
575 stack_ids <- mapM newSysLocalDs stack
576 trim_code <- matchEnvStack env_ids stack_ids (buildEnvStack env_ids' stack_ids)
578 in_ty = envStackType env_ids stack
579 in_ty' = envStackType env_ids' stack
580 arg_code = if env_ids' == env_ids then core_cmd else
581 do_map_arrow meth_ids in_ty in_ty' cmd_ty trim_code core_cmd
582 return (bindCmdEnv meth_ids arg_code, free_vars)
584 -- Given A | xs |- c :: [ts] t, builds c with xs fed back.
585 -- Typically needs to be prefixed with arr (\p -> ((xs)*ts))
588 :: DsCmdEnv -- arrow combinators
589 -> IdSet -- set of local vars available to this command
590 -> [Type] -- type of the stack
591 -> Type -- return type of the command
592 -> LHsCmd Id -- command to desugar
593 -> DsM (CoreExpr, -- desugared expression
594 IdSet, -- set of local vars that occur free
595 [Id]) -- set as a list, fed back
596 dsfixCmd ids local_vars stack cmd_ty cmd
597 = fixDs (\ ~(_,_,env_ids') -> do
598 (core_cmd, free_vars) <- dsLCmd ids local_vars env_ids' stack cmd_ty cmd
599 return (core_cmd, free_vars, varSetElems free_vars))
603 Translation of command judgements of the form
605 A | xs |- do { ss } :: [] t
609 dsCmdDo :: DsCmdEnv -- arrow combinators
610 -> IdSet -- set of local vars available to this statement
611 -> [Id] -- list of vars in the input to this statement
612 -- This is typically fed back,
613 -- so don't pull on it too early
614 -> Type -- return type of the statement
615 -> [LStmt Id] -- statements to desugar
616 -> LHsExpr Id -- body
617 -> DsM (CoreExpr, -- desugared expression
618 IdSet) -- set of local vars that occur free
620 -- A | xs |- c :: [] t
621 -- --------------------------
622 -- A | xs |- do { c } :: [] t
624 dsCmdDo ids local_vars env_ids res_ty [] body
625 = dsLCmd ids local_vars env_ids [] res_ty body
627 dsCmdDo ids local_vars env_ids res_ty (stmt:stmts) body = do
629 bound_vars = mkVarSet (collectLStmtBinders stmt)
630 local_vars' = local_vars `unionVarSet` bound_vars
631 (core_stmts, _, env_ids') <- fixDs (\ ~(_,_,env_ids') -> do
632 (core_stmts, fv_stmts) <- dsCmdDo ids local_vars' env_ids' res_ty stmts body
633 return (core_stmts, fv_stmts, varSetElems fv_stmts))
634 (core_stmt, fv_stmt) <- dsCmdLStmt ids local_vars env_ids env_ids' stmt
635 return (do_compose ids
636 (mkBigCoreVarTupTy env_ids)
637 (mkBigCoreVarTupTy env_ids')
644 A statement maps one local environment to another, and is represented
645 as an arrow from one tuple type to another. A statement sequence is
646 translated to a composition of such arrows.
