%
+% (c) The University of Glasgow 2006
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
%************************************************************************
\begin{code}
+{-# OPTIONS -w #-}
+-- The above warning supression flag is a temporary kludge.
+-- While working on this module you are encouraged to remove it and fix
+-- any warnings in the module. See
+-- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
+-- for details
+
module TcGadt (
- Refinement, emptyRefinement, gadtRefine,
- refineType, refineResType,
- dataConCanMatch,
+ Refinement, emptyRefinement, isEmptyRefinement,
+ gadtRefine,
+ refineType, refinePred, refineResType,
tcUnifyTys, BindFlag(..)
) where
-import HsSyn ( ExprCoFn(..), idCoercion, isIdCoercion )
-import Coercion ( Coercion, mkSymCoercion, mkTransCoercion, mkUnsafeCoercion,
- mkLeftCoercion, mkRightCoercion, mkCoKind, coercionKindPredTy,
- splitCoercionKind, decomposeCo )
-import TcType ( TvSubst(..), TvSubstEnv, substTy, mkTvSubst,
- substTyVar, zipTopTvSubst, typeKind,
- eqKind, isSubKind, repSplitAppTy_maybe,
- tcView
- )
-import Type ( Type, tyVarsOfType, tyVarsOfTypes, tcEqType, mkTyVarTy )
-import TypeRep ( Type(..), PredType(..) )
-import DataCon ( DataCon, dataConUnivTyVars, dataConEqSpec )
-import Var ( CoVar, TyVar, tyVarKind )
+#include "HsVersions.h"
+
+import HsSyn
+import Coercion
+import Type
+
+import TypeRep
+import Var
import VarEnv
import VarSet
-import ErrUtils ( Message )
-import Maybes ( MaybeErr(..), isJust )
-import Control.Monad ( foldM )
+import ErrUtils
+import Maybes
+import Control.Monad
import Outputable
-
-#include "HsVersions.h"
+import TcType
+import Unique
+import UniqFM
\end{code}
\begin{code}
data Refinement = Reft InScopeSet InternalReft
+
+type InternalReft = TyVarEnv (Coercion, Type)
-- INVARIANT: a->(co,ty) then co :: (a:=:ty)
-- Not necessarily idemopotent
emptyRefinement :: Refinement
emptyRefinement = (Reft emptyInScopeSet emptyVarEnv)
-refineType :: Refinement -> Type -> (ExprCoFn, Type)
+isEmptyRefinement :: Refinement -> Bool
+isEmptyRefinement (Reft _ env) = isEmptyVarEnv env
+
+refineType :: Refinement -> Type -> Maybe (Coercion, Type)
-- Apply the refinement to the type.
-- If (refineType r ty) = (co, ty')
-- Then co :: ty:=:ty'
+-- Nothing => the refinement does nothing to this type
refineType (Reft in_scope env) ty
| not (isEmptyVarEnv env), -- Common case
any (`elemVarEnv` env) (varSetElems (tyVarsOfType ty))
- = (ExprCoFn (substTy co_subst ty), substTy tv_subst ty)
+ = Just (substTy co_subst ty, substTy tv_subst ty)
| otherwise
- = (idCoercion, ty) -- The type doesn't mention any refined type variables
+ = Nothing -- The type doesn't mention any refined type variables
where
tv_subst = mkTvSubst in_scope (mapVarEnv snd env)
co_subst = mkTvSubst in_scope (mapVarEnv fst env)
-refineResType :: Refinement -> Type -> (ExprCoFn, Type)
+refinePred :: Refinement -> PredType -> Maybe (Coercion, PredType)
+refinePred (Reft in_scope env) pred
+ | not (isEmptyVarEnv env), -- Common case
+ any (`elemVarEnv` env) (varSetElems (tyVarsOfPred pred))
