Comment-only: Fix a typo, and note that the PredTy case on SplitTyConApp_maybe was...

[ghc-hetmet.git] / compiler / typecheck / TcType.lhs

diff --git a/compiler/typecheck/TcType.lhs b/compiler/typecheck/TcType.lhs
index a382808..c10c2eb 100644 (file)
--- a/compiler/typecheck/TcType.lhs
+++ b/compiler/typecheck/TcType.lhs
@@ -10,7 +10,7 @@ compiler.  These parts
                newtypes, and predicates are meaningful. 
        * look through usage types
 
-The "tc" prefix is for "typechechecker", because the type checker
+The "tc" prefix is for "TypeChecker", because the type checker
 is the principal client.
 
 \begin{code}
@@ -169,7 +169,8 @@ import Type         (       -- Re-exports
                          pprType, pprParendType, pprTyThingCategory,
                          pprPred, pprTheta, pprThetaArrow, pprClassPred
                        )
-import TyCon           ( TyCon, isUnLiftedTyCon, isSynTyCon, synTyConDefn, tyConUnique )
+import TyCon           ( TyCon, isUnLiftedTyCon, isSynTyCon, isOpenTyCon,
+                         synTyConDefn, tyConUnique )    
 import DataCon         ( DataCon, dataConStupidTheta, dataConResTys )
 import Class           ( Class )
 import Var             ( TyVar, Id, isCoVar, isTcTyVar, mkTcTyVar, tyVarName, tyVarKind, tcTyVarDetails )
@@ -343,6 +344,7 @@ data SkolemInfo
        -- The rest are for non-scoped skolems
   | ClsSkol Class      -- Bound at a class decl
   | InstSkol Id                -- Bound at an instance decl
+  | FamInstSkol TyCon  -- Bound at a family instance decl
   | PatSkol DataCon    -- An existential type variable bound by a pattern for
            SrcSpan     -- a data constructor with an existential type. E.g.
                        --      data T = forall a. Eq a => MkT a
@@ -397,6 +399,7 @@ mkKindName unique = mkSystemName unique kind_var_occ
 
 kindVarRef :: KindVar -> IORef MetaDetails
 kindVarRef tc = 
+  ASSERT ( isTcTyVar tc )
   case tcTyVarDetails tc of
     MetaTv TauTv ref -> ref
     other            -> pprPanic "kindVarRef" (ppr tc)
@@ -470,7 +473,8 @@ pprSkolTvBinding :: TcTyVar -> SDoc
 -- Print info about the binding of a skolem tyvar, 
 -- or nothing if we don't have anything useful to say
 pprSkolTvBinding tv
-  = ppr_details (tcTyVarDetails tv)
+  = ASSERT ( isTcTyVar tv )
+    ppr_details (tcTyVarDetails tv)
   where
     ppr_details (MetaTv TauTv _)   = quotes (ppr tv) <+> ptext SLIT("is a meta type variable")
     ppr_details (MetaTv BoxTv _)   = quotes (ppr tv) <+> ptext SLIT("is a boxy type variable")
@@ -485,8 +489,13 @@ pprSkolTvBinding tv
 pprSkolInfo :: SkolemInfo -> SDoc
 pprSkolInfo (SigSkol ctxt)   = ptext SLIT("is bound by") <+> pprUserTypeCtxt ctxt
 pprSkolInfo (ClsSkol cls)    = ptext SLIT("is bound by the class declaration for") <+> quotes (ppr cls)
-pprSkolInfo (InstSkol df)    = ptext SLIT("is bound by the instance declaration at") <+> ppr (getSrcLoc df)
-pprSkolInfo (ArrowSkol loc)  = ptext SLIT("is bound by the arrow form at") <+> ppr loc
+pprSkolInfo (InstSkol df)    = 
+  ptext SLIT("is bound by the instance declaration at") <+> ppr (getSrcLoc df)
+pprSkolInfo (FamInstSkol tc) = 
+  ptext SLIT("is bound by the family instance declaration at") <+> 
+  ppr (getSrcLoc tc)
+pprSkolInfo (ArrowSkol loc)  = 
+  ptext SLIT("is bound by the arrow form at") <+> ppr loc
 pprSkolInfo (PatSkol dc loc) = sep [ptext SLIT("is bound by the pattern for") <+> quotes (ppr dc),
                                    nest 2 (ptext SLIT("at") <+> ppr loc)]
 pprSkolInfo (GenSkol tvs ty loc) = sep [sep [ptext SLIT("is bound by the polymorphic type"), 
@@ -591,8 +600,9 @@ isTauTy other                 = False
 
 isTauTyCon :: TyCon -> Bool
 -- Returns False for type synonyms whose expansion is a polytype
-isTauTyCon tc | isSynTyCon tc = isTauTy (snd (synTyConDefn tc))
-             | otherwise     = True
+isTauTyCon tc 
+  | isSynTyCon tc && not (isOpenTyCon tc) = isTauTy (snd (synTyConDefn tc))
+  | otherwise                             = True
 
 ---------------
 isBoxyTy :: TcType -> Bool
@@ -702,9 +712,17 @@ tcSplitTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
 tcSplitTyConApp_maybe ty | Just ty' <- tcView ty = tcSplitTyConApp_maybe ty'
 tcSplitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
 tcSplitTyConApp_maybe (FunTy arg res)   = Just (funTyCon, [arg,res])
+tcSplitTyConApp_maybe (AppTy arg res)   = Just (funTyCon, [arg,res])
        -- Newtypes are opaque, so they may be split
        -- However, predicates are not treated
        -- as tycon applications by the type checker
+
+-- XXX - 2006-09-24: This case is hard-coded in (rendering predicates opaque as well)
+--       to make the newly reworked newtype-deriving work on the trivial case:
+--              newtype T = T () deriving (Eq, Ord)
+--       Please remove this if the newtype-deriving scheme no longer produces a PredTy.
+tcSplitTyConApp_maybe (PredTy (ClassP _ [ty']))   = tcSplitTyConApp_maybe ty'
+
 tcSplitTyConApp_maybe other            = Nothing
 
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