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,
39 rnInScope, rnInScopeSet, lookupRnInScope,
41 -- * TidyEnv and its operation
60 %************************************************************************
64 %************************************************************************
67 -- | A set of variables that are in scope at some point
68 data InScopeSet = InScope (VarEnv Var) FastInt
69 -- The (VarEnv Var) is just a VarSet. But we write it like
70 -- this to remind ourselves that you can look up a Var in
71 -- the InScopeSet. Typically the InScopeSet contains the
72 -- canonical version of the variable (e.g. with an informative
73 -- unfolding), so this lookup is useful.
75 -- INVARIANT: the VarEnv maps (the Unique of) a variable to
76 -- a variable with the same Uniqua. (This was not
77 -- the case in the past, when we had a grevious hack
78 -- mapping var1 to var2.
80 -- The FastInt is a kind of hash-value used by uniqAway
81 -- For example, it might be the size of the set
82 -- INVARIANT: it's not zero; we use it as a multiplier in uniqAway
84 instance Outputable InScopeSet where
85 ppr (InScope s _) = ptext (sLit "InScope") <+> ppr s
87 emptyInScopeSet :: InScopeSet
88 emptyInScopeSet = InScope emptyVarSet (_ILIT(1))
90 getInScopeVars :: InScopeSet -> VarEnv Var
91 getInScopeVars (InScope vs _) = vs
93 mkInScopeSet :: VarEnv Var -> InScopeSet
94 mkInScopeSet in_scope = InScope in_scope (_ILIT(1))
96 extendInScopeSet :: InScopeSet -> Var -> InScopeSet
97 extendInScopeSet (InScope in_scope n) v = InScope (extendVarEnv in_scope v v) (n +# _ILIT(1))
99 extendInScopeSetList :: InScopeSet -> [Var] -> InScopeSet
100 extendInScopeSetList (InScope in_scope n) vs
101 = InScope (foldl (\s v -> extendVarEnv s v v) in_scope vs)
102 (n +# iUnbox (length vs))
104 extendInScopeSetSet :: InScopeSet -> VarEnv Var -> InScopeSet
105 extendInScopeSetSet (InScope in_scope n) vs
106 = InScope (in_scope `plusVarEnv` vs) (n +# iUnbox (sizeUFM vs))
108 delInScopeSet :: InScopeSet -> Var -> InScopeSet
109 delInScopeSet (InScope in_scope n) v = InScope (in_scope `delVarEnv` v) n
111 elemInScopeSet :: Var -> InScopeSet -> Bool
112 elemInScopeSet v (InScope in_scope _) = v `elemVarEnv` in_scope
114 -- | Look up a variable the 'InScopeSet'. This lets you map from
115 -- the variable's identity (unique) to its full value.
116 lookupInScope :: InScopeSet -> Var -> Maybe Var
117 lookupInScope (InScope in_scope _) v = lookupVarEnv in_scope v
119 lookupInScope_Directly :: InScopeSet -> Unique -> Maybe Var
120 lookupInScope_Directly (InScope in_scope _) uniq
121 = lookupVarEnv_Directly in_scope uniq
125 -- | @uniqAway in_scope v@ finds a unique that is not used in the
126 -- in-scope set, and gives that to v.