648 dsCmdLStmt :: DsCmdEnv -> IdSet -> [Id] -> [Id] -> LStmt Id
649 -> DsM (CoreExpr, IdSet)
650 dsCmdLStmt ids local_vars env_ids out_ids cmd
651 = dsCmdStmt ids local_vars env_ids out_ids (unLoc cmd)
654 :: DsCmdEnv -- arrow combinators
655 -> IdSet -- set of local vars available to this statement
656 -> [Id] -- list of vars in the input to this statement
657 -- This is typically fed back,
658 -- so don't pull on it too early
659 -> [Id] -- list of vars in the output of this statement
660 -> Stmt Id -- statement to desugar
661 -> DsM (CoreExpr, -- desugared expression
662 IdSet) -- set of local vars that occur free
664 -- A | xs1 |- c :: [] t
665 -- A | xs' |- do { ss } :: [] t'
666 -- ------------------------------
667 -- A | xs |- do { c; ss } :: [] t'
669 -- ---> arr (\ (xs) -> ((xs1),(xs'))) >>> first c >>>
672 dsCmdStmt ids local_vars env_ids out_ids (ExprStmt cmd _ c_ty) = do
673 (core_cmd, fv_cmd, env_ids1) <- dsfixCmd ids local_vars [] c_ty cmd
674 core_mux <- matchEnvStack env_ids []
675 (mkCorePairExpr (mkBigCoreVarTup env_ids1) (mkBigCoreVarTup out_ids))
677 in_ty = mkBigCoreVarTupTy env_ids
678 in_ty1 = mkBigCoreVarTupTy env_ids1
679 out_ty = mkBigCoreVarTupTy out_ids
680 before_c_ty = mkCorePairTy in_ty1 out_ty
681 after_c_ty = mkCorePairTy c_ty out_ty
682 snd_fn <- mkSndExpr c_ty out_ty
683 return (do_map_arrow ids in_ty before_c_ty out_ty core_mux $
684 do_compose ids before_c_ty after_c_ty out_ty
685 (do_first ids in_ty1 c_ty out_ty core_cmd) $
686 do_arr ids after_c_ty out_ty snd_fn,
687 extendVarSetList fv_cmd out_ids)
690 -- A | xs1 |- c :: [] t
691 -- A | xs' |- do { ss } :: [] t' xs2 = xs' - defs(p)
692 -- -----------------------------------
693 -- A | xs |- do { p <- c; ss } :: [] t'
695 -- ---> arr (\ (xs) -> ((xs1),(xs2))) >>> first c >>>
696 -- arr (\ (p, (xs2)) -> (xs')) >>> ss
698 -- It would be simpler and more consistent to do this using second,
699 -- but that's likely to be defined in terms of first.
701 dsCmdStmt ids local_vars env_ids out_ids (BindStmt pat cmd _ _) = do
702 (core_cmd, fv_cmd, env_ids1) <- dsfixCmd ids local_vars [] (hsLPatType pat) cmd
704 pat_ty = hsLPatType pat
705 pat_vars = mkVarSet (collectPatBinders pat)
706 env_ids2 = varSetElems (mkVarSet out_ids `minusVarSet` pat_vars)
707 env_ty2 = mkBigCoreVarTupTy env_ids2
709 -- multiplexing function
710 -- \ (xs) -> ((xs1),(xs2))
712 core_mux <- matchEnvStack env_ids []
713 (mkCorePairExpr (mkBigCoreVarTup env_ids1) (mkBigCoreVarTup env_ids2))
715 -- projection function
716 -- \ (p, (xs2)) -> (zs)
718 env_id <- newSysLocalDs env_ty2
719 uniqs <- newUniqueSupply
721 after_c_ty = mkCorePairTy pat_ty env_ty2
722 out_ty = mkBigCoreVarTupTy out_ids
723 body_expr = coreCaseTuple uniqs env_id env_ids2 (mkBigCoreVarTup out_ids)
725 fail_expr <- mkFailExpr (StmtCtxt DoExpr) out_ty
726 pat_id <- selectSimpleMatchVarL pat
727 match_code <- matchSimply (Var pat_id) (StmtCtxt DoExpr) pat body_expr fail_expr
728 pair_id <- newSysLocalDs after_c_ty
730 proj_expr = Lam pair_id (coreCasePair pair_id pat_id env_id match_code)
732 -- put it all together
734 in_ty = mkBigCoreVarTupTy env_ids
735 in_ty1 = mkBigCoreVarTupTy env_ids1
736 in_ty2 = mkBigCoreVarTupTy env_ids2
737 before_c_ty = mkCorePairTy in_ty1 in_ty2
738 return (do_map_arrow ids in_ty before_c_ty out_ty core_mux $
739 do_compose ids before_c_ty after_c_ty out_ty
740 (do_first ids in_ty1 pat_ty in_ty2 core_cmd) $
741 do_arr ids after_c_ty out_ty proj_expr,
742 fv_cmd `unionVarSet` (mkVarSet out_ids `minusVarSet` pat_vars))
744 -- A | xs' |- do { ss } :: [] t
745 -- --------------------------------------
746 -- A | xs |- do { let binds; ss } :: [] t
748 -- ---> arr (\ (xs) -> let binds in (xs')) >>> ss
750 dsCmdStmt ids local_vars env_ids out_ids (LetStmt binds) = do
751 -- build a new environment using the let bindings
752 core_binds <- dsLocalBinds binds (mkBigCoreVarTup out_ids)
753 -- match the old environment against the input
754 core_map <- matchEnvStack env_ids [] core_binds
756 (mkBigCoreVarTupTy env_ids)
757 (mkBigCoreVarTupTy out_ids)
759 exprFreeVars core_binds `intersectVarSet` local_vars)
761 -- A | ys |- do { ss; returnA -< ((xs1), (ys2)) } :: [] ...
