__color__	__group__	ticket	summary	component	version	type	owner	status	created	_changetime	_description	_reporter
4	 Release	1	graph operations don't detect duplicate-label errors	component1		defect	somebody	new	2010-05-10T17:12:06Z+0100	2010-05-10T17:18:47Z+0100	"Hoopl should detect a situation in which two graphs are spliced
and the labels of the blocks overlap.  At presesent, Hoopl uses
Data.IntSet.mapUnion and Data.IntSet.insert, neither of which
fails if a duplicate label appears.   Graph splicing and other
code needs to be modified to panic if labels overlap during splicing.
We therefore need something like
{{{

  unionWithKey (\l _ _ -> panic (""duplicate blocks with label "" ++ show l))
}}}
and similarly for insertion.
"	nr