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%
% (c) The University of Glasgow 2006
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\begin{code}
module VarEnv (
-- * Var, Id and TyVar environments (maps)
VarEnv, IdEnv, TyVarEnv, CoVarEnv,
-- ** Manipulating these environments
emptyVarEnv, unitVarEnv, mkVarEnv,
elemVarEnv, varEnvElts, varEnvKeys,
extendVarEnv, extendVarEnv_C, extendVarEnv_Acc, extendVarEnvList,
plusVarEnv, plusVarEnv_C, alterVarEnv,
delVarEnvList, delVarEnv,
minusVarEnv, intersectsVarEnv,
lookupVarEnv, lookupVarEnv_NF, lookupWithDefaultVarEnv,
mapVarEnv, zipVarEnv,
modifyVarEnv, modifyVarEnv_Directly,
isEmptyVarEnv, foldVarEnv,
elemVarEnvByKey, lookupVarEnv_Directly,
filterVarEnv_Directly, restrictVarEnv,
-- * The InScopeSet type
InScopeSet,
-- ** Operations on InScopeSets
emptyInScopeSet, mkInScopeSet, delInScopeSet,
extendInScopeSet, extendInScopeSetList, extendInScopeSetSet,
getInScopeVars, lookupInScope, lookupInScope_Directly,
unionInScope, elemInScopeSet, uniqAway,
-- * The RnEnv2 type
RnEnv2,
-- ** Operations on RnEnv2s
mkRnEnv2, rnBndr2, rnBndrs2,
rnOccL, rnOccR, inRnEnvL, inRnEnvR, rnOccL_maybe, rnOccR_maybe,
rnBndrL, rnBndrR, nukeRnEnvL, nukeRnEnvR,
delBndrL, delBndrR, delBndrsL, delBndrsR,
addRnInScopeSet,
rnEtaL, rnEtaR,
rnInScope, rnInScopeSet, lookupRnInScope,
-- * TidyEnv and its operation
TidyEnv,
emptyTidyEnv
) where
import OccName
import Var
import VarSet
import UniqFM
import Unique
import Util
import Maybes
import Outputable
import FastTypes
import StaticFlags
import FastString
\end{code}
%************************************************************************
%* *
In-scope sets
%* *
%************************************************************************
\begin{code}
-- | A set of variables that are in scope at some point
data InScopeSet = InScope (VarEnv Var) FastInt
-- The (VarEnv Var) is just a VarSet. But we write it like
-- this to remind ourselves that you can look up a Var in
-- the InScopeSet. Typically the InScopeSet contains the
-- canonical version of the variable (e.g. with an informative
-- unfolding), so this lookup is useful.
--
-- INVARIANT: the VarEnv maps (the Unique of) a variable to
-- a variable with the same Uniqua. (This was not
-- the case in the past, when we had a grevious hack
-- mapping var1 to var2.
--
-- The FastInt is a kind of hash-value used by uniqAway
-- For example, it might be the size of the set
-- INVARIANT: it's not zero; we use it as a multiplier in uniqAway
instance Outputable InScopeSet where
ppr (InScope s _) = ptext (sLit "InScope") <+> ppr s
emptyInScopeSet :: InScopeSet
emptyInScopeSet = InScope emptyVarSet (_ILIT(1))
getInScopeVars :: InScopeSet -> VarEnv Var
getInScopeVars (InScope vs _) = vs
mkInScopeSet :: VarEnv Var -> InScopeSet
mkInScopeSet in_scope = InScope in_scope (_ILIT(1))
extendInScopeSet :: InScopeSet -> Var -> InScopeSet
extendInScopeSet (InScope in_scope n) v = InScope (extendVarEnv in_scope v v) (n +# _ILIT(1))
extendInScopeSetList :: InScopeSet -> [Var] -> InScopeSet
extendInScopeSetList (InScope in_scope n) vs
= InScope (foldl (\s v -> extendVarEnv s v v) in_scope vs)
(n +# iUnbox (length vs))
extendInScopeSetSet :: InScopeSet -> VarEnv Var -> InScopeSet
extendInScopeSetSet (InScope in_scope n) vs
= InScope (in_scope `plusVarEnv` vs) (n +# iUnbox (sizeUFM vs))
delInScopeSet :: InScopeSet -> Var -> InScopeSet
delInScopeSet (InScope in_scope n) v = InScope (in_scope `delVarEnv` v) n
elemInScopeSet :: Var -> InScopeSet -> Bool
elemInScopeSet v (InScope in_scope _) = v `elemVarEnv` in_scope
-- | Look up a variable the 'InScopeSet'. This lets you map from
-- the variable's identity (unique) to its full value.
