use an explicit substitution
\begin{code}
-module Unify ( Subst,
- unifyTysX, unifyTyListsX,
- matchTy, matchTys
+module Unify ( unifyTysX, unifyTyListsX, unifyExtendTysX,
+ allDistinctTyVars,
+ match, matchTy, matchTys,
) where
-import Var ( GenTyVar, TyVar, tyVarKind )
-import VarEnv
-import VarSet ( varSetElems )
-import Type ( GenType(..), funTyCon, typeKind, tyVarsOfType, hasMoreBoxityInfo,
- splitAppTy_maybe
+#include "HsVersions.h"
+
+import TypeRep ( Type(..) ) -- friend
+import Type ( typeKind, tyVarsOfType, splitAppTy_maybe, getTyVar_maybe,
+ splitUTy, isUTy, deNoteType
+ )
+
+import PprType () -- Instances
+ -- This import isn't strictly necessary, but it makes sure that
+ -- PprType is below Unify in the hierarchy, which in turn makes
+ -- fewer modules boot-import PprType
+
+import Var ( tyVarKind )
+import VarSet
+import VarEnv ( TyVarSubstEnv, emptySubstEnv, lookupSubstEnv, extendSubstEnv,
+ SubstResult(..)
)
-import Unique ( Uniquable(..) )
-import Outputable( panic )
-import Util ( snocView )
+
+import Outputable
\end{code}
%************************************************************************
%* *
-\subsection{Unification wih a explicit substitution}
+\subsection{Unification with an explicit substitution}
+%* *
+%************************************************************************
+
+(allDistinctTyVars tys tvs) = True
+ iff
+all the types tys are type variables,
+distinct from each other and from tvs.
+
+This is useful when checking that unification hasn't unified signature
+type variables. For example, if the type sig is
+ f :: forall a b. a -> b -> b
+we want to check that 'a' and 'b' havn't
+ (a) been unified with a non-tyvar type
+ (b) been unified with each other (all distinct)
+ (c) been unified with a variable free in the environment
+
+\begin{code}
+allDistinctTyVars :: [Type] -> TyVarSet -> Bool
+
+allDistinctTyVars [] acc
+ = True
+allDistinctTyVars (ty:tys) acc
+ = case getTyVar_maybe ty of
+ Nothing -> False -- (a)
+ Just tv | tv `elemVarSet` acc -> False -- (b) or (c)
+ | otherwise -> allDistinctTyVars tys (acc `extendVarSet` tv)
+\end{code}
+
+%************************************************************************
+%* *
+\subsection{Unification with an explicit substitution}
%* *
%************************************************************************
Unify types with an explicit substitution and no monad.
+Ignore usage annotations.
\begin{code}
-type Subst flexi_tmpl flexi_result
- = ([GenTyVar flexi_tmpl], -- Set of template tyvars
- TyVarEnv (GenType flexi_result)) -- Not necessarily idempotent
-
-unifyTysX :: [GenTyVar flexi] -- Template tyvars
- -> GenType flexi
- -> GenType flexi
- -> Maybe (TyVarEnv (GenType flexi))
+type MySubst
+ = (TyVarSet, -- Set of template tyvars
+ TyVarSubstEnv) -- Not necessarily idempotent
+
+unifyTysX :: TyVarSet -- Template tyvars
+ -> Type
+ -> Type
+ -> Maybe TyVarSubstEnv
unifyTysX tmpl_tyvars ty1 ty2
- = uTysX ty1 ty2 (\(_,s) -> Just s) (tmpl_tyvars, emptyVarEnv)
-
-unifyTyListsX :: [GenTyVar flexi] -> [GenType flexi] -> [GenType flexi]
- -> Maybe (TyVarEnv (GenType flexi))
+ = uTysX ty1 ty2 (\(_,s) -> Just s) (tmpl_tyvars, emptySubstEnv)
+
+unifyExtendTysX :: TyVarSet -- Template tyvars
+ -> TyVarSubstEnv -- Substitution to start with
+ -> Type
+ -> Type
+ -> Maybe TyVarSubstEnv -- Extended substitution
+unifyExtendTysX tmpl_tyvars subst ty1 ty2
+ = uTysX ty1 ty2 (\(_,s) -> Just s) (tmpl_tyvars, subst)
+
+unifyTyListsX :: TyVarSet -> [Type] -> [Type]
+ -> Maybe TyVarSubstEnv
unifyTyListsX tmpl_tyvars tys1 tys2
- = uTyListsX tys1 tys2 (\(_,s) -> Just s) (tmpl_tyvars, emptyVarEnv)
+ = uTyListsX tys1 tys2 (\(_,s) -> Just s) (tmpl_tyvars, emptySubstEnv)
-uTysX :: GenType flexi
- -> GenType flexi
- -> (Subst flexi flexi -> Maybe result)
- -> Subst flexi flexi
+uTysX :: Type
+ -> Type
