2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
6 TcGenDeriv: Generating derived instance declarations
8 This module is nominally ``subordinate'' to @TcDeriv@, which is the
9 ``official'' interface to deriving-related things.
11 This is where we do all the grimy bindings' generation.
15 DerivAuxBinds, isDupAux,
27 FFoldType(..), functorLikeTraverse,
28 deepSubtypesContaining, foldDataConArgs,
30 gen_Traversable_binds,
34 #include "HsVersions.h"
61 import Data.List ( partition, intersperse )
65 type DerivAuxBinds = [DerivAuxBind]
67 data DerivAuxBind -- Please add these auxiliary top-level bindings
68 = GenCon2Tag TyCon -- The con2Tag for given TyCon
69 | GenTag2Con TyCon -- ...ditto tag2Con
70 | GenMaxTag TyCon -- ...and maxTag
71 -- All these generate ZERO-BASED tag operations
72 -- I.e first constructor has tag 0
74 -- Scrap your boilerplate
75 | MkDataCon DataCon -- For constructor C we get $cC :: Constr
76 | MkTyCon TyCon -- For tycon T we get $tT :: DataType
79 isDupAux :: DerivAuxBind -> DerivAuxBind -> Bool
80 isDupAux (GenCon2Tag tc1) (GenCon2Tag tc2) = tc1 == tc2
81 isDupAux (GenTag2Con tc1) (GenTag2Con tc2) = tc1 == tc2
82 isDupAux (GenMaxTag tc1) (GenMaxTag tc2) = tc1 == tc2
83 isDupAux (MkDataCon dc1) (MkDataCon dc2) = dc1 == dc2
84 isDupAux (MkTyCon tc1) (MkTyCon tc2) = tc1 == tc2
89 %************************************************************************
93 %************************************************************************
95 Here are the heuristics for the code we generate for @Eq@:
98 Let's assume we have a data type with some (possibly zero) nullary
99 data constructors and some ordinary, non-nullary ones (the rest,
100 also possibly zero of them). Here's an example, with both \tr{N}ullary
101 and \tr{O}rdinary data cons.
103 data Foo ... = N1 | N2 ... | Nn | O1 a b | O2 Int | O3 Double b b | ...
107 For the ordinary constructors (if any), we emit clauses to do The
111 (==) (O1 a1 b1) (O1 a2 b2) = a1 == a2 && b1 == b2
112 (==) (O2 a1) (O2 a2) = a1 == a2
113 (==) (O3 a1 b1 c1) (O3 a2 b2 c2) = a1 == a2 && b1 == b2 && c1 == c2
116 Note: if we're comparing unlifted things, e.g., if \tr{a1} and
117 \tr{a2} are \tr{Float#}s, then we have to generate
119 case (a1 `eqFloat#` a2) of
122 for that particular test.
125 If there are any nullary constructors, we emit a catch-all clause of
129 (==) a b = case (con2tag_Foo a) of { a# ->
130 case (con2tag_Foo b) of { b# ->
131 case (a# ==# b#) of {
136 If there aren't any nullary constructors, we emit a simpler
143 For the @(/=)@ method, we normally just use the default method.
145 If the type is an enumeration type, we could/may/should? generate
146 special code that calls @con2tag_Foo@, much like for @(==)@ shown
150 We thought about doing this: If we're also deriving @Ord@ for this
153 instance ... Eq (Foo ...) where
154 (==) a b = case (compare a b) of { _LT -> False; _EQ -> True ; _GT -> False}
155 (/=) a b = case (compare a b) of { _LT -> True ; _EQ -> False; _GT -> True }
157 However, that requires that \tr{Ord <whatever>} was put in the context
158 for the instance decl, which it probably wasn't, so the decls
159 produced don't get through the typechecker.
164 gen_Eq_binds :: SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds)
165 gen_Eq_binds loc tycon
166 = (method_binds, aux_binds)
168 (nullary_cons, nonnullary_cons)
169 | isNewTyCon tycon = ([], tyConDataCons tycon)
170 | otherwise = partition isNullarySrcDataCon (tyConDataCons tycon)
172 no_nullary_cons = null nullary_cons
174 rest | no_nullary_cons
175 = case tyConSingleDataCon_maybe tycon of
177 Nothing -> -- if cons don't match, then False
178 [([nlWildPat, nlWildPat], false_Expr)]
179 | otherwise -- calc. and compare the tags
181 untag_Expr tycon [(a_RDR,ah_RDR), (b_RDR,bh_RDR)]
182 (genOpApp (nlHsVar ah_RDR) eqInt_RDR (nlHsVar bh_RDR)))]
184 aux_binds | no_nullary_cons = []
185 | otherwise = [GenCon2Tag tycon]
187 method_binds = listToBag [eq_bind, ne_bind]
188 eq_bind = mk_FunBind loc eq_RDR (map pats_etc nonnullary_cons ++ rest)
189 ne_bind = mk_easy_FunBind loc ne_RDR [a_Pat, b_Pat] (
190 nlHsApp (nlHsVar not_RDR) (nlHsPar (nlHsVarApps eq_RDR [a_RDR, b_RDR])))
192 ------------------------------------------------------------------
195 con1_pat = nlConVarPat data_con_RDR as_needed
196 con2_pat = nlConVarPat data_con_RDR bs_needed
198 data_con_RDR = getRdrName data_con
199 con_arity = length tys_needed
200 as_needed = take con_arity as_RDRs
201 bs_needed = take con_arity bs_RDRs
202 tys_needed = dataConOrigArgTys data_con
204 ([con1_pat, con2_pat], nested_eq_expr tys_needed as_needed bs_needed)
206 nested_eq_expr [] [] [] = true_Expr
207 nested_eq_expr tys as bs
208 = foldl1 and_Expr (zipWith3Equal "nested_eq" nested_eq tys as bs)
210 nested_eq ty a b = nlHsPar (eq_Expr tycon ty (nlHsVar a) (nlHsVar b))
213 %************************************************************************
217 %************************************************************************
219 Note [Generating Ord instances]
220 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
221 Suppose constructors are K1..Kn, and some are nullary.
222 The general form we generate is:
224 * Do case on first argument
233 If i = 1, 2, n-1, n, generate a single case.
236 K2 ... -> ...eq_rhs(K2)...
239 Otherwise do a tag compare against the bigger range
240 (because this is the one most likely to succeed)
241 rhs_3 case tag b of tb ->
244 K3 ... -> ...eq_rhs(K3)....
247 * To make eq_rhs(K), which knows that
250 we just want to compare (a1,b1) then (a2,b2) etc.
251 Take care on the last field to tail-call into comparing av,bv
253 * To make nullary_rhs generate this
254 case con2tag a of a# ->
258 Several special cases:
260 * Two or fewer nullary constructors: don't generate nullary_rhs
262 * Be careful about unlifted comparisons. When comparing unboxed
263 values we can't call the overloaded functions.
264 See function unliftedOrdOp
266 Note [Do not rely on compare]
267 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
268 It's a bad idea to define only 'compare', and build the other binary
269 comparisions on top of it; see Trac #2130, #4019. Reason: we don't
270 want to laboriously make a three-way comparison, only to extract a
271 binary result, something like this:
272 (>) (I# x) (I# y) = case <# x y of
274 False -> case ==# x y of
278 So for sufficiently small types (few constructors, or all nullary)
279 we generate all methods; for large ones we just use 'compare'.
282 data OrdOp = OrdCompare | OrdLT | OrdLE | OrdGE | OrdGT
285 ordMethRdr :: OrdOp -> RdrName
288 OrdCompare -> compare_RDR
295 ltResult :: OrdOp -> LHsExpr RdrName
296 -- Knowing a<b, what is the result for a `op` b?
297 ltResult OrdCompare = ltTag_Expr
298 ltResult OrdLT = true_Expr
299 ltResult OrdLE = true_Expr
300 ltResult OrdGE = false_Expr
301 ltResult OrdGT = false_Expr
304 eqResult :: OrdOp -> LHsExpr RdrName
305 -- Knowing a=b, what is the result for a `op` b?
306 eqResult OrdCompare = eqTag_Expr
307 eqResult OrdLT = false_Expr
308 eqResult OrdLE = true_Expr
309 eqResult OrdGE = true_Expr
310 eqResult OrdGT = false_Expr
313 gtResult :: OrdOp -> LHsExpr RdrName
314 -- Knowing a>b, what is the result for a `op` b?
315 gtResult OrdCompare = gtTag_Expr
316 gtResult OrdLT = false_Expr
317 gtResult OrdLE = false_Expr
318 gtResult OrdGE = true_Expr
319 gtResult OrdGT = true_Expr
322 gen_Ord_binds :: SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds)
323 gen_Ord_binds loc tycon
324 | null tycon_data_cons -- No data-cons => invoke bale-out case
325 = (unitBag $ mk_FunBind loc compare_RDR [], [])
327 = (unitBag (mkOrdOp OrdCompare) `unionBags` other_ops, aux_binds)
329 aux_binds | single_con_type = []
330 | otherwise = [GenCon2Tag tycon]
332 -- Note [Do not rely on compare]
333 other_ops | (last_tag - first_tag) <= 2 -- 1-3 constructors
334 || null non_nullary_cons -- Or it's an enumeration
335 = listToBag (map mkOrdOp [OrdLT,OrdLE,OrdGE,OrdGT])
339 get_tag con = dataConTag con - fIRST_TAG
340 -- We want *zero-based* tags, because that's what
341 -- con2Tag returns (generated by untag_Expr)!
343 tycon_data_cons = tyConDataCons tycon
344 single_con_type = isSingleton tycon_data_cons
345 (first_con : _) = tycon_data_cons
346 (last_con : _) = reverse tycon_data_cons
347 first_tag = get_tag first_con
348 last_tag = get_tag last_con
350 (nullary_cons, non_nullary_cons) = partition isNullarySrcDataCon tycon_data_cons
353 mkOrdOp :: OrdOp -> LHsBind RdrName
354 -- Returns a binding op a b = ... compares a and b according to op ....
355 mkOrdOp op = mk_easy_FunBind loc (ordMethRdr op) [a_Pat, b_Pat] (mkOrdOpRhs op)
357 mkOrdOpRhs :: OrdOp -> LHsExpr RdrName
358 mkOrdOpRhs op -- RHS for comparing 'a' and 'b' according to op
359 | length nullary_cons <= 2 -- Two nullary or fewer, so use cases
360 = nlHsCase (nlHsVar a_RDR) $
361 map (mkOrdOpAlt op) tycon_data_cons
362 -- i.e. case a of { C1 x y -> case b of C1 x y -> ....compare x,y...
