2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
8 VarEnv, IdEnv, TyVarEnv,
9 emptyVarEnv, unitVarEnv, mkVarEnv,
10 elemVarEnv, varEnvElts, varEnvKeys,
11 extendVarEnv, extendVarEnv_C, extendVarEnvList,
12 plusVarEnv, plusVarEnv_C,
13 delVarEnvList, delVarEnv,
14 lookupVarEnv, lookupVarEnv_NF, lookupWithDefaultVarEnv,
16 modifyVarEnv, modifyVarEnv_Directly,
17 isEmptyVarEnv, foldVarEnv,
18 elemVarEnvByKey, lookupVarEnv_Directly,
19 filterVarEnv_Directly,
22 InScopeSet, emptyInScopeSet, mkInScopeSet, delInScopeSet,
23 extendInScopeSet, extendInScopeSetList, extendInScopeSetSet,
25 getInScopeVars, lookupInScope, elemInScopeSet, uniqAway,
28 -- RnEnv2 and its operations
29 RnEnv2, mkRnEnv2, rnBndr2, rnBndrs2, rnOccL, rnOccR, inRnEnvL, inRnEnvR,
30 rnBndrL, rnBndrR, nukeRnEnvL, nukeRnEnvR, extendRnInScopeList,
31 rnInScope, rnInScopeSet, lookupRnInScope,
37 #include "HsVersions.h"
51 %************************************************************************
55 %************************************************************************
58 data InScopeSet = InScope (VarEnv Var) FastInt
59 -- The Int# is a kind of hash-value used by uniqAway
60 -- For example, it might be the size of the set
61 -- INVARIANT: it's not zero; we use it as a multiplier in uniqAway
63 instance Outputable InScopeSet where
64 ppr (InScope s _) = ptext SLIT("InScope") <+> ppr s
66 emptyInScopeSet :: InScopeSet
67 emptyInScopeSet = InScope emptyVarSet (_ILIT(1))
69 getInScopeVars :: InScopeSet -> VarEnv Var
70 getInScopeVars (InScope vs _) = vs
72 mkInScopeSet :: VarEnv Var -> InScopeSet
73 mkInScopeSet in_scope = InScope in_scope (_ILIT(1))
75 extendInScopeSet :: InScopeSet -> Var -> InScopeSet
76 extendInScopeSet (InScope in_scope n) v = InScope (extendVarEnv in_scope v v) (n +# _ILIT(1))
78 extendInScopeSetList :: InScopeSet -> [Var] -> InScopeSet
79 extendInScopeSetList (InScope in_scope n) vs
80 = InScope (foldl (\s v -> extendVarEnv s v v) in_scope vs)
81 (n +# iUnbox (length vs))
83 extendInScopeSetSet :: InScopeSet -> VarEnv Var -> InScopeSet
84 extendInScopeSetSet (InScope in_scope n) vs
85 = InScope (in_scope `plusVarEnv` vs) (n +# iUnbox (sizeUFM vs))
87 modifyInScopeSet :: InScopeSet -> Var -> Var -> InScopeSet
88 -- Exploit the fact that the in-scope "set" is really a map
89 -- Make old_v map to new_v
90 modifyInScopeSet (InScope in_scope n) old_v new_v = InScope (extendVarEnv in_scope old_v new_v) (n +# _ILIT(1))
92 delInScopeSet :: InScopeSet -> Var -> InScopeSet
93 delInScopeSet (InScope in_scope n) v = InScope (in_scope `delVarEnv` v) n
95 mapInScopeSet :: (Var -> Var) -> InScopeSet -> InScopeSet
96 mapInScopeSet f (InScope in_scope n) = InScope (mapVarEnv f in_scope) n
98 elemInScopeSet :: Var -> InScopeSet -> Bool
99 elemInScopeSet v (InScope in_scope _) = v `elemVarEnv` in_scope
101 lookupInScope :: InScopeSet -> Var -> Maybe Var
102 -- It's important to look for a fixed point
103 -- When we see (case x of y { I# v -> ... })
104 -- we add [x -> y] to the in-scope set (Simplify.simplCaseBinder).
