#7395: DefaultSignatures conflict with default implementations
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Reporter: cgaebel | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 7.6.1
Keywords: DefaultSignatures | Os: Unknown/Multiple
Architecture: Unknown/Multiple | Failure: GHC rejects valid program
Difficulty: Unknown | Testcase:
Blockedby: | Blocking:
Related: |
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Comment(by hvr):
just a thought:
...what if the default-signature implementation would be only selectable
by using the `deriving` facilities for auto-derivable classes? I.e. by
using
{{{
#!hs
data A = A { unA :: Int }
deriving (Generic,Klass)
}}}
or
{{{
#!hs
data A = A { unA :: Int }
deriving Generic
deriving instance Klass A
}}}
would both result in `A` getting the default-signature based
implementation, wheras
{{{
#!hs
data A = A { unA :: Int }
deriving Generic
instance Klass A
}}}
would get the "ordinary" default implementation (as if the default-
signature implementation wasn't there). Wouldn't this help the issue at
hand by making the choice explicit?
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7395#comment:7>
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