2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
4 \section[DsExpr]{Matching expressions (Exprs)}
7 #include "HsVersions.h"
9 module DsExpr ( dsExpr ) where
12 import DsLoop -- partly to get dsBinds, partly to chk dsExpr
14 import HsSyn ( HsExpr(..), HsLit(..), ArithSeqInfo(..),
15 Match, Qual, HsBinds, Stmt, PolyType )
16 import TcHsSyn ( TypecheckedHsExpr(..), TypecheckedHsBinds(..),
17 TypecheckedRecordBinds(..), TypecheckedPat(..)
22 import DsCCall ( dsCCall )
23 import DsListComp ( dsListComp )
24 import DsUtils ( mkAppDs, mkConDs, mkPrimDs, dsExprToAtom,
25 mkErrorAppDs, showForErr, EquationInfo,
28 import Match ( matchWrapper )
30 import CoreUnfold ( UnfoldingDetails(..), UnfoldingGuidance(..),
32 import CoreUtils ( coreExprType, substCoreExpr, argToExpr,
33 mkCoreIfThenElse, unTagBinders )
34 import CostCentre ( mkUserCC )
35 import FieldLabel ( fieldLabelType, FieldLabel )
36 import Id ( mkTupleCon, idType, nullIdEnv, addOneToIdEnv,
37 getIdUnfolding, dataConArgTys, dataConFieldLabels,
38 recordSelectorFieldLabel
40 import Literal ( mkMachInt, Literal(..) )
41 import MagicUFs ( MagicUnfoldingFun )
42 import Name ( Name{--O only-} )
43 import PprStyle ( PprStyle(..) )
44 import PprType ( GenType )
45 import PrelInfo ( mkTupleTy, unitTy, nilDataCon, consDataCon,
46 charDataCon, charTy, rEC_CON_ERROR_ID,
49 import Pretty ( ppShow, ppBesides, ppPStr, ppStr )
50 import TyCon ( isDataTyCon, isNewTyCon )
51 import Type ( splitSigmaTy, splitFunTy, typePrimRep,
52 getAppDataTyCon, getAppTyCon, applyTy
54 import TyVar ( nullTyVarEnv, addOneToTyVarEnv, GenTyVar{-instance Eq-} )
55 import Usage ( UVar(..) )
56 import Util ( zipEqual, pprError, panic, assertPanic )
58 maybeBoxedPrimType = panic "DsExpr.maybeBoxedPrimType"
59 splitTyArgs = panic "DsExpr.splitTyArgs"
61 mk_nil_con ty = mkCon nilDataCon [] [ty] [] -- micro utility...
64 The funny business to do with variables is that we look them up in the
65 Id-to-Id and Id-to-Id maps that the monadery is carrying
66 around; if we get hits, we use the value accordingly.
68 %************************************************************************
70 \subsection[DsExpr-vars-and-cons]{Variables and constructors}
72 %************************************************************************
75 dsExpr :: TypecheckedHsExpr -> DsM CoreExpr
77 dsExpr (HsVar var) = dsApp (HsVar var) []
80 %************************************************************************
82 \subsection[DsExpr-literals]{Literals}
84 %************************************************************************
86 We give int/float literals type Integer and Rational, respectively.
87 The typechecker will (presumably) have put \tr{from{Integer,Rational}s}
90 ToDo: put in range checks for when converting "i"
91 (or should that be in the typechecker?)
93 For numeric literals, we try to detect there use at a standard type
94 (Int, Float, etc.) are directly put in the right constructor.
95 [NB: down with the @App@ conversion.]
96 Otherwise, we punt, putting in a "NoRep" Core literal (where the
97 representation decisions are delayed)...