127 uniqAway :: InScopeSet -> Var -> Var
128 -- It starts with v's current unique, of course, in the hope that it won't
129 -- have to change, and thereafter uses a combination of that and the hash-code
130 -- found in the in-scope set
131 uniqAway in_scope var
132 | var `elemInScopeSet` in_scope = uniqAway' in_scope var -- Make a new one
133 | otherwise = var -- Nothing to do
135 uniqAway' :: InScopeSet -> Var -> Var
136 -- This one *always* makes up a new variable
137 uniqAway' (InScope set n) var
140 orig_unique = getUnique var
142 | debugIsOn && (k ># _ILIT(1000))
143 = pprPanic "uniqAway loop:" (ppr (iBox k) <+> text "tries" <+> ppr var <+> int (iBox n))
144 | uniq `elemVarSetByKey` set = try (k +# _ILIT(1))
145 | debugIsOn && opt_PprStyle_Debug && (k ># _ILIT(3))
146 = pprTrace "uniqAway:" (ppr (iBox k) <+> text "tries" <+> ppr var <+> int (iBox n))
147 setVarUnique var uniq
148 | otherwise = setVarUnique var uniq
150 uniq = deriveUnique orig_unique (iBox (n *# k))
153 %************************************************************************
157 %************************************************************************
160 -- | When we are comparing (or matching) types or terms, we are faced with
161 -- \"going under\" corresponding binders. E.g. when comparing:
165 -- Basically we want to rename [@x@ -> @y@] or [@y@ -> @x@], but there are lots of
166 -- things we must be careful of. In particular, @x@ might be free in @e2@, or
167 -- y in @e1@. So the idea is that we come up with a fresh binder that is free
168 -- in neither, and rename @x@ and @y@ respectively. That means we must maintain:
170 -- 1. A renaming for the left-hand expression
172 -- 2. A renaming for the right-hand expressions
174 -- 3. An in-scope set
176 -- Furthermore, when matching, we want to be able to have an 'occurs check',
181 -- matching with [@f@ -> @y@]. So for each expression we want to know that set of
182 -- locally-bound variables. That is precisely the domain of the mappings 1.
183 -- and 2., but we must ensure that we always extend the mappings as we go in.
185 -- All of this information is bundled up in the 'RnEnv2'
187 = RV2 { envL :: VarEnv Var -- Renaming for Left term
188 , envR :: VarEnv Var -- Renaming for Right term
189 , in_scope :: InScopeSet } -- In scope in left or right terms
191 -- The renamings envL and envR are *guaranteed* to contain a binding
192 -- for every variable bound as we go into the term, even if it is not
193 -- renamed. That way we can ask what variables are locally bound
194 -- (inRnEnvL, inRnEnvR)
196 mkRnEnv2 :: InScopeSet -> RnEnv2
197 mkRnEnv2 vars = RV2 { envL = emptyVarEnv
201 extendRnInScopeList :: RnEnv2 -> [Var] -> RnEnv2
202 extendRnInScopeList env vs
203 = env { in_scope = extendInScopeSetList (in_scope env) vs }
205 rnInScope :: Var -> RnEnv2 -> Bool
206 rnInScope x env = x `elemInScopeSet` in_scope env
208 rnInScopeSet :: RnEnv2 -> InScopeSet
209 rnInScopeSet = in_scope
211 rnBndrs2 :: RnEnv2 -> [Var] -> [Var] -> RnEnv2
212 -- ^ Applies 'rnBndr2' to several variables: the two variable lists must be of equal length
213 rnBndrs2 env bsL bsR = foldl2 rnBndr2 env bsL bsR
215 rnBndr2 :: RnEnv2 -> Var -> Var -> RnEnv2
216 -- ^ @rnBndr2 env bL bR@ goes under a binder @bL@ in the Left term,
217 -- and binder @bR@ in the Right term.
218 -- It finds a new binder, @new_b@,
219 -- and returns an environment mapping @bL -> new_b@ and @bR -> new_b@
220 rnBndr2 (RV2 { envL = envL, envR = envR, in_scope = in_scope }) bL bR
221 = RV2 { envL = extendVarEnv envL bL new_b -- See Note
222 , envR = extendVarEnv envR bR new_b -- [Rebinding]
223 , in_scope = extendInScopeSet in_scope new_b }
225 -- Find a new binder not in scope in either term
226 new_b | not (bL `elemInScopeSet` in_scope) = bL
227 | not (bR `elemInScopeSet` in_scope) = bR
228 | otherwise = uniqAway' in_scope bL
231 -- If the new var is the same as the old one, note that
232 -- the extendVarEnv *deletes* any current renaming
233 -- E.g. (\x. \x. ...) ~ (\y. \z. ...)
