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"
44 import MkCore ( eRROR_ID )
62 import Data.List ( partition, intersperse )
66 type DerivAuxBinds = [DerivAuxBind]
68 data DerivAuxBind -- Please add these auxiliary top-level bindings
69 = GenCon2Tag TyCon -- The con2Tag for given TyCon
70 | GenTag2Con TyCon -- ...ditto tag2Con
71 | GenMaxTag TyCon -- ...and maxTag
72 -- All these generate ZERO-BASED tag operations
73 -- I.e first constructor has tag 0
75 -- Scrap your boilerplate
76 | MkDataCon DataCon -- For constructor C we get $cC :: Constr
77 | MkTyCon TyCon -- For tycon T we get $tT :: DataType
80 isDupAux :: DerivAuxBind -> DerivAuxBind -> Bool
81 isDupAux (GenCon2Tag tc1) (GenCon2Tag tc2) = tc1 == tc2
82 isDupAux (GenTag2Con tc1) (GenTag2Con tc2) = tc1 == tc2
83 isDupAux (GenMaxTag tc1) (GenMaxTag tc2) = tc1 == tc2
84 isDupAux (MkDataCon dc1) (MkDataCon dc2) = dc1 == dc2
85 isDupAux (MkTyCon tc1) (MkTyCon tc2) = tc1 == tc2
90 %************************************************************************
94 %************************************************************************
96 Here are the heuristics for the code we generate for @Eq@:
99 Let's assume we have a data type with some (possibly zero) nullary
100 data constructors and some ordinary, non-nullary ones (the rest,
101 also possibly zero of them). Here's an example, with both \tr{N}ullary
102 and \tr{O}rdinary data cons.
104 data Foo ... = N1 | N2 ... | Nn | O1 a b | O2 Int | O3 Double b b | ...
108 For the ordinary constructors (if any), we emit clauses to do The
112 (==) (O1 a1 b1) (O1 a2 b2) = a1 == a2 && b1 == b2
113 (==) (O2 a1) (O2 a2) = a1 == a2
114 (==) (O3 a1 b1 c1) (O3 a2 b2 c2) = a1 == a2 && b1 == b2 && c1 == c2
117 Note: if we're comparing unlifted things, e.g., if \tr{a1} and
118 \tr{a2} are \tr{Float#}s, then we have to generate
120 case (a1 `eqFloat#` a2) of
123 for that particular test.
126 If there are any nullary constructors, we emit a catch-all clause of
130 (==) a b = case (con2tag_Foo a) of { a# ->
131 case (con2tag_Foo b) of { b# ->
132 case (a# ==# b#) of {
137 If there aren't any nullary constructors, we emit a simpler
144 For the @(/=)@ method, we normally just use the default method.
146 If the type is an enumeration type, we could/may/should? generate
147 special code that calls @con2tag_Foo@, much like for @(==)@ shown
151 We thought about doing this: If we're also deriving @Ord@ for this
154 instance ... Eq (Foo ...) where
155 (==) a b = case (compare a b) of { _LT -> False; _EQ -> True ; _GT -> False}
156 (/=) a b = case (compare a b) of { _LT -> True ; _EQ -> False; _GT -> True }
158 However, that requires that \tr{Ord <whatever>} was put in the context
159 for the instance decl, which it probably wasn't, so the decls
160 produced don't get through the typechecker.
165 gen_Eq_binds :: SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds)
166 gen_Eq_binds loc tycon
167 = (method_binds, aux_binds)
169 (nullary_cons, nonnullary_cons)
170 | isNewTyCon tycon = ([], tyConDataCons tycon)
171 | otherwise = partition isNullarySrcDataCon (tyConDataCons tycon)
173 no_nullary_cons = null nullary_cons
175 rest | no_nullary_cons
176 = case tyConSingleDataCon_maybe tycon of
178 Nothing -> -- if cons don't match, then False
179 [([nlWildPat, nlWildPat], false_Expr)]
180 | otherwise -- calc. and compare the tags
182 untag_Expr tycon [(a_RDR,ah_RDR), (b_RDR,bh_RDR)]
183 (genOpApp (nlHsVar ah_RDR) eqInt_RDR (nlHsVar bh_RDR)))]
185 aux_binds | no_nullary_cons = []
186 | otherwise = [GenCon2Tag tycon]
188 method_binds = listToBag [eq_bind, ne_bind]
189 eq_bind = mk_FunBind loc eq_RDR (map pats_etc nonnullary_cons ++ rest)
190 ne_bind = mk_easy_FunBind loc ne_RDR [a_Pat, b_Pat] (
191 nlHsApp (nlHsVar not_RDR) (nlHsPar (nlHsVarApps eq_RDR [a_RDR, b_RDR])))
193 ------------------------------------------------------------------
196 con1_pat = nlConVarPat data_con_RDR as_needed
197 con2_pat = nlConVarPat data_con_RDR bs_needed
199 data_con_RDR = getRdrName data_con
200 con_arity = length tys_needed
201 as_needed = take con_arity as_RDRs
202 bs_needed = take con_arity bs_RDRs
203 tys_needed = dataConOrigArgTys data_con
205 ([con1_pat, con2_pat], nested_eq_expr tys_needed as_needed bs_needed)
207 nested_eq_expr [] [] [] = true_Expr
208 nested_eq_expr tys as bs
209 = foldl1 and_Expr (zipWith3Equal "nested_eq" nested_eq tys as bs)
211 nested_eq ty a b = nlHsPar (eq_Expr tycon ty (nlHsVar a) (nlHsVar b))
214 %************************************************************************
218 %************************************************************************
220 Note [Generating Ord instances]
221 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
222 Suppose constructors are K1..Kn, and some are nullary.
223 The general form we generate is:
225 * Do case on first argument
234 If i = 1, 2, n-1, n, generate a single case.
237 K2 ... -> ...eq_rhs(K2)...
240 Otherwise do a tag compare against the bigger range
241 (because this is the one most likely to succeed)
242 rhs_3 case tag b of tb ->
245 K3 ... -> ...eq_rhs(K3)....
248 * To make eq_rhs(K), which knows that
251 we just want to compare (a1,b1) then (a2,b2) etc.
252 Take care on the last field to tail-call into comparing av,bv
254 * To make nullary_rhs generate this
255 case con2tag a of a# ->
259 Several special cases:
261 * Two or fewer nullary constructors: don't generate nullary_rhs
263 * Be careful about unlifted comparisons. When comparing unboxed
264 values we can't call the overloaded functions.
265 See function unliftedOrdOp
267 Note [Do not rely on compare]
268 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
269 It's a bad idea to define only 'compare', and build the other binary
270 comparisions on top of it; see Trac #2130, #4019. Reason: we don't
271 want to laboriously make a three-way comparison, only to extract a
272 binary result, something like this:
273 (>) (I# x) (I# y) = case <# x y of
275 False -> case ==# x y of
279 So for sufficiently small types (few constructors, or all nullary)
280 we generate all methods; for large ones we just use 'compare'.
283 data OrdOp = OrdCompare | OrdLT | OrdLE | OrdGE | OrdGT
286 ordMethRdr :: OrdOp -> RdrName
289 OrdCompare -> compare_RDR
296 ltResult :: OrdOp -> LHsExpr RdrName
297 -- Knowing a<b, what is the result for a `op` b?
298 ltResult OrdCompare = ltTag_Expr
299 ltResult OrdLT = true_Expr
300 ltResult OrdLE = true_Expr
301 ltResult OrdGE = false_Expr
302 ltResult OrdGT = false_Expr
305 eqResult :: OrdOp -> LHsExpr RdrName
306 -- Knowing a=b, what is the result for a `op` b?
307 eqResult OrdCompare = eqTag_Expr
308 eqResult OrdLT = false_Expr
309 eqResult OrdLE = true_Expr
310 eqResult OrdGE = true_Expr
311 eqResult OrdGT = false_Expr
314 gtResult :: OrdOp -> LHsExpr RdrName
315 -- Knowing a>b, what is the result for a `op` b?
316 gtResult OrdCompare = gtTag_Expr
317 gtResult OrdLT = false_Expr
318 gtResult OrdLE = false_Expr
319 gtResult OrdGE = true_Expr
320 gtResult OrdGT = true_Expr
323 gen_Ord_binds :: SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds)
324 gen_Ord_binds loc tycon
325 | null tycon_data_cons -- No data-cons => invoke bale-out case
326 = (unitBag $ mk_FunBind loc compare_RDR [], [])
328 = (unitBag (mkOrdOp OrdCompare) `unionBags` other_ops, aux_binds)
330 aux_binds | single_con_type = []
331 | otherwise = [GenCon2Tag tycon]
333 -- Note [Do not rely on compare]
334 other_ops | (last_tag - first_tag) <= 2 -- 1-3 constructors
335 || null non_nullary_cons -- Or it's an enumeration
336 = listToBag (map mkOrdOp [OrdLT,OrdLE,OrdGE,OrdGT])
340 get_tag con = dataConTag con - fIRST_TAG
341 -- We want *zero-based* tags, because that's what
342 -- con2Tag returns (generated by untag_Expr)!
344 tycon_data_cons = tyConDataCons tycon
345 single_con_type = isSingleton tycon_data_cons
346 (first_con : _) = tycon_data_cons
347 (last_con : _) = reverse tycon_data_cons
348 first_tag = get_tag first_con
349 last_tag = get_tag last_con
351 (nullary_cons, non_nullary_cons) = partition isNullarySrcDataCon tycon_data_cons
354 mkOrdOp :: OrdOp -> LHsBind RdrName
355 -- Returns a binding op a b = ... compares a and b according to op ....
356 mkOrdOp op = mk_easy_FunBind loc (ordMethRdr op) [a_Pat, b_Pat] (mkOrdOpRhs op)
358 mkOrdOpRhs :: OrdOp -> LHsExpr RdrName
359 mkOrdOpRhs op -- RHS for comparing 'a' and 'b' according to op
360 | length nullary_cons <= 2 -- Two nullary or fewer, so use cases
361 = nlHsCase (nlHsVar a_RDR) $
362 map (mkOrdOpAlt op) tycon_data_cons
363 -- i.e. case a of { C1 x y -> case b of C1 x y -> ....compare x,y...
