overlapping pattern matching weirdness

[nobody]

the following code gives me the error message below in
GHCi:

> context :: Lattice -> Context State Constraint
> context lat = case lat of 
>	fromBigLattice -> bigC
>	fromSmallLattice -> smallC
>       _ -> error "non-existing lattice..."

GHCi:

Logic.lhs:92:
    Warning: Pattern match(es) are overlapped
	     In a case alternative:
		 fromSmallLattice -> ...
		 _ -> ...
ghc.exe: panic! (the `impossible' happened, GHC version
6.2.1):
	Bytecode generator can't handle unboxed tuples. 
Possibly due
	to foreign import/export decls in source.  Workaround:
	compile this module to a .o file, then restart session.

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


the Lattice type is a tuple... 
for more details, contact
stijn@jaist.ac.jp

[simonmar]

Logged In: YES 
user_id=48280

Could you please provide the code so we can reproduce the
bug.  Thanks.

[nobody]

Logged In: NO 

Not a bug: fromBigLattice and fromSmallLattice are
variables, which certainly overlap with each other and _.

[simonmar]

Logged In: YES 
user_id=48280

Submitter can't reproduce the panic, so I'm closing the bug.