235 -- Inside \x \y { [x->y], [y->y], {y} }
236 -- \x \z { [x->x], [y->y, z->x], {y,x} }
238 rnBndrL :: RnEnv2 -> Var -> (RnEnv2, Var)
239 -- ^ Similar to 'rnBndr2' but used when there's a binder on the left
240 -- side only. Useful when eta-expanding
241 rnBndrL (RV2 { envL = envL, envR = envR, in_scope = in_scope }) bL
242 = (RV2 { envL = extendVarEnv envL bL new_b
243 , envR = extendVarEnv envR new_b new_b -- Note [rnBndrLR]
244 , in_scope = extendInScopeSet in_scope new_b }, new_b)
246 new_b = uniqAway in_scope bL
248 rnBndrR :: RnEnv2 -> Var -> (RnEnv2, Var)
249 -- ^ Similar to 'rnBndr2' but used when there's a binder on the right
250 -- side only. Useful when eta-expanding
251 rnBndrR (RV2 { envL = envL, envR = envR, in_scope = in_scope }) bR
252 = (RV2 { envL = extendVarEnv envL new_b new_b -- Note [rnBndrLR]
253 , envR = extendVarEnv envR bR new_b
254 , in_scope = extendInScopeSet in_scope new_b }, new_b)
256 new_b = uniqAway in_scope bR
260 -- Notice that in rnBndrL, rnBndrR, we extend envR, envL respectively
261 -- with a binding [new_b -> new_b], where new_b is the new binder.
262 -- This is important when doing eta expansion; e.g. matching (\x.M) ~ N
263 -- In effect we switch to (\x'.M) ~ (\x'.N x'), where x' is new_b
264 -- So we must add x' to the env of both L and R. (x' is fresh, so it
265 -- can't capture anything in N.)
267 -- If we don't do this, we can get silly matches like
268 -- forall a. \y.a ~ v
269 -- succeeding with [x -> v y], which is bogus of course
271 rnOccL, rnOccR :: RnEnv2 -> Var -> Var
272 -- ^ Look up the renaming of an occurrence in the left or right term
273 rnOccL (RV2 { envL = env }) v = lookupVarEnv env v `orElse` v
274 rnOccR (RV2 { envR = env }) v = lookupVarEnv env v `orElse` v
276 inRnEnvL, inRnEnvR :: RnEnv2 -> Var -> Bool
277 -- ^ Tells whether a variable is locally bound
278 inRnEnvL (RV2 { envL = env }) v = v `elemVarEnv` env
279 inRnEnvR (RV2 { envR = env }) v = v `elemVarEnv` env
281 lookupRnInScope :: RnEnv2 -> Var -> Var
282 lookupRnInScope env v = lookupInScope (in_scope env) v `orElse` v
284 nukeRnEnvL, nukeRnEnvR :: RnEnv2 -> RnEnv2
285 -- ^ Wipe the left or right side renaming
286 nukeRnEnvL env = env { envL = emptyVarEnv }
287 nukeRnEnvR env = env { envR = emptyVarEnv }
291 %************************************************************************
295 %************************************************************************
298 -- | When tidying up print names, we keep a mapping of in-scope occ-names
299 -- (the 'TidyOccEnv') and a Var-to-Var of the current renamings
300 type TidyEnv = (TidyOccEnv, VarEnv Var)
302 emptyTidyEnv :: TidyEnv
303 emptyTidyEnv = (emptyTidyOccEnv, emptyVarEnv)
307 %************************************************************************