364 -- C2 x -> case b of C2 x -> ....comopare x.... }
366 | null non_nullary_cons -- All nullary, so go straight to comparing tags
369 | otherwise -- Mixed nullary and non-nullary
370 = nlHsCase (nlHsVar a_RDR) $
371 (map (mkOrdOpAlt op) non_nullary_cons
372 ++ [mkSimpleHsAlt nlWildPat (mkTagCmp op)])
375 mkOrdOpAlt :: OrdOp -> DataCon -> LMatch RdrName
376 -- Make the alternative (Ki a1 a2 .. av ->
377 mkOrdOpAlt op data_con
378 = mkSimpleHsAlt (nlConVarPat data_con_RDR as_needed) (mkInnerRhs op data_con)
380 as_needed = take (dataConSourceArity data_con) as_RDRs
381 data_con_RDR = getRdrName data_con
383 mkInnerRhs op data_con
385 = nlHsCase (nlHsVar b_RDR) [ mkInnerEqAlt op data_con ]
388 = nlHsCase (nlHsVar b_RDR) [ mkInnerEqAlt op data_con
389 , mkSimpleHsAlt nlWildPat (ltResult op) ]
391 = nlHsCase (nlHsVar b_RDR) [ mkInnerEqAlt op data_con
392 , mkSimpleHsAlt nlWildPat (gtResult op) ]
394 | tag == first_tag + 1
395 = nlHsCase (nlHsVar b_RDR) [ mkSimpleHsAlt (nlConWildPat first_con) (gtResult op)
396 , mkInnerEqAlt op data_con
397 , mkSimpleHsAlt nlWildPat (ltResult op) ]
398 | tag == last_tag - 1
399 = nlHsCase (nlHsVar b_RDR) [ mkSimpleHsAlt (nlConWildPat last_con) (ltResult op)
400 , mkInnerEqAlt op data_con
401 , mkSimpleHsAlt nlWildPat (gtResult op) ]
403 | tag > last_tag `div` 2 -- lower range is larger
404 = untag_Expr tycon [(b_RDR, bh_RDR)] $
405 nlHsIf (genOpApp (nlHsVar bh_RDR) ltInt_RDR tag_lit)
406 (gtResult op) $ -- Definitely GT
407 nlHsCase (nlHsVar b_RDR) [ mkInnerEqAlt op data_con
408 , mkSimpleHsAlt nlWildPat (ltResult op) ]
410 | otherwise -- upper range is larger
411 = untag_Expr tycon [(b_RDR, bh_RDR)] $
412 nlHsIf (genOpApp (nlHsVar bh_RDR) gtInt_RDR tag_lit)
413 (ltResult op) $ -- Definitely LT
414 nlHsCase (nlHsVar b_RDR) [ mkInnerEqAlt op data_con
415 , mkSimpleHsAlt nlWildPat (gtResult op) ]
417 tag = get_tag data_con
418 tag_lit = noLoc (HsLit (HsIntPrim (toInteger tag)))
420 mkInnerEqAlt :: OrdOp -> DataCon -> LMatch RdrName
421 -- First argument 'a' known to be built with K
422 -- Returns a case alternative Ki b1 b2 ... bv -> compare (a1,a2,...) with (b1,b2,...)
423 mkInnerEqAlt op data_con
424 = mkSimpleHsAlt (nlConVarPat data_con_RDR bs_needed) $
425 mkCompareFields tycon op (dataConOrigArgTys data_con)
427 data_con_RDR = getRdrName data_con
428 bs_needed = take (dataConSourceArity data_con) bs_RDRs
430 mkTagCmp :: OrdOp -> LHsExpr RdrName
431 -- Both constructors known to be nullary
432 -- genreates (case data2Tag a of a# -> case data2Tag b of b# -> a# `op` b#
433 mkTagCmp op = untag_Expr tycon [(a_RDR, ah_RDR),(b_RDR, bh_RDR)] $
434 unliftedOrdOp tycon intPrimTy op ah_RDR bh_RDR
436 mkCompareFields :: TyCon -> OrdOp -> [Type] -> LHsExpr RdrName
437 -- Generates nested comparisons for (a1,a2...) against (b1,b2,...)
438 -- where the ai,bi have the given types
439 mkCompareFields tycon op tys
440 = go tys as_RDRs bs_RDRs
442 go [] _ _ = eqResult op
444 | isUnLiftedType ty = unliftedOrdOp tycon ty op a b
445 | otherwise = genOpApp (nlHsVar a) (ordMethRdr op) (nlHsVar b)
446 go (ty:tys) (a:as) (b:bs) = mk_compare ty a b
450 go _ _ _ = panic "mkCompareFields"
452 -- (mk_compare ty a b) generates
453 -- (case (compare a b) of { LT -> <lt>; EQ -> <eq>; GT -> <bt> })
454 -- but with suitable special cases for
455 mk_compare ty a b lt eq gt
457 = unliftedCompare lt_op eq_op a_expr b_expr lt eq gt
459 = nlHsCase (nlHsPar (nlHsApp (nlHsApp (nlHsVar compare_RDR) a_expr) b_expr))
460 [mkSimpleHsAlt (nlNullaryConPat ltTag_RDR) lt,
461 mkSimpleHsAlt (nlNullaryConPat eqTag_RDR) eq,
462 mkSimpleHsAlt (nlNullaryConPat gtTag_RDR) gt]
466 (lt_op, _, eq_op, _, _) = primOrdOps "Ord" tycon ty
468 unliftedOrdOp :: TyCon -> Type -> OrdOp -> RdrName -> RdrName -> LHsExpr RdrName
469 unliftedOrdOp tycon ty op a b
471 OrdCompare -> unliftedCompare lt_op eq_op a_expr b_expr
472 ltTag_Expr eqTag_Expr gtTag_Expr
478 (lt_op, le_op, eq_op, ge_op, gt_op) = primOrdOps "Ord" tycon ty
479 wrap prim_op = genOpApp a_expr (primOpRdrName prim_op) b_expr
483 unliftedCompare :: PrimOp -> PrimOp
484 -> LHsExpr RdrName -> LHsExpr RdrName -- What to cmpare
485 -> LHsExpr RdrName -> LHsExpr RdrName -> LHsExpr RdrName -- Three results
487 -- Return (if a < b then lt else if a == b then eq else gt)
488 unliftedCompare lt_op eq_op a_expr b_expr lt eq gt
489 = nlHsIf (genOpApp a_expr (primOpRdrName lt_op) b_expr) lt $
490 -- Test (<) first, not (==), becuase the latter
491 -- is true less often, so putting it first would
492 -- mean more tests (dynamically)
493 nlHsIf (genOpApp a_expr (primOpRdrName eq_op) b_expr) eq gt
495 nlConWildPat :: DataCon -> LPat RdrName
496 -- The pattern (K {})
497 nlConWildPat con = noLoc (ConPatIn (noLoc (getRdrName con))
498 (RecCon (HsRecFields { rec_flds = []
499 , rec_dotdot = Nothing })))
504 %************************************************************************
508 %************************************************************************
510 @Enum@ can only be derived for enumeration types. For a type
512 data Foo ... = N1 | N2 | ... | Nn
515 we use both @con2tag_Foo@ and @tag2con_Foo@ functions, as well as a
516 @maxtag_Foo@ variable (all generated by @gen_tag_n_con_binds@).
519 instance ... Enum (Foo ...) where
520 succ x = toEnum (1 + fromEnum x)
521 pred x = toEnum (fromEnum x - 1)
523 toEnum i = tag2con_Foo i
525 enumFrom a = map tag2con_Foo [con2tag_Foo a .. maxtag_Foo]
529 = case con2tag_Foo a of
530 a# -> map tag2con_Foo (enumFromTo (I# a#) maxtag_Foo)
533 = map tag2con_Foo [con2tag_Foo a, con2tag_Foo b .. maxtag_Foo]
537 = case con2tag_Foo a of { a# ->
538 case con2tag_Foo b of { b# ->
539 map tag2con_Foo (enumFromThenTo (I# a#) (I# b#) maxtag_Foo)
