2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
8 -- * Var, Id and TyVar environments (maps)
9 VarEnv, IdEnv, TyVarEnv,
11 -- ** Manipulating these environments
12 emptyVarEnv, unitVarEnv, mkVarEnv,
13 elemVarEnv, varEnvElts, varEnvKeys,
14 extendVarEnv, extendVarEnv_C, extendVarEnv_Acc, extendVarEnvList,
15 plusVarEnv, plusVarEnv_C,
16 delVarEnvList, delVarEnv,
17 minusVarEnv, intersectsVarEnv,
18 lookupVarEnv, lookupVarEnv_NF, lookupWithDefaultVarEnv,
20 modifyVarEnv, modifyVarEnv_Directly,
21 isEmptyVarEnv, foldVarEnv,
22 elemVarEnvByKey, lookupVarEnv_Directly,
23 filterVarEnv_Directly, restrictVarEnv,
25 -- * The InScopeSet type
28 -- ** Operations on InScopeSets
29 emptyInScopeSet, mkInScopeSet, delInScopeSet,
30 extendInScopeSet, extendInScopeSetList, extendInScopeSetSet,
31 getInScopeVars, lookupInScope, lookupInScope_Directly,
32 unionInScope, elemInScopeSet, uniqAway,
37 -- ** Operations on RnEnv2s
38 mkRnEnv2, rnBndr2, rnBndrs2, rnOccL, rnOccR, inRnEnvL, inRnEnvR,
39 rnBndrL, rnBndrR, nukeRnEnvL, nukeRnEnvR, extendRnInScopeList,
41 rnInScope, rnInScopeSet, lookupRnInScope,
43 -- * TidyEnv and its operation
62 %************************************************************************
66 %************************************************************************
69 -- | A set of variables that are in scope at some point
70 data InScopeSet = InScope (VarEnv Var) FastInt
71 -- The (VarEnv Var) is just a VarSet. But we write it like
72 -- this to remind ourselves that you can look up a Var in
73 -- the InScopeSet. Typically the InScopeSet contains the
74 -- canonical version of the variable (e.g. with an informative
75 -- unfolding), so this lookup is useful.
77 -- INVARIANT: the VarEnv maps (the Unique of) a variable to
78 -- a variable with the same Uniqua. (This was not
79 -- the case in the past, when we had a grevious hack
80 -- mapping var1 to var2.
82 -- The FastInt is a kind of hash-value used by uniqAway
83 -- For example, it might be the size of the set
84 -- INVARIANT: it's not zero; we use it as a multiplier in uniqAway
86 instance Outputable InScopeSet where
87 ppr (InScope s _) = ptext (sLit "InScope") <+> ppr s
89 emptyInScopeSet :: InScopeSet
90 emptyInScopeSet = InScope emptyVarSet (_ILIT(1))
92 getInScopeVars :: InScopeSet -> VarEnv Var
93 getInScopeVars (InScope vs _) = vs
95 mkInScopeSet :: VarEnv Var -> InScopeSet
96 mkInScopeSet in_scope = InScope in_scope (_ILIT(1))
98 extendInScopeSet :: InScopeSet -> Var -> InScopeSet
99 extendInScopeSet (InScope in_scope n) v = InScope (extendVarEnv in_scope v v) (n +# _ILIT(1))
101 extendInScopeSetList :: InScopeSet -> [Var] -> InScopeSet
102 extendInScopeSetList (InScope in_scope n) vs
103 = InScope (foldl (\s v -> extendVarEnv s v v) in_scope vs)
104 (n +# iUnbox (length vs))
106 extendInScopeSetSet :: InScopeSet -> VarEnv Var -> InScopeSet
107 extendInScopeSetSet (InScope in_scope n) vs
108 = InScope (in_scope `plusVarEnv` vs) (n +# iUnbox (sizeUFM vs))
110 delInScopeSet :: InScopeSet -> Var -> InScopeSet
111 delInScopeSet (InScope in_scope n) v = InScope (in_scope `delVarEnv` v) n
113 elemInScopeSet :: Var -> InScopeSet -> Bool
114 elemInScopeSet v (InScope in_scope _) = v `elemVarEnv` in_scope
116 -- | Look up a variable the 'InScopeSet'. This lets you map from
117 -- the variable's identity (unique) to its full value.