lookupInScope :: InScopeSet -> Var -> Maybe Var
lookupInScope (InScope in_scope _) v = lookupVarEnv in_scope v
lookupInScope_Directly :: InScopeSet -> Unique -> Maybe Var
lookupInScope_Directly (InScope in_scope _) uniq
= lookupVarEnv_Directly in_scope uniq
unionInScope :: InScopeSet -> InScopeSet -> InScopeSet
unionInScope (InScope s1 _) (InScope s2 n2)
= InScope (s1 `plusVarEnv` s2) n2
\end{code}
\begin{code}
-- | @uniqAway in_scope v@ finds a unique that is not used in the
-- in-scope set, and gives that to v.
uniqAway :: InScopeSet -> Var -> Var
-- It starts with v's current unique, of course, in the hope that it won't
-- have to change, and thereafter uses a combination of that and the hash-code
-- found in the in-scope set
uniqAway in_scope var
| var `elemInScopeSet` in_scope = uniqAway' in_scope var -- Make a new one
| otherwise = var -- Nothing to do
uniqAway' :: InScopeSet -> Var -> Var
-- This one *always* makes up a new variable
uniqAway' (InScope set n) var
= try (_ILIT(1))
where
orig_unique = getUnique var
try k
| debugIsOn && (k ># _ILIT(1000))
= pprPanic "uniqAway loop:" (ppr (iBox k) <+> text "tries" <+> ppr var <+> int (iBox n))
| uniq `elemVarSetByKey` set = try (k +# _ILIT(1))
| debugIsOn && opt_PprStyle_Debug && (k ># _ILIT(3))
= pprTrace "uniqAway:" (ppr (iBox k) <+> text "tries" <+> ppr var <+> int (iBox n))
setVarUnique var uniq
| otherwise = setVarUnique var uniq
where
uniq = deriveUnique orig_unique (iBox (n *# k))
\end{code}
%************************************************************************
%* *
Dual renaming
%* *
%************************************************************************
\begin{code}
-- | When we are comparing (or matching) types or terms, we are faced with
-- \"going under\" corresponding binders. E.g. when comparing:
--
-- > \x. e1 ~ \y. e2
--
-- Basically we want to rename [@x@ -> @y@] or [@y@ -> @x@], but there are lots of
-- things we must be careful of. In particular, @x@ might be free in @e2@, or
-- y in @e1@. So the idea is that we come up with a fresh binder that is free
-- in neither, and rename @x@ and @y@ respectively. That means we must maintain:
--
-- 1. A renaming for the left-hand expression
--
-- 2. A renaming for the right-hand expressions
--
-- 3. An in-scope set
--
-- Furthermore, when matching, we want to be able to have an 'occurs check',
-- to prevent:
--
-- > \x. f ~ \y. y
--
-- matching with [@f@ -> @y@]. So for each expression we want to know that set of
-- locally-bound variables. That is precisely the domain of the mappings 1.
-- and 2., but we must ensure that we always extend the mappings as we go in.