105 -- When we lookup up an occurrence of x, we map to y, but then
106 -- we want to look up y in case it has acquired more evaluation information by now.
107 lookupInScope (InScope in_scope _) v
110 go v = case lookupVarEnv in_scope v of
111 Just v' | v == v' -> Just v' -- Reached a fixed point
117 uniqAway :: InScopeSet -> Var -> Var
118 -- (uniqAway in_scope v) finds a unique that is not used in the
119 -- in-scope set, and gives that to v. It starts with v's current unique, of course,
120 -- in the hope that it won't have to change it, and thereafter uses a combination
121 -- of that and the hash-code found in the in-scope set
122 uniqAway in_scope var
123 | var `elemInScopeSet` in_scope = uniqAway' in_scope var -- Make a new one
124 | otherwise = var -- Nothing to do
126 uniqAway' :: InScopeSet -> Var -> Var
127 -- This one *always* makes up a new variable
128 uniqAway' (InScope set n) var
131 orig_unique = getUnique var
135 = pprPanic "uniqAway loop:" (ppr (iBox k) <+> text "tries" <+> ppr var <+> int (iBox n))
137 | uniq `elemVarSetByKey` set = try (k +# _ILIT(1))
139 | opt_PprStyle_Debug && k ># _ILIT(3)
140 = pprTrace "uniqAway:" (ppr (iBox k) <+> text "tries" <+> ppr var <+> int (iBox n))
141 setVarUnique var uniq
143 | otherwise = setVarUnique var uniq
145 uniq = deriveUnique orig_unique (iBox (n *# k))
149 %************************************************************************
153 %************************************************************************
155 When we are comparing (or matching) types or terms, we are faced with
156 "going under" corresponding binders. E.g. when comparing
159 Basically we want to rename [x->y] or [y->x], but there are lots of
160 things we must be careful of. In particular, x might be free in e2, or
161 y in e1. So the idea is that we come up with a fresh binder that is free
162 in neither, and rename x and y respectively. That means we must maintain
163 a) a renaming for the left-hand expression
164 b) a renaming for the right-hand expressions
167 Furthermore, when matching, we want to be able to have an 'occurs check',
170 matching with f->y. So for each expression we want to know that set of
171 locally-bound variables. That is precisely the domain of the mappings (a)
172 and (b), but we must ensure that we always extend the mappings as we go in.
177 = RV2 { envL :: VarEnv Var -- Renaming for Left term
178 , envR :: VarEnv Var -- Renaming for Right term
179 , in_scope :: InScopeSet } -- In scope in left or right terms
181 -- The renamings envL and envR are *guaranteed* to contain a binding
182 -- for every variable bound as we go into the term, even if it is not
183 -- renamed. That way we can ask what variables are locally bound
184 -- (inRnEnvL, inRnEnvR)
186 mkRnEnv2 :: InScopeSet -> RnEnv2
187 mkRnEnv2 vars = RV2 { envL = emptyVarEnv
191 extendRnInScopeList :: RnEnv2 -> [Var] -> RnEnv2
192 extendRnInScopeList env vs
193 = env { in_scope = extendInScopeSetList (in_scope env) vs }
195 rnInScope :: Var -> RnEnv2 -> Bool
196 rnInScope x env = x `elemInScopeSet` in_scope env
198 rnInScopeSet :: RnEnv2 -> InScopeSet
199 rnInScopeSet = in_scope
201 rnBndrs2 :: RnEnv2 -> [Var] -> [Var] -> RnEnv2
202 -- Arg lists must be of equal length
203 rnBndrs2 env bsL bsR = foldl2 rnBndr2 env bsL bsR
205 rnBndr2 :: RnEnv2 -> Var -> Var -> RnEnv2
206 -- (rnBndr2 env bL bR) go under a binder bL in the Left term 1,
207 -- and binder bR in the Right term
208 -- It finds a new binder, new_b,
209 -- and returns an environment mapping bL->new_b and bR->new_b resp.
