[commit: ghc] master: When quantifying associated types, we may have TyVars involved, not just TcTyVars (6464d37)

[Simon Peyton Jones]

Repository : ssh://darcs.haskell.org//srv/darcs/ghc

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/6464d377b85c1b20a2bfb29eb579e88f36bce333

>---------------------------------------------------------------

commit 6464d377b85c1b20a2bfb29eb579e88f36bce333
Author: Simon Peyton Jones <simonpj at microsoft.com>
Date:   Tue Jan 29 08:57:05 2013 +0000

    When quantifying associated types, we may have TyVars involved, not just TcTyVars
    This required a little adjustment in zonkQuantifiedTyVars

>---------------------------------------------------------------

 compiler/typecheck/TcHsType.lhs |    8 ++++----
 compiler/typecheck/TcMType.lhs  |   13 +++++++++++--
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/compiler/typecheck/TcHsType.lhs b/compiler/typecheck/TcHsType.lhs
index cd5e029..69b97ce 100644
--- a/compiler/typecheck/TcHsType.lhs
+++ b/compiler/typecheck/TcHsType.lhs
@@ -886,7 +886,7 @@ tcScopedKindVars kv_ns thing_inside
   = tcExtendTyVarEnv (map mkKindSigVar kv_ns) thing_inside
 
 tcHsTyVarBndrs :: LHsTyVarBndrs Name 
-	       -> ([TyVar] -> TcM r)
+	       -> ([TcTyVar] -> TcM r)
 	       -> TcM r
 -- Bind the type variables to skolems, each with a meta-kind variable kind
 tcHsTyVarBndrs (HsQTvs { hsq_kvs = kvs, hsq_tvs = hs_tvs }) thing_inside
@@ -895,7 +895,7 @@ tcHsTyVarBndrs (HsQTvs { hsq_kvs = kvs, hsq_tvs = hs_tvs }) thing_inside
        ; traceTc "tcHsTyVarBndrs" (ppr hs_tvs $$ ppr tvs)
        ; tcExtendTyVarEnv tvs (thing_inside tvs) }
 
-tcHsTyVarBndr :: LHsTyVarBndr Name -> TcM TyVar
+tcHsTyVarBndr :: LHsTyVarBndr Name -> TcM TcTyVar
 -- Return a type variable 
 -- initialised with a kind variable.
 -- Typically the Kind inside the KindedTyVar will be a tyvar with a mutable kind 
@@ -907,7 +907,7 @@ tcHsTyVarBndr :: LHsTyVarBndr Name -> TcM TyVar
 --   instance C (a,b) where
 --     type F (a,b) c = ...
 -- Here a,b will be in scope when processing the associated type instance for F.
--- See Note [Associated type tyvar names] in TyCon
+-- See Note [Associated type tyvar names] in Class
 tcHsTyVarBndr (L _ hs_tv)
   = do { let name = hsTyVarName hs_tv
        ; mb_tv <- tcLookupLcl_maybe name
@@ -915,7 +915,7 @@ tcHsTyVarBndr (L _ hs_tv)
            Just (ATyVar _ tv) -> return tv ;
            _ -> do
        { kind <- case hs_tv of
-                   UserTyVar {} -> newMetaKindVar
+                   UserTyVar {}       -> newMetaKindVar
                    KindedTyVar _ kind -> tcLHsKind kind
        ; return (mkTcTyVar name kind (SkolemTv False)) } } }
 
diff --git a/compiler/typecheck/TcMType.lhs b/compiler/typecheck/TcMType.lhs
index 8af1e4c..f0dd6e9 100644
--- a/compiler/typecheck/TcMType.lhs
+++ b/compiler/typecheck/TcMType.lhs
@@ -547,9 +547,12 @@ defaultKindVarToStar kv
 
 zonkQuantifiedTyVars :: [TcTyVar] -> TcM [TcTyVar]
 -- A kind variable k may occur *after* a tyvar mentioning k in its kind
+-- Can be given a mixture of TcTyVars and TyVars, in the case of
+-- associated type declarations
 zonkQuantifiedTyVars tyvars
   = do { let (kvs, tvs) = partition isKindVar tyvars
-             (meta_kvs, skolem_kvs) = partition isMetaTyVar kvs
+             (meta_kvs, skolem_kvs) 
+                  = partition (\kv -> isTcTyVar kv && isMetaTyVar kv) kvs
 
              -- In the non-PolyKinds case, default the kind variables
              -- to *, and zonk the tyvars as usual.  Notice that this
@@ -562,10 +565,16 @@ zonkQuantifiedTyVars tyvars
                       do { mapM_ defaultKindVarToStar meta_kvs
                          ; return skolem_kvs }  -- Should be empty
 
-       ; mapM zonkQuantifiedTyVar (qkvs ++ tvs) }
+       ; mapM zonk_quant (qkvs ++ tvs) }
            -- Because of the order, any kind variables
            -- mentioned in the kinds of the type variables refer to
            -- the now-quantified versions
+  where
+    zonk_quant tkv
+      | isTcTyVar tkv = zonkQuantifiedTyVar tkv
+      | otherwise     = return tkv
+      -- For associated types, we have the class variables 
+      -- in scope, and they are TyVars not TcTyVars
 
 zonkQuantifiedTyVar :: TcTyVar -> TcM TcTyVar
 -- The quantified type variables often include meta type variables