363 -- C2 x -> case b of C2 x -> ....comopare x.... }
365 | null non_nullary_cons -- All nullary, so go straight to comparing tags
368 | otherwise -- Mixed nullary and non-nullary
369 = nlHsCase (nlHsVar a_RDR) $
370 (map (mkOrdOpAlt op) non_nullary_cons
371 ++ [mkSimpleHsAlt nlWildPat (mkTagCmp op)])
374 mkOrdOpAlt :: OrdOp -> DataCon -> LMatch RdrName
375 -- Make the alternative (Ki a1 a2 .. av ->
376 mkOrdOpAlt op data_con
377 = mkSimpleHsAlt (nlConVarPat data_con_RDR as_needed) (mkInnerRhs op data_con)
379 as_needed = take (dataConSourceArity data_con) as_RDRs
380 data_con_RDR = getRdrName data_con
382 mkInnerRhs op data_con
384 = nlHsCase (nlHsVar b_RDR) [ mkInnerEqAlt op data_con ]
387 = nlHsCase (nlHsVar b_RDR) [ mkInnerEqAlt op data_con
388 , mkSimpleHsAlt nlWildPat (ltResult op) ]
390 = nlHsCase (nlHsVar b_RDR) [ mkInnerEqAlt op data_con
391 , mkSimpleHsAlt nlWildPat (gtResult op) ]
393 | tag == first_tag + 1
394 = nlHsCase (nlHsVar b_RDR) [ mkSimpleHsAlt (nlConWildPat first_con) (gtResult op)
395 , mkInnerEqAlt op data_con
396 , mkSimpleHsAlt nlWildPat (ltResult op) ]
397 | tag == last_tag - 1
398 = nlHsCase (nlHsVar b_RDR) [ mkSimpleHsAlt (nlConWildPat last_con) (ltResult op)
399 , mkInnerEqAlt op data_con
400 , mkSimpleHsAlt nlWildPat (gtResult op) ]
402 | tag > last_tag `div` 2 -- lower range is larger
403 = untag_Expr tycon [(b_RDR, bh_RDR)] $
404 nlHsIf (genOpApp (nlHsVar bh_RDR) ltInt_RDR tag_lit)
405 (gtResult op) $ -- Definitely GT
406 nlHsCase (nlHsVar b_RDR) [ mkInnerEqAlt op data_con
407 , mkSimpleHsAlt nlWildPat (ltResult op) ]
409 | otherwise -- upper range is larger
410 = untag_Expr tycon [(b_RDR, bh_RDR)] $
411 nlHsIf (genOpApp (nlHsVar bh_RDR) gtInt_RDR tag_lit)
412 (ltResult op) $ -- Definitely LT
413 nlHsCase (nlHsVar b_RDR) [ mkInnerEqAlt op data_con
414 , mkSimpleHsAlt nlWildPat (gtResult op) ]
416 tag = get_tag data_con
417 tag_lit = noLoc (HsLit (HsIntPrim (toInteger tag)))
419 mkInnerEqAlt :: OrdOp -> DataCon -> LMatch RdrName
420 -- First argument 'a' known to be built with K
421 -- Returns a case alternative Ki b1 b2 ... bv -> compare (a1,a2,...) with (b1,b2,...)
422 mkInnerEqAlt op data_con
423 = mkSimpleHsAlt (nlConVarPat data_con_RDR bs_needed) $
424 mkCompareFields tycon op (dataConOrigArgTys data_con)
426 data_con_RDR = getRdrName data_con
427 bs_needed = take (dataConSourceArity data_con) bs_RDRs
429 mkTagCmp :: OrdOp -> LHsExpr RdrName
430 -- Both constructors known to be nullary
431 -- genreates (case data2Tag a of a# -> case data2Tag b of b# -> a# `op` b#
432 mkTagCmp op = untag_Expr tycon [(a_RDR, ah_RDR),(b_RDR, bh_RDR)] $
433 unliftedOrdOp tycon intPrimTy op ah_RDR bh_RDR
435 mkCompareFields :: TyCon -> OrdOp -> [Type] -> LHsExpr RdrName
436 -- Generates nested comparisons for (a1,a2...) against (b1,b2,...)
437 -- where the ai,bi have the given types
438 mkCompareFields tycon op tys
439 = go tys as_RDRs bs_RDRs
441 go [] _ _ = eqResult op
443 | isUnLiftedType ty = unliftedOrdOp tycon ty op a b
444 | otherwise = genOpApp (nlHsVar a) (ordMethRdr op) (nlHsVar b)
445 go (ty:tys) (a:as) (b:bs) = mk_compare ty a b
449 go _ _ _ = panic "mkCompareFields"
451 -- (mk_compare ty a b) generates
452 -- (case (compare a b) of { LT -> <lt>; EQ -> <eq>; GT -> <bt> })
453 -- but with suitable special cases for
454 mk_compare ty a b lt eq gt
456 = unliftedCompare lt_op eq_op a_expr b_expr lt eq gt
458 = nlHsCase (nlHsPar (nlHsApp (nlHsApp (nlHsVar compare_RDR) a_expr) b_expr))
459 [mkSimpleHsAlt (nlNullaryConPat ltTag_RDR) lt,
460 mkSimpleHsAlt (nlNullaryConPat eqTag_RDR) eq,
461 mkSimpleHsAlt (nlNullaryConPat gtTag_RDR) gt]
465 (lt_op, _, eq_op, _, _) = primOrdOps "Ord" tycon ty
467 unliftedOrdOp :: TyCon -> Type -> OrdOp -> RdrName -> RdrName -> LHsExpr RdrName
468 unliftedOrdOp tycon ty op a b
470 OrdCompare -> unliftedCompare lt_op eq_op a_expr b_expr
471 ltTag_Expr eqTag_Expr gtTag_Expr
477 (lt_op, le_op, eq_op, ge_op, gt_op) = primOrdOps "Ord" tycon ty
478 wrap prim_op = genOpApp a_expr (primOpRdrName prim_op) b_expr
482 unliftedCompare :: PrimOp -> PrimOp
483 -> LHsExpr RdrName -> LHsExpr RdrName -- What to cmpare
484 -> LHsExpr RdrName -> LHsExpr RdrName -> LHsExpr RdrName -- Three results
486 -- Return (if a < b then lt else if a == b then eq else gt)
487 unliftedCompare lt_op eq_op a_expr b_expr lt eq gt
488 = nlHsIf (genOpApp a_expr (primOpRdrName lt_op) b_expr) lt $
489 -- Test (<) first, not (==), becuase the latter
490 -- is true less often, so putting it first would
491 -- mean more tests (dynamically)
492 nlHsIf (genOpApp a_expr (primOpRdrName eq_op) b_expr) eq gt
494 nlConWildPat :: DataCon -> LPat RdrName
495 -- The pattern (K {})
496 nlConWildPat con = noLoc (ConPatIn (noLoc (getRdrName con))
497 (RecCon (HsRecFields { rec_flds = []
498 , rec_dotdot = Nothing })))
503 %************************************************************************
507 %************************************************************************
509 @Enum@ can only be derived for enumeration types. For a type
511 data Foo ... = N1 | N2 | ... | Nn
514 we use both @con2tag_Foo@ and @tag2con_Foo@ functions, as well as a
515 @maxtag_Foo@ variable (all generated by @gen_tag_n_con_binds@).
518 instance ... Enum (Foo ...) where
519 succ x = toEnum (1 + fromEnum x)
520 pred x = toEnum (fromEnum x - 1)
522 toEnum i = tag2con_Foo i
524 enumFrom a = map tag2con_Foo [con2tag_Foo a .. maxtag_Foo]
528 = case con2tag_Foo a of
529 a# -> map tag2con_Foo (enumFromTo (I# a#) maxtag_Foo)
532 = map tag2con_Foo [con2tag_Foo a, con2tag_Foo b .. maxtag_Foo]
536 = case con2tag_Foo a of { a# ->
537 case con2tag_Foo b of { b# ->
538 map tag2con_Foo (enumFromThenTo (I# a#) (I# b#) maxtag_Foo)