+ = Just (mkPredTy (substPred co_subst pred), substPred tv_subst pred)
+ | otherwise
+ = Nothing -- The type doesn't mention any refined type variables
+ where
+ tv_subst = mkTvSubst in_scope (mapVarEnv snd env)
+ co_subst = mkTvSubst in_scope (mapVarEnv fst env)
+
+refineResType :: Refinement -> Type -> (HsWrapper, Type)
-- Like refineType, but returns the 'sym' coercion
-- If (refineResType r ty) = (co, ty')
-- Then co :: ty':=:ty
+-- It's convenient to return a HsWrapper here
refineResType reft ty
= case refineType reft ty of
- (ExprCoFn co, ty1) -> (ExprCoFn (mkSymCoercion co), ty1)
- (id_co, ty1) -> ASSERT( isIdCoercion id_co )
- (idCoercion, ty1)
+ Just (co, ty1) -> (WpCo (mkSymCoercion co), ty1)
+ Nothing -> (idHsWrapper, ty)
\end{code}
ex_tvs co_vars
-- Precondition: fvs( co_vars ) # env1
-- That is, the kinds of the co_vars are a
--- fixed point of the incoming refinement
+-- fixed point of the incoming refinement
- = initUM (tryToBind tv_set) $
+ = ASSERT2( not $ any (`elemVarEnv` env1) (varSetElems $ tyVarsOfTypes $ map tyVarKind co_vars),
+ ppr env1 $$ ppr co_vars $$ ppr (map tyVarKind co_vars) )
+ initUM (tryToBind tv_set) $
do { -- Run the unifier, starting with an empty env
; env2 <- foldM do_one emptyInternalReft co_vars
-- non-idempotent substitution
; let tmp_env = env1 `plusVarEnv` env2
out_env = fixTvCoEnv in_scope' tmp_env
- ; return (Reft in_scope' out_env) }
+ ; WARN( not (null (badReftElts tmp_env)), ppr (badReftElts tmp_env) $$ ppr tmp_env )
+ WARN( not (null (badReftElts out_env)), ppr (badReftElts out_env) $$ ppr out_env )
+ return (Reft in_scope' out_env) }
where
tv_set = mkVarSet ex_tvs
in_scope' = foldr extend in_scope co_vars
+
+ -- For each co_var, add it *and* the tyvars it mentions, to in_scope
extend co_var in_scope
- = extendInScopeSetSet (extendInScopeSet in_scope co_var)
- (tyVarsOfType (tyVarKind co_var))
+ = extendInScopeSetSet in_scope $
+ extendVarSet (tyVarsOfType (tyVarKind co_var)) co_var
do_one reft co_var = unify reft (TyVarTy co_var) ty1 ty2
where
(ty1,ty2) = splitCoercionKind (tyVarKind co_var)
-\end{code}
+\end{code}
%************************************************************************
%* *
where
fixpt = mapVarEnv step env
- step (co, ty) = (co1, ty')
+ step (co, ty) = case refineType (Reft in_scope fixpt) ty of
+ Nothing -> (co, ty)
+ Just (co', ty') -> (mkTransCoercion co co', ty')
-- Apply fixpt one step:
-- Use refineType to get a substituted type, ty', and a coercion, co_fn,
-- which justifies the substitution. If the coercion is not the identity
-- then use transitivity with the original coercion
- where
- (co_fn, ty') = refineType (Reft in_scope fixpt) ty
- co1 | ExprCoFn co'' <- co_fn = mkTransCoercion co'' co
- -- This trans looks backwards, but it
- -- works somehow
- | otherwise = ASSERT( isIdCoercion co_fn ) co
-----------------------------
fixTvSubstEnv :: InScopeSet -> TvSubstEnv -> TvSubstEnv
fixpt = mapVarEnv (substTy (mkTvSubst in_scope fixpt)) env
----------------------------
-dataConCanMatch :: DataCon -> [Type] -> Bool
--- Returns True iff the data con can match a scrutinee of type (T tys)
