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, 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,
24 -- * The InScopeSet type
27 -- ** Operations on InScopeSets
28 emptyInScopeSet, mkInScopeSet, delInScopeSet,
29 extendInScopeSet, extendInScopeSetList, extendInScopeSetSet,
30 getInScopeVars, lookupInScope, elemInScopeSet, uniqAway,
35 -- ** Operations on RnEnv2s
36 mkRnEnv2, rnBndr2, rnBndrs2, rnOccL, rnOccR, inRnEnvL, inRnEnvR,
37 rnBndrL, rnBndrR, nukeRnEnvL, nukeRnEnvR, extendRnInScopeList,
38 rnInScope, rnInScopeSet, lookupRnInScope,
40 -- * TidyEnv and its operation
59 %************************************************************************
63 %************************************************************************
66 -- | A set of variables that are in scope at some point
67 data InScopeSet = InScope (VarEnv Var) FastInt
68 -- The (VarEnv Var) is just a VarSet. But we write it like
69 -- this to remind ourselves that you can look up a Var in
70 -- the InScopeSet. Typically the InScopeSet contains the
71 -- canonical version of the variable (e.g. with an informative
72 -- unfolding), so this lookup is useful.
74 -- INVARIANT: the VarEnv maps (the Unique of) a variable to
75 -- a variable with the same Uniqua. (This was not
76 -- the case in the past, when we had a grevious hack
77 -- mapping var1 to var2.
79 -- The FastInt is a kind of hash-value used by uniqAway
80 -- For example, it might be the size of the set
81 -- INVARIANT: it's not zero; we use it as a multiplier in uniqAway
83 instance Outputable InScopeSet where
84 ppr (InScope s _) = ptext (sLit "InScope") <+> ppr s
86 emptyInScopeSet :: InScopeSet
87 emptyInScopeSet = InScope emptyVarSet (_ILIT(1))
89 getInScopeVars :: InScopeSet -> VarEnv Var
90 getInScopeVars (InScope vs _) = vs
92 mkInScopeSet :: VarEnv Var -> InScopeSet
93 mkInScopeSet in_scope = InScope in_scope (_ILIT(1))
95 extendInScopeSet :: InScopeSet -> Var -> InScopeSet
96 extendInScopeSet (InScope in_scope n) v = InScope (extendVarEnv in_scope v v) (n +# _ILIT(1))
98 extendInScopeSetList :: InScopeSet -> [Var] -> InScopeSet
99 extendInScopeSetList (InScope in_scope n) vs
100 = InScope (foldl (\s v -> extendVarEnv s v v) in_scope vs)
101 (n +# iUnbox (length vs))
103 extendInScopeSetSet :: InScopeSet -> VarEnv Var -> InScopeSet
104 extendInScopeSetSet (InScope in_scope n) vs
105 = InScope (in_scope `plusVarEnv` vs) (n +# iUnbox (sizeUFM vs))
107 delInScopeSet :: InScopeSet -> Var -> InScopeSet
108 delInScopeSet (InScope in_scope n) v = InScope (in_scope `delVarEnv` v) n
110 elemInScopeSet :: Var -> InScopeSet -> Bool
111 elemInScopeSet v (InScope in_scope _) = v `elemVarEnv` in_scope
113 -- | Look up a variable the 'InScopeSet'. This lets you map from
114 -- the variable's identity (unique) to its full value.
115 lookupInScope :: InScopeSet -> Var -> Maybe Var
116 lookupInScope (InScope in_scope _) v = lookupVarEnv in_scope v
120 -- | @uniqAway in_scope v@ finds a unique that is not used in the
121 -- in-scope set, and gives that to v.