542 For @enumFromTo@ and @enumFromThenTo@, we use the default methods.
545 gen_Enum_binds :: SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds)
546 gen_Enum_binds loc tycon
547 = (method_binds, aux_binds)
549 method_binds = listToBag [
557 aux_binds = [GenCon2Tag tycon, GenTag2Con tycon, GenMaxTag tycon]
559 occ_nm = getOccString tycon
562 = mk_easy_FunBind loc succ_RDR [a_Pat] $
563 untag_Expr tycon [(a_RDR, ah_RDR)] $
564 nlHsIf (nlHsApps eq_RDR [nlHsVar (maxtag_RDR tycon),
565 nlHsVarApps intDataCon_RDR [ah_RDR]])
566 (illegal_Expr "succ" occ_nm "tried to take `succ' of last tag in enumeration")
567 (nlHsApp (nlHsVar (tag2con_RDR tycon))
568 (nlHsApps plus_RDR [nlHsVarApps intDataCon_RDR [ah_RDR],
572 = mk_easy_FunBind loc pred_RDR [a_Pat] $
573 untag_Expr tycon [(a_RDR, ah_RDR)] $
574 nlHsIf (nlHsApps eq_RDR [nlHsIntLit 0,
575 nlHsVarApps intDataCon_RDR [ah_RDR]])
576 (illegal_Expr "pred" occ_nm "tried to take `pred' of first tag in enumeration")
577 (nlHsApp (nlHsVar (tag2con_RDR tycon))
578 (nlHsApps plus_RDR [nlHsVarApps intDataCon_RDR [ah_RDR],
579 nlHsLit (HsInt (-1))]))
582 = mk_easy_FunBind loc toEnum_RDR [a_Pat] $
583 nlHsIf (nlHsApps and_RDR
584 [nlHsApps ge_RDR [nlHsVar a_RDR, nlHsIntLit 0],
585 nlHsApps le_RDR [nlHsVar a_RDR, nlHsVar (maxtag_RDR tycon)]])
586 (nlHsVarApps (tag2con_RDR tycon) [a_RDR])
587 (illegal_toEnum_tag occ_nm (maxtag_RDR tycon))
590 = mk_easy_FunBind loc enumFrom_RDR [a_Pat] $
591 untag_Expr tycon [(a_RDR, ah_RDR)] $
593 [nlHsVar (tag2con_RDR tycon),
594 nlHsPar (enum_from_to_Expr
595 (nlHsVarApps intDataCon_RDR [ah_RDR])
596 (nlHsVar (maxtag_RDR tycon)))]
599 = mk_easy_FunBind loc enumFromThen_RDR [a_Pat, b_Pat] $
600 untag_Expr tycon [(a_RDR, ah_RDR), (b_RDR, bh_RDR)] $
601 nlHsApp (nlHsVarApps map_RDR [tag2con_RDR tycon]) $
602 nlHsPar (enum_from_then_to_Expr
603 (nlHsVarApps intDataCon_RDR [ah_RDR])
604 (nlHsVarApps intDataCon_RDR [bh_RDR])
605 (nlHsIf (nlHsApps gt_RDR [nlHsVarApps intDataCon_RDR [ah_RDR],
606 nlHsVarApps intDataCon_RDR [bh_RDR]])
608 (nlHsVar (maxtag_RDR tycon))
612 = mk_easy_FunBind loc fromEnum_RDR [a_Pat] $
613 untag_Expr tycon [(a_RDR, ah_RDR)] $
614 (nlHsVarApps intDataCon_RDR [ah_RDR])
617 %************************************************************************
621 %************************************************************************
624 gen_Bounded_binds :: SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds)
625 gen_Bounded_binds loc tycon
626 | isEnumerationTyCon tycon
627 = (listToBag [ min_bound_enum, max_bound_enum ], [])
629 = ASSERT(isSingleton data_cons)
630 (listToBag [ min_bound_1con, max_bound_1con ], [])
632 data_cons = tyConDataCons tycon
634 ----- enum-flavored: ---------------------------
635 min_bound_enum = mkHsVarBind loc minBound_RDR (nlHsVar data_con_1_RDR)
636 max_bound_enum = mkHsVarBind loc maxBound_RDR (nlHsVar data_con_N_RDR)
638 data_con_1 = head data_cons
639 data_con_N = last data_cons
640 data_con_1_RDR = getRdrName data_con_1
641 data_con_N_RDR = getRdrName data_con_N
643 ----- single-constructor-flavored: -------------
644 arity = dataConSourceArity data_con_1
646 min_bound_1con = mkHsVarBind loc minBound_RDR $
647 nlHsVarApps data_con_1_RDR (nOfThem arity minBound_RDR)
648 max_bound_1con = mkHsVarBind loc maxBound_RDR $
649 nlHsVarApps data_con_1_RDR (nOfThem arity maxBound_RDR)
652 %************************************************************************
656 %************************************************************************
658 Deriving @Ix@ is only possible for enumeration types and
659 single-constructor types. We deal with them in turn.
661 For an enumeration type, e.g.,
663 data Foo ... = N1 | N2 | ... | Nn
665 things go not too differently from @Enum@:
667 instance ... Ix (Foo ...) where
669 = map tag2con_Foo [con2tag_Foo a .. con2tag_Foo b]
673 = case (con2tag_Foo a) of { a# ->
674 case (con2tag_Foo b) of { b# ->
675 map tag2con_Foo (enumFromTo (I# a#) (I# b#))
678 -- Generate code for unsafeIndex, becuase using index leads
679 -- to lots of redundant range tests
680 unsafeIndex c@(a, b) d
681 = case (con2tag_Foo d -# con2tag_Foo a) of
686 p_tag = con2tag_Foo c
688 p_tag >= con2tag_Foo a && p_tag <= con2tag_Foo b
692 = case (con2tag_Foo a) of { a_tag ->
693 case (con2tag_Foo b) of { b_tag ->
694 case (con2tag_Foo c) of { c_tag ->
695 if (c_tag >=# a_tag) then
701 (modulo suitable case-ification to handle the unlifted tags)
703 For a single-constructor type (NB: this includes all tuples), e.g.,
705 data Foo ... = MkFoo a b Int Double c c
707 we follow the scheme given in Figure~19 of the Haskell~1.2 report
711 gen_Ix_binds :: SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds)
713 gen_Ix_binds loc tycon
714 | isEnumerationTyCon tycon
715 = (enum_ixes, [GenCon2Tag tycon, GenTag2Con tycon, GenMaxTag tycon])
717 = (single_con_ixes, [GenCon2Tag tycon])
719 --------------------------------------------------------------
720 enum_ixes = listToBag [ enum_range, enum_index, enum_inRange ]
723 = mk_easy_FunBind loc range_RDR [nlTuplePat [a_Pat, b_Pat] Boxed] $
724 untag_Expr tycon [(a_RDR, ah_RDR)] $
725 untag_Expr tycon [(b_RDR, bh_RDR)] $
726 nlHsApp (nlHsVarApps map_RDR [tag2con_RDR tycon]) $
727 nlHsPar (enum_from_to_Expr
728 (nlHsVarApps intDataCon_RDR [ah_RDR])
729 (nlHsVarApps intDataCon_RDR [bh_RDR]))
732 = mk_easy_FunBind loc unsafeIndex_RDR
733 [noLoc (AsPat (noLoc c_RDR)
734 (nlTuplePat [a_Pat, nlWildPat] Boxed)),
736 untag_Expr tycon [(a_RDR, ah_RDR)] (
737 untag_Expr tycon [(d_RDR, dh_RDR)] (
739 rhs = nlHsVarApps intDataCon_RDR [c_RDR]
742 (genOpApp (nlHsVar dh_RDR) minusInt_RDR (nlHsVar ah_RDR))
743 [mkSimpleHsAlt (nlVarPat c_RDR) rhs]
748 = mk_easy_FunBind loc inRange_RDR [nlTuplePat [a_Pat, b_Pat] Boxed, c_Pat] $
749 untag_Expr tycon [(a_RDR, ah_RDR)] (
750 untag_Expr tycon [(b_RDR, bh_RDR)] (
751 untag_Expr tycon [(c_RDR, ch_RDR)] (
752 nlHsIf (genOpApp (nlHsVar ch_RDR) geInt_RDR (nlHsVar ah_RDR)) (
753 (genOpApp (nlHsVar ch_RDR) leInt_RDR (nlHsVar bh_RDR))
758 --------------------------------------------------------------
760 = listToBag [single_con_range, single_con_index, single_con_inRange]
763 = case tyConSingleDataCon_maybe tycon of -- just checking...
764 Nothing -> panic "get_Ix_binds"
767 con_arity = dataConSourceArity data_con
768 data_con_RDR = getRdrName data_con
770 as_needed = take con_arity as_RDRs
771 bs_needed = take con_arity bs_RDRs
772 cs_needed = take con_arity cs_RDRs
774 con_pat xs = nlConVarPat data_con_RDR xs
775 con_expr = nlHsVarApps data_con_RDR cs_needed
777 --------------------------------------------------------------
779 = mk_easy_FunBind loc range_RDR
780 [nlTuplePat [con_pat as_needed, con_pat bs_needed] Boxed] $
781 nlHsDo ListComp stmts con_expr
783 stmts = zipWith3Equal "single_con_range" mk_qual as_needed bs_needed cs_needed
785 mk_qual a b c = noLoc $ mkBindStmt (nlVarPat c)
786 (nlHsApp (nlHsVar range_RDR)
787 (mkLHsVarTuple [a,b]))
791 = mk_easy_FunBind loc unsafeIndex_RDR
792 [nlTuplePat [con_pat as_needed, con_pat bs_needed] Boxed,
794 -- We need to reverse the order we consider the components in
796 -- range (l,u) !! index (l,u) i == i -- when i is in range
797 -- (from http://haskell.org/onlinereport/ix.html) holds.
798 (mk_index (reverse $ zip3 as_needed bs_needed cs_needed))
800 -- index (l1,u1) i1 + rangeSize (l1,u1) * (index (l2,u2) i2 + ...)
