# Associate a `nclassdef` with its `mclassdef`
	#
	# Be careful, this method is unsafe, no checking is done when it's used.
	# The safe way to add mclass it's to use the `build_property`
	#
	# See `mclassdef2nclassdef`
	fun unsafe_add_mclassdef2nclassdef(mclassdef: MClassDef, nclassdef: AClassdef)
	do
		mclassdef2nclassdef[mclassdef] = nclassdef
	end