+ -> (MySubst -> Maybe result)
+ -> MySubst
-> Maybe result
uTysX (NoteTy _ ty1) ty2 k subst = uTysX ty1 ty2 k subst
| tyvar1 == tyvar2
= k subst
uTysX (TyVarTy tyvar1) ty2 k subst@(tmpls,_)
- | tyvar1 `elem` tmpls
+ | tyvar1 `elemVarSet` tmpls
= uVarX tyvar1 ty2 k subst
uTysX ty1 (TyVarTy tyvar2) k subst@(tmpls,_)
- | tyvar2 `elem` tmpls
+ | tyvar2 `elemVarSet` tmpls
= uVarX tyvar2 ty1 k subst
-- Functions; just check the two parts
uTysX ty1 (ForAllTy _ _) k subst = panic "Unify.uTysX subst:ForAllTy (2nd arg)"
#endif
+ -- Ignore usages
+uTysX (UsageTy _ t1) t2 k subst = uTysX t1 t2 k subst
+uTysX t1 (UsageTy _ t2) k subst = uTysX t1 t2 k subst
+
-- Anything else fails
uTysX ty1 ty2 k subst = Nothing
\begin{code}
-- Invariant: tv1 is a unifiable variable
uVarX tv1 ty2 k subst@(tmpls, env)
- = case lookupVarEnv env tv1 of
- Just ty1 -> -- Already bound
+ = case lookupSubstEnv env tv1 of
+ Just (DoneTy ty1) -> -- Already bound
uTysX ty1 ty2 k subst
Nothing -- Not already bound
- | typeKind ty2 `hasMoreBoxityInfo` tyVarKind tv1
+ | typeKind ty2 == tyVarKind tv1
&& occur_check_ok ty2
-> -- No kind mismatch nor occur check
- k (tmpls, extendVarEnv env tv1 ty2)
+ UASSERT( not (isUTy ty2) )
+ k (tmpls, extendSubstEnv env tv1 (DoneTy ty2))
| otherwise -> Nothing -- Fail if kind mis-match or occur check
where
occur_check_ok ty = all occur_check_ok_tv (varSetElems (tyVarsOfType ty))
occur_check_ok_tv tv | tv1 == tv = False
- | otherwise = case lookupVarEnv env tv of
- Nothing -> True
- Just ty -> occur_check_ok ty
+ | otherwise = case lookupSubstEnv env tv of
+ Nothing -> True
+ Just (DoneTy ty) -> occur_check_ok ty
\end{code}
types. It also fails on nested foralls.
@matchTys@ matches corresponding elements of a list of templates and
-types.
+types. It and @matchTy@ both ignore usage annotations, unlike the
+main function @match@.
\begin{code}
-matchTy :: [GenTyVar flexi_tmpl] -- Template tyvars
- -> GenType flexi_tmpl -- Template
- -> GenType flexi_result -- Proposed instance of template
- -> Maybe (TyVarEnv (GenType flexi_result)) -- Matching substitution
+matchTy :: TyVarSet -- Template tyvars
+ -> Type -- Template
+ -> Type -- Proposed instance of template
+ -> Maybe TyVarSubstEnv -- Matching substitution
-matchTys :: [GenTyVar flexi_tmpl] -- Template tyvars
- -> [GenType flexi_tmpl] -- Templates
- -> [GenType flexi_result] -- Proposed instance of template
- -> Maybe (TyVarEnv (GenType flexi_result), -- Matching substitution
- [GenType flexi_result]) -- Left over instance types
+matchTys :: TyVarSet -- Template tyvars
+ -> [Type] -- Templates
+ -> [Type] -- Proposed instance of template
+ -> Maybe (TyVarSubstEnv, -- Matching substitution
+ [Type]) -- Left over instance types
-matchTy tmpls ty1 ty2 = match ty1 ty2 (\(_,env) -> Just env)
- (tmpls, emptyVarEnv)
+matchTy tmpls ty1 ty2 = match False ty1 ty2 tmpls (\ senv -> Just senv) emptySubstEnv
-matchTys tmpls tys1 tys2 = match_list tys1 tys2 (\((_,env),tys) -> Just (env,tys))
- (tmpls, emptyVarEnv)
+matchTys tmpls tys1 tys2 = match_list False tys1 tys2 tmpls
+ (\ (senv,tys) -> Just (senv,tys))
+ emptySubstEnv
\end{code}
-@match@ is the main function.
+@match@ is the main function. It takes a flag indicating whether
+usage annotations are to be respected.
\begin{code}
-match :: GenType flexi_tmpl -> GenType flexi_result -- Current match pair
- -> (Subst flexi_tmpl flexi_result -> Maybe result) -- Continuation
- -> Subst flexi_tmpl flexi_result -- Current substitution
+match :: Bool -- Respect usages?
+ -> Type -> Type -- Current match pair
+ -> TyVarSet -- Template vars
+ -> (TyVarSubstEnv -> Maybe result) -- Continuation
+ -> TyVarSubstEnv -- Current subst
-> Maybe result
-- When matching against a type variable, see if the variable
-- has already been bound. If so, check that what it's bound to
-- is the same as ty; if not, bind it and carry on.
