If I create a module AModule
with a typeclass Foo
,
module AModule where
class Foo a where
bar :: a
and in another module BModule
import AModule
qualified and try to make some type an instance of Foo
, i.e.
module B where
import qualified AModule as A
instance A.Foo Int wh开发者_如何学Cere
A.bar = 0
GHC tells me "Qualified name in binding position: A.bar".
From what I understand, this is related to GHC ticket 3197, which is labeled as fixed. I'm running GHC 6.12.1 and am still getting the error. Am I just misunderstanding something here?
You don't need the A.
inside the instance declaration (See Haskell 98 report §4.3.2).
The following compiles on 6.12.3:
instance A.Foo Int where -- # A. here
bar = 0 -- # no A. here
main = print (A.bar :: Int) -- # A. here
精彩评论