--- where T is the type constructor for the data con
---
--- Instantiate the equations and try to unify them
-dataConCanMatch con tys
- = isJust (tcUnifyTys (\tv -> BindMe)
- (map (substTyVar subst . fst) eq_spec)
- (map snd eq_spec))
- where
- dc_tvs = dataConUnivTyVars con
- eq_spec = dataConEqSpec con
- subst = zipTopTvSubst dc_tvs tys
-
-----------------------------
tryToBind :: TyVarSet -> TyVar -> BindFlag
tryToBind tv_set tv | tv `elemVarSet` tv_set = BindMe
| otherwise = AvoidMe
-
\end{code}
%************************************************************************
\begin{code}
-type InternalReft = TyVarEnv (Coercion, Type)
-
--- INVARIANT: a->(co,ty) then co :: (a:=:ty)
--- Not necessarily idemopotent
+badReftElts :: InternalReft -> [(Unique, (Coercion,Type))]
+-- Return the BAD elements of the refinement
+-- Should be empty; used in asserions only
+badReftElts env
+ = filter (not . ok) (ufmToList env)
+ where
+ ok :: (Unique, (Coercion, Type)) -> Bool
+ ok (u, (co, ty)) | Just tv <- tcGetTyVar_maybe ty1
+ = varUnique tv == u && ty `tcEqType` ty2
+ | otherwise = False
+ where
+ (ty1,ty2) = coercionKind co
emptyInternalReft :: InternalReft
emptyInternalReft = emptyVarEnv
-> unify subst (mkTransCoercion (mkSymCoercion co') co) ty' ty
-- No, continue
- Nothing -> uUnrefined subst (if swap then mkSymCoercion co else co)
+ Nothing -> uUnrefined swap subst co
tv1 ty ty
-uUnrefined :: InternalReft -- An existing substitution to extend
+uUnrefined :: Bool -- Whether the input is swapped
+ -> InternalReft -- An existing substitution to extend
-> Coercion
-> TyVar -- Type variable to be unified
-> Type -- with this type
-> UM InternalReft
-- We know that tv1 isn't refined
--- PRE-CONDITION: in the call (uUnrefined r co tv ty ty'), we know that
--- co :: tv:=:ty
+-- PRE-CONDITION: in the call (uUnrefined False r co tv1 ty2 ty2'), we know that
+-- co :: tv1:=:ty2
+-- and if the first argument is True instead, we know
+-- co :: ty2:=:tv1
-uUnrefined subst co tv1 ty2 ty2'
+uUnrefined swap subst co tv1 ty2 ty2'
| Just ty2'' <- tcView ty2'
- = uUnrefined subst co tv1 ty2 ty2'' -- Unwrap synonyms
+ = uUnrefined swap subst co tv1 ty2 ty2'' -- Unwrap synonyms
-- This is essential, in case we have
-- type Foo a = a
-- and then unify a :=: Foo a
-uUnrefined subst co tv1 ty2 (TyVarTy tv2)
+uUnrefined swap subst co tv1 ty2 (TyVarTy tv2)
| tv1 == tv2 -- Same type variable
= return subst
-- Check to see whether tv2 is refined
- | Just (co',ty') <- lookupVarEnv subst tv2
- = uUnrefined subst (mkTransCoercion co co') tv1 ty' ty'
+ | Just (co',ty') <- lookupVarEnv subst tv2 -- co' :: tv2:=:ty'
+ = uUnrefined False subst (mkTransCoercion (doSwap swap co) co') tv1 ty' ty'
-- So both are unrefined; next, see if the kinds force the direction
| eqKind k1 k2 -- Can update either; so check the bind-flags
= do { b1 <- tvBindFlag tv1
; b2 <- tvBindFlag tv2
; case (b1,b2) of
- (BindMe, _) -> bind False tv1 ty2
+ (BindMe, _) -> bind swap tv1 ty2
- (AvoidMe, BindMe) -> bind True tv2 ty1
- (AvoidMe, _) -> bind False tv1 ty2
+ (AvoidMe, BindMe) -> bind (not swap) tv2 ty1
+ (AvoidMe, _) -> bind swap tv1 ty2
