6.6 strikes me again :)

[Simon Peyton-Jones]

Quite right; that's just as specified.  The coverage condition is
documented in the manual.  (GHC 6.4 and Hugs are too liberal, and
thereby risk divergence during type checking.)   If you want this
program to work, use -fallow-undecidable-instances

Simon

| -----Original Message-----
| From: glasgow-haskell-users-bounces at haskell.org
[mailto:glasgow-haskell-users-
| bounces at haskell.org] On Behalf Of Bulat Ziganshin
| Sent: 20 September 2006 14:14
| To: glasgow-haskell-users at haskell.org
| Subject: 6.6 strikes me again :)
| 
| Hello glasgow-haskell-users,
| 
| attached module compiles fine with ghc 6.4.2, hugs 2003+, but not with
| my ghc 6.5 snapshot. it says:
| 
| 66.hs:9:0:
|     Illegal instance declaration for `Stream m (StringReader r)'
|         (the Coverage Condition fails for one of the functional
dependencies)
|     In the instance declaration for `Stream m (StringReader r)'
| 
| --
| Best regards,
|  Bulat                          mailto:Bulat.Ziganshin at gmail.com