801 mk_index [] = nlHsIntLit 0
802 mk_index [(l,u,i)] = mk_one l u i
803 mk_index ((l,u,i) : rest)
808 (nlHsApp (nlHsVar unsafeRangeSize_RDR)
809 (mkLHsVarTuple [l,u]))
810 ) times_RDR (mk_index rest)
813 = nlHsApps unsafeIndex_RDR [mkLHsVarTuple [l,u], nlHsVar i]
817 = mk_easy_FunBind loc inRange_RDR
818 [nlTuplePat [con_pat as_needed, con_pat bs_needed] Boxed,
820 foldl1 and_Expr (zipWith3Equal "single_con_inRange" in_range as_needed bs_needed cs_needed)
822 in_range a b c = nlHsApps inRange_RDR [mkLHsVarTuple [a,b], nlHsVar c]
825 %************************************************************************
829 %************************************************************************
839 instance Read T where
843 do x <- ReadP.step Read.readPrec
844 Symbol "%%" <- Lex.lex
845 y <- ReadP.step Read.readPrec
849 -- Note the "+1" part; "T2 T1 {f1=3}" should parse ok
850 -- Record construction binds even more tightly than application
851 do Ident "T1" <- Lex.lex
853 Ident "f1" <- Lex.lex
855 x <- ReadP.reset Read.readPrec
857 return (T1 { f1 = x }))
860 do Ident "T2" <- Lex.lexP
861 x <- ReadP.step Read.readPrec
865 readListPrec = readListPrecDefault
866 readList = readListDefault
870 gen_Read_binds :: FixityEnv -> SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds)
872 gen_Read_binds get_fixity loc tycon
873 = (listToBag [read_prec, default_readlist, default_readlistprec], [])
875 -----------------------------------------------------------------------
877 = mkHsVarBind loc readList_RDR (nlHsVar readListDefault_RDR)
880 = mkHsVarBind loc readListPrec_RDR (nlHsVar readListPrecDefault_RDR)
881 -----------------------------------------------------------------------
883 data_cons = tyConDataCons tycon
884 (nullary_cons, non_nullary_cons) = partition isNullarySrcDataCon data_cons
886 read_prec = mkHsVarBind loc readPrec_RDR
887 (nlHsApp (nlHsVar parens_RDR) read_cons)
889 read_cons = foldr1 mk_alt (read_nullary_cons ++ read_non_nullary_cons)
890 read_non_nullary_cons = map read_non_nullary_con non_nullary_cons
893 = case nullary_cons of
895 [con] -> [nlHsDo DoExpr [bindLex (match_con con)] (result_expr con [])]
896 _ -> [nlHsApp (nlHsVar choose_RDR)
897 (nlList (map mk_pair nullary_cons))]
898 -- NB For operators the parens around (:=:) are matched by the
899 -- enclosing "parens" call, so here we must match the naked
902 match_con con | isSym con_str = symbol_pat con_str
903 | otherwise = ident_pat con_str
905 con_str = data_con_str con
906 -- For nullary constructors we must match Ident s for normal constrs
907 -- and Symbol s for operators
909 mk_pair con = mkLHsTupleExpr [nlHsLit (mkHsString (data_con_str con)),
912 read_non_nullary_con data_con
913 | is_infix = mk_parser infix_prec infix_stmts body
914 | is_record = mk_parser record_prec record_stmts body
915 -- Using these two lines instead allows the derived
916 -- read for infix and record bindings to read the prefix form
917 -- | is_infix = mk_alt prefix_parser (mk_parser infix_prec infix_stmts body)
918 -- | is_record = mk_alt prefix_parser (mk_parser record_prec record_stmts body)
919 | otherwise = prefix_parser
921 body = result_expr data_con as_needed
922 con_str = data_con_str data_con
924 prefix_parser = mk_parser prefix_prec prefix_stmts body
927 | isSym con_str = [read_punc "(", bindLex (symbol_pat con_str), read_punc ")"]
928 | otherwise = [bindLex (ident_pat con_str)]
931 | isSym con_str = [bindLex (symbol_pat con_str)]
932 | otherwise = [read_punc "`", bindLex (ident_pat con_str), read_punc "`"]
934 prefix_stmts -- T a b c
935 = read_prefix_con ++ read_args
937 infix_stmts -- a %% b, or a `T` b
942 record_stmts -- T { f1 = a, f2 = b }
945 ++ concat (intersperse [read_punc ","] field_stmts)
948 field_stmts = zipWithEqual "lbl_stmts" read_field labels as_needed
950 con_arity = dataConSourceArity data_con
951 labels = dataConFieldLabels data_con
952 dc_nm = getName data_con
953 is_infix = dataConIsInfix data_con
954 is_record = length labels > 0
955 as_needed = take con_arity as_RDRs
956 read_args = zipWithEqual "gen_Read_binds" read_arg as_needed (dataConOrigArgTys data_con)
957 (read_a1:read_a2:_) = read_args
959 prefix_prec = appPrecedence
960 infix_prec = getPrecedence get_fixity dc_nm
961 record_prec = appPrecedence + 1 -- Record construction binds even more tightly
962 -- than application; e.g. T2 T1 {x=2} means T2 (T1 {x=2})
964 ------------------------------------------------------------------------
966 ------------------------------------------------------------------------
967 mk_alt e1 e2 = genOpApp e1 alt_RDR e2 -- e1 +++ e2
968 mk_parser p ss b = nlHsApps prec_RDR [nlHsIntLit p, nlHsDo DoExpr ss b] -- prec p (do { ss ; b })
969 bindLex pat = noLoc (mkBindStmt pat (nlHsVar lexP_RDR)) -- pat <- lexP
970 con_app con as = nlHsVarApps (getRdrName con) as -- con as
971 result_expr con as = nlHsApp (nlHsVar returnM_RDR) (con_app con as) -- return (con as)
973 punc_pat s = nlConPat punc_RDR [nlLitPat (mkHsString s)] -- Punc 'c'
974 ident_pat s = nlConPat ident_RDR [nlLitPat (mkHsString s)] -- Ident "foo"
975 symbol_pat s = nlConPat symbol_RDR [nlLitPat (mkHsString s)] -- Symbol ">>"
977 data_con_str con = occNameString (getOccName con)
979 read_punc c = bindLex (punc_pat c)
980 read_arg a ty = ASSERT( not (isUnLiftedType ty) )
981 noLoc (mkBindStmt (nlVarPat a) (nlHsVarApps step_RDR [readPrec_RDR]))
983 read_field lbl a = read_lbl lbl ++
985 noLoc (mkBindStmt (nlVarPat a) (nlHsVarApps reset_RDR [readPrec_RDR]))]
987 -- When reading field labels we might encounter
992 read_lbl lbl | isSym lbl_str
994 bindLex (symbol_pat lbl_str),
997 = [bindLex (ident_pat lbl_str)]
999 lbl_str = occNameString (getOccName lbl)
1003 %************************************************************************
1007 %************************************************************************
1013 data Tree a = Leaf a | Tree a :^: Tree a
1015 instance (Show a) => Show (Tree a) where
1017 showsPrec d (Leaf m) = showParen (d > app_prec) showStr
1019 showStr = showString "Leaf " . showsPrec (app_prec+1) m
1021 showsPrec d (u :^: v) = showParen (d > up_prec) showStr
1023 showStr = showsPrec (up_prec+1) u .
1024 showString " :^: " .
1025 showsPrec (up_prec+1) v
1026 -- Note: right-associativity of :^: ignored
1028 up_prec = 5 -- Precedence of :^:
1029 app_prec = 10 -- Application has precedence one more than
1030 -- the most tightly-binding operator
1033 gen_Show_binds :: FixityEnv -> SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds)
1035 gen_Show_binds get_fixity loc tycon
1036 = (listToBag [shows_prec, show_list], [])
1038 -----------------------------------------------------------------------
1039 show_list = mkHsVarBind loc showList_RDR
1040 (nlHsApp (nlHsVar showList___RDR) (nlHsPar (nlHsApp (nlHsVar showsPrec_RDR) (nlHsIntLit 0))))
1041 -----------------------------------------------------------------------
1042 data_cons = tyConDataCons tycon
1043 shows_prec = mk_FunBind loc showsPrec_RDR (map pats_etc data_cons)
1046 | nullary_con = -- skip the showParen junk...
1047 ASSERT(null bs_needed)
1048 ([nlWildPat, con_pat], mk_showString_app op_con_str)
1051 showParen_Expr (nlHsPar (genOpApp a_Expr ge_RDR (nlHsLit (HsInt con_prec_plus_one))))
1052 (nlHsPar (nested_compose_Expr show_thingies)))
1054 data_con_RDR = getRdrName data_con
1055 con_arity = dataConSourceArity data_con
1056 bs_needed = take con_arity bs_RDRs
1057 arg_tys = dataConOrigArgTys data_con -- Correspond 1-1 with bs_needed
1058 con_pat = nlConVarPat data_con_RDR bs_needed
1059 nullary_con = con_arity == 0
1060 labels = dataConFieldLabels data_con
1061 lab_fields = length labels
1062 record_syntax = lab_fields > 0
1064 dc_nm = getName data_con
1065 dc_occ_nm = getOccName data_con
1066 con_str = occNameString dc_occ_nm
1067 op_con_str = wrapOpParens con_str
1068 backquote_str = wrapOpBackquotes con_str
1071 | is_infix = [show_arg1, mk_showString_app (" " ++ backquote_str ++ " "), show_arg2]
1072 | record_syntax = mk_showString_app (op_con_str ++ " {") :
1073 show_record_args ++ [mk_showString_app "}"]
1074 | otherwise = mk_showString_app (op_con_str ++ " ") : show_prefix_args
1076 show_label l = mk_showString_app (nm ++ " = ")
1077 -- Note the spaces around the "=" sign. If we don't have them
1078 -- then we get Foo { x=-1 } and the "=-" parses as a single
1079 -- lexeme. Only the space after the '=' is necessary, but
1080 -- it seems tidier to have them both sides.
1082 occ_nm = getOccName l
1083 nm = wrapOpParens (occNameString occ_nm)
1085 show_args = zipWith show_arg bs_needed arg_tys
1086 (show_arg1:show_arg2:_) = show_args
1087 show_prefix_args = intersperse (nlHsVar showSpace_RDR) show_args
1089 -- Assumption for record syntax: no of fields == no of labelled fields
1090 -- (and in same order)
1091 show_record_args = concat $
1092 intersperse [mk_showString_app ", "] $
1093 [ [show_label lbl, arg]
1094 | (lbl,arg) <- zipEqual "gen_Show_binds"
1097 -- Generates (showsPrec p x) for argument x, but it also boxes
1098 -- the argument first if necessary. Note that this prints unboxed
1099 -- things without any '#' decorations; could change that if need be
1100 show_arg b arg_ty = nlHsApps showsPrec_RDR [nlHsLit (HsInt arg_prec),
1101 box_if_necy "Show" tycon (nlHsVar b) arg_ty]
1104 is_infix = dataConIsInfix data_con
1105 con_prec_plus_one = 1 + getPrec is_infix get_fixity dc_nm
1106 arg_prec | record_syntax = 0 -- Record fields don't need parens
1107 | otherwise = con_prec_plus_one
1109 wrapOpParens :: String -> String
1110 wrapOpParens s | isSym s = '(' : s ++ ")"
1113 wrapOpBackquotes :: String -> String
1114 wrapOpBackquotes s | isSym s = s
1115 | otherwise = '`' : s ++ "`"
1117 isSym :: String -> Bool
1119 isSym (c : _) = startsVarSym c || startsConSym c
1121 mk_showString_app :: String -> LHsExpr RdrName
1122 mk_showString_app str = nlHsApp (nlHsVar showString_RDR) (nlHsLit (mkHsString str))
1126 getPrec :: Bool -> FixityEnv -> Name -> Integer
1127 getPrec is_infix get_fixity nm
1128 | not is_infix = appPrecedence
1129 | otherwise = getPrecedence get_fixity nm
1131 appPrecedence :: Integer
1132 appPrecedence = fromIntegral maxPrecedence + 1
1133 -- One more than the precedence of the most
1134 -- tightly-binding operator
1136 getPrecedence :: FixityEnv -> Name -> Integer
1137 getPrecedence get_fixity nm
1138 = case lookupFixity get_fixity nm of
1139 Fixity x _assoc -> fromIntegral x
1140 -- NB: the Report says that associativity is not taken
1141 -- into account for either Read or Show; hence we
1142 -- ignore associativity here
1146 %************************************************************************
1148 \subsection{Typeable}
1150 %************************************************************************
1158 instance Typeable2 T where
1159 typeOf2 _ = mkTyConApp (mkTyConRep "T") []
1161 We are passed the Typeable2 class as well as T
1164 gen_Typeable_binds :: SrcSpan -> TyCon -> LHsBinds RdrName
1165 gen_Typeable_binds loc tycon
1168 (mk_typeOf_RDR tycon) -- Name of appropriate type0f function
1170 (nlHsApps mkTypeRep_RDR [tycon_rep, nlList []])
1172 tycon_rep = nlHsVar mkTyConRep_RDR `nlHsApp` nlHsLit (mkHsString (showSDocOneLine (ppr tycon)))
1174 mk_typeOf_RDR :: TyCon -> RdrName
1175 -- Use the arity of the TyCon to make the right typeOfn function
1176 mk_typeOf_RDR tycon = varQual_RDR tYPEABLE (mkFastString ("typeOf" ++ suffix))
1178 arity = tyConArity tycon
1179 suffix | arity == 0 = ""
1180 | otherwise = show arity
1185 %************************************************************************
1189 %************************************************************************
1193 data T a b = T1 a b | T2
1197 $cT1 = mkDataCon $dT "T1" Prefix
1198 $cT2 = mkDataCon $dT "T2" Prefix
1199 $dT = mkDataType "Module.T" [] [$con_T1, $con_T2]
1200 -- the [] is for field labels.
