id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	os	architecture	failure	difficulty	testcase	blockedby	blocking	related
5684	ghc: panic! (the 'impossible' happened) (ghc 7.2.2)	selinger		"I seem to have found an ""impossible"" bug, and I am reporting it here as instructed.

The bug can be reliably reproduced with gcc-7.2.2. I can reproduce this bug with both the binaries from the generic 64-bit linux distribution ghc-7.2.2-x86_64-unknown-linux.tar.bz2, and the generic 32-bit linux distribution ghc-7.2.2-i386-unknown-linux.tar.bz2 (these were the only two I tried). 

Unfortunately, I can't publicly send the source code, because it is part of a confidential project. However, if this bug is not yet known/fixed, I can probably produce a minimal and ""sanitized"" example. 

Here is what I get:
{{{
ghc  -o qcs Main.hs
[ 9 of 10] Compiling BWT              ( BWT.hs, BWT.o )
ghc: panic! (the 'impossible' happened)
  (GHC version 7.2.2 for i386-unknown-linux):
        Unexpected given!

Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

make: *** [qcs] Error 1
}}}
Please let me know how I can proceed to collect more information on this bug! Thanks, -- Peter"	bug	closed	normal		Compiler	7.2.1	fixed		selinger@… dimitris@…	Unknown/Multiple	Unknown/Multiple	Compile-time crash		typecheck/should_fail/T5684.hs