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 lookupVarEnv, lookupVarEnv_NF, lookupWithDefaultVarEnv,
19 modifyVarEnv, modifyVarEnv_Directly,
20 isEmptyVarEnv, foldVarEnv,
21 elemVarEnvByKey, lookupVarEnv_Directly,
22 filterVarEnv_Directly, restrictVarEnv,
24 -- * The InScopeSet type
27 -- ** Operations on InScopeSets
28 emptyInScopeSet, mkInScopeSet, delInScopeSet,
29 extendInScopeSet, extendInScopeSetList, extendInScopeSetSet,
30 getInScopeVars, lookupInScope, lookupInScope_Directly,
31 elemInScopeSet, uniqAway,
36 -- ** Operations on RnEnv2s
37 mkRnEnv2, rnBndr2, rnBndrs2, rnOccL, rnOccR, inRnEnvL, inRnEnvR,
38 rnBndrL, rnBndrR, nukeRnEnvL, nukeRnEnvR, extendRnInScopeList,
40 rnInScope, rnInScopeSet, lookupRnInScope,
42 -- * TidyEnv and its operation
61 %************************************************************************
65 %************************************************************************
68 -- | A set of variables that are in scope at some point
69 data InScopeSet = InScope (VarEnv Var) FastInt
70 -- The (VarEnv Var) is just a VarSet. But we write it like
71 -- this to remind ourselves that you can look up a Var in
72 -- the InScopeSet. Typically the InScopeSet contains the
73 -- canonical version of the variable (e.g. with an informative
74 -- unfolding), so this lookup is useful.
76 -- INVARIANT: the VarEnv maps (the Unique of) a variable to
77 -- a variable with the same Uniqua. (This was not
78 -- the case in the past, when we had a grevious hack
79 -- mapping var1 to var2.
81 -- The FastInt is a kind of hash-value used by uniqAway
82 -- For example, it might be the size of the set
83 -- INVARIANT: it's not zero; we use it as a multiplier in uniqAway
85 instance Outputable InScopeSet where
86 ppr (InScope s _) = ptext (sLit "InScope") <+> ppr s
88 emptyInScopeSet :: InScopeSet
89 emptyInScopeSet = InScope emptyVarSet (_ILIT(1))
91 getInScopeVars :: InScopeSet -> VarEnv Var
92 getInScopeVars (InScope vs _) = vs
94 mkInScopeSet :: VarEnv Var -> InScopeSet
95 mkInScopeSet in_scope = InScope in_scope (_ILIT(1))
97 extendInScopeSet :: InScopeSet -> Var -> InScopeSet
98 extendInScopeSet (InScope in_scope n) v = InScope (extendVarEnv in_scope v v) (n +# _ILIT(1))
100 extendInScopeSetList :: InScopeSet -> [Var] -> InScopeSet
101 extendInScopeSetList (InScope in_scope n) vs
102 = InScope (foldl (\s v -> extendVarEnv s v v) in_scope vs)
103 (n +# iUnbox (length vs))
105 extendInScopeSetSet :: InScopeSet -> VarEnv Var -> InScopeSet
106 extendInScopeSetSet (InScope in_scope n) vs
107 = InScope (in_scope `plusVarEnv` vs) (n +# iUnbox (sizeUFM vs))
109 delInScopeSet :: InScopeSet -> Var -> InScopeSet
110 delInScopeSet (InScope in_scope n) v = InScope (in_scope `delVarEnv` v) n
112 elemInScopeSet :: Var -> InScopeSet -> Bool
113 elemInScopeSet v (InScope in_scope _) = v `elemVarEnv` in_scope
115 -- | Look up a variable the 'InScopeSet'. This lets you map from
116 -- the variable's identity (unique) to its full value.
117 lookupInScope :: InScopeSet -> Var -> Maybe Var
118 lookupInScope (InScope in_scope _) v = lookupVarEnv in_scope v
120 lookupInScope_Directly :: InScopeSet -> Unique -> Maybe Var
121 lookupInScope_Directly (InScope in_scope _) uniq
122 = lookupVarEnv_Directly in_scope uniq
126 -- | @uniqAway in_scope v@ finds a unique that is not used in the
127 -- in-scope set, and gives that to v.
