diff options
Diffstat (limited to 'compiler/GHC/Types/Var/Env.hs')
| -rw-r--r-- | compiler/GHC/Types/Var/Env.hs | 24 |
1 files changed, 16 insertions, 8 deletions
diff --git a/compiler/GHC/Types/Var/Env.hs b/compiler/GHC/Types/Var/Env.hs index 2704a2b39b..59bd1dbf56 100644 --- a/compiler/GHC/Types/Var/Env.hs +++ b/compiler/GHC/Types/Var/Env.hs @@ -24,6 +24,7 @@ module GHC.Types.Var.Env ( elemVarEnvByKey, filterVarEnv, restrictVarEnv, partitionVarEnv, varEnvDomain, + nonDetStrictFoldVarEnv_Directly, -- * Deterministic Var environments (maps) DVarEnv, DIdEnv, DTyVarEnv, @@ -318,25 +319,30 @@ rnBndr2 env bL bR = fst $ rnBndr2_var env bL bR rnBndr2_var :: RnEnv2 -> Var -> Var -> (RnEnv2, Var) -- ^ Similar to 'rnBndr2' but returns the new variable as well as the --- new environment +-- new environment. +-- Postcondition: the type of the returned Var is that of bR rnBndr2_var (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] + = (RV2 { envL = extendVarEnv envL bL new_b -- See Note + , envR = extendVarEnv envR bR new_b -- [Rebinding] , in_scope = extendInScopeSet in_scope new_b }, 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 + -- To avoid calling `uniqAway`, we try bL's Unique + -- But we always return a Var whose type is that of bR + new_b | not (bR `elemInScopeSet` in_scope) = bR + | not (bL `elemInScopeSet` in_scope) = bR `setVarUnique` varUnique bL + | otherwise = uniqAway' in_scope bR -- Note [Rebinding] -- ~~~~~~~~~~~~~~~~ -- If the new var is the same as the old one, note that - -- the extendVarEnv *deletes* any current renaming + -- the extendVarEnv *replaces* any current renaming -- E.g. (\x. \x. ...) ~ (\y. \z. ...) -- + -- envL envR in_scope -- Inside \x \y { [x->y], [y->y], {y} } - -- \x \z { [x->x], [y->y, z->x], {y,x} } + -- \x \z { [x->z], [y->y, z->z], {y,z} } + -- The envL binding [x->y] is replaced by [x->z] rnBndrL :: RnEnv2 -> Var -> (RnEnv2, Var) -- ^ Similar to 'rnBndr2' but used when there's a binder on the left @@ -530,6 +536,7 @@ lookupWithDefaultVarEnv :: VarEnv a -> a -> Var -> a elemVarEnv :: Var -> VarEnv a -> Bool elemVarEnvByKey :: Unique -> VarEnv a -> Bool disjointVarEnv :: VarEnv a -> VarEnv a -> Bool +nonDetStrictFoldVarEnv_Directly :: (Unique -> a -> r -> r) -> r -> VarEnv a -> r elemVarEnv = elemUFM elemVarEnvByKey = elemUFM_Directly @@ -565,6 +572,7 @@ unitVarEnv = unitUFM isEmptyVarEnv = isNullUFM partitionVarEnv = partitionUFM varEnvDomain = domUFMUnVarSet +nonDetStrictFoldVarEnv_Directly = nonDetStrictFoldUFM_Directly restrictVarEnv env vs = filterUFM_Directly keep env |