118 lookupInScope :: InScopeSet -> Var -> Maybe Var
119 lookupInScope (InScope in_scope _) v = lookupVarEnv in_scope v
121 lookupInScope_Directly :: InScopeSet -> Unique -> Maybe Var
122 lookupInScope_Directly (InScope in_scope _) uniq
123 = lookupVarEnv_Directly in_scope uniq
125 unionInScope :: InScopeSet -> InScopeSet -> InScopeSet
126 unionInScope (InScope s1 _) (InScope s2 n2)
127 = InScope (s1 `plusVarEnv` s2) n2
131 -- | @uniqAway in_scope v@ finds a unique that is not used in the
132 -- in-scope set, and gives that to v.
133 uniqAway :: InScopeSet -> Var -> Var
134 -- It starts with v's current unique, of course, in the hope that it won't
135 -- have to change, and thereafter uses a combination of that and the hash-code
136 -- found in the in-scope set
137 uniqAway in_scope var
138 | var `elemInScopeSet` in_scope = uniqAway' in_scope var -- Make a new one
139 | otherwise = var -- Nothing to do
141 uniqAway' :: InScopeSet -> Var -> Var
142 -- This one *always* makes up a new variable
143 uniqAway' (InScope set n) var
146 orig_unique = getUnique var
148 | debugIsOn && (k ># _ILIT(1000))
149 = pprPanic "uniqAway loop:" (ppr (iBox k) <+> text "tries" <+> ppr var <+> int (iBox n))
150 | uniq `elemVarSetByKey` set = try (k +# _ILIT(1))
151 | debugIsOn && opt_PprStyle_Debug && (k ># _ILIT(3))
152 = pprTrace "uniqAway:" (ppr (iBox k) <+> text "tries" <+> ppr var <+> int (iBox n))
153 setVarUnique var uniq
154 | otherwise = setVarUnique var uniq
156 uniq = deriveUnique orig_unique (iBox (n *# k))
159 %************************************************************************
163 %************************************************************************
166 -- | When we are comparing (or matching) types or terms, we are faced with
167 -- \"going under\" corresponding binders. E.g. when comparing:
171 -- Basically we want to rename [@x@ -> @y@] or [@y@ -> @x@], but there are lots of
172 -- things we must be careful of. In particular, @x@ might be free in @e2@, or
173 -- y in @e1@. So the idea is that we come up with a fresh binder that is free
174 -- in neither, and rename @x@ and @y@ respectively. That means we must maintain:
176 -- 1. A renaming for the left-hand expression
178 -- 2. A renaming for the right-hand expressions
180 -- 3. An in-scope set
182 -- Furthermore, when matching, we want to be able to have an 'occurs check',
187 -- matching with [@f@ -> @y@]. So for each expression we want to know that set of
188 -- locally-bound variables. That is precisely the domain of the mappings 1.
189 -- and 2., but we must ensure that we always extend the mappings as we go in.
191 -- All of this information is bundled up in the 'RnEnv2'
193 = RV2 { envL :: VarEnv Var -- Renaming for Left term
194 , envR :: VarEnv Var -- Renaming for Right term
195 , in_scope :: InScopeSet } -- In scope in left or right terms
197 -- The renamings envL and envR are *guaranteed* to contain a binding
198 -- for every variable bound as we go into the term, even if it is not
199 -- renamed. That way we can ask what variables are locally bound
200 -- (inRnEnvL, inRnEnvR)
202 mkRnEnv2 :: InScopeSet -> RnEnv2
203 mkRnEnv2 vars = RV2 { envL = emptyVarEnv
207 extendRnInScopeList :: RnEnv2 -> [Var] -> RnEnv2
208 extendRnInScopeList env vs
209 = env { in_scope = extendInScopeSetList (in_scope env) vs }
211 rnInScope :: Var -> RnEnv2 -> Bool
212 rnInScope x env = x `elemInScopeSet` in_scope env
214 rnInScopeSet :: RnEnv2 -> InScopeSet
215 rnInScopeSet = in_scope
217 rnBndrs2 :: RnEnv2 -> [Var] -> [Var] -> RnEnv2
218 -- ^ Applies 'rnBndr2' to several variables: the two variable lists must be of equal length
219 rnBndrs2 env bsL bsR = foldl2 rnBndr2 env bsL bsR
221 rnBndr2 :: RnEnv2 -> Var -> Var -> RnEnv2
222 -- ^ @rnBndr2 env bL bR@ goes under a binder @bL@ in the Left term,
223 -- and binder @bR@ in the Right term.