1202 instance (Data a, Data b) => Data (T a b) where
1203 gfoldl k z (T1 a b) = z T `k` a `k` b
1204 gfoldl k z T2 = z T2
1205 -- ToDo: add gmapT,Q,M, gfoldr
1207 gunfold k z c = case conIndex c of
1208 I# 1# -> k (k (z T1))
1211 toConstr (T1 _ _) = $cT1
1216 dataCast1 = gcast1 -- If T :: * -> *
1217 dataCast2 = gcast2 -- if T :: * -> * -> *
1221 gen_Data_binds :: SrcSpan
1223 -> (LHsBinds RdrName, -- The method bindings
1224 DerivAuxBinds) -- Auxiliary bindings
1225 gen_Data_binds loc tycon
1226 = (listToBag [gfoldl_bind, gunfold_bind, toCon_bind, dataTypeOf_bind]
1227 `unionBags` gcast_binds,
1228 -- Auxiliary definitions: the data type and constructors
1229 MkTyCon tycon : map MkDataCon data_cons)
1231 data_cons = tyConDataCons tycon
1232 n_cons = length data_cons
1233 one_constr = n_cons == 1
1236 gfoldl_bind = mk_FunBind loc gfoldl_RDR (map gfoldl_eqn data_cons)
1239 = ([nlVarPat k_RDR, nlVarPat z_RDR, nlConVarPat con_name as_needed],
1240 foldl mk_k_app (nlHsVar z_RDR `nlHsApp` nlHsVar con_name) as_needed)
1243 con_name = getRdrName con
1244 as_needed = take (dataConSourceArity con) as_RDRs
1245 mk_k_app e v = nlHsPar (nlHsOpApp e k_RDR (nlHsVar v))
1247 ------------ gunfold
1248 gunfold_bind = mk_FunBind loc
1250 [([k_Pat, z_Pat, if one_constr then nlWildPat else c_Pat],
1254 | one_constr = mk_unfold_rhs (head data_cons) -- No need for case
1255 | otherwise = nlHsCase (nlHsVar conIndex_RDR `nlHsApp` c_Expr)
1256 (map gunfold_alt data_cons)
1258 gunfold_alt dc = mkSimpleHsAlt (mk_unfold_pat dc) (mk_unfold_rhs dc)
1259 mk_unfold_rhs dc = foldr nlHsApp
1260 (nlHsVar z_RDR `nlHsApp` nlHsVar (getRdrName dc))
1261 (replicate (dataConSourceArity dc) (nlHsVar k_RDR))
1263 mk_unfold_pat dc -- Last one is a wild-pat, to avoid
1264 -- redundant test, and annoying warning
1265 | tag-fIRST_TAG == n_cons-1 = nlWildPat -- Last constructor
1266 | otherwise = nlConPat intDataCon_RDR [nlLitPat (HsIntPrim (toInteger tag))]
1270 ------------ toConstr
1271 toCon_bind = mk_FunBind loc toConstr_RDR (map to_con_eqn data_cons)
1272 to_con_eqn dc = ([nlWildConPat dc], nlHsVar (mk_constr_name dc))
1274 ------------ dataTypeOf
1275 dataTypeOf_bind = mk_easy_FunBind
1279 (nlHsVar (mk_data_type_name tycon))
1281 ------------ gcast1/2
1282 tycon_kind = tyConKind tycon
1283 gcast_binds | tycon_kind `eqKind` kind1 = mk_gcast dataCast1_RDR gcast1_RDR
1284 | tycon_kind `eqKind` kind2 = mk_gcast dataCast2_RDR gcast2_RDR
1285 | otherwise = emptyBag
1286 mk_gcast dataCast_RDR gcast_RDR
1287 = unitBag (mk_easy_FunBind loc dataCast_RDR [nlVarPat f_RDR]
1288 (nlHsVar gcast_RDR `nlHsApp` nlHsVar f_RDR))
1291 kind1, kind2 :: Kind
1292 kind1 = liftedTypeKind `mkArrowKind` liftedTypeKind
1293 kind2 = liftedTypeKind `mkArrowKind` kind1
1295 gfoldl_RDR, gunfold_RDR, toConstr_RDR, dataTypeOf_RDR, mkConstr_RDR,
1296 mkDataType_RDR, conIndex_RDR, prefix_RDR, infix_RDR,
1297 dataCast1_RDR, dataCast2_RDR, gcast1_RDR, gcast2_RDR,
1298 constr_RDR, dataType_RDR :: RdrName
1299 gfoldl_RDR = varQual_RDR gENERICS (fsLit "gfoldl")
1300 gunfold_RDR = varQual_RDR gENERICS (fsLit "gunfold")
1301 toConstr_RDR = varQual_RDR gENERICS (fsLit "toConstr")
1302 dataTypeOf_RDR = varQual_RDR gENERICS (fsLit "dataTypeOf")
1303 dataCast1_RDR = varQual_RDR gENERICS (fsLit "dataCast1")
1304 dataCast2_RDR = varQual_RDR gENERICS (fsLit "dataCast2")
1305 gcast1_RDR = varQual_RDR tYPEABLE (fsLit "gcast1")
1306 gcast2_RDR = varQual_RDR tYPEABLE (fsLit "gcast2")
1307 mkConstr_RDR = varQual_RDR gENERICS (fsLit "mkConstr")
1308 constr_RDR = tcQual_RDR gENERICS (fsLit "Constr")
1309 mkDataType_RDR = varQual_RDR gENERICS (fsLit "mkDataType")
1310 dataType_RDR = tcQual_RDR gENERICS (fsLit "DataType")
1311 conIndex_RDR = varQual_RDR gENERICS (fsLit "constrIndex")
1312 prefix_RDR = dataQual_RDR gENERICS (fsLit "Prefix")
1313 infix_RDR = dataQual_RDR gENERICS (fsLit "Infix")
1318 %************************************************************************
1322 see http://www.mail-archive.com/haskell-prime@haskell.org/msg02116.html
1325 %************************************************************************
1329 data T a = T1 Int a | T2 (T a)
1331 We generate the instance:
1333 instance Functor T where
1334 fmap f (T1 b1 a) = T1 b1 (f a)
1335 fmap f (T2 ta) = T2 (fmap f ta)
1337 Notice that we don't simply apply 'fmap' to the constructor arguments.
1339 - Do nothing to an argument whose type doesn't mention 'a'
1340 - Apply 'f' to an argument of type 'a'
1341 - Apply 'fmap f' to other arguments
1342 That's why we have to recurse deeply into the constructor argument types,
1343 rather than just one level, as we typically do.
1345 What about types with more than one type parameter? In general, we only
1346 derive Functor for the last position:
1348 data S a b = S1 [b] | S2 (a, T a b)
1349 instance Functor (S a) where
1350 fmap f (S1 bs) = S1 (fmap f bs)
1351 fmap f (S2 (p,q)) = S2 (a, fmap f q)
1353 However, we have special cases for
1357 More formally, we write the derivation of fmap code over type variable
1358 'a for type 'b as ($fmap 'a 'b). In this general notation the derived
1361 instance Functor T where
1362 fmap f (T1 x1 x2) = T1 ($(fmap 'a 'b1) x1) ($(fmap 'a 'a) x2)
1363 fmap f (T2 x1) = T2 ($(fmap 'a '(T a)) x1)
1365 $(fmap 'a 'b) x = x -- when b does not contain a
1366 $(fmap 'a 'a) x = f x
1367 $(fmap 'a '(b1,b2)) x = case x of (x1,x2) -> ($(fmap 'a 'b1) x1, $(fmap 'a 'b2) x2)
1368 $(fmap 'a '(T b1 b2)) x = fmap $(fmap 'a 'b2) x -- when a only occurs in the last parameter, b2
1369 $(fmap 'a '(b -> c)) x = \b -> $(fmap 'a' 'c) (x ($(cofmap 'a 'b) b))
1371 For functions, the type parameter 'a can occur in a contravariant position,
1372 which means we need to derive a function like:
1374 cofmap :: (a -> b) -> (f b -> f a)
1376 This is pretty much the same as $fmap, only without the $(cofmap 'a 'a) case:
1378 $(cofmap 'a 'b) x = x -- when b does not contain a
1379 $(cofmap 'a 'a) x = error "type variable in contravariant position"
1380 $(cofmap 'a '(b1,b2)) x = case x of (x1,x2) -> ($(cofmap 'a 'b1) x1, $(cofmap 'a 'b2) x2)
1381 $(cofmap 'a '[b]) x = map $(cofmap 'a 'b) x
1382 $(cofmap 'a '(T b1 b2)) x = fmap $(cofmap 'a 'b2) x -- when a only occurs in the last parameter, b2
1383 $(cofmap 'a '(b -> c)) x = \b -> $(cofmap 'a' 'c) (x ($(fmap 'a 'c) b))
1386 gen_Functor_binds :: SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds)
1387 gen_Functor_binds loc tycon
1388 = (unitBag fmap_bind, [])
1390 data_cons = tyConDataCons tycon
1391 fmap_bind = L loc $ mkRdrFunBind (L loc fmap_RDR) eqns
1393 fmap_eqn con = evalState (match_for_con [f_Pat] con parts) bs_RDRs
1395 parts = foldDataConArgs ft_fmap con
1397 eqns | null data_cons = [mkSimpleMatch [nlWildPat, nlWildPat]
1398 (error_Expr "Void fmap")]
1399 | otherwise = map fmap_eqn data_cons
1401 ft_fmap :: FFoldType (LHsExpr RdrName -> State [RdrName] (LHsExpr RdrName))
1402 -- Tricky higher order type; I can't say I fully understand this code :-(
1403 ft_fmap = FT { ft_triv = \x -> return x -- fmap f x = x
1404 , ft_var = \x -> return (nlHsApp f_Expr x) -- fmap f x = f x
1405 , ft_fun = \g h x -> mkSimpleLam (\b -> h =<< (nlHsApp x `fmap` g b))
1406 -- fmap f x = \b -> h (x (g b))
1407 , ft_tup = mkSimpleTupleCase match_for_con -- fmap f x = case x of (a1,a2,..) -> (g1 a1,g2 a2,..)
