[nhc-bugs] Instances of qualified imported classes

[Ian Lynagh]

Hi,

While getting hat to work with ghc6 I've come across the following
issue:

If Bar.hs is this:

-----
module Bar where

class Bar a where
    bar :: a -> Bool
-----

and Foo.hs is this:

-----
module Foo where

import qualified Bar 

data Foo = Foo

instance Bar.Bar Foo where
    bar _ = True
-----

then ghc 6.0.1 is happy enough, but nhc98 v1.16 doesn't like bar being
used unqualified:

$ make clean
rm -f *.o *.hi
$ make ghc
ghc6 -c Bar.hs
ghc6 -c Foo.hs
$ make clean
rm -f *.o *.hi
$ make nhc
nhc98 -c Bar.hs
nhc98 -c Foo.hs
======  Errors when renaming:
The identifier bar instantiated at 9:5 does not belong to this class.
make: *** [nhc] Error 1
$ 

If I qualify bar:

-----
module Foo where

import qualified Bar 

data Foo = Foo

instance Bar.Bar Foo where
    Bar.bar _ = True
-----

then the roles are reversed:

$ make clean
rm -f *.o *.hi
$ make ghc
ghc6 -c Bar.hs
ghc6 -c Foo.hs
Foo.hs:11: Qualified name in function definition: Bar.bar
make: *** [ghc] Error 1
$ make clean
rm -f *.o *.hi
$ make nhc
nhc98 -c Bar.hs
nhc98 -c Foo.hs
$ 

hugs agrees with GHC 6 on both, and the report seems to agree on the
latter (I haven't looked for what it says on the former, but it seems
reasonable behaviour).


Thanks
Ian