--
-- All of this information is bundled up in the 'RnEnv2'
data RnEnv2
= RV2 { envL :: VarEnv Var -- Renaming for Left term
, envR :: VarEnv Var -- Renaming for Right term
, in_scope :: InScopeSet } -- In scope in left or right terms
-- The renamings envL and envR are *guaranteed* to contain a binding
-- for every variable bound as we go into the term, even if it is not
-- renamed. That way we can ask what variables are locally bound
-- (inRnEnvL, inRnEnvR)
mkRnEnv2 :: InScopeSet -> RnEnv2
mkRnEnv2 vars = RV2 { envL = emptyVarEnv
, envR = emptyVarEnv
, in_scope = vars }
addRnInScopeSet :: RnEnv2 -> VarEnv Var -> RnEnv2
addRnInScopeSet env vs
| isEmptyVarEnv vs = env
| otherwise = env { in_scope = extendInScopeSetSet (in_scope env) vs }
rnInScope :: Var -> RnEnv2 -> Bool
rnInScope x env = x `elemInScopeSet` in_scope env
rnInScopeSet :: RnEnv2 -> InScopeSet
rnInScopeSet = in_scope
rnBndrs2 :: RnEnv2 -> [Var] -> [Var] -> RnEnv2
-- ^ Applies 'rnBndr2' to several variables: the two variable lists must be of equal length
rnBndrs2 env bsL bsR = foldl2 rnBndr2 env bsL bsR
rnBndr2 :: RnEnv2 -> Var -> Var -> RnEnv2
-- ^ @rnBndr2 env bL bR@ goes under a binder @bL@ in the Left term,
-- and binder @bR@ in the Right term.
-- It finds a new binder, @new_b@,
-- and returns an environment mapping @bL -> new_b@ and @bR -> new_b@
rnBndr2 (RV2 { envL = envL, envR = envR, in_scope = in_scope }) bL bR
= RV2 { envL = extendVarEnv envL bL new_b -- See Note
, envR = extendVarEnv envR bR new_b -- [Rebinding]
, in_scope = extendInScopeSet in_scope new_b }
where
-- Find a new binder not in scope in either term
new_b | not (bL `elemInScopeSet` in_scope) = bL
| not (bR `elemInScopeSet` in_scope) = bR
| otherwise = uniqAway' in_scope bL
-- Note [Rebinding]
-- If the new var is the same as the old one, note that
-- the extendVarEnv *deletes* any current renaming
-- E.g. (\x. \x. ...) ~ (\y. \z. ...)
--
-- Inside \x \y { [x->y], [y->y], {y} }
-- \x \z { [x->x], [y->y, z->x], {y,x} }
rnBndrL :: RnEnv2 -> Var -> (RnEnv2, Var)
-- ^ Similar to 'rnBndr2' but used when there's a binder on the left
-- side only.
rnBndrL (RV2 { envL = envL, envR = envR, in_scope = in_scope }) bL
= (RV2 { envL = extendVarEnv envL bL new_b
, envR = envR
, in_scope = extendInScopeSet in_scope new_b }, new_b)
where
new_b = uniqAway in_scope bL
rnBndrR :: RnEnv2 -> Var -> (RnEnv2, Var)
-- ^ Similar to 'rnBndr2' but used when there's a binder on the right
-- side only.
rnBndrR (RV2 { envL = envL, envR = envR, in_scope = in_scope }) bR
= (RV2 { envR = extendVarEnv envR bR new_b
, envL = envL
, in_scope = extendInScopeSet in_scope new_b }, new_b)
where
new_b = uniqAway in_scope bR
rnEtaL :: RnEnv2 -> Var -> (RnEnv2, Var)
-- ^ Similar to 'rnBndrL' but used for eta expansion
-- See Note [Eta expansion]