1408 , ft_ty_app = \_ g x -> do gg <- mkSimpleLam g -- fmap f x = fmap g x
1409 return $ nlHsApps fmap_RDR [gg,x]
1410 , ft_forall = \_ g x -> g x
1411 , ft_bad_app = panic "in other argument"
1412 , ft_co_var = panic "contravariant" }
1414 match_for_con = mkSimpleConMatch $
1415 \con_name xsM -> do xs <- sequence xsM
1416 return (nlHsApps con_name xs) -- Con (g1 v1) (g2 v2) ..
1419 Utility functions related to Functor deriving.
1421 Since several things use the same pattern of traversal, this is abstracted into functorLikeTraverse.
1422 This function works like a fold: it makes a value of type 'a' in a bottom up way.
1425 -- Generic traversal for Functor deriving
1426 data FFoldType a -- Describes how to fold over a Type in a functor like way
1427 = FT { ft_triv :: a -- Does not contain variable
1428 , ft_var :: a -- The variable itself
1429 , ft_co_var :: a -- The variable itself, contravariantly
1430 , ft_fun :: a -> a -> a -- Function type
1431 , ft_tup :: Boxity -> [a] -> a -- Tuple type
1432 , ft_ty_app :: Type -> a -> a -- Type app, variable only in last argument
1433 , ft_bad_app :: a -- Type app, variable other than in last argument
1434 , ft_forall :: TcTyVar -> a -> a -- Forall type
1437 functorLikeTraverse :: TyVar -- ^ Variable to look for
1438 -> FFoldType a -- ^ How to fold
1439 -> Type -- ^ Type to process
1441 functorLikeTraverse var (FT { ft_triv = caseTrivial, ft_var = caseVar
1442 , ft_co_var = caseCoVar, ft_fun = caseFun
1443 , ft_tup = caseTuple, ft_ty_app = caseTyApp
1444 , ft_bad_app = caseWrongArg, ft_forall = caseForAll })
1447 where -- go returns (result of type a, does type contain var)
1448 go co ty | Just ty' <- coreView ty = go co ty'
1449 go co (TyVarTy v) | v == var = (if co then caseCoVar else caseVar,True)
1450 go co (FunTy (PredTy _) b) = go co b
1451 go co (FunTy x y) | xc || yc = (caseFun xr yr,True)
1452 where (xr,xc) = go (not co) x
1454 go co (AppTy x y) | xc = (caseWrongArg, True)
1455 | yc = (caseTyApp x yr, True)
1456 where (_, xc) = go co x
1458 go co ty@(TyConApp con args)
1459 | isTupleTyCon con = (caseTuple (tupleTyConBoxity con) xrs,True)
1460 | null args = (caseTrivial,False) -- T
1461 | or (init xcs) = (caseWrongArg,True) -- T (..var..) ty
1462 | last xcs = -- T (..no var..) ty
1463 (caseTyApp (fst (splitAppTy ty)) (last xrs),True)
1464 where (xrs,xcs) = unzip (map (go co) args)
1465 go co (ForAllTy v x) | v /= var && xc = (caseForAll v xr,True)
1466 where (xr,xc) = go co x
1467 go _ _ = (caseTrivial,False)
1469 -- Return all syntactic subterms of ty that contain var somewhere
1470 -- These are the things that should appear in instance constraints
1471 deepSubtypesContaining :: TyVar -> Type -> [TcType]
1472 deepSubtypesContaining tv
1473 = functorLikeTraverse tv
1476 , ft_fun = (++), ft_tup = \_ xs -> concat xs
1478 , ft_bad_app = panic "in other argument"
1479 , ft_co_var = panic "contravariant"
1480 , ft_forall = \v xs -> filterOut ((v `elemVarSet`) . tyVarsOfType) xs })
1483 foldDataConArgs :: FFoldType a -> DataCon -> [a]
1484 -- Fold over the arguments of the datacon
1485 foldDataConArgs ft con
1486 = map (functorLikeTraverse tv ft) (dataConOrigArgTys con)
1488 tv = last (dataConUnivTyVars con)
1489 -- Argument to derive for, 'a in the above description
1490 -- The validity checks have ensured that con is
1491 -- a vanilla data constructor
1493 -- Make a HsLam using a fresh variable from a State monad
1494 mkSimpleLam :: (LHsExpr id -> State [id] (LHsExpr id)) -> State [id] (LHsExpr id)
1495 -- (mkSimpleLam fn) returns (\x. fn(x))
1496 mkSimpleLam lam = do
1499 body <- lam (nlHsVar n)
1500 return (mkHsLam [nlVarPat n] body)
1502 mkSimpleLam2 :: (LHsExpr id -> LHsExpr id -> State [id] (LHsExpr id)) -> State [id] (LHsExpr id)
1503 mkSimpleLam2 lam = do
1504 (n1:n2:names) <- get
1506 body <- lam (nlHsVar n1) (nlHsVar n2)
1507 return (mkHsLam [nlVarPat n1,nlVarPat n2] body)
1509 -- "Con a1 a2 a3 -> fold [x1 a1, x2 a2, x3 a3]"
1510 mkSimpleConMatch :: Monad m => (RdrName -> [a] -> m (LHsExpr RdrName)) -> [LPat RdrName] -> DataCon -> [LHsExpr RdrName -> a] -> m (LMatch RdrName)
1511 mkSimpleConMatch fold extra_pats con insides = do
1512 let con_name = getRdrName con
1513 let vars_needed = takeList insides as_RDRs
1514 let pat = nlConVarPat con_name vars_needed
1515 rhs <- fold con_name (zipWith ($) insides (map nlHsVar vars_needed))
1516 return $ mkMatch (extra_pats ++ [pat]) rhs emptyLocalBinds
1518 -- "case x of (a1,a2,a3) -> fold [x1 a1, x2 a2, x3 a3]"
1519 mkSimpleTupleCase :: Monad m => ([LPat RdrName] -> DataCon -> [LHsExpr RdrName -> a] -> m (LMatch RdrName))
1520 -> Boxity -> [LHsExpr RdrName -> a] -> LHsExpr RdrName -> m (LHsExpr RdrName)
1521 mkSimpleTupleCase match_for_con boxity insides x = do
1522 let con = tupleCon boxity (length insides)
1523 match <- match_for_con [] con insides
1524 return $ nlHsCase x [match]
1528 %************************************************************************
1532 see http://www.mail-archive.com/haskell-prime@haskell.org/msg02116.html
1535 %************************************************************************
1537 Deriving Foldable instances works the same way as Functor instances,
1538 only Foldable instances are not possible for function types at all.
1539 Here the derived instance for the type T above is:
1541 instance Foldable T where
1542 foldr f z (T1 x1 x2 x3) = $(foldr 'a 'b1) x1 ( $(foldr 'a 'a) x2 ( $(foldr 'a 'b2) x3 z ) )
1546 $(foldr 'a 'b) x z = z -- when b does not contain a
1547 $(foldr 'a 'a) x z = f x z
1548 $(foldr 'a '(b1,b2)) x z = case x of (x1,x2) -> $(foldr 'a 'b1) x1 ( $(foldr 'a 'b2) x2 z )
1549 $(foldr 'a '(T b1 b2)) x z = foldr $(foldr 'a 'b2) x z -- when a only occurs in the last parameter, b2
1551 Note that the arguments to the real foldr function are the wrong way around,
1552 since (f :: a -> b -> b), while (foldr f :: b -> t a -> b).
1555 gen_Foldable_binds :: SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds)
1556 gen_Foldable_binds loc tycon
1557 = (unitBag foldr_bind, [])
1559 data_cons = tyConDataCons tycon
1561 foldr_bind = L loc $ mkRdrFunBind (L loc foldable_foldr_RDR) eqns
1562 eqns = map foldr_eqn data_cons
1563 foldr_eqn con = evalState (match_for_con z_Expr [f_Pat,z_Pat] con parts) bs_RDRs
1565 parts = foldDataConArgs ft_foldr con
1567 ft_foldr :: FFoldType (LHsExpr RdrName -> LHsExpr RdrName -> State [RdrName] (LHsExpr RdrName))
1568 ft_foldr = FT { ft_triv = \_ z -> return z -- foldr f z x = z
1569 , ft_var = \x z -> return (nlHsApps f_RDR [x,z]) -- foldr f z x = f x z
1570 , ft_tup = \b gs x z -> mkSimpleTupleCase (match_for_con z) b gs x
1571 , ft_ty_app = \_ g x z -> do gg <- mkSimpleLam2 g -- foldr f z x = foldr (\xx zz -> g xx zz) z x
1572 return $ nlHsApps foldable_foldr_RDR [gg,z,x]
1573 , ft_forall = \_ g x z -> g x z
1574 , ft_co_var = panic "covariant"
1575 , ft_fun = panic "function"
1576 , ft_bad_app = panic "in other argument" }
1578 match_for_con z = mkSimpleConMatch (\_con_name -> foldrM ($) z) -- g1 v1 (g2 v2 (.. z))
