Re: [GHC] #5684: ghc: panic! (the 'impossible' happened) (ghc 7.2.2)

2011-12-15 Thread GHC 
#5684: ghc: panic! (the 'impossible' happened) (ghc 7.2.2)
---+
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:  
  
---+
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 dimit...@microsoft.com
 Date:   Thu Dec 15 14:18:31 2011 +

 Exposing a useful assertion which was hidden inside a lazyness cloud.

-- 
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/5684#comment:4
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Re: [GHC] #5684: ghc: panic! (the 'impossible' happened) (ghc 7.2.2)

2011-12-14 Thread GHC 
#5684: ghc: panic! (the 'impossible' happened) (ghc 7.2.2)
+---
 Reporter:  selinger|  Owner:  
 Type:  bug | Status:  new 
 Priority:  normal  |  Component:  Compiler
  Version:  7.2.1   |   Keywords:  
   Os:  Unknown/Multiple|   Architecture:  Unknown/Multiple
  Failure:  Compile-time crash  |   Testcase:  
Blockedby:  |   Blocking:  
  Related:  |  
+---
Changes (by dimitris):

 * cc: dimitris@… (added)


Comment:

 OK in HEAD it seems the panic has gone but the file has type errors. Is
 the following what you
 expected?:

 /home/dimitris/extra-investigations/Bug.hs:49:22:
 Couldn't match type `[]' with `(-) Int'
 When using functional dependencies to combine
   Myclass [a] [qa] [ca],
 arising from the dependency `a - qa'
 in the instance declaration at /home/dimitris/extra-
 investigations/Bug.hs:16:10
   Myclass [Bool] (Int - Int) cb,
 arising from a use of `fun1'
 at /home/dimitris/extra-investigations/Bug.hs:49:22-25
 In the expression: fun1 (fun8 5) (a, b, False)
 In a pattern binding: (a', b', m') = fun1 (fun8 5) (a, b, False)
 dimitris@cam-04-unx:/64playpen/dimitris/GHC-HEAD/ghc$

-- 
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/5684#comment:2
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Re: [GHC] #5684: ghc: panic! (the 'impossible' happened) (ghc 7.2.2)

2011-12-14 Thread GHC 
#5684: ghc: panic! (the 'impossible' happened) (ghc 7.2.2)
+---
 Reporter:  selinger|  Owner:  
 Type:  bug | Status:  new 
 Priority:  normal  |  Component:  Compiler
  Version:  7.2.1   |   Keywords:  
   Os:  Unknown/Multiple|   Architecture:  Unknown/Multiple
  Failure:  Compile-time crash  |   Testcase:  
Blockedby:  |   Blocking:  
  Related:  |  
+---

Comment(by selinger):

 Yes, the type error is about right. Were you able to reproduce this in
 7.2.2? The bug seems to be unstable, i.e., small changes in the source
 code make it go away. So it may be okay in HEAD because whatever the
 problem was has been fixed (which would be great), or because HEAD
 compiles some things in a slightly different order (in which case the bug
 may still be present, and may just not manifest with this particular
 example).

-- 
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/5684#comment:3
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Re: [GHC] #5684: ghc: panic! (the 'impossible' happened) (ghc 7.2.2) (was: ghc: panic! (the 'impossible' happened))

2011-12-13 Thread GHC 
#5684: ghc: panic! (the 'impossible' happened) (ghc 7.2.2)
+---
 Reporter:  selinger|  Owner:  
 Type:  bug | Status:  new 
 Priority:  normal  |  Component:  Compiler
  Version:  7.2.1   |   Keywords:  
   Os:  Unknown/Multiple|   Architecture:  Unknown/Multiple
  Failure:  Compile-time crash  |   Testcase:  
Blockedby:  |   Blocking:  
  Related:  |  
+---
Changes (by selinger):

 * cc: selinger@… (added)
  * failure:  None/Unknown = Compile-time crash


Comment:

 I attached a file that reproduces this bug. When compiling this file with
 ghc Bug.hs, using ghc 7.2.2, I reproducibly obtain the error:

 {{{
 ghc: panic! (the 'impossible' happened)
   (GHC version 7.2.2 for x86_64-unknown-linux):
 Unexpected given!

 Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
 }}}

 The file itself is nonsense, and in fact contains some type errors.
 However, it shouldn't kill the compiler.

-- 
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/5684#comment:1
GHC http://www.haskell.org/ghc/
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