128 uniqAway :: InScopeSet -> Var -> Var
129 -- It starts with v's current unique, of course, in the hope that it won't
130 -- have to change, and thereafter uses a combination of that and the hash-code
131 -- found in the in-scope set
132 uniqAway in_scope var
133 | var `elemInScopeSet` in_scope = uniqAway' in_scope var -- Make a new one
134 | otherwise = var -- Nothing to do
136 uniqAway' :: InScopeSet -> Var -> Var
137 -- This one *always* makes up a new variable
138 uniqAway' (InScope set n) var
141 orig_unique = getUnique var
143 | debugIsOn && (k ># _ILIT(1000))
144 = pprPanic "uniqAway loop:" (ppr (iBox k) <+> text "tries" <+> ppr var <+> int (iBox n))
145 | uniq `elemVarSetByKey` set = try (k +# _ILIT(1))
146 | debugIsOn && opt_PprStyle_Debug && (k ># _ILIT(3))
147 = pprTrace "uniqAway:" (ppr (iBox k) <+> text "tries" <+> ppr var <+> int (iBox n))
148 setVarUnique var uniq
149 | otherwise = setVarUnique var uniq
151 uniq = deriveUnique orig_unique (iBox (n *# k))
154 %************************************************************************
158 %************************************************************************
161 -- | When we are comparing (or matching) types or terms, we are faced with
162 -- \"going under\" corresponding binders. E.g. when comparing:
166 -- Basically we want to rename [@x@ -> @y@] or [@y@ -> @x@], but there are lots of
167 -- things we must be careful of. In particular, @x@ might be free in @e2@, or
168 -- y in @e1@. So the idea is that we come up with a fresh binder that is free
169 -- in neither, and rename @x@ and @y@ respectively. That means we must maintain:
171 -- 1. A renaming for the left-hand expression
173 -- 2. A renaming for the right-hand expressions
175 -- 3. An in-scope set
177 -- Furthermore, when matching, we want to be able to have an 'occurs check',
182 -- matching with [@f@ -> @y@]. So for each expression we want to know that set of
183 -- locally-bound variables. That is precisely the domain of the mappings 1.
184 -- and 2., but we must ensure that we always extend the mappings as we go in.
186 -- All of this information is bundled up in the 'RnEnv2'
188 = RV2 { envL :: VarEnv Var -- Renaming for Left term
189 , envR :: VarEnv Var -- Renaming for Right term
190 , in_scope :: InScopeSet } -- In scope in left or right terms
192 -- The renamings envL and envR are *guaranteed* to contain a binding
193 -- for every variable bound as we go into the term, even if it is not
194 -- renamed. That way we can ask what variables are locally bound
195 -- (inRnEnvL, inRnEnvR)
197 mkRnEnv2 :: InScopeSet -> RnEnv2
198 mkRnEnv2 vars = RV2 { envL = emptyVarEnv
202 extendRnInScopeList :: RnEnv2 -> [Var] -> RnEnv2
203 extendRnInScopeList env vs
204 = env { in_scope = extendInScopeSetList (in_scope env) vs }
206 rnInScope :: Var -> RnEnv2 -> Bool
207 rnInScope x env = x `elemInScopeSet` in_scope env
209 rnInScopeSet :: RnEnv2 -> InScopeSet
210 rnInScopeSet = in_scope
212 rnBndrs2 :: RnEnv2 -> [Var] -> [Var] -> RnEnv2
213 -- ^ Applies 'rnBndr2' to several variables: the two variable lists must be of equal length
214 rnBndrs2 env bsL bsR = foldl2 rnBndr2 env bsL bsR
216 rnBndr2 :: RnEnv2 -> Var -> Var -> RnEnv2
217 -- ^ @rnBndr2 env bL bR@ goes under a binder @bL@ in the Left term,
218 -- and binder @bR@ in the Right term.
219 -- It finds a new binder, @new_b@,
220 -- and returns an environment mapping @bL -> new_b@ and @bR -> new_b@
221 rnBndr2 (RV2 { envL = envL, envR = envR, in_scope = in_scope }) bL bR
222 = RV2 { envL = extendVarEnv envL bL new_b -- See Note
223 , envR = extendVarEnv envR bR new_b -- [Rebinding]
224 , in_scope = extendInScopeSet in_scope new_b }
226 -- Find a new binder not in scope in either term
227 new_b | not (bL `elemInScopeSet` in_scope) = bL
228 | not (bR `elemInScopeSet` in_scope) = bR
229 | otherwise = uniqAway' in_scope bL
232 -- If the new var is the same as the old one, note that
233 -- the extendVarEnv *deletes* any current renaming
234 -- E.g. (\x. \x. ...) ~ (\y. \z. ...)