(WildCard, WildCard) -> return subst
(WildCard, Skolem) -> return subst
- (WildCard, _) -> bind True tv2 ty1
+ (WildCard, _) -> bind (not swap) tv2 ty1
(Skolem, WildCard) -> return subst
(Skolem, Skolem) -> failWith (misMatch ty1 ty2)
- (Skolem, _) -> bind True tv2 ty1
+ (Skolem, _) -> bind (not swap) tv2 ty1
}
- | k1 `isSubKind` k2 = bindTv subst (mkSymCoercion co) tv2 ty1 -- Must update tv2
- | k2 `isSubKind` k1 = bindTv subst co tv1 ty2 -- Must update tv1
+ | k1 `isSubKind` k2 = bindTv (not swap) subst co tv2 ty1 -- Must update tv2
+ | k2 `isSubKind` k1 = bindTv swap subst co tv1 ty2 -- Must update tv1
| otherwise = failWith (kindMisMatch tv1 ty2)
where
ty1 = TyVarTy tv1
k1 = tyVarKind tv1
k2 = tyVarKind tv2
- bind swap tv ty =
- ASSERT2( (coercionKindPredTy co1 `tcEqType` mkCoKind (mkTyVarTy tv) ty)
- , (text "Refinement invariant failure: co = " <+> ppr co <+> ppr (coercionKindPredTy co) $$ text "subst = " <+> ppr tv <+> ppr (mkCoKind (mkTyVarTy tv) ty)))
- return (extendVarEnv subst tv (co1,ty))
- where
- co1 = if swap then mkSymCoercion co else co
-
-uUnrefined subst co tv1 ty2 ty2' -- ty2 is not a type variable
+ bind swap tv ty = extendReft swap subst tv co ty
+
+uUnrefined swap subst co tv1 ty2 ty2' -- ty2 is not a type variable
| tv1 `elemVarSet` substTvSet subst (tyVarsOfType ty2')
= failWith (occursCheck tv1 ty2) -- Occurs check
| not (k2 `isSubKind` k1)
= failWith (kindMisMatch tv1 ty2) -- Kind check
| otherwise
- = bindTv subst co tv1 ty2 -- Bind tyvar to the synonym if poss
+ = bindTv swap subst co tv1 ty2 -- Bind tyvar to the synonym if poss
where
k1 = tyVarKind tv1
k2 = typeKind ty2'
Nothing -> unitVarSet tv
Just (_,ty) -> substTvSet subst (tyVarsOfType ty)
-bindTv subst co tv ty -- ty is not a type variable
- = ASSERT2( (coercionKindPredTy co `tcEqType` mkCoKind (mkTyVarTy tv) ty),
- (text "Refinement invariant failure: co = " <+> ppr co <+> ppr (coercionKindPredTy co) $$ text "subst = " <+> ppr tv <+> ppr (mkCoKind (mkTyVarTy tv) ty)) )
- do { b <- tvBindFlag tv
+bindTv swap subst co tv ty -- ty is not a type variable
+ = do { b <- tvBindFlag tv
; case b of
Skolem -> failWith (misMatch (TyVarTy tv) ty)
WildCard -> return subst
- other -> return (extendVarEnv subst tv (co,ty))
+ other -> extendReft swap subst tv co ty
}
+
+doSwap :: Bool -> Coercion -> Coercion
+doSwap swap co = if swap then mkSymCoercion co else co
+
+extendReft :: Bool
+ -> InternalReft
+ -> TyVar
+ -> Coercion
+ -> Type
+ -> UM InternalReft
+extendReft swap subst tv co ty
+ = ASSERT2( (coercionKindPredTy co1 `tcEqType` mkCoKind (mkTyVarTy tv) ty),
+ (text "Refinement invariant failure: co = " <+> ppr co1 <+> ppr (coercionKindPredTy co1) $$ text "subst = " <+> ppr tv <+> ppr (mkCoKind (mkTyVarTy tv) ty)) )
+ return (extendVarEnv subst tv (co1, ty))
+ where
+ co1 = doSwap swap co
+
\end{code}
%************************************************************************
occursCheck tv ty
= hang (ptext SLIT("Can't construct the infinite type"))
2 (ppr tv <+> equals <+> ppr ty)
-\end{code}
\ No newline at end of file
+\end{code}
projects / ghc-hetmet.git / blobdiff