122 uniqAway :: InScopeSet -> Var -> Var
123 -- It starts with v's current unique, of course, in the hope that it won't
124 -- have to change, and thereafter uses a combination of that and the hash-code
125 -- found in the in-scope set
126 uniqAway in_scope var
127 | var `elemInScopeSet` in_scope = uniqAway' in_scope var -- Make a new one
128 | otherwise = var -- Nothing to do
130 uniqAway' :: InScopeSet -> Var -> Var
131 -- This one *always* makes up a new variable
132 uniqAway' (InScope set n) var
135 orig_unique = getUnique var
137 | debugIsOn && (k ># _ILIT(1000))
138 = pprPanic "uniqAway loop:" (ppr (iBox k) <+> text "tries" <+> ppr var <+> int (iBox n))
139 | uniq `elemVarSetByKey` set = try (k +# _ILIT(1))
140 | debugIsOn && opt_PprStyle_Debug && (k ># _ILIT(3))
141 = pprTrace "uniqAway:" (ppr (iBox k) <+> text "tries" <+> ppr var <+> int (iBox n))
142 setVarUnique var uniq
143 | otherwise = setVarUnique var uniq
145 uniq = deriveUnique orig_unique (iBox (n *# k))
148 %************************************************************************
152 %************************************************************************
155 -- | When we are comparing (or matching) types or terms, we are faced with
156 -- \"going under\" corresponding binders. E.g. when comparing:
160 -- Basically we want to rename [@x@ -> @y@] or [@y@ -> @x@], but there are lots of
161 -- things we must be careful of. In particular, @x@ might be free in @e2@, or
162 -- y in @e1@. So the idea is that we come up with a fresh binder that is free
163 -- in neither, and rename @x@ and @y@ respectively. That means we must maintain:
165 -- 1. A renaming for the left-hand expression
167 -- 2. A renaming for the right-hand expressions
169 -- 3. An in-scope set
171 -- Furthermore, when matching, we want to be able to have an 'occurs check',
176 -- matching with [@f@ -> @y@]. So for each expression we want to know that set of
177 -- locally-bound variables. That is precisely the domain of the mappings 1.
178 -- and 2., but we must ensure that we always extend the mappings as we go in.
180 -- All of this information is bundled up in the 'RnEnv2'
182 = RV2 { envL :: VarEnv Var -- Renaming for Left term
183 , envR :: VarEnv Var -- Renaming for Right term
184 , in_scope :: InScopeSet } -- In scope in left or right terms
186 -- The renamings envL and envR are *guaranteed* to contain a binding
187 -- for every variable bound as we go into the term, even if it is not
188 -- renamed. That way we can ask what variables are locally bound
189 -- (inRnEnvL, inRnEnvR)
191 mkRnEnv2 :: InScopeSet -> RnEnv2
192 mkRnEnv2 vars = RV2 { envL = emptyVarEnv
196 extendRnInScopeList :: RnEnv2 -> [Var] -> RnEnv2
197 extendRnInScopeList env vs
198 = env { in_scope = extendInScopeSetList (in_scope env) vs }
200 rnInScope :: Var -> RnEnv2 -> Bool
201 rnInScope x env = x `elemInScopeSet` in_scope env
203 rnInScopeSet :: RnEnv2 -> InScopeSet
204 rnInScopeSet = in_scope
206 rnBndrs2 :: RnEnv2 -> [Var] -> [Var] -> RnEnv2
207 -- ^ Applies 'rnBndr2' to several variables: the two variable lists must be of equal length
208 rnBndrs2 env bsL bsR = foldl2 rnBndr2 env bsL bsR
210 rnBndr2 :: RnEnv2 -> Var -> Var -> RnEnv2
211 -- ^ @rnBndr2 env bL bR@ goes under a binder @bL@ in the Left term,
212 -- and binder @bR@ in the Right term.