236 -- Inside \x \y { [x->y], [y->y], {y} }
237 -- \x \z { [x->x], [y->y, z->x], {y,x} }
239 rnBndrL :: RnEnv2 -> Var -> (RnEnv2, Var)
240 -- ^ Similar to 'rnBndr2' but used when there's a binder on the left
242 rnBndrL (RV2 { envL = envL, envR = envR, in_scope = in_scope }) bL
243 = (RV2 { envL = extendVarEnv envL bL new_b
245 , in_scope = extendInScopeSet in_scope new_b }, new_b)
247 new_b = uniqAway in_scope bL
249 rnBndrR :: RnEnv2 -> Var -> (RnEnv2, Var)
250 -- ^ Similar to 'rnBndr2' but used when there's a binder on the right
252 rnBndrR (RV2 { envL = envL, envR = envR, in_scope = in_scope }) bR
253 = (RV2 { envR = extendVarEnv envR bR new_b
255 , in_scope = extendInScopeSet in_scope new_b }, new_b)
257 new_b = uniqAway in_scope bR
259 rnEtaL :: RnEnv2 -> Var -> (RnEnv2, Var)
260 -- ^ Similar to 'rnBndrL' but used for eta expansion
261 -- See Note [Eta expansion]
262 rnEtaL (RV2 { envL = envL, envR = envR, in_scope = in_scope }) bL
263 = (RV2 { envL = extendVarEnv envL bL new_b
264 , envR = extendVarEnv envR new_b new_b -- Note [Eta expansion]
265 , in_scope = extendInScopeSet in_scope new_b }, new_b)
267 new_b = uniqAway in_scope bL
269 rnEtaR :: RnEnv2 -> Var -> (RnEnv2, Var)
270 -- ^ Similar to 'rnBndr2' but used for eta expansion
271 -- See Note [Eta expansion]
272 rnEtaR (RV2 { envL = envL, envR = envR, in_scope = in_scope }) bR
273 = (RV2 { envL = extendVarEnv envL new_b new_b -- Note [Eta expansion]
274 , envR = extendVarEnv envR bR new_b
275 , in_scope = extendInScopeSet in_scope new_b }, new_b)
277 new_b = uniqAway in_scope bR
279 rnOccL, rnOccR :: RnEnv2 -> Var -> Var
280 -- ^ Look up the renaming of an occurrence in the left or right term
281 rnOccL (RV2 { envL = env }) v = lookupVarEnv env v `orElse` v
282 rnOccR (RV2 { envR = env }) v = lookupVarEnv env v `orElse` v
284 inRnEnvL, inRnEnvR :: RnEnv2 -> Var -> Bool
285 -- ^ Tells whether a variable is locally bound
286 inRnEnvL (RV2 { envL = env }) v = v `elemVarEnv` env
287 inRnEnvR (RV2 { envR = env }) v = v `elemVarEnv` env
289 lookupRnInScope :: RnEnv2 -> Var -> Var
290 lookupRnInScope env v = lookupInScope (in_scope env) v `orElse` v
292 nukeRnEnvL, nukeRnEnvR :: RnEnv2 -> RnEnv2
293 -- ^ Wipe the left or right side renaming
294 nukeRnEnvL env = env { envL = emptyVarEnv }
295 nukeRnEnvR env = env { envR = emptyVarEnv }
302 we rename x to x' with, where x' is not in scope in
303 either term. Then we want to behave as if we'd seen
305 Since x' isn't in scope in N, the form (\x'. N x') doesn't
306 capture any variables in N. But we must nevertheless extend
307 the envR with a binding [x' -> x'], to support the occurs check.
308 For example, if we don't do this, we can get silly matches like
310 succeeding with [a -> v y], which is bogus of course.