-match (TyVarTy v) ty k = \ s@(tmpls,env) ->
- if v `elem` tmpls then
- -- v is a template variable
- case lookupVarEnv env v of
- Nothing -> k (tmpls, extendVarEnv env v ty)
- Just ty' | ty' == ty -> k s -- Succeeds
- | otherwise -> Nothing -- Fails
- else
- -- v is not a template variable; ty had better match
- -- Can't use (==) because types differ
- case ty of
- TyVarTy v' | getUnique v == getUnique v'
- -> k s -- Success
- other -> Nothing -- Failure
-
-match (FunTy arg1 res1) (FunTy arg2 res2) k = match arg1 arg2 (match res1 res2 k)
-match (AppTy fun1 arg1) ty2 k = case splitAppTy_maybe ty2 of
- Just (fun2,arg2) -> match fun1 fun2 (match arg1 arg2 k)
- Nothing -> \ _ -> Nothing -- Fail
-match (TyConApp tc1 tys1) (TyConApp tc2 tys2) k | tc1 == tc2
- = match_list tys1 tys2 ( \(s,tys2') ->
- if null tys2' then
- k s -- Succeed
- else
- Nothing -- Fail
- )
+match uflag (TyVarTy v) ty tmpls k senv
+ | v `elemVarSet` tmpls
+ = -- v is a template variable
+ case lookupSubstEnv senv v of
+ Nothing -> UASSERT( not (isUTy ty) )
+ k (extendSubstEnv senv v (DoneTy ty))
+ Just (DoneTy ty') | ty' == ty -> k senv -- Succeeds
+ | otherwise -> Nothing -- Fails
+
+ | otherwise
+ = -- v is not a template variable; ty had better match
+ -- Can't use (==) because types differ
+ case deNoteType ty of
+ TyVarTy v' | v == v' -> k senv -- Success
+ other -> Nothing -- Failure
+ -- This deNoteType is *required* and cost me much pain. I guess
+ -- the reason the Note-stripping case is *last* rather than first
+ -- is to preserve type synonyms etc., so I'm not moving it to the
+ -- top; but this means that (without the deNotetype) a type
+ -- variable may not match the pattern (TyVarTy v') as one would
+ -- expect, due to an intervening Note. KSW 2000-06.
+
+match uflag (FunTy arg1 res1) (FunTy arg2 res2) tmpls k senv
+ = match uflag arg1 arg2 tmpls (match uflag res1 res2 tmpls k) senv
+
+match uflag (AppTy fun1 arg1) ty2 tmpls k senv
+ = case splitAppTy_maybe ty2 of
+ Just (fun2,arg2) -> match uflag fun1 fun2 tmpls (match uflag arg1 arg2 tmpls k) senv
+ Nothing -> Nothing -- Fail
+
+match uflag (TyConApp tc1 tys1) (TyConApp tc2 tys2) tmpls k senv
+ | tc1 == tc2
+ = match_list uflag tys1 tys2 tmpls k' senv
+ where
+ k' (senv', tys2') | null tys2' = k senv' -- Succeed
+ | otherwise = Nothing -- Fail
+
+match False (UsageTy _ ty1) ty2 tmpls k senv = match False ty1 ty2 tmpls k senv
+match False ty1 (UsageTy _ ty2) tmpls k senv = match False ty1 ty2 tmpls k senv
+
+match True (UsageTy u1 ty1) (UsageTy u2 ty2) tmpls k senv
+ = match True u1 u2 tmpls (match True ty1 ty2 tmpls k) senv
+match True ty1@(UsageTy _ _) ty2 tmpls k senv
+ = case splitUTy ty2 of { (u,ty2') -> match True ty1 ty2' tmpls k senv }
+match True ty1 ty2@(UsageTy _ _) tmpls k senv
+ = case splitUTy ty1 of { (u,ty1') -> match True ty1' ty2 tmpls k senv }
-- With type synonyms, we have to be careful for the exact
-- same reasons as in the unifier. Please see the
-- considerable commentary there before changing anything
-- here! (WDP 95/05)
-match (NoteTy _ ty1) ty2 k = match ty1 ty2 k
-match ty1 (NoteTy _ ty2) k = match ty1 ty2 k
+match uflag (NoteTy _ ty1) ty2 tmpls k senv = match uflag ty1 ty2 tmpls k senv
+match uflag ty1 (NoteTy _ ty2) tmpls k senv = match uflag ty1 ty2 tmpls k senv
-- Catch-all fails
-match _ _ _ = \s -> Nothing
+match _ _ _ _ _ _ = Nothing
-match_list [] tys2 k = \s -> k (s, tys2)
-match_list (ty1:tys1) [] k = \s -> Nothing -- Not enough arg tys => failure
-match_list (ty1:tys1) (ty2:tys2) k = match ty1 ty2 (match_list tys1 tys2 k)
+match_list uflag [] tys2 tmpls k senv = k (senv, tys2)
+match_list uflag (ty1:tys1) [] tmpls k senv = Nothing -- Not enough arg tys => failure
+match_list uflag (ty1:tys1) (ty2:tys2) tmpls k senv
+ = match uflag ty1 ty2 tmpls (match_list uflag tys1 tys2 tmpls k) senv
\end{code}
+
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