id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	os	architecture	failure	difficulty	testcase	blockedby	blocking	related
2367	ASSERT failed! file basicTypes/MkId.lhs line 643	batterseapower		"This is exposed by running the testsuite on a stage2 compiler with -DDEBUG. The tests triggering it are:
* gadt/ubx-records
* gadt/records

The affected context is:

{{{
    mk_alt data_con
      =   ASSERT2( data_ty `tcEqType` field_ty, 
                   ppr data_con $$ ppr data_ty $$ ppr field_ty )
          mkReboxingAlt rebox_uniqs data_con (ex_tvs ++ co_tvs ++ arg_vs) rhs
      where
           -- get pattern binders with types appropriately instantiated
        arg_uniqs = map mkBuiltinUnique [arg_base..]
        (ex_tvs, co_tvs, arg_vs) = dataConOrigInstPat arg_uniqs data_con 
                                                      scrut_ty_args
}}}

The precise error is:
{{{
=====> ubx-records(normal)
cd . && '/Users/mbolingbroke/Programming/Checkouts/ghc.working/compiler/stage2/ghc-inplace' -fforce-recomp -dcore-lint -dcmm-lint -Di386_apple_darwin  -dno-debug-output -o ubx-records ubx-records.hs    >ubx-records.comp.stderr 2>&1
Compile failed (status 256) errors were:
ghc-6.9.20080614: panic! (the 'impossible' happened)
  (GHC version 6.9.20080614 for i386-apple-darwin):
	ASSERT failed! file basicTypes/MkId.lhs line 643
main:Main.T1{d r6q}
ipv_B3{tv} [tv]
a{tv a6G} [tv]
}}}"	merge	closed	normal	6.8 branch	Compiler	6.9	fixed			MacOS X	Unknown/Multiple		Unknown	gadt/records