99 See also below where we look for @DictApps@ for \tr{plusInt}, etc.
102 dsExpr (HsLitOut (HsString s) _)
104 = returnDs (mk_nil_con charTy)
108 the_char = mkCon charDataCon [] [] [LitArg (MachChar (_HEAD_ s))]
109 the_nil = mk_nil_con charTy
111 mkConDs consDataCon [charTy] [the_char, the_nil]
113 -- "_" => build (\ c n -> c 'c' n) -- LATER
115 -- "str" ==> build (\ c n -> foldr charTy T c n "str")
118 dsExpr (HsLitOut (HsString str) _)
119 = newTyVarsDs [alphaTyVar] `thenDs` \ [new_tyvar] ->
121 new_ty = mkTyVarTy new_tyvar
124 charTy `mkFunTy` (new_ty `mkFunTy` new_ty),
126 mkForallTy [alphaTyVar]
127 ((charTy `mkFunTy` (alphaTy `mkFunTy` alphaTy))
128 `mkFunTy` (alphaTy `mkFunTy` alphaTy))
129 ] `thenDs` \ [c,n,g] ->
130 returnDs (mkBuild charTy new_tyvar c n g (
132 (CoTyApp (CoTyApp (Var foldrId) charTy) new_ty) *** ensure non-prim type ***
133 [VarArg c,VarArg n,LitArg (NoRepStr str)]))
136 -- otherwise, leave it as a NoRepStr;
137 -- the Core-to-STG pass will wrap it in an application of "unpackCStringId".
139 dsExpr (HsLitOut (HsString str) _)
140 = returnDs (Lit (NoRepStr str))
142 dsExpr (HsLitOut (HsLitLit s) ty)
143 = returnDs ( mkCon data_con [] [] [LitArg (MachLitLit s kind)] )
146 = case (maybeBoxedPrimType ty) of
147 Just (boxing_data_con, prim_ty)
148 -> (boxing_data_con, typePrimRep prim_ty)
150 -> pprError "ERROR: ``literal-literal'' not a single-constructor type: "
151 (ppBesides [ppPStr s, ppStr "; type: ", ppr PprDebug ty])
153 dsExpr (HsLitOut (HsInt i) _)
154 = returnDs (Lit (NoRepInteger i))
156 dsExpr (HsLitOut (HsFrac r) _)
157 = returnDs (Lit (NoRepRational r))
159 -- others where we know what to do:
161 dsExpr (HsLitOut (HsIntPrim i) _)
162 = if (i >= toInteger minInt && i <= toInteger maxInt) then
163 returnDs (Lit (mkMachInt i))
165 error ("ERROR: Int constant " ++ show i ++ out_of_range_msg)
167 dsExpr (HsLitOut (HsFloatPrim f) _)
168 = returnDs (Lit (MachFloat f))
169 -- ToDo: range checking needed!
171 dsExpr (HsLitOut (HsDoublePrim d) _)
172 = returnDs (Lit (MachDouble d))
173 -- ToDo: range checking needed!
175 dsExpr (HsLitOut (HsChar c) _)
176 = returnDs ( mkCon charDataCon [] [] [LitArg (MachChar c)] )
178 dsExpr (HsLitOut (HsCharPrim c) _)
179 = returnDs (Lit (MachChar c))
181 dsExpr (HsLitOut (HsStringPrim s) _)
182 = returnDs (Lit (MachStr s))
184 -- end of literals magic. --
186 dsExpr expr@(HsLam a_Match)
187 = matchWrapper LambdaMatch [a_Match] "lambda" `thenDs` \ (binders, matching_code) ->
188 returnDs ( mkValLam binders matching_code )
190 dsExpr expr@(HsApp e1 e2) = dsApp expr []
191 dsExpr expr@(OpApp e1 op e2) = dsApp expr []
194 Operator sections. At first it looks as if we can convert
203 But no! expr might be a redex, and we can lose laziness badly this
208 for example. So we convert instead to
210 let y = expr in \x -> op y x
212 If \tr{expr} is actually just a variable, say, then the simplifier
216 dsExpr (SectionL expr op)
217 = dsExpr op `thenDs` \ core_op ->
218 dsExpr expr `thenDs` \ core_expr ->
219 dsExprToAtom core_expr $ \ y_atom ->
221 -- for the type of x, we need the type of op's 2nd argument
223 x_ty = case (splitSigmaTy (coreExprType core_op)) of { (_, _, tau_ty) ->
224 case (splitTyArgs tau_ty) of {
225 ((_:arg2_ty:_), _) -> arg2_ty;
226 _ -> panic "dsExpr:SectionL:arg 2 ty"
229 newSysLocalDs x_ty `thenDs` \ x_id ->
230 returnDs (mkValLam [x_id] (core_op `App` y_atom `App` VarArg x_id))
