Re: [GHC] #7395: DefaultSignatures conflict with default implementations
#7395: DefaultSignatures conflict with default implementations --+- Reporter: cgaebel| Owner: Type: feature request| 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: 7346 | --+- Changes (by PHO): * cc: pho@… (added) -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7395#comment:13 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #7395: DefaultSignatures conflict with default implementations
#7395: DefaultSignatures conflict with default implementations --+- 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: 7346 | --+- Comment(by simonpj): See email debate here [http://www.haskell.org/pipermail/libraries/2012-November/018750.html] -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7395#comment:11 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #7395: DefaultSignatures conflict with default implementations
#7395: DefaultSignatures conflict with default implementations --+- Reporter: cgaebel| Owner: Type: feature request| 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: 7346 | --+- Changes (by simonpj): * type: bug = feature request -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7395#comment:12 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #7395: DefaultSignatures conflict with default implementations
#7395: DefaultSignatures conflict with default implementations --+- 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: 7346 | --+- Changes (by dreixel): * related: = 7346 Comment: Replying to [comment:7 hvr]: just a thought: ...what if the default-signature implementation would be only selectable by using the `deriving` facilities for auto-derivable classes? I can see the advantages, but there are also some problems. First, it only works if ALL the methods of the class have defaults (with signature or not). Second, when using normal deriving (not standalone) the compiler has to figure out the context for the instance, and this is not easy in general... See also #7346. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7395#comment:10 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #7395: DefaultSignatures conflict with default implementations
#7395: DefaultSignatures conflict with default implementations --+- 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: | --+- Changes (by basvandijk): * cc: v.dijk.bas@… (added) -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7395#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #7395: DefaultSignatures conflict with default implementations
#7395: DefaultSignatures conflict with default implementations
--+-
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: |
--+-
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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Re: [GHC] #7395: DefaultSignatures conflict with default implementations
#7395: DefaultSignatures conflict with default implementations --+- 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: | --+- Comment(by cgaebel): +1 to hvr's idea. This would have the additional (very awesome) benefit of allowing the deriving of Show, Read, Eq, Ord, etc. to be implemented in a library (Prelude?) instead of living as compiler magic. This bug just got a whole lot more exciting. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7395#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #7395: DefaultSignatures conflict with default implementations
#7395: DefaultSignatures conflict with default implementations --+- 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: | --+- Changes (by hvr): * cc: hvr@… (added) -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7395#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #7395: DefaultSignatures conflict with default implementations
#7395: DefaultSignatures conflict with default implementations --+- 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: http://hpaste.org/77290 Blockedby: |Blocking: Related: | --+- Changes (by simonpj): * difficulty: = Unknown Comment: You did not attach a test case! -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7395#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #7395: DefaultSignatures conflict with default implementations
#7395: DefaultSignatures conflict with default implementations
--+-
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: http://hpaste.org/77290
Blockedby: |Blocking:
Related: |
--+-
Comment(by tibbe):
A test case is linked under the Test Case attribute above. Here's the
same test case, inlined:
{{{
{-# LANGUAGE DefaultSignatures, TypeOperators, FlexibleContexts,
DeriveGeneric #-}
module Main ( main ) where
import GHC.Generics
class Klass a where
func :: a - Int
func _ = 0
-- This implementation is incompatible with the one above. What should
-- happen instead is that this instance is selected whenever
availible,
-- and the one above should be used as a fallback.
default func :: (Generic a, GKlass (Rep a)) = a - Int
func = gfunc . from
class GKlass f where
gfunc :: f a - Int
instance GKlass U1 where
gfunc _ = 0
instance Klass a = GKlass (K1 i a) where
gfunc = (+1) . func . unK1
instance GKlass a = GKlass (M1 i c a) where
gfunc = gfunc . unM1
instance (GKlass a, GKlass b) = GKlass (a :*: b) where
gfunc (x :*: y) = 1 + gfunc x + gfunc y
instance (GKlass a, GKlass b) = GKlass (a :+: b) where
gfunc (L1 x) = 1 + gfunc x
gfunc (R1 x) = 1 + gfunc x
instance Klass Int where
func = id
data A = A { unA :: Int }
deriving Generic
-- A has a Generic instance. Therefore, should use gfunc.
instance Klass A
data B = B { unB :: Int }
-- B does not have a Generic instance. Therefore, should use func.
instance Klass B
main :: IO ()
main = print (func $ A 3, func $ B 3)
}}}
--
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7395#comment:2
GHC http://www.haskell.org/ghc/
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Re: [GHC] #7395: DefaultSignatures conflict with default implementations
#7395: DefaultSignatures conflict with default implementations --+- 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: | --+- Changes (by igloo): * testcase: http://hpaste.org/77290 = -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7395#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #7395: DefaultSignatures conflict with default implementations
#7395: DefaultSignatures conflict with default implementations --+- 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: | --+- Comment(by cgaebel): Doesn't GHC already backtrack for things like UndecidableInstances? Or does it do something else? Can we apply that here? -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7395#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