224 -- It finds a new binder, @new_b@,
225 -- and returns an environment mapping @bL -> new_b@ and @bR -> new_b@
226 rnBndr2 (RV2 { envL = envL, envR = envR, in_scope = in_scope }) bL bR
227 = RV2 { envL = extendVarEnv envL bL new_b -- See Note
228 , envR = extendVarEnv envR bR new_b -- [Rebinding]
229 , in_scope = extendInScopeSet in_scope new_b }
231 -- Find a new binder not in scope in either term
232 new_b | not (bL `elemInScopeSet` in_scope) = bL
233 | not (bR `elemInScopeSet` in_scope) = bR
234 | otherwise = uniqAway' in_scope bL
237 -- If the new var is the same as the old one, note that
238 -- the extendVarEnv *deletes* any current renaming
239 -- E.g. (\x. \x. ...) ~ (\y. \z. ...)
241 -- Inside \x \y { [x->y], [y->y], {y} }
242 -- \x \z { [x->x], [y->y, z->x], {y,x} }
244 rnBndrL :: RnEnv2 -> Var -> (RnEnv2, Var)
245 -- ^ Similar to 'rnBndr2' but used when there's a binder on the left
247 rnBndrL (RV2 { envL = envL, envR = envR, in_scope = in_scope }) bL
248 = (RV2 { envL = extendVarEnv envL bL new_b
250 , in_scope = extendInScopeSet in_scope new_b }, new_b)
252 new_b = uniqAway in_scope bL
254 rnBndrR :: RnEnv2 -> Var -> (RnEnv2, Var)
255 -- ^ Similar to 'rnBndr2' but used when there's a binder on the right
257 rnBndrR (RV2 { envL = envL, envR = envR, in_scope = in_scope }) bR
258 = (RV2 { envR = extendVarEnv envR bR new_b
260 , in_scope = extendInScopeSet in_scope new_b }, new_b)
262 new_b = uniqAway in_scope bR
264 rnEtaL :: RnEnv2 -> Var -> (RnEnv2, Var)
265 -- ^ Similar to 'rnBndrL' but used for eta expansion
266 -- See Note [Eta expansion]
267 rnEtaL (RV2 { envL = envL, envR = envR, in_scope = in_scope }) bL
268 = (RV2 { envL = extendVarEnv envL bL new_b
269 , envR = extendVarEnv envR new_b new_b -- Note [Eta expansion]
270 , in_scope = extendInScopeSet in_scope new_b }, new_b)
272 new_b = uniqAway in_scope bL
274 rnEtaR :: RnEnv2 -> Var -> (RnEnv2, Var)
275 -- ^ Similar to 'rnBndr2' but used for eta expansion
276 -- See Note [Eta expansion]
277 rnEtaR (RV2 { envL = envL, envR = envR, in_scope = in_scope }) bR
278 = (RV2 { envL = extendVarEnv envL new_b new_b -- Note [Eta expansion]
279 , envR = extendVarEnv envR bR new_b
280 , in_scope = extendInScopeSet in_scope new_b }, new_b)
282 new_b = uniqAway in_scope bR
284 rnOccL, rnOccR :: RnEnv2 -> Var -> Var
285 -- ^ Look up the renaming of an occurrence in the left or right term
286 rnOccL (RV2 { envL = env }) v = lookupVarEnv env v `orElse` v
287 rnOccR (RV2 { envR = env }) v = lookupVarEnv env v `orElse` v
289 inRnEnvL, inRnEnvR :: RnEnv2 -> Var -> Bool
290 -- ^ Tells whether a variable is locally bound
291 inRnEnvL (RV2 { envL = env }) v = v `elemVarEnv` env
292 inRnEnvR (RV2 { envR = env }) v = v `elemVarEnv` env
294 lookupRnInScope :: RnEnv2 -> Var -> Var
295 lookupRnInScope env v = lookupInScope (in_scope env) v `orElse` v
297 nukeRnEnvL, nukeRnEnvR :: RnEnv2 -> RnEnv2
298 -- ^ Wipe the left or right side renaming
299 nukeRnEnvL env = env { envL = emptyVarEnv }
300 nukeRnEnvR env = env { envR = emptyVarEnv }
307 we rename x to x' with, where x' is not in scope in
308 either term. Then we want to behave as if we'd seen
310 Since x' isn't in scope in N, the form (\x'. N x') doesn't
311 capture any variables in N. But we must nevertheless extend
312 the envR with a binding [x' -> x'], to support the occurs check.
313 For example, if we don't do this, we can get silly matches like
315 succeeding with [a -> v y], which is bogus of course.
