Ticket #2664 (closed bug: fixed)

Opened 5 years ago

Last modified 2 years ago

type family + data family + typeclass + type error causes GHC to diverge

Reported by: ryani Owned by: chak
Priority: low Milestone: 7.0.1
Component: Compiler Version: 6.11
Keywords: Cc:
Operating System: Unknown/Multiple Architecture: Unknown/Multiple
Type of failure: None/Unknown Difficulty: Unknown
Test Case: indexed-types/should_fail/T2664, T2664a Blocked By:
Blocking: Related Tickets:

Description 

ryani:~ ryani$ ghc-6.11.20081005 -c overflow.hs 
<about 15 seconds pass>
stack overflow: use +RTS -K<size> to increase it
ryani:~ ryani$

Attachments

overflow.hs Download (1.0 KB) - added by ryani 5 years ago.

Change History

Changed 5 years ago by ryani

  Changed 5 years ago by simonpj

  • owner set to chak
  • difficulty set to Unknown

  Changed 5 years ago by igloo

  • priority changed from normal to high
  • milestone set to 6.10.1

  Changed 5 years ago by igloo

  • priority changed from high to normal

Type-family-related bugs aren't release critical

  Changed 5 years ago by igloo

  • milestone changed from 6.10.1 to 6.10 branch

  Changed 4 years ago by igloo

  • milestone changed from 6.10 branch to 6.12 branch

follow-up: ↓ 7   Changed 4 years ago by simonpj

HEAD gives 

WARNING: file compiler/types/Coercion.lhs line 465
Strange! Type mismatch in trans coercion, probably a bug
...plus some more...

But Manuel thinks the WARNING has false positives. (Maybe we should nuke it.)

Simon

in reply to: ↑ 6   Changed 4 years ago by chak

Replying to simonpj:

HEAD gives 

WARNING: file compiler/types/Coercion.lhs line 465
Strange! Type mismatch in trans coercion, probably a bug
...plus some more...

But Manuel thinks the WARNING has false positives. (Maybe we should nuke it.)

One case of false positives is when one of the compared types contains an unzonked type variable. I believe this situation arises during solving quality constraints. In most other places where trans coercions are made, the test may be accurate. So, if we knew the caller, it would be easier to say whether a particular warning may potentially be a false positive.

  Changed 3 years ago by igloo

  • milestone changed from 6.12 branch to 6.12.3

  Changed 3 years ago by igloo

  • priority changed from normal to low
  • milestone changed from 6.12.3 to 6.14.1

  Changed 2 years ago by simonpj

  • status changed from new to closed
  • failure set to None/Unknown
  • resolution set to fixed
  • testcase set to indexed-types/should_fail/T2664, T2664a

Works now. Tests added.

Simon

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