Better pretty-printing for TvSubst

compiler/types/Type.lhs

@@ -1135,9 +1135,9 @@ zip_ty_env tvs      tys      env   = pprTrace "Var/Type length mismatch: " (ppr
 
 instance Outputable TvSubst where
   ppr (TvSubst ins env) 
-    = sep[ ptext SLIT("<TvSubst"),
-	   nest 2 (ptext SLIT("In scope:") <+> ppr ins), 
-	   nest 2 (ptext SLIT("Env:") <+> ppr env) ]
+    = brackets $ sep[ ptext SLIT("TvSubst"),
+		      nest 2 (ptext SLIT("In scope:") <+> ppr ins), 
+		      nest 2 (ptext SLIT("Env:") <+> ppr env) ]
 \end{code}
 
 %************************************************************************