543 For @enumFromTo@ and @enumFromThenTo@, we use the default methods.
546 gen_Enum_binds :: SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds)
547 gen_Enum_binds loc tycon
548 = (method_binds, aux_binds)
550 method_binds = listToBag [
558 aux_binds = [GenCon2Tag tycon, GenTag2Con tycon, GenMaxTag tycon]
560 occ_nm = getOccString tycon
563 = mk_easy_FunBind loc succ_RDR [a_Pat] $
564 untag_Expr tycon [(a_RDR, ah_RDR)] $
565 nlHsIf (nlHsApps eq_RDR [nlHsVar (maxtag_RDR tycon),
566 nlHsVarApps intDataCon_RDR [ah_RDR]])
567 (illegal_Expr "succ" occ_nm "tried to take `succ' of last tag in enumeration")
568 (nlHsApp (nlHsVar (tag2con_RDR tycon))
569 (nlHsApps plus_RDR [nlHsVarApps intDataCon_RDR [ah_RDR],
573 = mk_easy_FunBind loc pred_RDR [a_Pat] $
574 untag_Expr tycon [(a_RDR, ah_RDR)] $
575 nlHsIf (nlHsApps eq_RDR [nlHsIntLit 0,
576 nlHsVarApps intDataCon_RDR [ah_RDR]])
577 (illegal_Expr "pred" occ_nm "tried to take `pred' of first tag in enumeration")
578 (nlHsApp (nlHsVar (tag2con_RDR tycon))
579 (nlHsApps plus_RDR [nlHsVarApps intDataCon_RDR [ah_RDR],
580 nlHsLit (HsInt (-1))]))
583 = mk_easy_FunBind loc toEnum_RDR [a_Pat] $
584 nlHsIf (nlHsApps and_RDR
585 [nlHsApps ge_RDR [nlHsVar a_RDR, nlHsIntLit 0],
586 nlHsApps le_RDR [nlHsVar a_RDR, nlHsVar (maxtag_RDR tycon)]])
587 (nlHsVarApps (tag2con_RDR tycon) [a_RDR])
588 (illegal_toEnum_tag occ_nm (maxtag_RDR tycon))
591 = mk_easy_FunBind loc enumFrom_RDR [a_Pat] $
592 untag_Expr tycon [(a_RDR, ah_RDR)] $
594 [nlHsVar (tag2con_RDR tycon),
595 nlHsPar (enum_from_to_Expr
596 (nlHsVarApps intDataCon_RDR [ah_RDR])
597 (nlHsVar (maxtag_RDR tycon)))]
600 = mk_easy_FunBind loc enumFromThen_RDR [a_Pat, b_Pat] $
601 untag_Expr tycon [(a_RDR, ah_RDR), (b_RDR, bh_RDR)] $
602 nlHsApp (nlHsVarApps map_RDR [tag2con_RDR tycon]) $
603 nlHsPar (enum_from_then_to_Expr
604 (nlHsVarApps intDataCon_RDR [ah_RDR])
605 (nlHsVarApps intDataCon_RDR [bh_RDR])
606 (nlHsIf (nlHsApps gt_RDR [nlHsVarApps intDataCon_RDR [ah_RDR],
607 nlHsVarApps intDataCon_RDR [bh_RDR]])
609 (nlHsVar (maxtag_RDR tycon))
613 = mk_easy_FunBind loc fromEnum_RDR [a_Pat] $
614 untag_Expr tycon [(a_RDR, ah_RDR)] $
615 (nlHsVarApps intDataCon_RDR [ah_RDR])
618 %************************************************************************
622 %************************************************************************
625 gen_Bounded_binds :: SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds)
626 gen_Bounded_binds loc tycon
627 | isEnumerationTyCon tycon
628 = (listToBag [ min_bound_enum, max_bound_enum ], [])
630 = ASSERT(isSingleton data_cons)
631 (listToBag [ min_bound_1con, max_bound_1con ], [])
633 data_cons = tyConDataCons tycon
635 ----- enum-flavored: ---------------------------
636 min_bound_enum = mkHsVarBind loc minBound_RDR (nlHsVar data_con_1_RDR)
637 max_bound_enum = mkHsVarBind loc maxBound_RDR (nlHsVar data_con_N_RDR)
639 data_con_1 = head data_cons
640 data_con_N = last data_cons
641 data_con_1_RDR = getRdrName data_con_1
642 data_con_N_RDR = getRdrName data_con_N
644 ----- single-constructor-flavored: -------------
645 arity = dataConSourceArity data_con_1
647 min_bound_1con = mkHsVarBind loc minBound_RDR $
648 nlHsVarApps data_con_1_RDR (nOfThem arity minBound_RDR)
649 max_bound_1con = mkHsVarBind loc maxBound_RDR $
650 nlHsVarApps data_con_1_RDR (nOfThem arity maxBound_RDR)
653 %************************************************************************
657 %************************************************************************
659 Deriving @Ix@ is only possible for enumeration types and
660 single-constructor types. We deal with them in turn.
662 For an enumeration type, e.g.,
664 data Foo ... = N1 | N2 | ... | Nn
666 things go not too differently from @Enum@:
668 instance ... Ix (Foo ...) where
670 = map tag2con_Foo [con2tag_Foo a .. con2tag_Foo b]
674 = case (con2tag_Foo a) of { a# ->
675 case (con2tag_Foo b) of { b# ->
676 map tag2con_Foo (enumFromTo (I# a#) (I# b#))
679 -- Generate code for unsafeIndex, becuase using index leads
680 -- to lots of redundant range tests
681 unsafeIndex c@(a, b) d
682 = case (con2tag_Foo d -# con2tag_Foo a) of
687 p_tag = con2tag_Foo c
689 p_tag >= con2tag_Foo a && p_tag <= con2tag_Foo b
693 = case (con2tag_Foo a) of { a_tag ->
694 case (con2tag_Foo b) of { b_tag ->
695 case (con2tag_Foo c) of { c_tag ->
696 if (c_tag >=# a_tag) then
702 (modulo suitable case-ification to handle the unlifted tags)
704 For a single-constructor type (NB: this includes all tuples), e.g.,
706 data Foo ... = MkFoo a b Int Double c c
708 we follow the scheme given in Figure~19 of the Haskell~1.2 report
712 gen_Ix_binds :: SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds)
714 gen_Ix_binds loc tycon
715 | isEnumerationTyCon tycon
716 = (enum_ixes, [GenCon2Tag tycon, GenTag2Con tycon, GenMaxTag tycon])
718 = (single_con_ixes, [GenCon2Tag tycon])
720 --------------------------------------------------------------
721 enum_ixes = listToBag [ enum_range, enum_index, enum_inRange ]
724 = mk_easy_FunBind loc range_RDR [nlTuplePat [a_Pat, b_Pat] Boxed] $
725 untag_Expr tycon [(a_RDR, ah_RDR)] $
726 untag_Expr tycon [(b_RDR, bh_RDR)] $
727 nlHsApp (nlHsVarApps map_RDR [tag2con_RDR tycon]) $
728 nlHsPar (enum_from_to_Expr
729 (nlHsVarApps intDataCon_RDR [ah_RDR])
730 (nlHsVarApps intDataCon_RDR [bh_RDR]))
733 = mk_easy_FunBind loc unsafeIndex_RDR
734 [noLoc (AsPat (noLoc c_RDR)
735 (nlTuplePat [a_Pat, nlWildPat] Boxed)),
737 untag_Expr tycon [(a_RDR, ah_RDR)] (
738 untag_Expr tycon [(d_RDR, dh_RDR)] (
740 rhs = nlHsVarApps intDataCon_RDR [c_RDR]
743 (genOpApp (nlHsVar dh_RDR) minusInt_RDR (nlHsVar ah_RDR))
744 [mkSimpleHsAlt (nlVarPat c_RDR) rhs]
749 = mk_easy_FunBind loc inRange_RDR [nlTuplePat [a_Pat, b_Pat] Boxed, c_Pat] $
750 untag_Expr tycon [(a_RDR, ah_RDR)] (
751 untag_Expr tycon [(b_RDR, bh_RDR)] (
752 untag_Expr tycon [(c_RDR, ch_RDR)] (
753 nlHsIf (genOpApp (nlHsVar ch_RDR) geInt_RDR (nlHsVar ah_RDR)) (
754 (genOpApp (nlHsVar ch_RDR) leInt_RDR (nlHsVar bh_RDR))
759 --------------------------------------------------------------
761 = listToBag [single_con_range, single_con_index, single_con_inRange]
764 = case tyConSingleDataCon_maybe tycon of -- just checking...
765 Nothing -> panic "get_Ix_binds"
768 con_arity = dataConSourceArity data_con
769 data_con_RDR = getRdrName data_con
771 as_needed = take con_arity as_RDRs
772 bs_needed = take con_arity bs_RDRs
773 cs_needed = take con_arity cs_RDRs
775 con_pat xs = nlConVarPat data_con_RDR xs
776 con_expr = nlHsVarApps data_con_RDR cs_needed
778 --------------------------------------------------------------
780 = mk_easy_FunBind loc range_RDR
781 [nlTuplePat [con_pat as_needed, con_pat bs_needed] Boxed] $
782 nlHsDo ListComp stmts con_expr
784 stmts = zipWith3Equal "single_con_range" mk_qual as_needed bs_needed cs_needed
786 mk_qual a b c = noLoc $ mkBindStmt (nlVarPat c)
787 (nlHsApp (nlHsVar range_RDR)
788 (mkLHsVarTuple [a,b]))
792 = mk_easy_FunBind loc unsafeIndex_RDR
793 [nlTuplePat [con_pat as_needed, con_pat bs_needed] Boxed,
795 -- We need to reverse the order we consider the components in
797 -- range (l,u) !! index (l,u) i == i -- when i is in range
798 -- (from http://haskell.org/onlinereport/ix.html) holds.
799 (mk_index (reverse $ zip3 as_needed bs_needed cs_needed))
801 -- index (l1,u1) i1 + rangeSize (l1,u1) * (index (l2,u2) i2 + ...)