762 -- A | xs' |- do { ss' } :: [] t
763 -- ------------------------------------
764 -- A | xs |- do { rec ss; ss' } :: [] t
766 -- xs1 = xs' /\ defs(ss)
767 -- xs2 = xs' - defs(ss)
768 -- ys1 = ys - defs(ss)
769 -- ys2 = ys /\ defs(ss)
771 -- ---> arr (\(xs) -> ((ys1),(xs2))) >>>
772 -- first (loop (arr (\((ys1),~(ys2)) -> (ys)) >>> ss)) >>>
773 -- arr (\((xs1),(xs2)) -> (xs')) >>> ss'
775 dsCmdStmt ids local_vars env_ids out_ids
776 (RecStmt { recS_stmts = stmts, recS_later_ids = later_ids, recS_rec_ids = rec_ids
777 , recS_rec_rets = rhss, recS_dicts = _binds }) = do
778 let -- ToDo: ****** binds not desugared; ROSS PLEASE FIX ********
779 env2_id_set = mkVarSet out_ids `minusVarSet` mkVarSet later_ids
780 env2_ids = varSetElems env2_id_set
781 env2_ty = mkBigCoreVarTupTy env2_ids
783 -- post_loop_fn = \((later_ids),(env2_ids)) -> (out_ids)
785 uniqs <- newUniqueSupply
786 env2_id <- newSysLocalDs env2_ty
788 later_ty = mkBigCoreVarTupTy later_ids
789 post_pair_ty = mkCorePairTy later_ty env2_ty
790 post_loop_body = coreCaseTuple uniqs env2_id env2_ids (mkBigCoreVarTup out_ids)
792 post_loop_fn <- matchEnvStack later_ids [env2_id] post_loop_body
796 (core_loop, env1_id_set, env1_ids)
797 <- dsRecCmd ids local_vars stmts later_ids rec_ids rhss
799 -- pre_loop_fn = \(env_ids) -> ((env1_ids),(env2_ids))
802 env1_ty = mkBigCoreVarTupTy env1_ids
803 pre_pair_ty = mkCorePairTy env1_ty env2_ty
804 pre_loop_body = mkCorePairExpr (mkBigCoreVarTup env1_ids)
805 (mkBigCoreVarTup env2_ids)
807 pre_loop_fn <- matchEnvStack env_ids [] pre_loop_body
809 -- arr pre_loop_fn >>> first (loop (...)) >>> arr post_loop_fn
812 env_ty = mkBigCoreVarTupTy env_ids
813 out_ty = mkBigCoreVarTupTy out_ids
814 core_body = do_map_arrow ids env_ty pre_pair_ty out_ty
816 (do_compose ids pre_pair_ty post_pair_ty out_ty
817 (do_first ids env1_ty later_ty env2_ty
819 (do_arr ids post_pair_ty out_ty
822 return (core_body, env1_id_set `unionVarSet` env2_id_set)
824 dsCmdStmt _ _ _ _ s = pprPanic "dsCmdStmt" (ppr s)
826 -- loop (arr (\ ((env1_ids), ~(rec_ids)) -> (env_ids)) >>>
828 -- arr (\ (out_ids) -> ((later_ids),(rhss))) >>>
830 dsRecCmd :: DsCmdEnv -> VarSet -> [LStmt Id] -> [Var] -> [Var] -> [HsExpr Id]
831 -> DsM (CoreExpr, VarSet, [Var])
832 dsRecCmd ids local_vars stmts later_ids rec_ids rhss = do
834 rec_id_set = mkVarSet rec_ids
835 out_ids = varSetElems (mkVarSet later_ids `unionVarSet` rec_id_set)
836 out_ty = mkBigCoreVarTupTy out_ids
837 local_vars' = local_vars `unionVarSet` rec_id_set
839 -- mk_pair_fn = \ (out_ids) -> ((later_ids),(rhss))
841 core_rhss <- mapM dsExpr rhss
843 later_tuple = mkBigCoreVarTup later_ids
844 later_ty = mkBigCoreVarTupTy later_ids