rnEtaL (RV2 { envL = envL, envR = envR, in_scope = in_scope }) bL
= (RV2 { envL = extendVarEnv envL bL new_b
, envR = extendVarEnv envR new_b new_b -- Note [Eta expansion]
, in_scope = extendInScopeSet in_scope new_b }, new_b)
where
new_b = uniqAway in_scope bL
rnEtaR :: RnEnv2 -> Var -> (RnEnv2, Var)
-- ^ Similar to 'rnBndr2' but used for eta expansion
-- See Note [Eta expansion]
rnEtaR (RV2 { envL = envL, envR = envR, in_scope = in_scope }) bR
= (RV2 { envL = extendVarEnv envL new_b new_b -- Note [Eta expansion]
, envR = extendVarEnv envR bR new_b
, in_scope = extendInScopeSet in_scope new_b }, new_b)
where
new_b = uniqAway in_scope bR
delBndrL, delBndrR :: RnEnv2 -> Var -> RnEnv2
delBndrL rn@(RV2 { envL = env, in_scope = in_scope }) v
= rn { envL = env `delVarEnv` v, in_scope = in_scope `extendInScopeSet` v }
delBndrR rn@(RV2 { envR = env, in_scope = in_scope }) v
= rn { envR = env `delVarEnv` v, in_scope = in_scope `extendInScopeSet` v }
delBndrsL, delBndrsR :: RnEnv2 -> [Var] -> RnEnv2
delBndrsL rn@(RV2 { envL = env, in_scope = in_scope }) v
= rn { envL = env `delVarEnvList` v, in_scope = in_scope `extendInScopeSetList` v }
delBndrsR rn@(RV2 { envR = env, in_scope = in_scope }) v
= rn { envR = env `delVarEnvList` v, in_scope = in_scope `extendInScopeSetList` v }
rnOccL, rnOccR :: RnEnv2 -> Var -> Var
-- ^ Look up the renaming of an occurrence in the left or right term
rnOccL (RV2 { envL = env }) v = lookupVarEnv env v `orElse` v
rnOccR (RV2 { envR = env }) v = lookupVarEnv env v `orElse` v
rnOccL_maybe, rnOccR_maybe :: RnEnv2 -> Var -> Maybe Var
-- ^ Look up the renaming of an occurrence in the left or right term
rnOccL_maybe (RV2 { envL = env }) v = lookupVarEnv env v
rnOccR_maybe (RV2 { envR = env }) v = lookupVarEnv env v
inRnEnvL, inRnEnvR :: RnEnv2 -> Var -> Bool
-- ^ Tells whether a variable is locally bound
inRnEnvL (RV2 { envL = env }) v = v `elemVarEnv` env
inRnEnvR (RV2 { envR = env }) v = v `elemVarEnv` env
lookupRnInScope :: RnEnv2 -> Var -> Var
lookupRnInScope env v = lookupInScope (in_scope env) v `orElse` v
nukeRnEnvL, nukeRnEnvR :: RnEnv2 -> RnEnv2
-- ^ Wipe the left or right side renaming
nukeRnEnvL env = env { envL = emptyVarEnv }
nukeRnEnvR env = env { envR = emptyVarEnv }
\end{code}
Note [Eta expansion]
~~~~~~~~~~~~~~~~~~~~
When matching
(\x.M) ~ N
we rename x to x' with, where x' is not in scope in
either term. Then we want to behave as if we'd seen
(\x'.M) ~ (\x'.N x')
Since x' isn't in scope in N, the form (\x'. N x') doesn't
capture any variables in N. But we must nevertheless extend
the envR with a binding [x' -> x'], to support the occurs check.
For example, if we don't do this, we can get silly matches like
forall a. (\y.a) ~ v
succeeding with [a -> v y], which is bogus of course.
