-
+%
+% (c) The University of Glasgow 2006
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
-\section{@VarEnvs@: Variable environments}
\begin{code}
module VarEnv (
-- InScopeSet
InScopeSet, emptyInScopeSet, mkInScopeSet, delInScopeSet,
- extendInScopeSet, extendInScopeSetList, modifyInScopeSet,
+ extendInScopeSet, extendInScopeSetList, extendInScopeSetSet,
+ modifyInScopeSet,
getInScopeVars, lookupInScope, elemInScopeSet, uniqAway,
mapInScopeSet,
-- RnEnv2 and its operations
RnEnv2, mkRnEnv2, rnBndr2, rnBndrs2, rnOccL, rnOccR, inRnEnvL, inRnEnvR,
- rnBndrL, rnBndrR, nukeRnEnvL, nukeRnEnvR,
+ rnBndrL, rnBndrR, nukeRnEnvL, nukeRnEnvR, extendRnInScopeList,
+ rnInScope, rnInScopeSet, lookupRnInScope,
-- TidyEnvs
TidyEnv, emptyTidyEnv
#include "HsVersions.h"
-import OccName ( TidyOccEnv, emptyTidyOccEnv )
-import Var ( Var, setVarUnique )
+import OccName
+import Var
import VarSet
import UniqFM
-import Unique ( Unique, deriveUnique, getUnique )
-import Util ( zipEqual, foldl2 )
-import Maybes ( orElse, isJust )
-import StaticFlags( opt_PprStyle_Debug )
+import Unique
+import Util
+import Maybes
+import StaticFlags
import Outputable
import FastTypes
\end{code}
= 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))
+
modifyInScopeSet :: InScopeSet -> Var -> Var -> InScopeSet
-- Exploit the fact that the in-scope "set" is really a map
-- Make old_v map to new_v
, envR = emptyVarEnv
, in_scope = vars }
+extendRnInScopeList :: RnEnv2 -> [Var] -> RnEnv2
+extendRnInScopeList env vs
+ = env { in_scope = extendInScopeSetList (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
-- Arg lists must be of equal length
rnBndrs2 env bsL bsR = foldl2 rnBndr2 env bsL bsR
rnBndrL, rnBndrR :: RnEnv2 -> Var -> (RnEnv2, Var)
-- Used when there's a binder on one side or the other only
-- Useful when eta-expanding
+--
rnBndrL (RV2 { envL = envL, envR = envR, in_scope = in_scope }) bL
= (RV2 { envL = extendVarEnv envL bL new_b
- , envR = envR
+ , envR = extendVarEnv envR new_b new_b -- Note [rnBndrLR]
, in_scope = extendInScopeSet in_scope new_b }, new_b)
where
- new_b | not (bL `elemInScopeSet` in_scope) = bL
- | otherwise = uniqAway' in_scope bL
+ new_b = uniqAway in_scope bL
rnBndrR (RV2 { envL = envL, envR = envR, in_scope = in_scope }) bR
- = (RV2 { envL = envL
+ = (RV2 { envL = extendVarEnv envL new_b new_b -- Note [rnBndrLR]
, envR = extendVarEnv envR bR new_b
, in_scope = extendInScopeSet in_scope new_b }, new_b)
where
- new_b | not (bR `elemInScopeSet` in_scope) = bR
- | otherwise = uniqAway' in_scope bR
+ new_b = uniqAway in_scope bR
+
+-- Note [rnBndrLR]
+-- ~~~~~~~~~~~~~~~
+-- Notice that in rnBndrL, rnBndrR, we extend envR, envL respectively
+-- with a binding [new_b -> new_b], where new_b is the new binder.
+-- This is important when doing eta expansion; e.g. matching (\x.M) ~ N
+-- In effect we switch to (\x'.M) ~ (\x'.N x'), where x' is new_b
+-- So we must add x' to the env of both L and R. (x' is fresh, so it
+-- can't capture anything in N.)
+--
+-- If we don't do this, we can get silly matches like
+-- forall a. \y.a ~ v
+-- succeeding with [x -> v y], which is bogus of course
rnOccL, rnOccR :: RnEnv2 -> Var -> Var
-- Look up the renaming of an occurrence in the left or right term
inRnEnvL, inRnEnvR :: RnEnv2 -> Var -> Bool
-- Tells whether a variable is locally bound
-inRnEnvL (RV2 { envL = env }) v = isJust (lookupVarEnv env v)
-inRnEnvR (RV2 { envR = env }) v = isJust (lookupVarEnv env v)
+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
nukeRnEnvL env = env { envL = emptyVarEnv }