Migrate cvs diff from fptools-assoc branch

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

diff --git a/compiler/typecheck/TcMType.lhs b/compiler/typecheck/TcMType.lhs
index fe51df1..11ec9d9 100644 (file)
--- a/compiler/typecheck/TcMType.lhs
+++ b/compiler/typecheck/TcMType.lhs
@@ -200,9 +200,13 @@ newMetaTyVar box_info kind
        ; ref <- newMutVar Flexi ;
        ; let name = mkSysTvName uniq fs 
              fs = case box_info of
-                       BoxTv   -> FSLIT("bx")
+                       BoxTv   -> FSLIT("t")
                        TauTv   -> FSLIT("t")
                        SigTv _ -> FSLIT("a")
+               -- We give BoxTv and TauTv the same string, because
+               -- otherwise we get user-visible differences in error
+               -- messages, which are confusing.  If you want to see
+               -- the box_info of each tyvar, use -dppr-debug
        ; return (mkTcTyVar name kind (MetaTv box_info ref)) }
 
 instMetaTyVar :: BoxInfo -> TyVar -> TcM TcTyVar