210 rnBndr2 (RV2 { envL = envL, envR = envR, in_scope = in_scope }) bL bR
211 = RV2 { envL = extendVarEnv envL bL new_b -- See Note
212 , envR = extendVarEnv envR bR new_b -- [Rebinding]
213 , in_scope = extendInScopeSet in_scope new_b }
215 -- Find a new binder not in scope in either term
216 new_b | not (bL `elemInScopeSet` in_scope) = bL
217 | not (bR `elemInScopeSet` in_scope) = bR
218 | otherwise = uniqAway' in_scope bL
221 -- If the new var is the same as the old one, note that
222 -- the extendVarEnv *deletes* any current renaming
223 -- E.g. (\x. \x. ...) ~ (\y. \z. ...)
225 -- Inside \x \y { [x->y], [y->y], {y} }
226 -- \x \z { [x->x], [y->y, z->x], {y,x} }
228 rnBndrL, rnBndrR :: RnEnv2 -> Var -> (RnEnv2, Var)
229 -- Used when there's a binder on one side or the other only
230 -- Useful when eta-expanding
232 rnBndrL (RV2 { envL = envL, envR = envR, in_scope = in_scope }) bL
233 = (RV2 { envL = extendVarEnv envL bL new_b
234 , envR = extendVarEnv envR new_b new_b -- Note [rnBndrLR]
235 , in_scope = extendInScopeSet in_scope new_b }, new_b)
237 new_b = uniqAway in_scope bL
239 rnBndrR (RV2 { envL = envL, envR = envR, in_scope = in_scope }) bR
240 = (RV2 { envL = extendVarEnv envL new_b new_b -- Note [rnBndrLR]
241 , envR = extendVarEnv envR bR new_b
242 , in_scope = extendInScopeSet in_scope new_b }, new_b)
244 new_b = uniqAway in_scope bR
248 -- Notice that in rnBndrL, rnBndrR, we extend envR, envL respectively
249 -- with a binding [new_b -> new_b], where new_b is the new binder.
250 -- This is important when doing eta expansion; e.g. matching (\x.M) ~ N
251 -- In effect we switch to (\x'.M) ~ (\x'.N x'), where x' is new_b
252 -- So we must add x' to the env of both L and R. (x' is fresh, so it
253 -- can't capture anything in N.)
255 -- If we don't do this, we can get silly matches like
256 -- forall a. \y.a ~ v
257 -- succeeding with [x -> v y], which is bogus of course
259 rnOccL, rnOccR :: RnEnv2 -> Var -> Var
260 -- Look up the renaming of an occurrence in the left or right term
261 rnOccL (RV2 { envL = env }) v = lookupVarEnv env v `orElse` v
262 rnOccR (RV2 { envR = env }) v = lookupVarEnv env v `orElse` v
264 inRnEnvL, inRnEnvR :: RnEnv2 -> Var -> Bool
265 -- Tells whether a variable is locally bound
266 inRnEnvL (RV2 { envL = env }) v = v `elemVarEnv` env
267 inRnEnvR (RV2 { envR = env }) v = v `elemVarEnv` env
269 lookupRnInScope :: RnEnv2 -> Var -> Var
270 lookupRnInScope env v = lookupInScope (in_scope env) v `orElse` v
272 nukeRnEnvL, nukeRnEnvR :: RnEnv2 -> RnEnv2
273 nukeRnEnvL env = env { envL = emptyVarEnv }
274 nukeRnEnvR env = env { envR = emptyVarEnv }
278 %************************************************************************
282 %************************************************************************
284 When tidying up print names, we keep a mapping of in-scope occ-names
285 (the TidyOccEnv) and a Var-to-Var of the current renamings.