802 mk_index [] = nlHsIntLit 0
803 mk_index [(l,u,i)] = mk_one l u i
804 mk_index ((l,u,i) : rest)
809 (nlHsApp (nlHsVar unsafeRangeSize_RDR)
810 (mkLHsVarTuple [l,u]))
811 ) times_RDR (mk_index rest)
814 = nlHsApps unsafeIndex_RDR [mkLHsVarTuple [l,u], nlHsVar i]
818 = mk_easy_FunBind loc inRange_RDR
819 [nlTuplePat [con_pat as_needed, con_pat bs_needed] Boxed,
821 foldl1 and_Expr (zipWith3Equal "single_con_inRange" in_range as_needed bs_needed cs_needed)
823 in_range a b c = nlHsApps inRange_RDR [mkLHsVarTuple [a,b], nlHsVar c]
826 %************************************************************************
830 %************************************************************************
840 instance Read T where
844 do x <- ReadP.step Read.readPrec
845 Symbol "%%" <- Lex.lex
846 y <- ReadP.step Read.readPrec
850 -- Note the "+1" part; "T2 T1 {f1=3}" should parse ok
851 -- Record construction binds even more tightly than application
852 do Ident "T1" <- Lex.lex
854 Ident "f1" <- Lex.lex
856 x <- ReadP.reset Read.readPrec
858 return (T1 { f1 = x }))
861 do Ident "T2" <- Lex.lexP
862 x <- ReadP.step Read.readPrec
866 readListPrec = readListPrecDefault
867 readList = readListDefault
871 gen_Read_binds :: FixityEnv -> SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds)
873 gen_Read_binds get_fixity loc tycon
874 = (listToBag [read_prec, default_readlist, default_readlistprec], [])
876 -----------------------------------------------------------------------
878 = mkHsVarBind loc readList_RDR (nlHsVar readListDefault_RDR)
881 = mkHsVarBind loc readListPrec_RDR (nlHsVar readListPrecDefault_RDR)
882 -----------------------------------------------------------------------
884 data_cons = tyConDataCons tycon
885 (nullary_cons, non_nullary_cons) = partition isNullarySrcDataCon data_cons
887 read_prec = mkHsVarBind loc readPrec_RDR
888 (nlHsApp (nlHsVar parens_RDR) read_cons)
890 read_cons = foldr1 mk_alt (read_nullary_cons ++ read_non_nullary_cons)
891 read_non_nullary_cons = map read_non_nullary_con non_nullary_cons
894 = case nullary_cons of
896 [con] -> [nlHsDo DoExpr (match_con con) (result_expr con [])]
897 _ -> [nlHsApp (nlHsVar choose_RDR)
898 (nlList (map mk_pair nullary_cons))]
899 -- NB For operators the parens around (:=:) are matched by the
900 -- enclosing "parens" call, so here we must match the naked
903 match_con con | isSym con_str = [symbol_pat con_str]
904 | otherwise = ident_h_pat con_str
906 con_str = data_con_str con
907 -- For nullary constructors we must match Ident s for normal constrs
908 -- and Symbol s for operators
910 mk_pair con = mkLHsTupleExpr [nlHsLit (mkHsString (data_con_str con)),
913 read_non_nullary_con data_con
914 | is_infix = mk_parser infix_prec infix_stmts body
915 | is_record = mk_parser record_prec record_stmts body
916 -- Using these two lines instead allows the derived
917 -- read for infix and record bindings to read the prefix form
918 -- | is_infix = mk_alt prefix_parser (mk_parser infix_prec infix_stmts body)
919 -- | is_record = mk_alt prefix_parser (mk_parser record_prec record_stmts body)
920 | otherwise = prefix_parser
922 body = result_expr data_con as_needed
923 con_str = data_con_str data_con
925 prefix_parser = mk_parser prefix_prec prefix_stmts body
928 | isSym con_str = [read_punc "(", symbol_pat con_str, read_punc ")"]
929 | otherwise = ident_h_pat con_str
932 | isSym con_str = [symbol_pat con_str]
933 | otherwise = [read_punc "`"] ++ ident_h_pat con_str ++ [read_punc "`"]
935 prefix_stmts -- T a b c
936 = read_prefix_con ++ read_args
938 infix_stmts -- a %% b, or a `T` b
943 record_stmts -- T { f1 = a, f2 = b }
946 ++ concat (intersperse [read_punc ","] field_stmts)
949 field_stmts = zipWithEqual "lbl_stmts" read_field labels as_needed
951 con_arity = dataConSourceArity data_con
952 labels = dataConFieldLabels data_con
953 dc_nm = getName data_con
954 is_infix = dataConIsInfix data_con
955 is_record = length labels > 0
956 as_needed = take con_arity as_RDRs
957 read_args = zipWithEqual "gen_Read_binds" read_arg as_needed (dataConOrigArgTys data_con)
958 (read_a1:read_a2:_) = read_args
960 prefix_prec = appPrecedence
961 infix_prec = getPrecedence get_fixity dc_nm
962 record_prec = appPrecedence + 1 -- Record construction binds even more tightly
963 -- than application; e.g. T2 T1 {x=2} means T2 (T1 {x=2})
965 ------------------------------------------------------------------------
967 ------------------------------------------------------------------------
968 mk_alt e1 e2 = genOpApp e1 alt_RDR e2 -- e1 +++ e2
969 mk_parser p ss b = nlHsApps prec_RDR [nlHsIntLit p, nlHsDo DoExpr ss b] -- prec p (do { ss ; b })
970 bindLex pat = noLoc (mkBindStmt pat (nlHsVar lexP_RDR)) -- pat <- lexP
971 con_app con as = nlHsVarApps (getRdrName con) as -- con as
972 result_expr con as = nlHsApp (nlHsVar returnM_RDR) (con_app con as) -- return (con as)
974 punc_pat s = nlConPat punc_RDR [nlLitPat (mkHsString s)] -- Punc 'c'
976 -- For constructors and field labels ending in '#', we hackily
977 -- let the lexer generate two tokens, and look for both in sequence
978 -- Thus [Ident "I"; Symbol "#"]. See Trac #5041
979 ident_h_pat s | Just (ss, '#') <- snocView s = [ ident_pat ss, symbol_pat "#" ]
980 | otherwise = [ ident_pat s ]
982 ident_pat s = bindLex $ nlConPat ident_RDR [nlLitPat (mkHsString s)] -- Ident "foo" <- lexP
983 symbol_pat s = bindLex $ nlConPat symbol_RDR [nlLitPat (mkHsString s)] -- Symbol ">>" <- lexP
985 data_con_str con = occNameString (getOccName con)
987 read_punc c = bindLex (punc_pat c)
988 read_arg a ty = ASSERT( not (isUnLiftedType ty) )
989 noLoc (mkBindStmt (nlVarPat a) (nlHsVarApps step_RDR [readPrec_RDR]))
991 read_field lbl a = read_lbl lbl ++
993 noLoc (mkBindStmt (nlVarPat a) (nlHsVarApps reset_RDR [readPrec_RDR]))]
995 -- When reading field labels we might encounter
1000 read_lbl lbl | isSym lbl_str
1001 = [read_punc "(", symbol_pat lbl_str, read_punc ")"]
1003 = ident_h_pat lbl_str
1005 lbl_str = occNameString (getOccName lbl)
1009 %************************************************************************
1013 %************************************************************************
1019 data Tree a = Leaf a | Tree a :^: Tree a
1021 instance (Show a) => Show (Tree a) where
1023 showsPrec d (Leaf m) = showParen (d > app_prec) showStr
1025 showStr = showString "Leaf " . showsPrec (app_prec+1) m
1027 showsPrec d (u :^: v) = showParen (d > up_prec) showStr
1029 showStr = showsPrec (up_prec+1) u .
1030 showString " :^: " .
1031 showsPrec (up_prec+1) v
1032 -- Note: right-associativity of :^: ignored
1034 up_prec = 5 -- Precedence of :^:
1035 app_prec = 10 -- Application has precedence one more than
1036 -- the most tightly-binding operator
1039 gen_Show_binds :: FixityEnv -> SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds)
1041 gen_Show_binds get_fixity loc tycon
1042 = (listToBag [shows_prec, show_list], [])
1044 -----------------------------------------------------------------------
1045 show_list = mkHsVarBind loc showList_RDR
1046 (nlHsApp (nlHsVar showList___RDR) (nlHsPar (nlHsApp (nlHsVar showsPrec_RDR) (nlHsIntLit 0))))
1047 -----------------------------------------------------------------------
1048 data_cons = tyConDataCons tycon
1049 shows_prec = mk_FunBind loc showsPrec_RDR (map pats_etc data_cons)
1052 | nullary_con = -- skip the showParen junk...
1053 ASSERT(null bs_needed)
1054 ([nlWildPat, con_pat], mk_showString_app op_con_str)
1057 showParen_Expr (nlHsPar (genOpApp a_Expr ge_RDR (nlHsLit (HsInt con_prec_plus_one))))
1058 (nlHsPar (nested_compose_Expr show_thingies)))
1060 data_con_RDR = getRdrName data_con
1061 con_arity = dataConSourceArity data_con
1062 bs_needed = take con_arity bs_RDRs
1063 arg_tys = dataConOrigArgTys data_con -- Correspond 1-1 with bs_needed
1064 con_pat = nlConVarPat data_con_RDR bs_needed
1065 nullary_con = con_arity == 0
1066 labels = dataConFieldLabels data_con
1067 lab_fields = length labels
1068 record_syntax = lab_fields > 0
1070 dc_nm = getName data_con
1071 dc_occ_nm = getOccName data_con
1072 con_str = occNameString dc_occ_nm
1073 op_con_str = wrapOpParens con_str
1074 backquote_str = wrapOpBackquotes con_str
1077 | is_infix = [show_arg1, mk_showString_app (" " ++ backquote_str ++ " "), show_arg2]
1078 | record_syntax = mk_showString_app (op_con_str ++ " {") :
1079 show_record_args ++ [mk_showString_app "}"]
1080 | otherwise = mk_showString_app (op_con_str ++ " ") : show_prefix_args
1082 show_label l = mk_showString_app (nm ++ " = ")
1083 -- Note the spaces around the "=" sign. If we don't have them
1084 -- then we get Foo { x=-1 } and the "=-" parses as a single
1085 -- lexeme. Only the space after the '=' is necessary, but
1086 -- it seems tidier to have them both sides.
1088 occ_nm = getOccName l
1089 nm = wrapOpParens (occNameString occ_nm)
1091 show_args = zipWith show_arg bs_needed arg_tys
1092 (show_arg1:show_arg2:_) = show_args
1093 show_prefix_args = intersperse (nlHsVar showSpace_RDR) show_args
1095 -- Assumption for record syntax: no of fields == no of labelled fields
1096 -- (and in same order)
1097 show_record_args = concat $
1098 intersperse [mk_showString_app ", "] $
1099 [ [show_label lbl, arg]
1100 | (lbl,arg) <- zipEqual "gen_Show_binds"
1103 -- Generates (showsPrec p x) for argument x, but it also boxes
1104 -- the argument first if necessary. Note that this prints unboxed
1105 -- things without any '#' decorations; could change that if need be
1106 show_arg b arg_ty = nlHsApps showsPrec_RDR [nlHsLit (HsInt arg_prec),
1107 box_if_necy "Show" tycon (nlHsVar b) arg_ty]
1110 is_infix = dataConIsInfix data_con
1111 con_prec_plus_one = 1 + getPrec is_infix get_fixity dc_nm
1112 arg_prec | record_syntax = 0 -- Record fields don't need parens
1113 | otherwise = con_prec_plus_one
1115 wrapOpParens :: String -> String
1116 wrapOpParens s | isSym s = '(' : s ++ ")"
1119 wrapOpBackquotes :: String -> String
1120 wrapOpBackquotes s | isSym s = s
1121 | otherwise = '`' : s ++ "`"
1123 isSym :: String -> Bool
1125 isSym (c : _) = startsVarSym c || startsConSym c
1127 mk_showString_app :: String -> LHsExpr RdrName
1128 mk_showString_app str = nlHsApp (nlHsVar showString_RDR) (nlHsLit (mkHsString str))
1132 getPrec :: Bool -> FixityEnv -> Name -> Integer
1133 getPrec is_infix get_fixity nm
1134 | not is_infix = appPrecedence
1135 | otherwise = getPrecedence get_fixity nm
1137 appPrecedence :: Integer
1138 appPrecedence = fromIntegral maxPrecedence + 1
1139 -- One more than the precedence of the most
1140 -- tightly-binding operator
1142 getPrecedence :: FixityEnv -> Name -> Integer
1143 getPrecedence get_fixity nm
1144 = case lookupFixity get_fixity nm of
1145 Fixity x _assoc -> fromIntegral x
1146 -- NB: the Report says that associativity is not taken
1147 -- into account for either Read or Show; hence we
1148 -- ignore associativity here
1152 %************************************************************************
1154 \subsection{Typeable}
1156 %************************************************************************
1164 instance Typeable2 T where
1165 typeOf2 _ = mkTyConApp (mkTyConRep "T") []
1167 We are passed the Typeable2 class as well as T
1170 gen_Typeable_binds :: SrcSpan -> TyCon -> LHsBinds RdrName
1171 gen_Typeable_binds loc tycon
1174 (mk_typeOf_RDR tycon) -- Name of appropriate type0f function
1176 (nlHsApps mkTypeRep_RDR [tycon_rep, nlList []])
1178 tycon_rep = nlHsVar mkTyConRep_RDR `nlHsApp` nlHsLit (mkHsString (showSDocOneLine (ppr tycon)))
1180 mk_typeOf_RDR :: TyCon -> RdrName
1181 -- Use the arity of the TyCon to make the right typeOfn function
1182 mk_typeOf_RDR tycon = varQual_RDR tYPEABLE (mkFastString ("typeOf" ++ suffix))
1184 arity = tyConArity tycon
1185 suffix | arity == 0 = ""
1186 | otherwise = show arity
1191 %************************************************************************
1195 %************************************************************************
1199 data T a b = T1 a b | T2
1203 $cT1 = mkDataCon $dT "T1" Prefix
1204 $cT2 = mkDataCon $dT "T2" Prefix
1205 $dT = mkDataType "Module.T" [] [$con_T1, $con_T2]
1206 -- the [] is for field labels.