845 rec_tuple = mkBigCoreTup core_rhss
846 rec_ty = mkBigCoreVarTupTy rec_ids
847 out_pair = mkCorePairExpr later_tuple rec_tuple
848 out_pair_ty = mkCorePairTy later_ty rec_ty
850 mk_pair_fn <- matchEnvStack out_ids [] out_pair
854 (core_stmts, fv_stmts, env_ids) <- dsfixCmdStmts ids local_vars' out_ids stmts
856 -- squash_pair_fn = \ ((env1_ids), ~(rec_ids)) -> (env_ids)
858 rec_id <- newSysLocalDs rec_ty
860 env1_id_set = fv_stmts `minusVarSet` rec_id_set
861 env1_ids = varSetElems env1_id_set
862 env1_ty = mkBigCoreVarTupTy env1_ids
863 in_pair_ty = mkCorePairTy env1_ty rec_ty
864 core_body = mkBigCoreTup (map selectVar env_ids)
867 | v `elemVarSet` rec_id_set
868 = mkTupleSelector rec_ids v rec_id (Var rec_id)
871 squash_pair_fn <- matchEnvStack env1_ids [rec_id] core_body
873 -- loop (arr squash_pair_fn >>> ss >>> arr mk_pair_fn)
876 env_ty = mkBigCoreVarTupTy env_ids
877 core_loop = do_loop ids env1_ty later_ty rec_ty
878 (do_map_arrow ids in_pair_ty env_ty out_pair_ty
880 (do_compose ids env_ty out_ty out_pair_ty
882 (do_arr ids out_ty out_pair_ty mk_pair_fn)))
884 return (core_loop, env1_id_set, env1_ids)
887 A sequence of statements (as in a rec) is desugared to an arrow between
892 :: DsCmdEnv -- arrow combinators
893 -> IdSet -- set of local vars available to this statement
894 -> [Id] -- output vars of these statements
895 -> [LStmt Id] -- statements to desugar
896 -> DsM (CoreExpr, -- desugared expression
897 IdSet, -- set of local vars that occur free
900 dsfixCmdStmts ids local_vars out_ids stmts
901 = fixDs (\ ~(_,_,env_ids) -> do
902 (core_stmts, fv_stmts) <- dsCmdStmts ids local_vars env_ids out_ids stmts
903 return (core_stmts, fv_stmts, varSetElems fv_stmts))
906 :: DsCmdEnv -- arrow combinators
907 -> IdSet -- set of local vars available to this statement
908 -> [Id] -- list of vars in the input to these statements
909 -> [Id] -- output vars of these statements
910 -> [LStmt Id] -- statements to desugar
911 -> DsM (CoreExpr, -- desugared expression
912 IdSet) -- set of local vars that occur free
914 dsCmdStmts ids local_vars env_ids out_ids [stmt]
915 = dsCmdLStmt ids local_vars env_ids out_ids stmt
917 dsCmdStmts ids local_vars env_ids out_ids (stmt:stmts) = do
919 bound_vars = mkVarSet (collectLStmtBinders stmt)
920 local_vars' = local_vars `unionVarSet` bound_vars
921 (core_stmts, _fv_stmts, env_ids') <- dsfixCmdStmts ids local_vars' out_ids stmts
922 (core_stmt, fv_stmt) <- dsCmdLStmt ids local_vars env_ids env_ids' stmt
923 return (do_compose ids
924 (mkBigCoreVarTupTy env_ids)
925 (mkBigCoreVarTupTy env_ids')
926 (mkBigCoreVarTupTy out_ids)
931 dsCmdStmts _ _ _ _ [] = panic "dsCmdStmts []"
