#3714: Associated types missing useful functionality
---------------------------------+------------------------------------------
Reporter: simonpj | Owner: chak
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 6.10.4
Keywords: | Difficulty:
Os: Unknown/Multiple | Testcase:
Architecture: Unknown/Multiple | Failure: None/Unknown
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Martijn van Steenbergen pointed out this program:
{{{
{-# LANGUAGE TypeFamilies #-}
module M where
-- Accepted
type family T1 f e :: *
class C1 f where
op1 :: T1 f e -> Either e a
-- Rejected
class C2 f where
type T2 f e :: *
op2 :: T2 f e -> Either e a
}}}
At the moment (HEAD) the C1/T1 version is accepted but the C2/T2
declarations are rejected:
{{{
TF.hs:12:3: Not in scope: type variable `e'
}}}
I think this is just a bug.
Simon
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3714>
GHC <http://www.haskell.org/ghc/>
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