232 -- dsExpr (SectionR op expr) -- \ x -> op x expr
233 dsExpr (SectionR op expr)
234 = dsExpr op `thenDs` \ core_op ->
235 dsExpr expr `thenDs` \ core_expr ->
236 dsExprToAtom core_expr $ \ y_atom ->
238 -- for the type of x, we need the type of op's 1st argument
240 x_ty = case (splitSigmaTy (coreExprType core_op)) of { (_, _, tau_ty) ->
241 case (splitTyArgs tau_ty) of {
242 ((arg1_ty:_), _) -> arg1_ty;
243 _ -> panic "dsExpr:SectionR:arg 1 ty"
246 newSysLocalDs x_ty `thenDs` \ x_id ->
247 returnDs (mkValLam [x_id] (core_op `App` VarArg x_id `App` y_atom))
249 dsExpr (CCall label args may_gc is_asm result_ty)
250 = mapDs dsExpr args `thenDs` \ core_args ->
251 dsCCall label core_args may_gc is_asm result_ty
252 -- dsCCall does all the unboxification, etc.
254 dsExpr (HsSCC cc expr)
255 = dsExpr expr `thenDs` \ core_expr ->
256 getModuleAndGroupDs `thenDs` \ (mod_name, group_name) ->
257 returnDs ( SCC (mkUserCC cc mod_name group_name) core_expr)
259 dsExpr expr@(HsCase discrim matches src_loc)
260 = putSrcLocDs src_loc $
261 dsExpr discrim `thenDs` \ core_discrim ->
262 matchWrapper CaseMatch matches "case" `thenDs` \ ([discrim_var], matching_code) ->
263 returnDs ( mkCoLetAny (NonRec discrim_var core_discrim) matching_code )
265 dsExpr (ListComp expr quals)
266 = dsExpr expr `thenDs` \ core_expr ->
267 dsListComp core_expr quals
269 dsExpr (HsLet binds expr)
270 = dsBinds binds `thenDs` \ core_binds ->
271 dsExpr expr `thenDs` \ core_expr ->
272 returnDs ( mkCoLetsAny core_binds core_expr )
274 dsExpr (HsDoOut stmts m_id mz_id src_loc)
275 = putSrcLocDs src_loc $
276 panic "dsExpr:HsDoOut"
278 dsExpr (HsIf guard_expr then_expr else_expr src_loc)
279 = putSrcLocDs src_loc $
280 dsExpr guard_expr `thenDs` \ core_guard ->
281 dsExpr then_expr `thenDs` \ core_then ->
282 dsExpr else_expr `thenDs` \ core_else ->
283 returnDs (mkCoreIfThenElse core_guard core_then core_else)
288 Type lambda and application
289 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
291 dsExpr (TyLam tyvars expr)
292 = dsExpr expr `thenDs` \ core_expr ->
293 returnDs (mkTyLam tyvars core_expr)
295 dsExpr expr@(TyApp e tys) = dsApp expr []
299 Various data construction things
300 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
302 dsExpr (ExplicitListOut ty xs)
304 [] -> returnDs (mk_nil_con ty)
306 dsExpr y `thenDs` \ core_hd ->
307 dsExpr (ExplicitListOut ty ys) `thenDs` \ core_tl ->
308 mkConDs consDataCon [ty] [core_hd, core_tl]
310 dsExpr (ExplicitTuple expr_list)
311 = mapDs dsExpr expr_list `thenDs` \ core_exprs ->
312 mkConDs (mkTupleCon (length expr_list))
313 (map coreExprType core_exprs)
316 -- Two cases, one for ordinary constructors and one for newtype constructors
317 dsExpr (HsCon con tys args)
318 | isDataTyCon tycon -- The usual datatype case
319 = mapDs dsExpr args `thenDs` \ args_exprs ->
320 mkConDs con tys args_exprs
322 | otherwise -- The newtype case
323 = ASSERT( isNewTyCon tycon )
324 ASSERT( null rest_args )
325 dsExpr first_arg `thenDs` \ arg_expr ->
326 returnDs (Coerce (CoerceIn con) result_ty arg_expr)
329 (first_arg:rest_args) = args
330 (args_tys, result_ty) = splitFunTy (foldl applyTy (idType con) tys)
331 (tycon,_) = getAppTyCon result_ty
333 dsExpr (ArithSeqOut expr (From from))
334 = dsExpr expr `thenDs` \ expr2 ->
335 dsExpr from `thenDs` \ from2 ->
336 mkAppDs expr2 [] [from2]