1208 instance (Data a, Data b) => Data (T a b) where
1209 gfoldl k z (T1 a b) = z T `k` a `k` b
1210 gfoldl k z T2 = z T2
1211 -- ToDo: add gmapT,Q,M, gfoldr
1213 gunfold k z c = case conIndex c of
1214 I# 1# -> k (k (z T1))
1217 toConstr (T1 _ _) = $cT1
1222 dataCast1 = gcast1 -- If T :: * -> *
1223 dataCast2 = gcast2 -- if T :: * -> * -> *
1227 gen_Data_binds :: SrcSpan
1229 -> (LHsBinds RdrName, -- The method bindings
1230 DerivAuxBinds) -- Auxiliary bindings
1231 gen_Data_binds loc tycon
1232 = (listToBag [gfoldl_bind, gunfold_bind, toCon_bind, dataTypeOf_bind]
1233 `unionBags` gcast_binds,
1234 -- Auxiliary definitions: the data type and constructors
1235 MkTyCon tycon : map MkDataCon data_cons)
1237 data_cons = tyConDataCons tycon
1238 n_cons = length data_cons
1239 one_constr = n_cons == 1
1242 gfoldl_bind = mk_FunBind loc gfoldl_RDR (map gfoldl_eqn data_cons)
1245 = ([nlVarPat k_RDR, nlVarPat z_RDR, nlConVarPat con_name as_needed],
1246 foldl mk_k_app (nlHsVar z_RDR `nlHsApp` nlHsVar con_name) as_needed)
1249 con_name = getRdrName con
1250 as_needed = take (dataConSourceArity con) as_RDRs
1251 mk_k_app e v = nlHsPar (nlHsOpApp e k_RDR (nlHsVar v))
1253 ------------ gunfold
1254 gunfold_bind = mk_FunBind loc
1256 [([k_Pat, z_Pat, if one_constr then nlWildPat else c_Pat],
1260 | one_constr = mk_unfold_rhs (head data_cons) -- No need for case
1261 | otherwise = nlHsCase (nlHsVar conIndex_RDR `nlHsApp` c_Expr)
1262 (map gunfold_alt data_cons)
1264 gunfold_alt dc = mkSimpleHsAlt (mk_unfold_pat dc) (mk_unfold_rhs dc)
1265 mk_unfold_rhs dc = foldr nlHsApp
1266 (nlHsVar z_RDR `nlHsApp` nlHsVar (getRdrName dc))
1267 (replicate (dataConSourceArity dc) (nlHsVar k_RDR))
1269 mk_unfold_pat dc -- Last one is a wild-pat, to avoid
1270 -- redundant test, and annoying warning
1271 | tag-fIRST_TAG == n_cons-1 = nlWildPat -- Last constructor
1272 | otherwise = nlConPat intDataCon_RDR [nlLitPat (HsIntPrim (toInteger tag))]
1276 ------------ toConstr
1277 toCon_bind = mk_FunBind loc toConstr_RDR (map to_con_eqn data_cons)
1278 to_con_eqn dc = ([nlWildConPat dc], nlHsVar (mk_constr_name dc))
1280 ------------ dataTypeOf
1281 dataTypeOf_bind = mk_easy_FunBind
1285 (nlHsVar (mk_data_type_name tycon))
1287 ------------ gcast1/2
1288 tycon_kind = tyConKind tycon
1289 gcast_binds | tycon_kind `eqKind` kind1 = mk_gcast dataCast1_RDR gcast1_RDR
1290 | tycon_kind `eqKind` kind2 = mk_gcast dataCast2_RDR gcast2_RDR
1291 | otherwise = emptyBag
1292 mk_gcast dataCast_RDR gcast_RDR
1293 = unitBag (mk_easy_FunBind loc dataCast_RDR [nlVarPat f_RDR]
1294 (nlHsVar gcast_RDR `nlHsApp` nlHsVar f_RDR))
1297 kind1, kind2 :: Kind
1298 kind1 = liftedTypeKind `mkArrowKind` liftedTypeKind
1299 kind2 = liftedTypeKind `mkArrowKind` kind1
1301 gfoldl_RDR, gunfold_RDR, toConstr_RDR, dataTypeOf_RDR, mkConstr_RDR,
1302 mkDataType_RDR, conIndex_RDR, prefix_RDR, infix_RDR,
1303 dataCast1_RDR, dataCast2_RDR, gcast1_RDR, gcast2_RDR,
1304 constr_RDR, dataType_RDR :: RdrName
1305 gfoldl_RDR = varQual_RDR gENERICS (fsLit "gfoldl")
1306 gunfold_RDR = varQual_RDR gENERICS (fsLit "gunfold")
1307 toConstr_RDR = varQual_RDR gENERICS (fsLit "toConstr")
1308 dataTypeOf_RDR = varQual_RDR gENERICS (fsLit "dataTypeOf")
1309 dataCast1_RDR = varQual_RDR gENERICS (fsLit "dataCast1")
1310 dataCast2_RDR = varQual_RDR gENERICS (fsLit "dataCast2")
1311 gcast1_RDR = varQual_RDR tYPEABLE (fsLit "gcast1")
1312 gcast2_RDR = varQual_RDR tYPEABLE (fsLit "gcast2")
1313 mkConstr_RDR = varQual_RDR gENERICS (fsLit "mkConstr")
1314 constr_RDR = tcQual_RDR gENERICS (fsLit "Constr")
1315 mkDataType_RDR = varQual_RDR gENERICS (fsLit "mkDataType")
1316 dataType_RDR = tcQual_RDR gENERICS (fsLit "DataType")
1317 conIndex_RDR = varQual_RDR gENERICS (fsLit "constrIndex")
1318 prefix_RDR = dataQual_RDR gENERICS (fsLit "Prefix")
1319 infix_RDR = dataQual_RDR gENERICS (fsLit "Infix")
1324 %************************************************************************
1328 see http://www.mail-archive.com/haskell-prime@haskell.org/msg02116.html
1331 %************************************************************************
1335 data T a = T1 Int a | T2 (T a)
1337 We generate the instance:
1339 instance Functor T where
1340 fmap f (T1 b1 a) = T1 b1 (f a)
1341 fmap f (T2 ta) = T2 (fmap f ta)
1343 Notice that we don't simply apply 'fmap' to the constructor arguments.
1345 - Do nothing to an argument whose type doesn't mention 'a'
1346 - Apply 'f' to an argument of type 'a'
1347 - Apply 'fmap f' to other arguments
1348 That's why we have to recurse deeply into the constructor argument types,
1349 rather than just one level, as we typically do.
1351 What about types with more than one type parameter? In general, we only
1352 derive Functor for the last position:
1354 data S a b = S1 [b] | S2 (a, T a b)
1355 instance Functor (S a) where
1356 fmap f (S1 bs) = S1 (fmap f bs)
1357 fmap f (S2 (p,q)) = S2 (a, fmap f q)
1359 However, we have special cases for
1363 More formally, we write the derivation of fmap code over type variable
1364 'a for type 'b as ($fmap 'a 'b). In this general notation the derived
1367 instance Functor T where
1368 fmap f (T1 x1 x2) = T1 ($(fmap 'a 'b1) x1) ($(fmap 'a 'a) x2)
1369 fmap f (T2 x1) = T2 ($(fmap 'a '(T a)) x1)
1371 $(fmap 'a 'b) x = x -- when b does not contain a
1372 $(fmap 'a 'a) x = f x
1373 $(fmap 'a '(b1,b2)) x = case x of (x1,x2) -> ($(fmap 'a 'b1) x1, $(fmap 'a 'b2) x2)
1374 $(fmap 'a '(T b1 b2)) x = fmap $(fmap 'a 'b2) x -- when a only occurs in the last parameter, b2
1375 $(fmap 'a '(b -> c)) x = \b -> $(fmap 'a' 'c) (x ($(cofmap 'a 'b) b))
1377 For functions, the type parameter 'a can occur in a contravariant position,
1378 which means we need to derive a function like:
1380 cofmap :: (a -> b) -> (f b -> f a)
1382 This is pretty much the same as $fmap, only without the $(cofmap 'a 'a) case:
1384 $(cofmap 'a 'b) x = x -- when b does not contain a
1385 $(cofmap 'a 'a) x = error "type variable in contravariant position"
1386 $(cofmap 'a '(b1,b2)) x = case x of (x1,x2) -> ($(cofmap 'a 'b1) x1, $(cofmap 'a 'b2) x2)
1387 $(cofmap 'a '[b]) x = map $(cofmap 'a 'b) x
1388 $(cofmap 'a '(T b1 b2)) x = fmap $(cofmap 'a 'b2) x -- when a only occurs in the last parameter, b2
1389 $(cofmap 'a '(b -> c)) x = \b -> $(cofmap 'a' 'c) (x ($(fmap 'a 'c) b))
1392 gen_Functor_binds :: SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds)
1393 gen_Functor_binds loc tycon
1394 = (unitBag fmap_bind, [])
1396 data_cons = tyConDataCons tycon
1397 fmap_bind = L loc $ mkRdrFunBind (L loc fmap_RDR) eqns
1399 fmap_eqn con = evalState (match_for_con [f_Pat] con parts) bs_RDRs
1401 parts = foldDataConArgs ft_fmap con
1403 eqns | null data_cons = [mkSimpleMatch [nlWildPat, nlWildPat]
1404 (error_Expr "Void fmap")]
1405 | otherwise = map fmap_eqn data_cons
1407 ft_fmap :: FFoldType (LHsExpr RdrName -> State [RdrName] (LHsExpr RdrName))
1408 -- Tricky higher order type; I can't say I fully understand this code :-(
1409 ft_fmap = FT { ft_triv = \x -> return x -- fmap f x = x
1410 , ft_var = \x -> return (nlHsApp f_Expr x) -- fmap f x = f x
1411 , ft_fun = \g h x -> mkSimpleLam (\b -> h =<< (nlHsApp x `fmap` g b))
1412 -- fmap f x = \b -> h (x (g b))
1413 , ft_tup = mkSimpleTupleCase match_for_con -- fmap f x = case x of (a1,a2,..) -> (g1 a1,g2 a2,..)