288 type TidyEnv = (TidyOccEnv, VarEnv Var)
290 emptyTidyEnv :: TidyEnv
291 emptyTidyEnv = (emptyTidyOccEnv, emptyVarEnv)
295 %************************************************************************
297 \subsection{@VarEnv@s}
299 %************************************************************************
302 type VarEnv elt = UniqFM elt
303 type IdEnv elt = VarEnv elt
304 type TyVarEnv elt = VarEnv elt
306 emptyVarEnv :: VarEnv a
307 mkVarEnv :: [(Var, a)] -> VarEnv a
308 zipVarEnv :: [Var] -> [a] -> VarEnv a
309 unitVarEnv :: Var -> a -> VarEnv a
310 extendVarEnv :: VarEnv a -> Var -> a -> VarEnv a
311 extendVarEnv_C :: (a->a->a) -> VarEnv a -> Var -> a -> VarEnv a
312 plusVarEnv :: VarEnv a -> VarEnv a -> VarEnv a
313 extendVarEnvList :: VarEnv a -> [(Var, a)] -> VarEnv a
315 lookupVarEnv_Directly :: VarEnv a -> Unique -> Maybe a
316 filterVarEnv_Directly :: (Unique -> a -> Bool) -> VarEnv a -> VarEnv a
317 delVarEnvList :: VarEnv a -> [Var] -> VarEnv a
318 delVarEnv :: VarEnv a -> Var -> VarEnv a
319 plusVarEnv_C :: (a -> a -> a) -> VarEnv a -> VarEnv a -> VarEnv a
320 mapVarEnv :: (a -> b) -> VarEnv a -> VarEnv b
321 modifyVarEnv :: (a -> a) -> VarEnv a -> Var -> VarEnv a
322 varEnvElts :: VarEnv a -> [a]
323 varEnvKeys :: VarEnv a -> [Unique]
325 isEmptyVarEnv :: VarEnv a -> Bool
326 lookupVarEnv :: VarEnv a -> Var -> Maybe a
327 lookupVarEnv_NF :: VarEnv a -> Var -> a
328 lookupWithDefaultVarEnv :: VarEnv a -> a -> Var -> a
329 elemVarEnv :: Var -> VarEnv a -> Bool
330 elemVarEnvByKey :: Unique -> VarEnv a -> Bool
331 foldVarEnv :: (a -> b -> b) -> b -> VarEnv a -> b
336 elemVarEnvByKey = elemUFM_Directly
337 extendVarEnv = addToUFM
338 extendVarEnv_C = addToUFM_C
339 extendVarEnvList = addListToUFM
340 plusVarEnv_C = plusUFM_C
341 delVarEnvList = delListFromUFM
342 delVarEnv = delFromUFM
344 lookupVarEnv = lookupUFM
345 lookupWithDefaultVarEnv = lookupWithDefaultUFM
348 emptyVarEnv = emptyUFM
352 isEmptyVarEnv = isNullUFM
354 lookupVarEnv_Directly = lookupUFM_Directly
355 filterVarEnv_Directly = filterUFM_Directly
357 zipVarEnv tyvars tys = mkVarEnv (zipEqual "zipVarEnv" tyvars tys)
358 lookupVarEnv_NF env id = case lookupVarEnv env id of
360 Nothing -> panic "lookupVarEnv_NF: Nothing"
363 @modifyVarEnv@: Look up a thing in the VarEnv,
364 then mash it with the modify function, and put it back.
367 modifyVarEnv mangle_fn env key
368 = case (lookupVarEnv env key) of
370 Just xx -> extendVarEnv env key (mangle_fn xx)
372 modifyVarEnv_Directly :: (a -> a) -> UniqFM a -> Unique -> UniqFM a
373 modifyVarEnv_Directly mangle_fn env key
374 = case (lookupUFM_Directly env key) of
376 Just xx -> addToUFM_Directly env key (mangle_fn xx)