338 dsExpr (ArithSeqOut expr (FromTo from two))
339 = dsExpr expr `thenDs` \ expr2 ->
340 dsExpr from `thenDs` \ from2 ->
341 dsExpr two `thenDs` \ two2 ->
342 mkAppDs expr2 [] [from2, two2]
344 dsExpr (ArithSeqOut expr (FromThen from thn))
345 = dsExpr expr `thenDs` \ expr2 ->
346 dsExpr from `thenDs` \ from2 ->
347 dsExpr thn `thenDs` \ thn2 ->
348 mkAppDs expr2 [] [from2, thn2]
350 dsExpr (ArithSeqOut expr (FromThenTo from thn two))
351 = dsExpr expr `thenDs` \ expr2 ->
352 dsExpr from `thenDs` \ from2 ->
353 dsExpr thn `thenDs` \ thn2 ->
354 dsExpr two `thenDs` \ two2 ->
355 mkAppDs expr2 [] [from2, thn2, two2]
358 Record construction and update
359 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
360 For record construction we do this (assuming T has three arguments)
364 let err = /\a -> recConErr a
365 T (recConErr t1 "M.lhs/230/op1")
367 (recConErr t1 "M.lhs/230/op3")
369 recConErr then converts its arugment string into a proper message
370 before printing it as
372 M.lhs, line 230: missing field op1 was evaluated
376 dsExpr (RecordCon con_expr rbinds)
377 = dsExpr con_expr `thenDs` \ con_expr' ->
379 con_id = get_con con_expr'
380 (arg_tys, _) = splitFunTy (coreExprType con_expr')
383 = case [rhs | (sel_id,rhs,_) <- rbinds,
384 lbl == recordSelectorFieldLabel sel_id] of
385 (rhs:rhss) -> ASSERT( null rhss )
387 [] -> mkErrorAppDs rEC_CON_ERROR_ID arg_ty (showForErr lbl)
389 mapDs mk_arg (arg_tys `zipEqual` dataConFieldLabels con_id) `thenDs` \ con_args ->
390 mkAppDs con_expr' [] con_args
392 -- "con_expr'" is simply an application of the constructor Id
393 -- to types and (perhaps) dictionaries. This gets the constructor...
394 get_con (Var con) = con
395 get_con (App fun _) = get_con fun
398 Record update is a little harder. Suppose we have the decl:
400 data T = T1 {op1, op2, op3 :: Int}
401 | T2 {op4, op2 :: Int}
404 Then we translate as follows:
410 T1 op1 _ op3 -> T1 op1 op2 op3
411 T2 op4 _ -> T2 op4 op2
412 other -> recUpdError "M.lhs/230"
414 It's important that we use the constructor Ids for T1, T2 etc on the
415 RHSs, and do not generate a Core Con directly, because the constructor
416 might do some argument-evaluation first; and may have to throw away some
420 dsExpr (RecordUpdOut record_expr dicts rbinds)
421 = dsExpr record_expr `thenDs` \ record_expr' ->
423 -- Desugar the rbinds, and generate let-bindings if
424 -- necessary so that we don't lose sharing
425 dsRbinds rbinds $ \ rbinds' ->
427 record_ty = coreExprType record_expr'
428 (tycon, inst_tys, cons) = _trace "getAppDataTyCon.DsExpr" $ getAppDataTyCon record_ty
429 cons_to_upd = filter has_all_fields cons
431 -- initial_args are passed to every constructor
432 initial_args = map TyArg inst_tys ++ map VarArg dicts
434 mk_val_arg (field, arg_id)
435 = case [arg | (f, arg) <- rbinds',
436 field == recordSelectorFieldLabel f] of
437 (arg:args) -> ASSERT(null args)
442 = newSysLocalsDs (dataConArgTys con inst_tys) `thenDs` \ arg_ids ->
444 val_args = map mk_val_arg (dataConFieldLabels con `zipEqual` arg_ids)
446 returnDs (con, arg_ids, mkGenApp (mkGenApp (Var con) initial_args) val_args)
449 | length cons_to_upd == length cons
452 = newSysLocalDs record_ty `thenDs` \ deflt_id ->
453 mkErrorAppDs rEC_UPD_ERROR_ID record_ty "" `thenDs` \ err ->
454 returnDs (BindDefault deflt_id err)
456 mapDs mk_alt cons_to_upd `thenDs` \ alts ->
457 mk_default `thenDs` \ deflt ->