318 %************************************************************************
322 %************************************************************************
325 -- | When tidying up print names, we keep a mapping of in-scope occ-names
326 -- (the 'TidyOccEnv') and a Var-to-Var of the current renamings
327 type TidyEnv = (TidyOccEnv, VarEnv Var)
329 emptyTidyEnv :: TidyEnv
330 emptyTidyEnv = (emptyTidyOccEnv, emptyVarEnv)
334 %************************************************************************
336 \subsection{@VarEnv@s}
338 %************************************************************************
341 type VarEnv elt = UniqFM elt
342 type IdEnv elt = VarEnv elt
343 type TyVarEnv elt = VarEnv elt
345 emptyVarEnv :: VarEnv a
346 mkVarEnv :: [(Var, a)] -> VarEnv a
347 zipVarEnv :: [Var] -> [a] -> VarEnv a
348 unitVarEnv :: Var -> a -> VarEnv a
349 extendVarEnv :: VarEnv a -> Var -> a -> VarEnv a
350 extendVarEnv_C :: (a->a->a) -> VarEnv a -> Var -> a -> VarEnv a
351 extendVarEnv_Acc :: (a->b->b) -> (a->b) -> VarEnv b -> Var -> a -> VarEnv b
352 plusVarEnv :: VarEnv a -> VarEnv a -> VarEnv a
353 extendVarEnvList :: VarEnv a -> [(Var, a)] -> VarEnv a
355 lookupVarEnv_Directly :: VarEnv a -> Unique -> Maybe a
356 filterVarEnv_Directly :: (Unique -> a -> Bool) -> VarEnv a -> VarEnv a
357 restrictVarEnv :: VarEnv a -> VarSet -> VarEnv a
358 delVarEnvList :: VarEnv a -> [Var] -> VarEnv a
359 delVarEnv :: VarEnv a -> Var -> VarEnv a
360 minusVarEnv :: VarEnv a -> VarEnv a -> VarEnv a
361 intersectsVarEnv :: VarEnv a -> VarEnv a -> Bool
362 plusVarEnv_C :: (a -> a -> a) -> VarEnv a -> VarEnv a -> VarEnv a
363 mapVarEnv :: (a -> b) -> VarEnv a -> VarEnv b
364 modifyVarEnv :: (a -> a) -> VarEnv a -> Var -> VarEnv a
365 varEnvElts :: VarEnv a -> [a]
366 varEnvKeys :: VarEnv a -> [Unique]
368 isEmptyVarEnv :: VarEnv a -> Bool
369 lookupVarEnv :: VarEnv a -> Var -> Maybe a
370 lookupVarEnv_NF :: VarEnv a -> Var -> a
371 lookupWithDefaultVarEnv :: VarEnv a -> a -> Var -> a
372 elemVarEnv :: Var -> VarEnv a -> Bool
373 elemVarEnvByKey :: Unique -> VarEnv a -> Bool
374 foldVarEnv :: (a -> b -> b) -> b -> VarEnv a -> b
379 elemVarEnvByKey = elemUFM_Directly
380 extendVarEnv = addToUFM
381 extendVarEnv_C = addToUFM_C
382 extendVarEnv_Acc = addToUFM_Acc
383 extendVarEnvList = addListToUFM
384 plusVarEnv_C = plusUFM_C
385 delVarEnvList = delListFromUFM
386 delVarEnv = delFromUFM
387 minusVarEnv = minusUFM
388 intersectsVarEnv e1 e2 = not (isEmptyVarEnv (e1 `intersectUFM` e2))
390 lookupVarEnv = lookupUFM
391 lookupWithDefaultVarEnv = lookupWithDefaultUFM
394 emptyVarEnv = emptyUFM
398 isEmptyVarEnv = isNullUFM
400 lookupVarEnv_Directly = lookupUFM_Directly
401 filterVarEnv_Directly = filterUFM_Directly
403 restrictVarEnv env vs = filterVarEnv_Directly keep env
405 keep u _ = u `elemVarSetByKey` vs
407 zipVarEnv tyvars tys = mkVarEnv (zipEqual "zipVarEnv" tyvars tys)
408 lookupVarEnv_NF env id = case lookupVarEnv env id of
410 Nothing -> panic "lookupVarEnv_NF: Nothing"
413 @modifyVarEnv@: Look up a thing in the VarEnv,
414 then mash it with the modify function, and put it back.
417 modifyVarEnv mangle_fn env key
418 = case (lookupVarEnv env key) of
420 Just xx -> extendVarEnv env key (mangle_fn xx)
422 modifyVarEnv_Directly :: (a -> a) -> UniqFM a -> Unique -> UniqFM a
423 modifyVarEnv_Directly mangle_fn env key
424 = case (lookupUFM_Directly env key) of
426 Just xx -> addToUFM_Directly env key (mangle_fn xx)