[ ghc-Bugs-1117672 ] overlapping pattern matching weirdness

Bugs item #1117672, was opened at 2005-02-06 21:10
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Nobody/Anonymous (nobody)
Assigned to: Nobody/Anonymous (nobody)
Summary: overlapping pattern matching weirdness

Initial Comment:
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@xxxxxxxxxxx,
or http://sourceforge.net/projects/ghc/.


the Lattice type is a tuple... 
for more details, contact
stijn@xxxxxxxxxxx

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