935 Match a list of expressions against a list of patterns, left-to-right.
938 matchSimplys :: [CoreExpr] -- Scrutinees
939 -> HsMatchContext Name -- Match kind
940 -> [LPat Id] -- Patterns they should match
941 -> CoreExpr -- Return this if they all match
942 -> CoreExpr -- Return this if they don't
944 matchSimplys [] _ctxt [] result_expr _fail_expr = return result_expr
945 matchSimplys (exp:exps) ctxt (pat:pats) result_expr fail_expr = do
946 match_code <- matchSimplys exps ctxt pats result_expr fail_expr
947 matchSimply exp ctxt pat match_code fail_expr
948 matchSimplys _ _ _ _ _ = panic "matchSimplys"
951 List of leaf expressions, with set of variables bound in each
954 leavesMatch :: LMatch Id -> [(LHsExpr Id, IdSet)]
955 leavesMatch (L _ (Match pats _ (GRHSs grhss binds)))
957 defined_vars = mkVarSet (collectPatsBinders pats)
959 mkVarSet (collectLocalBinders binds)
962 mkVarSet (collectLStmtsBinders stmts)
963 `unionVarSet` defined_vars)
964 | L _ (GRHS stmts expr) <- grhss]
967 Replace the leaf commands in a match
971 :: Type -- new result type
972 -> [LHsExpr Id] -- replacement leaf expressions of that type
973 -> LMatch Id -- the matches of a case command
974 -> ([LHsExpr Id],-- remaining leaf expressions
975 LMatch Id) -- updated match
976 replaceLeavesMatch _res_ty leaves (L loc (Match pat mt (GRHSs grhss binds)))
978 (leaves', grhss') = mapAccumL replaceLeavesGRHS leaves grhss
980 (leaves', L loc (Match pat mt (GRHSs grhss' binds)))
983 :: [LHsExpr Id] -- replacement leaf expressions of that type
984 -> LGRHS Id -- rhss of a case command
985 -> ([LHsExpr Id],-- remaining leaf expressions
986 LGRHS Id) -- updated GRHS
987 replaceLeavesGRHS (leaf:leaves) (L loc (GRHS stmts _))
988 = (leaves, L loc (GRHS stmts leaf))
989 replaceLeavesGRHS [] _ = panic "replaceLeavesGRHS []"
992 Balanced fold of a non-empty list.
995 foldb :: (a -> a -> a) -> [a] -> a
996 foldb _ [] = error "foldb of empty list"
998 foldb f xs = foldb f (fold_pairs xs)
1001 fold_pairs [x] = [x]
1002 fold_pairs (x1:x2:xs) = f x1 x2:fold_pairs xs
1005 Note [Dictionary binders in ConPatOut] See also same Note in HsUtils
1006 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1007 The following functions to collect value variables from patterns are
1008 copied from HsUtils, with one change: we also collect the dictionary
1009 bindings (pat_binds) from ConPatOut. We need them for cases like
1011 h :: Arrow a => Int -> a (Int,Int) Int
1012 h x = proc (y,z) -> case compare x y of
1013 GT -> returnA -< z+x
1015 The type checker turns the case into
1018 GT { p77 = plusInt } -> returnA -< p77 z x
1020 Here p77 is a local binding for the (+) operation.
1022 See comments in HsUtils for why the other version does not include
1026 collectPatBinders :: OutputableBndr a => LPat a -> [a]
1027 collectPatBinders pat = collectl pat []
1029 collectPatsBinders :: OutputableBndr a => [LPat a] -> [a]
1030 collectPatsBinders pats = foldr collectl [] pats
1032 ---------------------
1033 collectl :: OutputableBndr a => LPat a -> [a] -> [a]
1034 -- See Note [Dictionary binders in ConPatOut]
1035 collectl (L _ pat) bndrs
1038 go (VarPat var) = var : bndrs
1039 go (VarPatOut var bs) = var : collectHsBindsBinders bs
1041 go (WildPat _) = bndrs
1042 go (LazyPat pat) = collectl pat bndrs
1043 go (BangPat pat) = collectl pat bndrs
1044 go (AsPat (L _ a) pat) = a : collectl pat bndrs
1045 go (ParPat pat) = collectl pat bndrs
1047 go (ListPat pats _) = foldr collectl bndrs pats
1048 go (PArrPat pats _) = foldr collectl bndrs pats
1049 go (TuplePat pats _ _) = foldr collectl bndrs pats
1051 go (ConPatIn _ ps) = foldr collectl bndrs (hsConPatArgs ps)
1052 go (ConPatOut {pat_args=ps, pat_binds=ds}) =
1053 collectHsBindsBinders ds
1054 ++ foldr collectl bndrs (hsConPatArgs ps)
1055 go (LitPat _) = bndrs
1056 go (NPat _ _ _) = bndrs
1057 go (NPlusKPat (L _ n) _ _ _) = n : bndrs
1059 go (SigPatIn pat _) = collectl pat bndrs
1060 go (SigPatOut pat _) = collectl pat bndrs
1061 go (TypePat _) = bndrs
1062 go (CoPat _ pat _) = collectl (noLoc pat) bndrs
1063 go (ViewPat _ pat _) = collectl pat bndrs
1064 go p@(QuasiQuotePat {}) = pprPanic "collectl/go" (ppr p)