213 -- It finds a new binder, @new_b@,
214 -- and returns an environment mapping @bL -> new_b@ and @bR -> new_b@
215 rnBndr2 (RV2 { envL = envL, envR = envR, in_scope = in_scope }) bL bR
216 = RV2 { envL = extendVarEnv envL bL new_b -- See Note
217 , envR = extendVarEnv envR bR new_b -- [Rebinding]
218 , in_scope = extendInScopeSet in_scope new_b }
220 -- Find a new binder not in scope in either term
221 new_b | not (bL `elemInScopeSet` in_scope) = bL
222 | not (bR `elemInScopeSet` in_scope) = bR
223 | otherwise = uniqAway' in_scope bL
226 -- If the new var is the same as the old one, note that
227 -- the extendVarEnv *deletes* any current renaming
228 -- E.g. (\x. \x. ...) ~ (\y. \z. ...)
230 -- Inside \x \y { [x->y], [y->y], {y} }
231 -- \x \z { [x->x], [y->y, z->x], {y,x} }
233 rnBndrL :: RnEnv2 -> Var -> (RnEnv2, Var)
234 -- ^ Similar to 'rnBndr2' but used when there's a binder on the left
235 -- side only. Useful when eta-expanding
236 rnBndrL (RV2 { envL = envL, envR = envR, in_scope = in_scope }) bL
237 = (RV2 { envL = extendVarEnv envL bL new_b
238 , envR = extendVarEnv envR new_b new_b -- Note [rnBndrLR]
239 , in_scope = extendInScopeSet in_scope new_b }, new_b)
241 new_b = uniqAway in_scope bL
243 rnBndrR :: RnEnv2 -> Var -> (RnEnv2, Var)
244 -- ^ Similar to 'rnBndr2' but used when there's a binder on the right
245 -- side only. Useful when eta-expanding
246 rnBndrR (RV2 { envL = envL, envR = envR, in_scope = in_scope }) bR
247 = (RV2 { envL = extendVarEnv envL new_b new_b -- Note [rnBndrLR]
248 , envR = extendVarEnv envR bR new_b
249 , in_scope = extendInScopeSet in_scope new_b }, new_b)
251 new_b = uniqAway in_scope bR
255 -- Notice that in rnBndrL, rnBndrR, we extend envR, envL respectively
256 -- with a binding [new_b -> new_b], where new_b is the new binder.
257 -- This is important when doing eta expansion; e.g. matching (\x.M) ~ N
258 -- In effect we switch to (\x'.M) ~ (\x'.N x'), where x' is new_b
259 -- So we must add x' to the env of both L and R. (x' is fresh, so it
260 -- can't capture anything in N.)
262 -- If we don't do this, we can get silly matches like
263 -- forall a. \y.a ~ v
264 -- succeeding with [x -> v y], which is bogus of course
266 rnOccL, rnOccR :: RnEnv2 -> Var -> Var
267 -- ^ Look up the renaming of an occurrence in the left or right term
268 rnOccL (RV2 { envL = env }) v = lookupVarEnv env v `orElse` v
269 rnOccR (RV2 { envR = env }) v = lookupVarEnv env v `orElse` v
271 inRnEnvL, inRnEnvR :: RnEnv2 -> Var -> Bool
272 -- ^ Tells whether a variable is locally bound
273 inRnEnvL (RV2 { envL = env }) v = v `elemVarEnv` env
274 inRnEnvR (RV2 { envR = env }) v = v `elemVarEnv` env
276 lookupRnInScope :: RnEnv2 -> Var -> Var
277 lookupRnInScope env v = lookupInScope (in_scope env) v `orElse` v
279 nukeRnEnvL, nukeRnEnvR :: RnEnv2 -> RnEnv2
280 -- ^ Wipe the left or right side renaming
281 nukeRnEnvL env = env { envL = emptyVarEnv }
282 nukeRnEnvR env = env { envR = emptyVarEnv }