309 \subsection{@VarEnv@s}
311 %************************************************************************
314 type VarEnv elt = UniqFM elt
315 type IdEnv elt = VarEnv elt
316 type TyVarEnv elt = VarEnv elt
318 emptyVarEnv :: VarEnv a
319 mkVarEnv :: [(Var, a)] -> VarEnv a
320 zipVarEnv :: [Var] -> [a] -> VarEnv a
321 unitVarEnv :: Var -> a -> VarEnv a
322 extendVarEnv :: VarEnv a -> Var -> a -> VarEnv a
323 extendVarEnv_C :: (a->a->a) -> VarEnv a -> Var -> a -> VarEnv a
324 extendVarEnv_Acc :: (a->b->b) -> (a->b) -> VarEnv b -> Var -> a -> VarEnv b
325 plusVarEnv :: VarEnv a -> VarEnv a -> VarEnv a
326 extendVarEnvList :: VarEnv a -> [(Var, a)] -> VarEnv a
328 lookupVarEnv_Directly :: VarEnv a -> Unique -> Maybe a
329 filterVarEnv_Directly :: (Unique -> a -> Bool) -> VarEnv a -> VarEnv a
330 restrictVarEnv :: VarEnv a -> VarSet -> VarEnv a
331 delVarEnvList :: VarEnv a -> [Var] -> VarEnv a
332 delVarEnv :: VarEnv a -> Var -> VarEnv a
333 plusVarEnv_C :: (a -> a -> a) -> VarEnv a -> VarEnv a -> VarEnv a
334 mapVarEnv :: (a -> b) -> VarEnv a -> VarEnv b
335 modifyVarEnv :: (a -> a) -> VarEnv a -> Var -> VarEnv a
336 varEnvElts :: VarEnv a -> [a]
337 varEnvKeys :: VarEnv a -> [Unique]
339 isEmptyVarEnv :: VarEnv a -> Bool
340 lookupVarEnv :: VarEnv a -> Var -> Maybe a
341 lookupVarEnv_NF :: VarEnv a -> Var -> a
342 lookupWithDefaultVarEnv :: VarEnv a -> a -> Var -> a
343 elemVarEnv :: Var -> VarEnv a -> Bool
344 elemVarEnvByKey :: Unique -> VarEnv a -> Bool
345 foldVarEnv :: (a -> b -> b) -> b -> VarEnv a -> b
350 elemVarEnvByKey = elemUFM_Directly
351 extendVarEnv = addToUFM
352 extendVarEnv_C = addToUFM_C
353 extendVarEnv_Acc = addToUFM_Acc
354 extendVarEnvList = addListToUFM
355 plusVarEnv_C = plusUFM_C
356 delVarEnvList = delListFromUFM
357 delVarEnv = delFromUFM
359 lookupVarEnv = lookupUFM
360 lookupWithDefaultVarEnv = lookupWithDefaultUFM
363 emptyVarEnv = emptyUFM
367 isEmptyVarEnv = isNullUFM
369 lookupVarEnv_Directly = lookupUFM_Directly
370 filterVarEnv_Directly = filterUFM_Directly
372 restrictVarEnv env vs = filterVarEnv_Directly keep env
374 keep u _ = u `elemVarSetByKey` vs
376 zipVarEnv tyvars tys = mkVarEnv (zipEqual "zipVarEnv" tyvars tys)
377 lookupVarEnv_NF env id = case lookupVarEnv env id of
379 Nothing -> panic "lookupVarEnv_NF: Nothing"
382 @modifyVarEnv@: Look up a thing in the VarEnv,
383 then mash it with the modify function, and put it back.
386 modifyVarEnv mangle_fn env key
387 = case (lookupVarEnv env key) of
389 Just xx -> extendVarEnv env key (mangle_fn xx)
391 modifyVarEnv_Directly :: (a -> a) -> UniqFM a -> Unique -> UniqFM a
392 modifyVarEnv_Directly mangle_fn env key
393 = case (lookupUFM_Directly env key) of
395 Just xx -> addToUFM_Directly env key (mangle_fn xx)