#5520: Spurious warning with new associated types and MultiParamTypeClasses
---------------------------------+------------------------------------------
Reporter: batterseapower | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 7.3 | Keywords:
Testcase: | Blockedby:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: Incorrect warning at
compile-time
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Consider this program:
{{{
{-# LANGUAGE TypeFamilies, MultiParamTypeClasses #-}
module Overlap where
class Foo a b where
type Typ a
instance Foo Int Int where
type Typ Int = Bool
instance Foo Int Bool where
}}}
We get a warning:
{{{
Overlap.hs:10:1:
Warning: No explicit AT declaration for `Typ'
In the instance declaration for `Foo Int Bool'
}}}
But inserting such an AT declaration would be an error!
{{{
Overlap.hs:8:8:
Conflicting family instance declarations:
type Typ Int -- Defined at Overlap.hs:8:8
type Typ Int -- Defined at Overlap.hs:11:8
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5520>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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