Fix Trac #959: a long-standing bug in instantiating otherwise-unbound type variables

[ghc-hetmet.git] / compiler / iface / IfaceType.lhs

diff --git a/compiler/iface/IfaceType.lhs b/compiler/iface/IfaceType.lhs
index 1688344..2db1908 100644 (file)
--- a/compiler/iface/IfaceType.lhs
+++ b/compiler/iface/IfaceType.lhs
@@ -68,32 +68,41 @@ data IfacePredType  -- NewTypes are handled as ordinary TyConApps
 
 type IfaceContext = [IfacePredType]
 
--- NB: If you add a data constructor, remember to add a case to
---     IfaceSyn.eqIfTc!
 data IfaceTyCon        -- Abbreviations for common tycons with known names
   = IfaceTc Name       -- The common case
   | IfaceIntTc | IfaceBoolTc | IfaceCharTc
   | IfaceListTc | IfacePArrTc
   | IfaceTupTc Boxity Arity 
+  | IfaceAnyTc IfaceKind    -- Used for AnyTyCon (see Note [Any Types] in TysPrim)
   | IfaceLiftedTypeKindTc | IfaceOpenTypeKindTc | IfaceUnliftedTypeKindTc
   | IfaceUbxTupleKindTc | IfaceArgTypeKindTc 
-  deriving( Eq )
 
 ifaceTyConName :: IfaceTyCon -> Name
-ifaceTyConName IfaceIntTc        = intTyConName
-ifaceTyConName IfaceBoolTc       = boolTyConName
-ifaceTyConName IfaceCharTc       = charTyConName
-ifaceTyConName IfaceListTc       = listTyConName
-ifaceTyConName IfacePArrTc       = parrTyConName
-ifaceTyConName (IfaceTupTc bx ar) = getName (tupleTyCon bx ar)
+ifaceTyConName IfaceIntTc             = intTyConName
+ifaceTyConName IfaceBoolTc            = boolTyConName
+ifaceTyConName IfaceCharTc            = charTyConName
+ifaceTyConName IfaceListTc            = listTyConName
+ifaceTyConName IfacePArrTc            = parrTyConName
+ifaceTyConName (IfaceTupTc bx ar)      = getName (tupleTyCon bx ar)
 ifaceTyConName IfaceLiftedTypeKindTc   = liftedTypeKindTyConName
 ifaceTyConName IfaceOpenTypeKindTc     = openTypeKindTyConName
 ifaceTyConName IfaceUnliftedTypeKindTc = unliftedTypeKindTyConName
 ifaceTyConName IfaceUbxTupleKindTc     = ubxTupleKindTyConName
 ifaceTyConName IfaceArgTypeKindTc      = argTypeKindTyConName
-ifaceTyConName (IfaceTc ext)      = ext
+ifaceTyConName (IfaceTc ext)           = ext
+ifaceTyConName (IfaceAnyTc kind)       = pprPanic "ifaceTyConName" (ppr (IfaceAnyTc kind))
+                                        -- Note [The Name of an IfaceAnyTc]
 \end{code}
 
+Note [The Name of an IfaceAnyTc]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+It isn't easy to get the Name of an IfaceAnyTc in a pure way.  What you
+really need to do is to transform it to a TyCon, and get the Name of that.
+But doing so needs the monad.
+
+In fact, ifaceTyConName is only used for instances and rules, and we don't
+expect to instantiate those at these (internal-ish) Any types, so rather
+than solve this potential problem now, I'm going to defer it until it happens!
 
 %************************************************************************
 %*                                                                     *
@@ -312,6 +321,7 @@ toIfaceType (PredTy st) =
 toIfaceTyCon :: TyCon -> IfaceTyCon
 toIfaceTyCon tc 
   | isTupleTyCon tc = IfaceTupTc (tupleTyConBoxity tc) (tyConArity tc)
+  | isAnyTyCon tc   = IfaceAnyTc (toIfaceKind (tyConKind tc))
   | otherwise      = toIfaceTyCon_name (tyConName tc)
 
 toIfaceTyCon_name :: Name -> IfaceTyCon
@@ -323,7 +333,8 @@ toIfaceTyCon_name nm
 
 toIfaceWiredInTyCon :: TyCon -> Name -> IfaceTyCon
 toIfaceWiredInTyCon tc nm
-  | isTupleTyCon tc                 =  IfaceTupTc (tupleTyConBoxity tc) (tyConArity tc)
+  | isTupleTyCon tc                 = IfaceTupTc  (tupleTyConBoxity tc) (tyConArity tc)
+  | isAnyTyCon tc                   = IfaceAnyTc (toIfaceKind (tyConKind tc))
   | nm == intTyConName              = IfaceIntTc
   | nm == boolTyConName             = IfaceBoolTc 
   | nm == charTyConName             = IfaceCharTc