1414 , ft_ty_app = \_ g x -> do gg <- mkSimpleLam g -- fmap f x = fmap g x
1415 return $ nlHsApps fmap_RDR [gg,x]
1416 , ft_forall = \_ g x -> g x
1417 , ft_bad_app = panic "in other argument"
1418 , ft_co_var = panic "contravariant" }
1420 match_for_con = mkSimpleConMatch $
1421 \con_name xsM -> do xs <- sequence xsM
1422 return (nlHsApps con_name xs) -- Con (g1 v1) (g2 v2) ..
1425 Utility functions related to Functor deriving.
1427 Since several things use the same pattern of traversal, this is abstracted into functorLikeTraverse.
1428 This function works like a fold: it makes a value of type 'a' in a bottom up way.
1431 -- Generic traversal for Functor deriving
1432 data FFoldType a -- Describes how to fold over a Type in a functor like way
1433 = FT { ft_triv :: a -- Does not contain variable
1434 , ft_var :: a -- The variable itself
1435 , ft_co_var :: a -- The variable itself, contravariantly
1436 , ft_fun :: a -> a -> a -- Function type
1437 , ft_tup :: Boxity -> [a] -> a -- Tuple type
1438 , ft_ty_app :: Type -> a -> a -- Type app, variable only in last argument
1439 , ft_bad_app :: a -- Type app, variable other than in last argument
1440 , ft_forall :: TcTyVar -> a -> a -- Forall type
1443 functorLikeTraverse :: TyVar -- ^ Variable to look for
1444 -> FFoldType a -- ^ How to fold
1445 -> Type -- ^ Type to process
1447 functorLikeTraverse var (FT { ft_triv = caseTrivial, ft_var = caseVar
1448 , ft_co_var = caseCoVar, ft_fun = caseFun
1449 , ft_tup = caseTuple, ft_ty_app = caseTyApp
1450 , ft_bad_app = caseWrongArg, ft_forall = caseForAll })
1453 where -- go returns (result of type a, does type contain var)
1454 go co ty | Just ty' <- coreView ty = go co ty'
1455 go co (TyVarTy v) | v == var = (if co then caseCoVar else caseVar,True)
1456 go co (FunTy (PredTy _) b) = go co b
1457 go co (FunTy x y) | xc || yc = (caseFun xr yr,True)
1458 where (xr,xc) = go (not co) x
1460 go co (AppTy x y) | xc = (caseWrongArg, True)
1461 | yc = (caseTyApp x yr, True)
1462 where (_, xc) = go co x
1464 go co ty@(TyConApp con args)
1465 | not (or xcs) = (caseTrivial, False) -- Variable does not occur
1466 -- At this point we know that xrs, xcs is not empty,
1467 -- and at least one xr is True
1468 | isTupleTyCon con = (caseTuple (tupleTyConBoxity con) xrs, True)
1469 | or (init xcs) = (caseWrongArg, True) -- T (..var..) ty
1470 | otherwise = -- T (..no var..) ty
1471 (caseTyApp (fst (splitAppTy ty)) (last xrs), True)
1472 where (xrs,xcs) = unzip (map (go co) args)
1473 go co (ForAllTy v x) | v /= var && xc = (caseForAll v xr,True)
1474 where (xr,xc) = go co x
1475 go _ _ = (caseTrivial,False)
1477 -- Return all syntactic subterms of ty that contain var somewhere
1478 -- These are the things that should appear in instance constraints
1479 deepSubtypesContaining :: TyVar -> Type -> [TcType]
1480 deepSubtypesContaining tv
1481 = functorLikeTraverse tv
1484 , ft_fun = (++), ft_tup = \_ xs -> concat xs
1486 , ft_bad_app = panic "in other argument"
1487 , ft_co_var = panic "contravariant"
1488 , ft_forall = \v xs -> filterOut ((v `elemVarSet`) . tyVarsOfType) xs })
1491 foldDataConArgs :: FFoldType a -> DataCon -> [a]
1492 -- Fold over the arguments of the datacon
1493 foldDataConArgs ft con
1494 = map (functorLikeTraverse tv ft) (dataConOrigArgTys con)
1496 tv = last (dataConUnivTyVars con)
1497 -- Argument to derive for, 'a in the above description
1498 -- The validity checks have ensured that con is
1499 -- a vanilla data constructor
1501 -- Make a HsLam using a fresh variable from a State monad
1502 mkSimpleLam :: (LHsExpr id -> State [id] (LHsExpr id)) -> State [id] (LHsExpr id)
1503 -- (mkSimpleLam fn) returns (\x. fn(x))
1504 mkSimpleLam lam = do
1507 body <- lam (nlHsVar n)
1508 return (mkHsLam [nlVarPat n] body)
1510 mkSimpleLam2 :: (LHsExpr id -> LHsExpr id -> State [id] (LHsExpr id)) -> State [id] (LHsExpr id)
1511 mkSimpleLam2 lam = do
1512 (n1:n2:names) <- get
1514 body <- lam (nlHsVar n1) (nlHsVar n2)
1515 return (mkHsLam [nlVarPat n1,nlVarPat n2] body)
1517 -- "Con a1 a2 a3 -> fold [x1 a1, x2 a2, x3 a3]"
1518 mkSimpleConMatch :: Monad m => (RdrName -> [a] -> m (LHsExpr RdrName)) -> [LPat RdrName] -> DataCon -> [LHsExpr RdrName -> a] -> m (LMatch RdrName)
1519 mkSimpleConMatch fold extra_pats con insides = do
1520 let con_name = getRdrName con
1521 let vars_needed = takeList insides as_RDRs
1522 let pat = nlConVarPat con_name vars_needed
1523 rhs <- fold con_name (zipWith ($) insides (map nlHsVar vars_needed))
1524 return $ mkMatch (extra_pats ++ [pat]) rhs emptyLocalBinds
1526 -- "case x of (a1,a2,a3) -> fold [x1 a1, x2 a2, x3 a3]"
1527 mkSimpleTupleCase :: Monad m => ([LPat RdrName] -> DataCon -> [LHsExpr RdrName -> a] -> m (LMatch RdrName))
1528 -> Boxity -> [LHsExpr RdrName -> a] -> LHsExpr RdrName -> m (LHsExpr RdrName)
1529 mkSimpleTupleCase match_for_con boxity insides x = do
1530 let con = tupleCon boxity (length insides)
1531 match <- match_for_con [] con insides
1532 return $ nlHsCase x [match]
1536 %************************************************************************
1540 see http://www.mail-archive.com/haskell-prime@haskell.org/msg02116.html
1543 %************************************************************************
1545 Deriving Foldable instances works the same way as Functor instances,
1546 only Foldable instances are not possible for function types at all.
1547 Here the derived instance for the type T above is:
1549 instance Foldable T where
1550 foldr f z (T1 x1 x2 x3) = $(foldr 'a 'b1) x1 ( $(foldr 'a 'a) x2 ( $(foldr 'a 'b2) x3 z ) )
1554 $(foldr 'a 'b) x z = z -- when b does not contain a
1555 $(foldr 'a 'a) x z = f x z
1556 $(foldr 'a '(b1,b2)) x z = case x of (x1,x2) -> $(foldr 'a 'b1) x1 ( $(foldr 'a 'b2) x2 z )
1557 $(foldr 'a '(T b1 b2)) x z = foldr $(foldr 'a 'b2) x z -- when a only occurs in the last parameter, b2
1559 Note that the arguments to the real foldr function are the wrong way around,
1560 since (f :: a -> b -> b), while (foldr f :: b -> t a -> b).
1563 gen_Foldable_binds :: SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds)
1564 gen_Foldable_binds loc tycon
1565 = (unitBag foldr_bind, [])
1567 data_cons = tyConDataCons tycon
1569 foldr_bind = L loc $ mkRdrFunBind (L loc foldable_foldr_RDR) eqns
1570 eqns = map foldr_eqn data_cons
1571 foldr_eqn con = evalState (match_for_con z_Expr [f_Pat,z_Pat] con parts) bs_RDRs
1573 parts = foldDataConArgs ft_foldr con
1575 ft_foldr :: FFoldType (LHsExpr RdrName -> LHsExpr RdrName -> State [RdrName] (LHsExpr RdrName))
1576 ft_foldr = FT { ft_triv = \_ z -> return z -- foldr f z x = z
1577 , ft_var = \x z -> return (nlHsApps f_RDR [x,z]) -- foldr f z x = f x z
1578 , ft_tup = \b gs x z -> mkSimpleTupleCase (match_for_con z) b gs x
1579 , ft_ty_app = \_ g x z -> do gg <- mkSimpleLam2 g -- foldr f z x = foldr (\xx zz -> g xx zz) z x
1580 return $ nlHsApps foldable_foldr_RDR [gg,z,x]
1581 , ft_forall = \_ g x z -> g x z
1582 , ft_co_var = panic "covariant"
1583 , ft_fun = panic "function"
1584 , ft_bad_app = panic "in other argument" }
1586 match_for_con z = mkSimpleConMatch (\_con_name -> foldrM ($) z) -- g1 v1 (g2 v2 (.. z))
