module VarEnv (
VarEnv, IdEnv, TyVarEnv,
emptyVarEnv, unitVarEnv, mkVarEnv,
- elemVarEnv, varEnvElts,
+ elemVarEnv, varEnvElts, varEnvKeys,
extendVarEnv, extendVarEnv_C, extendVarEnvList,
plusVarEnv, plusVarEnv_C,
delVarEnvList, delVarEnv,
mapVarEnv, zipVarEnv,
modifyVarEnv, modifyVarEnv_Directly,
isEmptyVarEnv, foldVarEnv,
- lookupVarEnv_Directly,
+ elemVarEnvByKey, lookupVarEnv_Directly,
filterVarEnv_Directly,
-- InScopeSet
InScopeSet, emptyInScopeSet, mkInScopeSet, delInScopeSet,
extendInScopeSet, extendInScopeSetList, modifyInScopeSet,
getInScopeVars, lookupInScope, elemInScopeSet, uniqAway,
+ mapInScopeSet,
+
+ -- RnEnv2 and its operations
+ RnEnv2, mkRnEnv2, rnBndr2, rnBndrs2, rnOccL, rnOccR, inRnEnvL, inRnEnvR,
+ rnBndrL, rnBndrR, nukeRnEnvL, nukeRnEnvR,
-- TidyEnvs
TidyEnv, emptyTidyEnv
import VarSet
import UniqFM
import Unique ( Unique, deriveUnique, getUnique )
-import Util ( zipEqual )
-import CmdLineOpts ( opt_PprStyle_Debug )
+import Util ( zipEqual, foldl2 )
+import Maybes ( orElse, isJust )
+import StaticFlags( opt_PprStyle_Debug )
import Outputable
import FastTypes
\end{code}
delInScopeSet :: InScopeSet -> Var -> InScopeSet
delInScopeSet (InScope in_scope n) v = InScope (in_scope `delVarEnv` v) n
+mapInScopeSet :: (Var -> Var) -> InScopeSet -> InScopeSet
+mapInScopeSet f (InScope in_scope n) = InScope (mapVarEnv f in_scope) n
+
elemInScopeSet :: Var -> InScopeSet -> Bool
elemInScopeSet v (InScope in_scope n) = v `elemVarEnv` in_scope
-- in-scope set, and gives that to v. It starts with v's current unique, of course,
-- in the hope that it won't have to change it, and thereafter uses a combination
-- of that and the hash-code found in the in-scope set
-uniqAway (InScope set n) var
- | not (var `elemVarSet` set) = var -- Nothing to do
- | otherwise = try 1#
+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 1#
where
orig_unique = getUnique var
try k
%************************************************************************
%* *
+ Dual renaming
+%* *
+%************************************************************************
+
+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
+ a) a renaming for the left-hand expression
+ b) a renaming for the right-hand expressions
+ c) 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 (a)
+and (b), but we must ensure that we always extend the mappings as we go in.
+
+
+\begin{code}
+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 }
+
+rnBndrs2 :: RnEnv2 -> [Var] -> [Var] -> RnEnv2
+-- Arg lists must be of equal length
+rnBndrs2 env bsL bsR = foldl2 rnBndr2 env bsL bsR
+
+rnBndr2 :: RnEnv2 -> Var -> Var -> RnEnv2
+-- (rnBndr2 env bL bR) go under a binder bL in the Left term 1,
+-- 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 resp.
+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, 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
+ , in_scope = extendInScopeSet in_scope new_b }, new_b)
+ where
+ new_b | not (bL `elemInScopeSet` in_scope) = bL
+ | otherwise = uniqAway' in_scope bL
+
+rnBndrR (RV2 { envL = envL, envR = envR, in_scope = in_scope }) bR
+ = (RV2 { envL = envL
+ , 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
+
+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
+
+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)
+
+nukeRnEnvL, nukeRnEnvR :: RnEnv2 -> RnEnv2
+nukeRnEnvL env = env { envL = emptyVarEnv }
+nukeRnEnvR env = env { envR = emptyVarEnv }
+\end{code}
+
+
+%************************************************************************
+%* *
Tidying
%* *
%************************************************************************
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
extendVarEnv = addToUFM
extendVarEnv_C = addToUFM_C
extendVarEnvList = addListToUFM
mkVarEnv = listToUFM
emptyVarEnv = emptyUFM
varEnvElts = eltsUFM
+varEnvKeys = keysUFM
unitVarEnv = unitUFM
isEmptyVarEnv = isNullUFM
foldVarEnv = foldUFM
lookupVarEnv_Directly = lookupUFM_Directly
filterVarEnv_Directly = filterUFM_Directly
-zipVarEnv tyvars tys = mkVarEnv (zipEqual "zipVarEnv" tyvars tys)
-lookupVarEnv_NF env id = case (lookupVarEnv env id) of { Just xx -> xx }
+zipVarEnv tyvars tys = mkVarEnv (zipEqual "zipVarEnv" tyvars tys)
+lookupVarEnv_NF env id = case (lookupVarEnv env id) of { Just xx -> xx }
\end{code}
@modifyVarEnv@: Look up a thing in the VarEnv,
projects / ghc-hetmet.git / blobdiff