313 %************************************************************************
317 %************************************************************************
320 -- | When tidying up print names, we keep a mapping of in-scope occ-names
321 -- (the 'TidyOccEnv') and a Var-to-Var of the current renamings
322 type TidyEnv = (TidyOccEnv, VarEnv Var)
324 emptyTidyEnv :: TidyEnv
325 emptyTidyEnv = (emptyTidyOccEnv, emptyVarEnv)
329 %************************************************************************
331 \subsection{@VarEnv@s}
333 %************************************************************************
336 type VarEnv elt = UniqFM elt
337 type IdEnv elt = VarEnv elt
338 type TyVarEnv elt = VarEnv elt
340 emptyVarEnv :: VarEnv a
341 mkVarEnv :: [(Var, a)] -> VarEnv a
342 zipVarEnv :: [Var] -> [a] -> VarEnv a
343 unitVarEnv :: Var -> a -> VarEnv a
344 extendVarEnv :: VarEnv a -> Var -> a -> VarEnv a
345 extendVarEnv_C :: (a->a->a) -> VarEnv a -> Var -> a -> VarEnv a
346 extendVarEnv_Acc :: (a->b->b) -> (a->b) -> VarEnv b -> Var -> a -> VarEnv b
347 plusVarEnv :: VarEnv a -> VarEnv a -> VarEnv a
348 extendVarEnvList :: VarEnv a -> [(Var, a)] -> VarEnv a
350 lookupVarEnv_Directly :: VarEnv a -> Unique -> Maybe a
351 filterVarEnv_Directly :: (Unique -> a -> Bool) -> VarEnv a -> VarEnv a
352 restrictVarEnv :: VarEnv a -> VarSet -> VarEnv a
353 delVarEnvList :: VarEnv a -> [Var] -> VarEnv a
354 delVarEnv :: VarEnv a -> Var -> VarEnv a
355 plusVarEnv_C :: (a -> a -> a) -> VarEnv a -> VarEnv a -> VarEnv a
356 mapVarEnv :: (a -> b) -> VarEnv a -> VarEnv b
357 modifyVarEnv :: (a -> a) -> VarEnv a -> Var -> VarEnv a
358 varEnvElts :: VarEnv a -> [a]
359 varEnvKeys :: VarEnv a -> [Unique]
361 isEmptyVarEnv :: VarEnv a -> Bool
362 lookupVarEnv :: VarEnv a -> Var -> Maybe a
363 lookupVarEnv_NF :: VarEnv a -> Var -> a
364 lookupWithDefaultVarEnv :: VarEnv a -> a -> Var -> a
365 elemVarEnv :: Var -> VarEnv a -> Bool
366 elemVarEnvByKey :: Unique -> VarEnv a -> Bool
367 foldVarEnv :: (a -> b -> b) -> b -> VarEnv a -> b
372 elemVarEnvByKey = elemUFM_Directly
373 extendVarEnv = addToUFM
374 extendVarEnv_C = addToUFM_C
375 extendVarEnv_Acc = addToUFM_Acc
376 extendVarEnvList = addListToUFM
377 plusVarEnv_C = plusUFM_C
378 delVarEnvList = delListFromUFM
379 delVarEnv = delFromUFM
381 lookupVarEnv = lookupUFM
382 lookupWithDefaultVarEnv = lookupWithDefaultUFM
385 emptyVarEnv = emptyUFM
389 isEmptyVarEnv = isNullUFM
391 lookupVarEnv_Directly = lookupUFM_Directly
392 filterVarEnv_Directly = filterUFM_Directly
394 restrictVarEnv env vs = filterVarEnv_Directly keep env
396 keep u _ = u `elemVarSetByKey` vs
398 zipVarEnv tyvars tys = mkVarEnv (zipEqual "zipVarEnv" tyvars tys)
399 lookupVarEnv_NF env id = case lookupVarEnv env id of
401 Nothing -> panic "lookupVarEnv_NF: Nothing"
404 @modifyVarEnv@: Look up a thing in the VarEnv,
405 then mash it with the modify function, and put it back.
408 modifyVarEnv mangle_fn env key
409 = case (lookupVarEnv env key) of
411 Just xx -> extendVarEnv env key (mangle_fn xx)
413 modifyVarEnv_Directly :: (a -> a) -> UniqFM a -> Unique -> UniqFM a
414 modifyVarEnv_Directly mangle_fn env key
415 = case (lookupUFM_Directly env key) of
417 Just xx -> addToUFM_Directly env key (mangle_fn xx)