286 %************************************************************************
290 %************************************************************************
293 -- | When tidying up print names, we keep a mapping of in-scope occ-names
294 -- (the 'TidyOccEnv') and a Var-to-Var of the current renamings
295 type TidyEnv = (TidyOccEnv, VarEnv Var)
297 emptyTidyEnv :: TidyEnv
298 emptyTidyEnv = (emptyTidyOccEnv, emptyVarEnv)
302 %************************************************************************
304 \subsection{@VarEnv@s}
306 %************************************************************************
309 type VarEnv elt = UniqFM elt
310 type IdEnv elt = VarEnv elt
311 type TyVarEnv elt = VarEnv elt
313 emptyVarEnv :: VarEnv a
314 mkVarEnv :: [(Var, a)] -> VarEnv a
315 zipVarEnv :: [Var] -> [a] -> VarEnv a
316 unitVarEnv :: Var -> a -> VarEnv a
317 extendVarEnv :: VarEnv a -> Var -> a -> VarEnv a
318 extendVarEnv_C :: (a->a->a) -> VarEnv a -> Var -> a -> VarEnv a
319 plusVarEnv :: VarEnv a -> VarEnv a -> VarEnv a
320 extendVarEnvList :: VarEnv a -> [(Var, a)] -> VarEnv a
322 lookupVarEnv_Directly :: VarEnv a -> Unique -> Maybe a
323 filterVarEnv_Directly :: (Unique -> a -> Bool) -> VarEnv a -> VarEnv a
324 delVarEnvList :: VarEnv a -> [Var] -> VarEnv a
325 delVarEnv :: VarEnv a -> Var -> VarEnv a
326 plusVarEnv_C :: (a -> a -> a) -> VarEnv a -> VarEnv a -> VarEnv a
327 mapVarEnv :: (a -> b) -> VarEnv a -> VarEnv b
328 modifyVarEnv :: (a -> a) -> VarEnv a -> Var -> VarEnv a
329 varEnvElts :: VarEnv a -> [a]
330 varEnvKeys :: VarEnv a -> [Unique]
332 isEmptyVarEnv :: VarEnv a -> Bool
333 lookupVarEnv :: VarEnv a -> Var -> Maybe a
334 lookupVarEnv_NF :: VarEnv a -> Var -> a
335 lookupWithDefaultVarEnv :: VarEnv a -> a -> Var -> a
336 elemVarEnv :: Var -> VarEnv a -> Bool
337 elemVarEnvByKey :: Unique -> VarEnv a -> Bool
338 foldVarEnv :: (a -> b -> b) -> b -> VarEnv a -> b
343 elemVarEnvByKey = elemUFM_Directly
344 extendVarEnv = addToUFM
345 extendVarEnv_C = addToUFM_C
346 extendVarEnvList = addListToUFM
347 plusVarEnv_C = plusUFM_C
348 delVarEnvList = delListFromUFM
349 delVarEnv = delFromUFM
351 lookupVarEnv = lookupUFM
352 lookupWithDefaultVarEnv = lookupWithDefaultUFM
355 emptyVarEnv = emptyUFM
359 isEmptyVarEnv = isNullUFM
361 lookupVarEnv_Directly = lookupUFM_Directly
362 filterVarEnv_Directly = filterUFM_Directly
364 zipVarEnv tyvars tys = mkVarEnv (zipEqual "zipVarEnv" tyvars tys)
365 lookupVarEnv_NF env id = case lookupVarEnv env id of
367 Nothing -> panic "lookupVarEnv_NF: Nothing"
370 @modifyVarEnv@: Look up a thing in the VarEnv,
371 then mash it with the modify function, and put it back.
374 modifyVarEnv mangle_fn env key
375 = case (lookupVarEnv env key) of
377 Just xx -> extendVarEnv env key (mangle_fn xx)
379 modifyVarEnv_Directly :: (a -> a) -> UniqFM a -> Unique -> UniqFM a
380 modifyVarEnv_Directly mangle_fn env key
381 = case (lookupUFM_Directly env key) of
383 Just xx -> addToUFM_Directly env key (mangle_fn xx)