1590 %************************************************************************
1592 Traversable instances
1594 see http://www.mail-archive.com/haskell-prime@haskell.org/msg02116.html
1596 %************************************************************************
1598 Again, Traversable is much like Functor and Foldable.
1602 $(traverse 'a 'b) x = pure x -- when b does not contain a
1603 $(traverse 'a 'a) x = f x
1604 $(traverse 'a '(b1,b2)) x = case x of (x1,x2) -> (,) <$> $(traverse 'a 'b1) x1 <*> $(traverse 'a 'b2) x2
1605 $(traverse 'a '(T b1 b2)) x = traverse $(traverse 'a 'b2) x -- when a only occurs in the last parameter, b2
1607 Note that the generated code is not as efficient as it could be. For instance:
1609 data T a = T Int a deriving Traversable
1611 gives the function: traverse f (T x y) = T <$> pure x <*> f y
1612 instead of: traverse f (T x y) = T x <$> f y
1615 gen_Traversable_binds :: SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds)
1616 gen_Traversable_binds loc tycon
1617 = (unitBag traverse_bind, [])
1619 data_cons = tyConDataCons tycon
1621 traverse_bind = L loc $ mkRdrFunBind (L loc traverse_RDR) eqns
1622 eqns = map traverse_eqn data_cons
1623 traverse_eqn con = evalState (match_for_con [f_Pat] con parts) bs_RDRs
1625 parts = foldDataConArgs ft_trav con
1628 ft_trav :: FFoldType (LHsExpr RdrName -> State [RdrName] (LHsExpr RdrName))
1629 ft_trav = FT { ft_triv = \x -> return (nlHsApps pure_RDR [x]) -- traverse f x = pure x
1630 , ft_var = \x -> return (nlHsApps f_RDR [x]) -- travese f x = f x
1631 , ft_tup = mkSimpleTupleCase match_for_con -- travese f x z = case x of (a1,a2,..) ->
1632 -- (,,) <$> g1 a1 <*> g2 a2 <*> ..
1633 , ft_ty_app = \_ g x -> do gg <- mkSimpleLam g -- travese f x = travese (\xx -> g xx) x
1634 return $ nlHsApps traverse_RDR [gg,x]
1635 , ft_forall = \_ g x -> g x
1636 , ft_co_var = panic "covariant"
1637 , ft_fun = panic "function"
1638 , ft_bad_app = panic "in other argument" }
1640 match_for_con = mkSimpleConMatch $
1641 \con_name xsM -> do xs <- sequence xsM
1642 return (mkApCon (nlHsVar con_name) xs)
1644 -- ((Con <$> x1) <*> x2) <*> ..
1645 mkApCon con [] = nlHsApps pure_RDR [con]
1646 mkApCon con (x:xs) = foldl appAp (nlHsApps fmap_RDR [con,x]) xs
1647 where appAp x y = nlHsApps ap_RDR [x,y]
1652 %************************************************************************
1654 \subsection{Generating extra binds (@con2tag@ and @tag2con@)}
1656 %************************************************************************
1661 con2tag_Foo :: Foo ... -> Int#
1662 tag2con_Foo :: Int -> Foo ... -- easier if Int, not Int#
1663 maxtag_Foo :: Int -- ditto (NB: not unlifted)
1666 The `tags' here start at zero, hence the @fIRST_TAG@ (currently one)
1670 genAuxBind :: SrcSpan -> DerivAuxBind -> (LHsBind RdrName, LSig RdrName)
1671 genAuxBind loc (GenCon2Tag tycon)
1672 = (mk_FunBind loc rdr_name eqns,
1673 L loc (TypeSig (L loc rdr_name) (L loc sig_ty)))
1675 rdr_name = con2tag_RDR tycon
1678 mkSigmaTy (tyConTyVars tycon) (tyConStupidTheta tycon) $
1679 mkParentType tycon `mkFunTy` intPrimTy
1681 lots_of_constructors = tyConFamilySize tycon > 8
1682 -- was: mAX_FAMILY_SIZE_FOR_VEC_RETURNS
1683 -- but we don't do vectored returns any more.
1685 eqns | lots_of_constructors = [get_tag_eqn]
1686 | otherwise = map mk_eqn (tyConDataCons tycon)
1688 get_tag_eqn = ([nlVarPat a_RDR], nlHsApp (nlHsVar getTag_RDR) a_Expr)
1690 mk_eqn :: DataCon -> ([LPat RdrName], LHsExpr RdrName)
1691 mk_eqn con = ([nlWildConPat con],
1692 nlHsLit (HsIntPrim (toInteger ((dataConTag con) - fIRST_TAG))))
1694 genAuxBind loc (GenTag2Con tycon)
1695 = (mk_FunBind loc rdr_name
1696 [([nlConVarPat intDataCon_RDR [a_RDR]],
1697 nlHsApp (nlHsVar tagToEnum_RDR) a_Expr)],
1698 L loc (TypeSig (L loc rdr_name) (L loc sig_ty)))
1700 sig_ty = HsCoreTy $ mkForAllTys (tyConTyVars tycon) $
1701 intTy `mkFunTy` mkParentType tycon
1703 rdr_name = tag2con_RDR tycon
1705 genAuxBind loc (GenMaxTag tycon)
1706 = (mkHsVarBind loc rdr_name rhs,
1707 L loc (TypeSig (L loc rdr_name) (L loc sig_ty)))
1709 rdr_name = maxtag_RDR tycon
1710 sig_ty = HsCoreTy intTy
1711 rhs = nlHsApp (nlHsVar intDataCon_RDR) (nlHsLit (HsIntPrim max_tag))
1712 max_tag = case (tyConDataCons tycon) of
1713 data_cons -> toInteger ((length data_cons) - fIRST_TAG)
1715 genAuxBind loc (MkTyCon tycon) -- $dT
1716 = (mkHsVarBind loc rdr_name rhs,
1717 L loc (TypeSig (L loc rdr_name) sig_ty))
1719 rdr_name = mk_data_type_name tycon
1720 sig_ty = nlHsTyVar dataType_RDR
1721 constrs = [nlHsVar (mk_constr_name con) | con <- tyConDataCons tycon]
1722 rhs = nlHsVar mkDataType_RDR
1723 `nlHsApp` nlHsLit (mkHsString (showSDocOneLine (ppr tycon)))
1724 `nlHsApp` nlList constrs
1726 genAuxBind loc (MkDataCon dc) -- $cT1 etc
1727 = (mkHsVarBind loc rdr_name rhs,
1728 L loc (TypeSig (L loc rdr_name) sig_ty))
1730 rdr_name = mk_constr_name dc
1731 sig_ty = nlHsTyVar constr_RDR
1732 rhs = nlHsApps mkConstr_RDR constr_args
1735 = [ -- nlHsIntLit (toInteger (dataConTag dc)), -- Tag
1736 nlHsVar (mk_data_type_name (dataConTyCon dc)), -- DataType
1737 nlHsLit (mkHsString (occNameString dc_occ)), -- String name
1738 nlList labels, -- Field labels
1739 nlHsVar fixity] -- Fixity
1741 labels = map (nlHsLit . mkHsString . getOccString)
1742 (dataConFieldLabels dc)
1743 dc_occ = getOccName dc
1744 is_infix = isDataSymOcc dc_occ
1745 fixity | is_infix = infix_RDR
1746 | otherwise = prefix_RDR
1748 mk_data_type_name :: TyCon -> RdrName -- "$tT"
1749 mk_data_type_name tycon = mkAuxBinderName (tyConName tycon) mkDataTOcc
1751 mk_constr_name :: DataCon -> RdrName -- "$cC"
1752 mk_constr_name con = mkAuxBinderName (dataConName con) mkDataCOcc
1754 mkParentType :: TyCon -> Type
1755 -- Turn the representation tycon of a family into
1756 -- a use of its family constructor
1758 = case tyConFamInst_maybe tc of
1759 Nothing -> mkTyConApp tc (mkTyVarTys (tyConTyVars tc))
1760 Just (fam_tc,tys) -> mkTyConApp fam_tc tys
1763 %************************************************************************
1765 \subsection{Utility bits for generating bindings}
1767 %************************************************************************
1771 mk_FunBind :: SrcSpan -> RdrName
1772 -> [([LPat RdrName], LHsExpr RdrName)]
1774 mk_FunBind loc fun pats_and_exprs
1775 = L loc $ mkRdrFunBind (L loc fun) matches
1777 matches = [mkMatch p e emptyLocalBinds | (p,e) <-pats_and_exprs]
1779 mkRdrFunBind :: Located RdrName -> [LMatch RdrName] -> HsBind RdrName
1780 mkRdrFunBind fun@(L _ fun_rdr) matches
1781 | null matches = mkFunBind fun [mkMatch [] (error_Expr str) emptyLocalBinds]
1782 -- Catch-all eqn looks like
1783 -- fmap = error "Void fmap"
1784 -- It's needed if there no data cons at all,
1785 -- which can happen with -XEmptyDataDecls
1787 | otherwise = mkFunBind fun matches
1789 str = "Void " ++ occNameString (rdrNameOcc fun_rdr)
1793 box_if_necy :: String -- The class involved
1794 -> TyCon -- The tycon involved
1795 -> LHsExpr RdrName -- The argument
1796 -> Type -- The argument type
1797 -> LHsExpr RdrName -- Boxed version of the arg
1798 box_if_necy cls_str tycon arg arg_ty
1799 | isUnLiftedType arg_ty = nlHsApp (nlHsVar box_con) arg
1802 box_con = assoc_ty_id cls_str tycon box_con_tbl arg_ty
1804 ---------------------
1805 primOrdOps :: String -- The class involved
1806 -> TyCon -- The tycon involved
1808 -> (PrimOp, PrimOp, PrimOp, PrimOp, PrimOp) -- (lt,le,eq,ge,gt)
