Re: [GHC] #5316: ghc rejects a program at first but will accept it if one insists
#5316: ghc rejects a program at first but will accept it if one insists +--- Reporter: jcpetruzza | Owner: Type: bug| Status: closed Priority: normal | Milestone: Component: Compiler |Version: 7.0.4 Resolution: duplicate | Keywords: Testcase: | Blockedby: Difficulty: | Os: Unknown/Multiple Blocking: | Architecture: Unknown/Multiple Failure: GHC rejects valid program | +--- Changes (by igloo): * status: new = closed * resolution: = duplicate Comment: Thanks for the report. The overlapping instance in `System.Event.Manager` has been removed in the HEAD and 7.2, so this particular conflict won't arise again. The poor handling of instances in different modules is a known problem: see #2356. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/5316#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] #5316: ghc rejects a program at first but will accept it if one insists
#5316: ghc rejects a program at first but will accept it if one insists
+---
Reporter: jcpetruzza | Owner:
Type: bug| Status: new
Priority: normal | Milestone:
Component: Compiler |Version: 7.0.4
Resolution: | Keywords:
Testcase: | Blockedby:
Difficulty: | Os: Unknown/Multiple
Blocking: | Architecture: Unknown/Multiple
Failure: GHC rejects valid program |
+---
Changes (by jcpetruzza):
* status: closed = new
* resolution: duplicate =
Comment:
My apologies for reopening the ticket, but after going through #2356 I
can't see the duplication. What I am reporting here is that:
1) GHC will reject these modules only if compiled with optimizations on,
as witnessed by:
{{{
$ rm *hi *o
$ ghc --make -c T1 T2
[1 of 2] Compiling T2 ( T2.hs, T2.o )
[2 of 2] Compiling T1 ( T1.hs, T1.o )
$
}}}
2) GHC behaves differently if part of the program was already compiled.
Moreover, #2356 is about a design decision that makes it accept more
programs than the Report mandates, not less.
Since as of #2356 GHC accepts duplicated instances as long as they don't
conflict, I suspect that the real bug here is that the instance defined in
System.Event.Manager shouldn't be in scope at all when compiling T1 (the
first time).
Am I missing something?
--
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/5316#comment:2
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] #5316: ghc rejects a program at first but will accept it if one insists
#5316: ghc rejects a program at first but will accept it if one insists +--- Reporter: jcpetruzza | Owner: Type: bug| Status: new Priority: normal | Milestone: Component: Compiler |Version: 7.0.4 Resolution: | Keywords: Testcase: | Blockedby: Difficulty: | Os: Unknown/Multiple Blocking: | Architecture: Unknown/Multiple Failure: GHC rejects valid program | +--- Changes (by conal): * cc: conal@… (added) -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/5316#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
[GHC] #5316: ghc rejects a program at first but will accept it if one insists
#5316: ghc rejects a program at first but will accept it if one insists
-+--
Reporter: jcpetruzza| Owner:
Type: bug | Status: new
Priority: normal| Component: Compiler
Version: 7.0.4 |Keywords:
Testcase:| Blockedby:
Os: Unknown/Multiple |Blocking:
Architecture: Unknown/Multiple | Failure: GHC rejects valid program
-+--
Consider these two modules (boiled down example from the checkers
package):
{{{
{-# LANGUAGE ScopedTypeVariables, FlexibleContexts #-}
module T1
where
import Test.QuickCheck
import Text.Show.Functions ()
f :: forall m a b. ( Arbitrary (a-b) ) = m (a,b) - Property
f = const $ property (undefined :: (a-b) - Bool)
}}}
{{{
module T2 where
import Control.Concurrent
g = threadDelay maxBound
}}}
I see the following interaction:
{{{
$ rm *hi *.o
$ ghc --make -c -O T1 T2
[1 of 2] Compiling T2 ( T2.hs, T2.o )
[2 of 2] Compiling T1 ( T1.hs, T1.o )
T1.hs:12:13:
Overlapping instances for Show (a - b)
arising from a use of `property'
Matching instances:
instance Show (a - b) -- Defined in Text.Show.Functions
instance Show base:System.Event.Manager.IOCallback
-- Defined in base:System.Event.Manager
(The choice depends on the instantiation of `a, b'
To pick the first instance above, use -XIncoherentInstances
when compiling the other instance declarations)
In the second argument of `($)', namely
`property (undefined :: (a - b) - Bool)'
In the expression: const $ property (undefined :: (a - b) - Bool)
In an equation for `f':
f = const $ property (undefined :: (a - b) - Bool)
$ ghc --make -c -O T1 T2
[2 of 2] Compiling T1 ( T1.hs, T1.o )
$ ghc --make -c -O T1 T2
$ ls
T1.hi T1.hs T1.o T2.hi T2.hs T2.o
}}}
I see this consistent behaviour in versions 7.0.{1,2,3,4} but not with
6.12.1
--
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/5316
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
