[ ghc-Bugs-1274506 ] QuickCheck induced panic on :reload

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Bugs item #1274506, was opened at 2005-08-27 18:29
Message generated for change (Comment added) made by dons
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Category: GHCi
Group: 6.4
Status: Open
Resolution: None
Priority: 5
Submitted By: Don Stewart (dons)
Assigned to: Nobody/Anonymous (nobody)
Summary: QuickCheck induced panic on :reload

Initial Comment:
A broken QuickCheck property cause ghci to panic after
reloading the module. Seen in stable and head branch.

paprika$ ghci T.hs
*Main> do_test
                     test : *                         
      (0)
*Main> :reload
ghc-6.5: panic! (the `impossible' happened, GHC version
6.5):
        <<loop>>

Please report it as a compiler bug to
glasgow-haskell-bugs at haskell.org,
or http://sourceforge.net/projects/ghc/.

Changing the property to check for empty lists causes
the test to pass, and reload to work fine.

-- Don Stewart

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>Comment By: Don Stewart (dons)
Date: 2005-08-27 18:32

Message:
Logged In: YES 
user_id=880987

Here's the test case, since uploading files is annoying in
sourceforge:

import Test.QuickCheck.Batch

prop_silly :: [()] -> Bool
prop_silly xs = head xs == head xs 

do_test = runTests "test" defOpt [ run prop_silly ]


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