1809 primOrdOps str tycon ty = assoc_ty_id str tycon ord_op_tbl ty
1811 ord_op_tbl :: [(Type, (PrimOp, PrimOp, PrimOp, PrimOp, PrimOp))]
1813 = [(charPrimTy, (CharLtOp, CharLeOp, CharEqOp, CharGeOp, CharGtOp))
1814 ,(intPrimTy, (IntLtOp, IntLeOp, IntEqOp, IntGeOp, IntGtOp))
1815 ,(wordPrimTy, (WordLtOp, WordLeOp, WordEqOp, WordGeOp, WordGtOp))
1816 ,(addrPrimTy, (AddrLtOp, AddrLeOp, AddrEqOp, AddrGeOp, AddrGtOp))
1817 ,(floatPrimTy, (FloatLtOp, FloatLeOp, FloatEqOp, FloatGeOp, FloatGtOp))
1818 ,(doublePrimTy, (DoubleLtOp, DoubleLeOp, DoubleEqOp, DoubleGeOp, DoubleGtOp)) ]
1820 box_con_tbl :: [(Type, RdrName)]
1822 [(charPrimTy, getRdrName charDataCon)
1823 ,(intPrimTy, getRdrName intDataCon)
1824 ,(wordPrimTy, wordDataCon_RDR)
1825 ,(floatPrimTy, getRdrName floatDataCon)
1826 ,(doublePrimTy, getRdrName doubleDataCon)
1829 assoc_ty_id :: String -- The class involved
1830 -> TyCon -- The tycon involved
1831 -> [(Type,a)] -- The table
1833 -> a -- The result of the lookup
1834 assoc_ty_id cls_str _ tbl ty
1835 | null res = pprPanic "Error in deriving:" (text "Can't derive" <+> text cls_str <+>
1836 text "for primitive type" <+> ppr ty)
1837 | otherwise = head res
1839 res = [id | (ty',id) <- tbl, ty `tcEqType` ty']
1841 -----------------------------------------------------------------------
1843 and_Expr :: LHsExpr RdrName -> LHsExpr RdrName -> LHsExpr RdrName
1844 and_Expr a b = genOpApp a and_RDR b
1846 -----------------------------------------------------------------------
1848 eq_Expr :: TyCon -> Type -> LHsExpr RdrName -> LHsExpr RdrName -> LHsExpr RdrName
1849 eq_Expr tycon ty a b = genOpApp a eq_op b
1851 eq_op | not (isUnLiftedType ty) = eq_RDR
1852 | otherwise = primOpRdrName prim_eq
1853 (_, _, prim_eq, _, _) = primOrdOps "Eq" tycon ty
1857 untag_Expr :: TyCon -> [( RdrName, RdrName)] -> LHsExpr RdrName -> LHsExpr RdrName
1858 untag_Expr _ [] expr = expr
1859 untag_Expr tycon ((untag_this, put_tag_here) : more) expr
1860 = nlHsCase (nlHsPar (nlHsVarApps (con2tag_RDR tycon) [untag_this])) {-of-}
1861 [mkSimpleHsAlt (nlVarPat put_tag_here) (untag_Expr tycon more expr)]
1864 :: LHsExpr RdrName -> LHsExpr RdrName
1866 enum_from_then_to_Expr
1867 :: LHsExpr RdrName -> LHsExpr RdrName -> LHsExpr RdrName
1870 enum_from_to_Expr f t2 = nlHsApp (nlHsApp (nlHsVar enumFromTo_RDR) f) t2
1871 enum_from_then_to_Expr f t t2 = nlHsApp (nlHsApp (nlHsApp (nlHsVar enumFromThenTo_RDR) f) t) t2
1874 :: LHsExpr RdrName -> LHsExpr RdrName
1877 showParen_Expr e1 e2 = nlHsApp (nlHsApp (nlHsVar showParen_RDR) e1) e2
1879 nested_compose_Expr :: [LHsExpr RdrName] -> LHsExpr RdrName
1881 nested_compose_Expr [] = panic "nested_compose_expr" -- Arg is always non-empty
1882 nested_compose_Expr [e] = parenify e
1883 nested_compose_Expr (e:es)
1884 = nlHsApp (nlHsApp (nlHsVar compose_RDR) (parenify e)) (nested_compose_Expr es)
1886 -- impossible_Expr is used in case RHSs that should never happen.
1887 -- We generate these to keep the desugarer from complaining that they *might* happen!
1888 error_Expr :: String -> LHsExpr RdrName
1889 error_Expr string = nlHsApp (nlHsVar error_RDR) (nlHsLit (mkHsString string))
1891 -- illegal_Expr is used when signalling error conditions in the RHS of a derived
1892 -- method. It is currently only used by Enum.{succ,pred}
1893 illegal_Expr :: String -> String -> String -> LHsExpr RdrName
1894 illegal_Expr meth tp msg =
1895 nlHsApp (nlHsVar error_RDR) (nlHsLit (mkHsString (meth ++ '{':tp ++ "}: " ++ msg)))
1897 -- illegal_toEnum_tag is an extended version of illegal_Expr, which also allows you
1898 -- to include the value of a_RDR in the error string.
1899 illegal_toEnum_tag :: String -> RdrName -> LHsExpr RdrName
1900 illegal_toEnum_tag tp maxtag =
1901 nlHsApp (nlHsVar error_RDR)
1902 (nlHsApp (nlHsApp (nlHsVar append_RDR)
1903 (nlHsLit (mkHsString ("toEnum{" ++ tp ++ "}: tag ("))))
1904 (nlHsApp (nlHsApp (nlHsApp
1905 (nlHsVar showsPrec_RDR)
1909 (nlHsVar append_RDR)
1910 (nlHsLit (mkHsString ") is outside of enumeration's range (0,")))
1911 (nlHsApp (nlHsApp (nlHsApp
1912 (nlHsVar showsPrec_RDR)
1915 (nlHsLit (mkHsString ")"))))))
1917 parenify :: LHsExpr RdrName -> LHsExpr RdrName
1918 parenify e@(L _ (HsVar _)) = e
1919 parenify e = mkHsPar e
1921 -- genOpApp wraps brackets round the operator application, so that the
1922 -- renamer won't subsequently try to re-associate it.
1923 genOpApp :: LHsExpr RdrName -> RdrName -> LHsExpr RdrName -> LHsExpr RdrName
1924 genOpApp e1 op e2 = nlHsPar (nlHsOpApp e1 op e2)
1928 a_RDR, b_RDR, c_RDR, d_RDR, f_RDR, k_RDR, z_RDR, ah_RDR, bh_RDR, ch_RDR, dh_RDR
1930 a_RDR = mkVarUnqual (fsLit "a")
1931 b_RDR = mkVarUnqual (fsLit "b")
1932 c_RDR = mkVarUnqual (fsLit "c")
1933 d_RDR = mkVarUnqual (fsLit "d")
1934 f_RDR = mkVarUnqual (fsLit "f")
1935 k_RDR = mkVarUnqual (fsLit "k")
1936 z_RDR = mkVarUnqual (fsLit "z")
1937 ah_RDR = mkVarUnqual (fsLit "a#")
1938 bh_RDR = mkVarUnqual (fsLit "b#")
1939 ch_RDR = mkVarUnqual (fsLit "c#")
1940 dh_RDR = mkVarUnqual (fsLit "d#")
1942 as_RDRs, bs_RDRs, cs_RDRs :: [RdrName]
1943 as_RDRs = [ mkVarUnqual (mkFastString ("a"++show i)) | i <- [(1::Int) .. ] ]
1944 bs_RDRs = [ mkVarUnqual (mkFastString ("b"++show i)) | i <- [(1::Int) .. ] ]
1945 cs_RDRs = [ mkVarUnqual (mkFastString ("c"++show i)) | i <- [(1::Int) .. ] ]
1947 a_Expr, c_Expr, f_Expr, z_Expr, ltTag_Expr, eqTag_Expr, gtTag_Expr,
1948 false_Expr, true_Expr :: LHsExpr RdrName
1949 a_Expr = nlHsVar a_RDR
1950 -- b_Expr = nlHsVar b_RDR
1951 c_Expr = nlHsVar c_RDR
1952 f_Expr = nlHsVar f_RDR
1953 z_Expr = nlHsVar z_RDR
1954 ltTag_Expr = nlHsVar ltTag_RDR
1955 eqTag_Expr = nlHsVar eqTag_RDR
1956 gtTag_Expr = nlHsVar gtTag_RDR
1957 false_Expr = nlHsVar false_RDR
1958 true_Expr = nlHsVar true_RDR
1960 a_Pat, b_Pat, c_Pat, d_Pat, f_Pat, k_Pat, z_Pat :: LPat RdrName
1961 a_Pat = nlVarPat a_RDR
1962 b_Pat = nlVarPat b_RDR
1963 c_Pat = nlVarPat c_RDR
1964 d_Pat = nlVarPat d_RDR
1965 f_Pat = nlVarPat f_RDR
1966 k_Pat = nlVarPat k_RDR
1967 z_Pat = nlVarPat z_RDR
1969 con2tag_RDR, tag2con_RDR, maxtag_RDR :: TyCon -> RdrName
1970 -- Generates Orig s RdrName, for the binding positions
1971 con2tag_RDR tycon = mk_tc_deriv_name tycon mkCon2TagOcc
1972 tag2con_RDR tycon = mk_tc_deriv_name tycon mkTag2ConOcc
1973 maxtag_RDR tycon = mk_tc_deriv_name tycon mkMaxTagOcc
1975 mk_tc_deriv_name :: TyCon -> (OccName -> OccName) -> RdrName
1976 mk_tc_deriv_name tycon occ_fun = mkAuxBinderName (tyConName tycon) occ_fun
1978 mkAuxBinderName :: Name -> (OccName -> OccName) -> RdrName
1979 mkAuxBinderName parent occ_fun = mkRdrUnqual (occ_fun (nameOccName parent))
1980 -- Was: mkDerivedRdrName name occ_fun, which made an original name
1981 -- But: (a) that does not work well for standalone-deriving
1982 -- (b) an unqualified name is just fine, provided it can't clash with user code
1985 s RdrName for PrimOps. Can't be done in PrelNames, because PrimOp imports
1986 PrelNames, so PrelNames can't import PrimOp.
1989 primOpRdrName :: PrimOp -> RdrName
1990 primOpRdrName op = getRdrName (primOpId op)
1992 minusInt_RDR, eqInt_RDR, ltInt_RDR, geInt_RDR, gtInt_RDR, leInt_RDR,
1993 tagToEnum_RDR :: RdrName
1994 minusInt_RDR = primOpRdrName IntSubOp
1995 eqInt_RDR = primOpRdrName IntEqOp
1996 ltInt_RDR = primOpRdrName IntLtOp
1997 geInt_RDR = primOpRdrName IntGeOp
1998 gtInt_RDR = primOpRdrName IntGtOp
1999 leInt_RDR = primOpRdrName IntLeOp
2000 tagToEnum_RDR = primOpRdrName TagToEnumOp
2002 error_RDR :: RdrName
2003 error_RDR = getRdrName eRROR_ID