#1145: class instance lost during re-export & packaging
-------------------------+--------------------------------------------------
Reporter: conal | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 6.6
Severity: normal | Keywords:
Difficulty: Unknown | Testcase:
Architecture: Unknown | Os: Unknown
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The package [http://hackage.haskell.org/cgi-bin/hackage-
scripts/package/TV-0.2 TV] defines an instance OFun (in module
[http://darcs.haskell.org/packages/TV/doc/html/Interface-TV-OFun.html
Interface.TV.OFun], source
[http://darcs.haskell.org/packages/TV/doc/html/src/Interface/TV/OFun.hs.html
here]) for a type class
[http://darcs.haskell.org/packages/DeepArrow/doc/html/Data-
FunArr.html#t%3AFunArr| FunArr] in the package [http://hackage.haskell.org
/cgi-bin/hackage-scripts/package/DeepArrow-0.0.1 DeepArrow]. The module
[http://darcs.haskell.org/packages/TV/doc/html/Interface-TV.html
Interface.TV] (source
[http://darcs.haskell.org/packages/TV/doc/html/src/Interface/TV.hs.html
here]) re-exports Interface.TV.OFun in its entirety.
When I compile a test program that imports Interface.TV, under ghc-6.6,
the OFun instance of !FunArr is not found. If the test module also says
"import Interface.TV.OFun()", the instance is found. I get this behavior
with ghc, ghc --make, and ghci.
The test program:
{{{
module Bug where
import Interface.TV.UI
-- Required to pick up the FunArr instance for OFun. GHC bug?
import Interface.TV.OFun()
reverseT :: TV KIO (String -> String)
reverseT = tv (oTitle "reverse" defaultOut) reverse
revTwice :: TV KIO (String -> String)
revTwice = reverseT ->| reverseT
}}}
Test compile:
{{{
bash-3.2$ ghc -c Bug.hs
bash-3.2$
}}}
If I comment out the second import line, the problem surfaces:
{{{
ghc -c Bug.hs
Bug.hs:12:11:
No instance for (FunArr ar (Output KIO))
arising from use of `->|' at Bug.hs:12:11-31
Possible fix:
add an instance declaration for (FunArr ar (Output KIO))
In the expression: reverseT ->| reverseT
In the definition of `revTwice': revTwice = reverseT ->| reverseT
bash-3.2$
}}}
More details:
{{{
bash-3.2$ uname -a
CYGWIN_NT-5.1 Compy 1.5.24(0.156/4/2) 2007-01-31 10:57 i686 Cygwin
bash-3.2$ ghc --version
The Glorious Glasgow Haskell Compilation System, version 6.6
bash-3.2$ ghc -v -c Bug.hs
Glasgow Haskell Compiler, Version 6.6, for Haskell 98, compiled by GHC
version 6.6
Using package config file: c:\ghc\ghc-6.6\package.conf
wired-in package base mapped to base-2.0
wired-in package rts mapped to rts-1.0
wired-in package haskell98 mapped to haskell98-1.0
wired-in package template-haskell mapped to template-haskell-2.0
Hsc static flags: -static
Created temporary directory: c:/tmp/ghc3880_0
*** Checking old interface for main:Bug:
*** Parser:
*** Renamer/typechecker:
Bug.hs:12:11:
No instance for (FunArr ar (Output KIO))
arising from use of `->|' at Bug.hs:12:11-31
Possible fix:
add an instance declaration for (FunArr ar (Output KIO))
In the expression: reverseT ->| reverseT
In the definition of `revTwice': revTwice = reverseT ->| reverseT
*** Deleting temp files:
Deleting: c:/tmp/ghc3880_0/ghc3880_0.s
Warning: deleting non-existent c:/tmp/ghc3880_0/ghc3880_0.s
*** Deleting temp dirs:
Deleting: c:/tmp/ghc3880_0
bash-3.2$
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1145>
GHC <http://www.haskell.org/ghc/>
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