1582 %************************************************************************
1584 Traversable instances
1586 see http://www.mail-archive.com/haskell-prime@haskell.org/msg02116.html
1588 %************************************************************************
1590 Again, Traversable is much like Functor and Foldable.
1594 $(traverse 'a 'b) x = pure x -- when b does not contain a
1595 $(traverse 'a 'a) x = f x
1596 $(traverse 'a '(b1,b2)) x = case x of (x1,x2) -> (,) <$> $(traverse 'a 'b1) x1 <*> $(traverse 'a 'b2) x2
1597 $(traverse 'a '(T b1 b2)) x = traverse $(traverse 'a 'b2) x -- when a only occurs in the last parameter, b2
1599 Note that the generated code is not as efficient as it could be. For instance:
1601 data T a = T Int a deriving Traversable
1603 gives the function: traverse f (T x y) = T <$> pure x <*> f y
1604 instead of: traverse f (T x y) = T x <$> f y
1607 gen_Traversable_binds :: SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds)
1608 gen_Traversable_binds loc tycon
1609 = (unitBag traverse_bind, [])
1611 data_cons = tyConDataCons tycon
1613 traverse_bind = L loc $ mkRdrFunBind (L loc traverse_RDR) eqns
1614 eqns = map traverse_eqn data_cons
1615 traverse_eqn con = evalState (match_for_con [f_Pat] con parts) bs_RDRs
1617 parts = foldDataConArgs ft_trav con
1620 ft_trav :: FFoldType (LHsExpr RdrName -> State [RdrName] (LHsExpr RdrName))
1621 ft_trav = FT { ft_triv = \x -> return (nlHsApps pure_RDR [x]) -- traverse f x = pure x
1622 , ft_var = \x -> return (nlHsApps f_RDR [x]) -- travese f x = f x
1623 , ft_tup = mkSimpleTupleCase match_for_con -- travese f x z = case x of (a1,a2,..) ->
1624 -- (,,) <$> g1 a1 <*> g2 a2 <*> ..
1625 , ft_ty_app = \_ g x -> do gg <- mkSimpleLam g -- travese f x = travese (\xx -> g xx) x
1626 return $ nlHsApps traverse_RDR [gg,x]
1627 , ft_forall = \_ g x -> g x
1628 , ft_co_var = panic "covariant"
1629 , ft_fun = panic "function"
1630 , ft_bad_app = panic "in other argument" }
1632 match_for_con = mkSimpleConMatch $
1633 \con_name xsM -> do xs <- sequence xsM
1634 return (mkApCon (nlHsVar con_name) xs)
1636 -- ((Con <$> x1) <*> x2) <*> ..
1637 mkApCon con [] = nlHsApps pure_RDR [con]
1638 mkApCon con (x:xs) = foldl appAp (nlHsApps fmap_RDR [con,x]) xs
1639 where appAp x y = nlHsApps ap_RDR [x,y]
1644 %************************************************************************
1646 \subsection{Generating extra binds (@con2tag@ and @tag2con@)}
1648 %************************************************************************
1653 con2tag_Foo :: Foo ... -> Int#
1654 tag2con_Foo :: Int -> Foo ... -- easier if Int, not Int#
1655 maxtag_Foo :: Int -- ditto (NB: not unlifted)
1658 The `tags' here start at zero, hence the @fIRST_TAG@ (currently one)
1662 genAuxBind :: SrcSpan -> DerivAuxBind -> (LHsBind RdrName, LSig RdrName)
1663 genAuxBind loc (GenCon2Tag tycon)
1664 = (mk_FunBind loc rdr_name eqns,
1665 L loc (TypeSig (L loc rdr_name) (L loc sig_ty)))
1667 rdr_name = con2tag_RDR tycon
1670 mkForAllTys (tyConTyVars tycon) $
1671 mkParentType tycon `mkFunTy` intPrimTy
1673 lots_of_constructors = tyConFamilySize tycon > 8
1674 -- was: mAX_FAMILY_SIZE_FOR_VEC_RETURNS
1675 -- but we don't do vectored returns any more.
1677 eqns | lots_of_constructors = [get_tag_eqn]
1678 | otherwise = map mk_eqn (tyConDataCons tycon)
1680 get_tag_eqn = ([nlVarPat a_RDR], nlHsApp (nlHsVar getTag_RDR) a_Expr)
1682 mk_eqn :: DataCon -> ([LPat RdrName], LHsExpr RdrName)
1683 mk_eqn con = ([nlWildConPat con],
1684 nlHsLit (HsIntPrim (toInteger ((dataConTag con) - fIRST_TAG))))
1686 genAuxBind loc (GenTag2Con tycon)
1687 = (mk_FunBind loc rdr_name
1688 [([nlConVarPat intDataCon_RDR [a_RDR]],
1689 nlHsApp (nlHsVar tagToEnum_RDR) a_Expr)],
1690 L loc (TypeSig (L loc rdr_name) (L loc sig_ty)))
1692 sig_ty = HsCoreTy $ mkForAllTys (tyConTyVars tycon) $
1693 intTy `mkFunTy` mkParentType tycon
1695 rdr_name = tag2con_RDR tycon
1697 genAuxBind loc (GenMaxTag tycon)
1698 = (mkHsVarBind loc rdr_name rhs,
1699 L loc (TypeSig (L loc rdr_name) (L loc sig_ty)))
1701 rdr_name = maxtag_RDR tycon
1702 sig_ty = HsCoreTy intTy
1703 rhs = nlHsApp (nlHsVar intDataCon_RDR) (nlHsLit (HsIntPrim max_tag))
1704 max_tag = case (tyConDataCons tycon) of
1705 data_cons -> toInteger ((length data_cons) - fIRST_TAG)
1707 genAuxBind loc (MkTyCon tycon) -- $dT
1708 = (mkHsVarBind loc rdr_name rhs,
1709 L loc (TypeSig (L loc rdr_name) sig_ty))
1711 rdr_name = mk_data_type_name tycon
1712 sig_ty = nlHsTyVar dataType_RDR
1713 constrs = [nlHsVar (mk_constr_name con) | con <- tyConDataCons tycon]
1714 rhs = nlHsVar mkDataType_RDR
1715 `nlHsApp` nlHsLit (mkHsString (showSDocOneLine (ppr tycon)))
1716 `nlHsApp` nlList constrs
1718 genAuxBind loc (MkDataCon dc) -- $cT1 etc
1719 = (mkHsVarBind loc rdr_name rhs,
1720 L loc (TypeSig (L loc rdr_name) sig_ty))
1722 rdr_name = mk_constr_name dc
1723 sig_ty = nlHsTyVar constr_RDR
1724 rhs = nlHsApps mkConstr_RDR constr_args
1727 = [ -- nlHsIntLit (toInteger (dataConTag dc)), -- Tag
1728 nlHsVar (mk_data_type_name (dataConTyCon dc)), -- DataType
1729 nlHsLit (mkHsString (occNameString dc_occ)), -- String name
1730 nlList labels, -- Field labels
1731 nlHsVar fixity] -- Fixity
1733 labels = map (nlHsLit . mkHsString . getOccString)
1734 (dataConFieldLabels dc)
1735 dc_occ = getOccName dc
1736 is_infix = isDataSymOcc dc_occ
1737 fixity | is_infix = infix_RDR
1738 | otherwise = prefix_RDR
1740 mk_data_type_name :: TyCon -> RdrName -- "$tT"
1741 mk_data_type_name tycon = mkAuxBinderName (tyConName tycon) mkDataTOcc
1743 mk_constr_name :: DataCon -> RdrName -- "$cC"
1744 mk_constr_name con = mkAuxBinderName (dataConName con) mkDataCOcc
1746 mkParentType :: TyCon -> Type
1747 -- Turn the representation tycon of a family into
1748 -- a use of its family constructor
1750 = case tyConFamInst_maybe tc of
1751 Nothing -> mkTyConApp tc (mkTyVarTys (tyConTyVars tc))
1752 Just (fam_tc,tys) -> mkTyConApp fam_tc tys
1755 %************************************************************************
1757 \subsection{Utility bits for generating bindings}
1759 %************************************************************************
1763 mk_FunBind :: SrcSpan -> RdrName
1764 -> [([LPat RdrName], LHsExpr RdrName)]
1766 mk_FunBind loc fun pats_and_exprs
1767 = L loc $ mkRdrFunBind (L loc fun) matches
1769 matches = [mkMatch p e emptyLocalBinds | (p,e) <-pats_and_exprs]
1771 mkRdrFunBind :: Located RdrName -> [LMatch RdrName] -> HsBind RdrName
1772 mkRdrFunBind fun@(L _ fun_rdr) matches
1773 | null matches = mkFunBind fun [mkMatch [] (error_Expr str) emptyLocalBinds]
1774 -- Catch-all eqn looks like
1775 -- fmap = error "Void fmap"
1776 -- It's needed if there no data cons at all,
1777 -- which can happen with -XEmptyDataDecls
1779 | otherwise = mkFunBind fun matches
1781 str = "Void " ++ occNameString (rdrNameOcc fun_rdr)
1785 box_if_necy :: String -- The class involved
1786 -> TyCon -- The tycon involved
1787 -> LHsExpr RdrName -- The argument
1788 -> Type -- The argument type
1789 -> LHsExpr RdrName -- Boxed version of the arg
1790 box_if_necy cls_str tycon arg arg_ty
1791 | isUnLiftedType arg_ty = nlHsApp (nlHsVar box_con) arg
1794 box_con = assoc_ty_id cls_str tycon box_con_tbl arg_ty
1796 ---------------------
1797 primOrdOps :: String -- The class involved
1798 -> TyCon -- The tycon involved
1800 -> (PrimOp, PrimOp, PrimOp, PrimOp, PrimOp) -- (lt,le,eq,ge,gt)
1801 primOrdOps str tycon ty = assoc_ty_id str tycon ord_op_tbl ty