459 returnDs (Case record_expr' (AlgAlts alts deflt))
462 has_all_fields :: Id -> Bool
463 has_all_fields con_id
466 con_fields = dataConFieldLabels con_id
467 ok (sel_id, _, _) = recordSelectorFieldLabel sel_id `elem` con_fields
470 Dictionary lambda and application
471 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
472 @DictLam@ and @DictApp@ turn into the regular old things.
473 (OLD:) @DictFunApp@ also becomes a curried application, albeit slightly more
474 complicated; reminiscent of fully-applied constructors.
476 dsExpr (DictLam dictvars expr)
477 = dsExpr expr `thenDs` \ core_expr ->
478 returnDs( mkValLam dictvars core_expr )
482 dsExpr expr@(DictApp e dicts) -- becomes a curried application
486 @SingleDicts@ become @Locals@; @Dicts@ turn into tuples, unless
488 @ClassDictLam dictvars methods expr@ is ``the opposite'':
490 \ x -> case x of ( dictvars-and-methods-tuple ) -> expr
493 dsExpr (SingleDict dict) -- just a local
494 = lookupEnvWithDefaultDs dict (Var dict)
496 dsExpr (Dictionary dicts methods)
497 = -- hey, these things may have been substituted away...
498 zipWithDs lookupEnvWithDefaultDs
499 dicts_and_methods dicts_and_methods_exprs
500 `thenDs` \ core_d_and_ms ->
502 (case num_of_d_and_ms of
503 0 -> returnDs cocon_unit -- unit
505 1 -> returnDs (head core_d_and_ms) -- just a single Id
508 mkConDs (mkTupleCon num_of_d_and_ms)
509 (map coreExprType core_d_and_ms)
513 dicts_and_methods = dicts ++ methods
514 dicts_and_methods_exprs = map Var dicts_and_methods
515 num_of_d_and_ms = length dicts_and_methods
517 dsExpr (ClassDictLam dicts methods expr)
518 = dsExpr expr `thenDs` \ core_expr ->
519 case num_of_d_and_ms of
520 0 -> newSysLocalDs unitTy `thenDs` \ new_x ->
521 returnDs (mkValLam [new_x] core_expr)
524 returnDs (mkValLam dicts_and_methods core_expr)
527 newSysLocalDs tuple_ty `thenDs` \ new_x ->
529 Lam (ValBinder new_x)
532 [(tuple_con, dicts_and_methods, core_expr)]
535 num_of_d_and_ms = length dicts + length methods
536 dicts_and_methods = dicts ++ methods
537 tuple_ty = mkTupleTy num_of_d_and_ms (map idType dicts_and_methods)
538 tuple_con = mkTupleCon num_of_d_and_ms
541 -- HsSyn constructs that just shouldn't be here:
542 dsExpr (HsDo _ _) = panic "dsExpr:HsDo"
543 dsExpr (ExplicitList _) = panic "dsExpr:ExplicitList"
544 dsExpr (ExprWithTySig _ _) = panic "dsExpr:ExprWithTySig"
545 dsExpr (ArithSeqIn _) = panic "dsExpr:ArithSeqIn"
548 cocon_unit = mkCon (mkTupleCon 0) [] [] [] -- out here to avoid CAF (sigh)
549 out_of_range_msg -- ditto
550 = " out of range: [" ++ show minInt ++ ", " ++ show maxInt ++ "]\n"
553 %--------------------------------------------------------------------
555 @(dsApp e [t_1,..,t_n, e_1,..,e_n])@ returns something with the same
558 e t_1 ... t_n e_1 .. e_n
561 We're doing all this so we can saturate constructors (as painlessly as
565 type DsCoreArg = GenCoreArg CoreExpr{-NB!-} TyVar UVar
567 dsApp :: TypecheckedHsExpr -- expr to desugar
568 -> [DsCoreArg] -- accumulated ty/val args: NB:
569 -> DsM CoreExpr -- final result
571 dsApp (HsApp e1 e2) args
572 = dsExpr e2 `thenDs` \ core_e2 ->
573 dsApp e1 (VarArg core_e2 : args)
575 dsApp (OpApp e1 op e2) args
576 = dsExpr e1 `thenDs` \ core_e1 ->
577 dsExpr e2 `thenDs` \ core_e2 ->
578 dsApp op (VarArg core_e1 : VarArg core_e2 : args)
580 dsApp (DictApp expr dicts) args
581 = -- now, those dicts may have been substituted away...
