id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	os	architecture	failure	difficulty	testcase	blockedby	blocking	related
845	irrefutable pattern matching on unboxed tuple causes panic	Jason McCarty <jmccarty@…>		"Compiling the following program with -fglasgow-exts
  main = case (# (), () #) of ~(# _, _ #) -> return ()

causes GHC to fail with the message
  ghc-6.4.2: panic! (the `impossible' happened, GHC version 6.4.2):
          dsLExpr: tuple pattern:
  return @ () GHC.Base.()

The equivalent (I think) expression
  main = let (# _, _ #) = (# (), () #) in return ()
compiles without complaint.

This is GHC version 6.4.2 on i386 Debian with a 2.6.17.6 Linux kernel. I didn't test with any other unboxed types."	bug	closed	normal		Compiler	6.4.2	fixed			Linux	x86		Unknown