1803 ord_op_tbl :: [(Type, (PrimOp, PrimOp, PrimOp, PrimOp, PrimOp))]
1805 = [(charPrimTy, (CharLtOp, CharLeOp, CharEqOp, CharGeOp, CharGtOp))
1806 ,(intPrimTy, (IntLtOp, IntLeOp, IntEqOp, IntGeOp, IntGtOp))
1807 ,(wordPrimTy, (WordLtOp, WordLeOp, WordEqOp, WordGeOp, WordGtOp))
1808 ,(addrPrimTy, (AddrLtOp, AddrLeOp, AddrEqOp, AddrGeOp, AddrGtOp))
1809 ,(floatPrimTy, (FloatLtOp, FloatLeOp, FloatEqOp, FloatGeOp, FloatGtOp))
1810 ,(doublePrimTy, (DoubleLtOp, DoubleLeOp, DoubleEqOp, DoubleGeOp, DoubleGtOp)) ]
1812 box_con_tbl :: [(Type, RdrName)]
1814 [(charPrimTy, getRdrName charDataCon)
1815 ,(intPrimTy, getRdrName intDataCon)
1816 ,(wordPrimTy, wordDataCon_RDR)
1817 ,(floatPrimTy, getRdrName floatDataCon)
1818 ,(doublePrimTy, getRdrName doubleDataCon)
1821 assoc_ty_id :: String -- The class involved
1822 -> TyCon -- The tycon involved
1823 -> [(Type,a)] -- The table
1825 -> a -- The result of the lookup
1826 assoc_ty_id cls_str _ tbl ty
1827 | null res = pprPanic "Error in deriving:" (text "Can't derive" <+> text cls_str <+>
1828 text "for primitive type" <+> ppr ty)
1829 | otherwise = head res
1831 res = [id | (ty',id) <- tbl, ty `tcEqType` ty']
1833 -----------------------------------------------------------------------
1835 and_Expr :: LHsExpr RdrName -> LHsExpr RdrName -> LHsExpr RdrName
1836 and_Expr a b = genOpApp a and_RDR b
1838 -----------------------------------------------------------------------
1840 eq_Expr :: TyCon -> Type -> LHsExpr RdrName -> LHsExpr RdrName -> LHsExpr RdrName
1841 eq_Expr tycon ty a b = genOpApp a eq_op b
1843 eq_op | not (isUnLiftedType ty) = eq_RDR
1844 | otherwise = primOpRdrName prim_eq
1845 (_, _, prim_eq, _, _) = primOrdOps "Eq" tycon ty
1849 untag_Expr :: TyCon -> [( RdrName, RdrName)] -> LHsExpr RdrName -> LHsExpr RdrName
1850 untag_Expr _ [] expr = expr
1851 untag_Expr tycon ((untag_this, put_tag_here) : more) expr
1852 = nlHsCase (nlHsPar (nlHsVarApps (con2tag_RDR tycon) [untag_this])) {-of-}
1853 [mkSimpleHsAlt (nlVarPat put_tag_here) (untag_Expr tycon more expr)]
1856 :: LHsExpr RdrName -> LHsExpr RdrName
1858 enum_from_then_to_Expr
1859 :: LHsExpr RdrName -> LHsExpr RdrName -> LHsExpr RdrName
1862 enum_from_to_Expr f t2 = nlHsApp (nlHsApp (nlHsVar enumFromTo_RDR) f) t2
1863 enum_from_then_to_Expr f t t2 = nlHsApp (nlHsApp (nlHsApp (nlHsVar enumFromThenTo_RDR) f) t) t2
1866 :: LHsExpr RdrName -> LHsExpr RdrName
1869 showParen_Expr e1 e2 = nlHsApp (nlHsApp (nlHsVar showParen_RDR) e1) e2
1871 nested_compose_Expr :: [LHsExpr RdrName] -> LHsExpr RdrName
1873 nested_compose_Expr [] = panic "nested_compose_expr" -- Arg is always non-empty
1874 nested_compose_Expr [e] = parenify e
1875 nested_compose_Expr (e:es)
1876 = nlHsApp (nlHsApp (nlHsVar compose_RDR) (parenify e)) (nested_compose_Expr es)
1878 -- impossible_Expr is used in case RHSs that should never happen.
1879 -- We generate these to keep the desugarer from complaining that they *might* happen!
1880 error_Expr :: String -> LHsExpr RdrName
1881 error_Expr string = nlHsApp (nlHsVar error_RDR) (nlHsLit (mkHsString string))
1883 -- illegal_Expr is used when signalling error conditions in the RHS of a derived
1884 -- method. It is currently only used by Enum.{succ,pred}
1885 illegal_Expr :: String -> String -> String -> LHsExpr RdrName
1886 illegal_Expr meth tp msg =
1887 nlHsApp (nlHsVar error_RDR) (nlHsLit (mkHsString (meth ++ '{':tp ++ "}: " ++ msg)))
1889 -- illegal_toEnum_tag is an extended version of illegal_Expr, which also allows you
1890 -- to include the value of a_RDR in the error string.
1891 illegal_toEnum_tag :: String -> RdrName -> LHsExpr RdrName
1892 illegal_toEnum_tag tp maxtag =
1893 nlHsApp (nlHsVar error_RDR)
1894 (nlHsApp (nlHsApp (nlHsVar append_RDR)
1895 (nlHsLit (mkHsString ("toEnum{" ++ tp ++ "}: tag ("))))
1896 (nlHsApp (nlHsApp (nlHsApp
1897 (nlHsVar showsPrec_RDR)
1901 (nlHsVar append_RDR)
1902 (nlHsLit (mkHsString ") is outside of enumeration's range (0,")))
1903 (nlHsApp (nlHsApp (nlHsApp
1904 (nlHsVar showsPrec_RDR)
1907 (nlHsLit (mkHsString ")"))))))
1909 parenify :: LHsExpr RdrName -> LHsExpr RdrName
1910 parenify e@(L _ (HsVar _)) = e
1911 parenify e = mkHsPar e
1913 -- genOpApp wraps brackets round the operator application, so that the
1914 -- renamer won't subsequently try to re-associate it.
1915 genOpApp :: LHsExpr RdrName -> RdrName -> LHsExpr RdrName -> LHsExpr RdrName
1916 genOpApp e1 op e2 = nlHsPar (nlHsOpApp e1 op e2)
1920 a_RDR, b_RDR, c_RDR, d_RDR, f_RDR, k_RDR, z_RDR, ah_RDR, bh_RDR, ch_RDR, dh_RDR
1922 a_RDR = mkVarUnqual (fsLit "a")
1923 b_RDR = mkVarUnqual (fsLit "b")
1924 c_RDR = mkVarUnqual (fsLit "c")
1925 d_RDR = mkVarUnqual (fsLit "d")
1926 f_RDR = mkVarUnqual (fsLit "f")
1927 k_RDR = mkVarUnqual (fsLit "k")
1928 z_RDR = mkVarUnqual (fsLit "z")
1929 ah_RDR = mkVarUnqual (fsLit "a#")
1930 bh_RDR = mkVarUnqual (fsLit "b#")
1931 ch_RDR = mkVarUnqual (fsLit "c#")
1932 dh_RDR = mkVarUnqual (fsLit "d#")
1934 as_RDRs, bs_RDRs, cs_RDRs :: [RdrName]
1935 as_RDRs = [ mkVarUnqual (mkFastString ("a"++show i)) | i <- [(1::Int) .. ] ]
1936 bs_RDRs = [ mkVarUnqual (mkFastString ("b"++show i)) | i <- [(1::Int) .. ] ]
1937 cs_RDRs = [ mkVarUnqual (mkFastString ("c"++show i)) | i <- [(1::Int) .. ] ]
1939 a_Expr, c_Expr, f_Expr, z_Expr, ltTag_Expr, eqTag_Expr, gtTag_Expr,
1940 false_Expr, true_Expr :: LHsExpr RdrName
1941 a_Expr = nlHsVar a_RDR
1942 -- b_Expr = nlHsVar b_RDR
1943 c_Expr = nlHsVar c_RDR
1944 f_Expr = nlHsVar f_RDR
1945 z_Expr = nlHsVar z_RDR
1946 ltTag_Expr = nlHsVar ltTag_RDR
1947 eqTag_Expr = nlHsVar eqTag_RDR
1948 gtTag_Expr = nlHsVar gtTag_RDR
1949 false_Expr = nlHsVar false_RDR
1950 true_Expr = nlHsVar true_RDR
1952 a_Pat, b_Pat, c_Pat, d_Pat, f_Pat, k_Pat, z_Pat :: LPat RdrName
1953 a_Pat = nlVarPat a_RDR
1954 b_Pat = nlVarPat b_RDR
1955 c_Pat = nlVarPat c_RDR
1956 d_Pat = nlVarPat d_RDR
1957 f_Pat = nlVarPat f_RDR
1958 k_Pat = nlVarPat k_RDR
1959 z_Pat = nlVarPat z_RDR
1961 con2tag_RDR, tag2con_RDR, maxtag_RDR :: TyCon -> RdrName
1962 -- Generates Orig s RdrName, for the binding positions
1963 con2tag_RDR tycon = mk_tc_deriv_name tycon mkCon2TagOcc
1964 tag2con_RDR tycon = mk_tc_deriv_name tycon mkTag2ConOcc
1965 maxtag_RDR tycon = mk_tc_deriv_name tycon mkMaxTagOcc
1967 mk_tc_deriv_name :: TyCon -> (OccName -> OccName) -> RdrName
1968 mk_tc_deriv_name tycon occ_fun = mkAuxBinderName (tyConName tycon) occ_fun
1970 mkAuxBinderName :: Name -> (OccName -> OccName) -> RdrName
1971 mkAuxBinderName parent occ_fun = mkRdrUnqual (occ_fun (nameOccName parent))
1972 -- Was: mkDerivedRdrName name occ_fun, which made an original name
1973 -- But: (a) that does not work well for standalone-deriving
1974 -- (b) an unqualified name is just fine, provided it can't clash with user code
1977 s RdrName for PrimOps. Can't be done in PrelNames, because PrimOp imports
1978 PrelNames, so PrelNames can't import PrimOp.
1981 primOpRdrName :: PrimOp -> RdrName
1982 primOpRdrName op = getRdrName (primOpId op)
1984 minusInt_RDR, eqInt_RDR, ltInt_RDR, geInt_RDR, gtInt_RDR, leInt_RDR,
1985 tagToEnum_RDR :: RdrName
1986 minusInt_RDR = primOpRdrName IntSubOp
1987 eqInt_RDR = primOpRdrName IntEqOp
1988 ltInt_RDR = primOpRdrName IntLtOp
1989 geInt_RDR = primOpRdrName IntGeOp
1990 gtInt_RDR = primOpRdrName IntGtOp
1991 leInt_RDR = primOpRdrName IntLeOp
1992 tagToEnum_RDR = primOpRdrName TagToEnumOp
1994 error_RDR :: RdrName
1995 error_RDR = getRdrName eRROR_ID