582 zipWithDs lookupEnvWithDefaultDs dicts (map Var dicts)
583 `thenDs` \ core_dicts ->
584 dsApp expr (map VarArg core_dicts ++ args)
586 dsApp (TyApp expr tys) args
587 = dsApp expr (map TyArg tys ++ args)
589 -- we might should look out for SectionLs, etc., here, but we don't
592 = lookupEnvDs v `thenDs` \ maybe_expr ->
594 Just expr -> apply_to_args expr args
596 Nothing -> -- we're only saturating constructors and PrimOps
597 case getIdUnfolding v of
598 GenForm _ _ the_unfolding EssentialUnfolding
599 -> do_unfold nullTyVarEnv nullIdEnv (unTagBinders the_unfolding) args
601 _ -> apply_to_args (Var v) args
604 dsApp anything_else args
605 = dsExpr anything_else `thenDs` \ core_expr ->
606 apply_to_args core_expr args
608 -- a DsM version of mkGenApp:
609 apply_to_args :: CoreExpr -> [DsCoreArg] -> DsM CoreExpr
611 apply_to_args fun args
613 (ty_args, val_args) = foldr sep ([],[]) args
615 mkAppDs fun ty_args val_args
617 sep a@(LitArg l) (tys,vals) = (tys, (Lit l):vals)
618 sep a@(VarArg e) (tys,vals) = (tys, e:vals)
619 sep a@(TyArg ty) (tys,vals) = (ty:tys, vals)
620 sep a@(UsageArg _) _ = panic "DsExpr:apply_to_args:UsageArg"
625 dsRbinds :: TypecheckedRecordBinds -- The field bindings supplied
626 -> ([(Id, CoreArg)] -> DsM CoreExpr) -- A continuation taking the field
627 -- bindings with atomic rhss
628 -> DsM CoreExpr -- The result of the continuation,
629 -- wrapped in suitable Lets
631 dsRbinds [] continue_with
634 dsRbinds ((sel_id, rhs, pun_flag) : rbinds) continue_with
635 = dsExpr rhs `thenDs` \ rhs' ->
636 dsExprToAtom rhs' $ \ rhs_atom ->
637 dsRbinds rbinds $ \ rbinds' ->
638 continue_with ((sel_id, rhs_atom) : rbinds')
642 do_unfold ty_env val_env (Lam (TyBinder tyvar) body) (TyArg ty : args)
643 = do_unfold (addOneToTyVarEnv ty_env tyvar ty) val_env body args
645 do_unfold ty_env val_env (Lam (ValBinder binder) body) (VarArg expr : args)
646 = dsExprToAtom expr $ \ arg_atom ->
648 (addOneToIdEnv val_env binder (argToExpr arg_atom))
651 do_unfold ty_env val_env body args
652 = -- Clone the remaining part of the template
653 uniqSMtoDsM (substCoreExpr val_env ty_env body) `thenDs` \ body' ->
655 -- Apply result to remaining arguments
656 apply_to_args body' args