Opened 7 years ago

Closed 7 years ago

#7005 closed bug (fixed)

GHC 7.4.2 crashes with a panic when using type families and data kinds together

Reported by: Kangyuan Owned by:
Priority: normal Milestone:
Component: Compiler Version: 7.4.2
Keywords: panic typefamilies datakinds Cc:
Operating System: Unknown/Multiple Architecture: Unknown/Multiple
Type of failure: Compile-time crash Test Case:
Blocked By: Blocking:
Related Tickets: Differential Rev(s):
Wiki Page:


I have no idea how to isolate this bug, since it seems to span multiple modules. If I recompile the entire program (by doing a cabal clean beforehand) the bug disappears. But if I just touch one of the files and try to recompile, it gives me:

compiler output

[3 of 4] Compiling Checker          ( Checker.hs, dist/build/Hammer/Hammer-tmp/Checker.o )
ghc: panic! (the 'impossible' happened)
  (GHC version 7.4.2 for x86_64-unknown-linux):
        tyThingTyCon Data constructor `main:Types.Succ{d r2k}'

Please report this as a GHC bug:

The code I'm working on is at

The crash happens in both Linux and Windows, using packages from Haskell Platform.

Change History (2)

comment:1 Changed 7 years ago by simonpj

difficulty: Unknown
Status: newinfoneeded

Hard to be certain, but this looks #6025 and #6011, both of which are now fixed. Would you be able to try with HEAD or a development snapshot?


comment:2 Changed 7 years ago by igloo

Resolution: fixed
Status: infoneededclosed

No precise reproduction instructions, probably fixed, and no response from submitter, so closing.

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