#5684: ghc: panic! (the 'impossible' happened) (ghc 7.2.2)
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Reporter: selinger | Owner:
Type: bug | Status: closed
Priority: normal | Component: Compiler
Version: 7.2.1 | Resolution: fixed
Keywords: | Os:
Unknown/Multiple
Architecture: Unknown/Multiple | Failure: Compile-time
crash
Testcase: typecheck/should_fail/T5684.hs | Blockedby:
Blocking: | Related:
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Changes (by dimitris):
* status: new => closed
* testcase: => typecheck/should_fail/T5684.hs
* resolution: => fixed
Comment:
Thanks for the feedback. There were two things wrong in 7.2.1:
- An assertion was just false because of a broken invariant
- But, the assertion was hidden under a thunk and got triggered not at
the right place, potentially under random poking from who-knows-who.
Now, in HEAD by construction this invariant is true (so the real bug you
observed no longer manifests there). But the assertion is still there so I
did push a patch that makes the assertion trigger aggressively.
The test is in typecheck/should_fail/T5684.hs
and the comments in that test describe the problem in more technical
terms.
The relevant commit is:
commit bd13338da1649600b6a63ae7cbf60a35575940dc
Author: Dimitrios Vytiniotis <[email protected]>
Date: Thu Dec 15 14:18:31 2011 +0000
Exposing a useful assertion which was hidden inside a lazyness cloud.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5684#comment:4>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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