[project @ 2004-12-21 12:22:22 by simonpj]

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

diff --git a/ghc/compiler/typecheck/TcRnTypes.lhs b/ghc/compiler/typecheck/TcRnTypes.lhs
index 3b71b1d..ed1fb86 100644 (file)
--- a/ghc/compiler/typecheck/TcRnTypes.lhs
+++ b/ghc/compiler/typecheck/TcRnTypes.lhs
@@ -48,7 +48,7 @@ import HscTypes               ( FixityEnv,
                          GenAvailInfo(..), AvailInfo,
                          availName, IsBootInterface, Deprecations )
 import Packages                ( PackageId )
-import Type            ( Type, TvSubstEnv )
+import Type            ( Type, TvSubstEnv, pprParendType )
 import TcType          ( TcTyVarSet, TcType, TcTauType, TcThetaType, SkolemInfo,
                          TcPredType, TcKind, tcCmpPred, tcCmpType, tcCmpTypes )
 import InstEnv         ( DFunId, InstEnv )
@@ -386,15 +386,22 @@ topArrowCtxt = ArrCtxt { proc_level = topProcLevel, proc_banned = [] }
 
 data TcTyThing
   = AGlobal TyThing                    -- Used only in the return type of a lookup
+
   | ATcId   TcId ThLevel ProcLevel     -- Ids defined in this module; may not be fully zonked
-  | ATyVar  TyVar                      -- Type variables
+
+  | ATyVar  TyVar TcType               -- Type variables; tv -> type.  It can't just be a TyVar
+                                       -- that is mutated to point to the type it is bound to,
+                                       -- because that would make it a wobbly type, and we
+                                       -- want pattern-bound lexically-scoped type variables to
+                                       -- be able to stand for rigid types
+
   | AThing  TcKind                     -- Used temporarily, during kind checking, for the
                                        --      tycons and clases in this recursive group
 
 instance Outputable TcTyThing where    -- Debugging only
    ppr (AGlobal g)      = text "AGlobal" <+> ppr g
    ppr (ATcId g tl pl)  = text "ATcId" <+> ppr g <+> ppr tl <+> ppr pl
-   ppr (ATyVar t)       = text "ATyVar" <+> ppr t
+   ppr (ATyVar tv ty)   = text "ATyVar" <+> ppr tv <+> pprParendType ty
    ppr (AThing k)       = text "AThing" <+> ppr k
 \end{code}