%************************************************************************
%* *
Tidying
%* *
%************************************************************************
\begin{code}
-- | When tidying up print names, we keep a mapping of in-scope occ-names
-- (the 'TidyOccEnv') and a Var-to-Var of the current renamings
type TidyEnv = (TidyOccEnv, VarEnv Var)
emptyTidyEnv :: TidyEnv
emptyTidyEnv = (emptyTidyOccEnv, emptyVarEnv)
\end{code}
%************************************************************************
%* *
\subsection{@VarEnv@s}
%* *
%************************************************************************
\begin{code}
type VarEnv elt = UniqFM elt
type IdEnv elt = VarEnv elt
type TyVarEnv elt = VarEnv elt
type CoVarEnv elt = VarEnv elt
emptyVarEnv :: VarEnv a
mkVarEnv :: [(Var, a)] -> VarEnv a
zipVarEnv :: [Var] -> [a] -> VarEnv a
unitVarEnv :: Var -> a -> VarEnv a
alterVarEnv :: (Maybe a -> Maybe a) -> VarEnv a -> Var -> VarEnv a
extendVarEnv :: VarEnv a -> Var -> a -> VarEnv a
extendVarEnv_C :: (a->a->a) -> VarEnv a -> Var -> a -> VarEnv a
extendVarEnv_Acc :: (a->b->b) -> (a->b) -> VarEnv b -> Var -> a -> VarEnv b
plusVarEnv :: VarEnv a -> VarEnv a -> VarEnv a
extendVarEnvList :: VarEnv a -> [(Var, a)] -> VarEnv a
lookupVarEnv_Directly :: VarEnv a -> Unique -> Maybe a
filterVarEnv_Directly :: (Unique -> a -> Bool) -> VarEnv a -> VarEnv a
restrictVarEnv :: VarEnv a -> VarSet -> VarEnv a
delVarEnvList :: VarEnv a -> [Var] -> VarEnv a
delVarEnv :: VarEnv a -> Var -> VarEnv a
minusVarEnv :: VarEnv a -> VarEnv b -> VarEnv a
intersectsVarEnv :: VarEnv a -> VarEnv a -> Bool
plusVarEnv_C :: (a -> a -> a) -> VarEnv a -> VarEnv a -> VarEnv a
mapVarEnv :: (a -> b) -> VarEnv a -> VarEnv b
modifyVarEnv :: (a -> a) -> VarEnv a -> Var -> VarEnv a
varEnvElts :: VarEnv a -> [a]
varEnvKeys :: VarEnv a -> [Unique]
isEmptyVarEnv :: VarEnv a -> Bool
lookupVarEnv :: VarEnv a -> Var -> Maybe a
lookupVarEnv_NF :: VarEnv a -> Var -> a
lookupWithDefaultVarEnv :: VarEnv a -> a -> Var -> a
elemVarEnv :: Var -> VarEnv a -> Bool
elemVarEnvByKey :: Unique -> VarEnv a -> Bool
foldVarEnv :: (a -> b -> b) -> b -> VarEnv a -> b
\end{code}
\begin{code}
elemVarEnv = elemUFM
elemVarEnvByKey = elemUFM_Directly
alterVarEnv = alterUFM
extendVarEnv = addToUFM
extendVarEnv_C = addToUFM_C
extendVarEnv_Acc = addToUFM_Acc
extendVarEnvList = addListToUFM
plusVarEnv_C = plusUFM_C
delVarEnvList = delListFromUFM
delVarEnv = delFromUFM
minusVarEnv = minusUFM
intersectsVarEnv e1 e2 = not (isEmptyVarEnv (e1 `intersectUFM` e2))
plusVarEnv = plusUFM
lookupVarEnv = lookupUFM
lookupWithDefaultVarEnv = lookupWithDefaultUFM
mapVarEnv = mapUFM
mkVarEnv = listToUFM
emptyVarEnv = emptyUFM
varEnvElts = eltsUFM
varEnvKeys = keysUFM
unitVarEnv = unitUFM
isEmptyVarEnv = isNullUFM
foldVarEnv = foldUFM
lookupVarEnv_Directly = lookupUFM_Directly
filterVarEnv_Directly = filterUFM_Directly
restrictVarEnv env vs = filterVarEnv_Directly keep env
where
keep u _ = u `elemVarSetByKey` vs
zipVarEnv tyvars tys = mkVarEnv (zipEqual "zipVarEnv" tyvars tys)
lookupVarEnv_NF env id = case lookupVarEnv env id of
Just xx -> xx
Nothing -> panic "lookupVarEnv_NF: Nothing"
\end{code}
@modifyVarEnv@: Look up a thing in the VarEnv,
then mash it with the modify function, and put it back.
\begin{code}
modifyVarEnv mangle_fn env key
= case (lookupVarEnv env key) of
Nothing -> env
Just xx -> extendVarEnv env key (mangle_fn xx)
modifyVarEnv_Directly :: (a -> a) -> UniqFM a -> Unique -> UniqFM a
modifyVarEnv_Directly mangle_fn env key
= case (lookupUFM_Directly env key) of
Nothing -> env
Just xx -> addToUFM_Directly env key (mangle_fn xx)
\end{code}
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