# Return the most specific values defined in `mmodule` and its imported modules.
	# Unlike `lookup_values`, only the most specific value, according to importation, is returned.
	fun lookup_first_value(mmodule: MModule, min_visibility: MVisibility): nullable E
	do
		var mmodules = lookup_all_modules(mmodule, min_visibility)
		if mmodules.is_empty then return null
		mmodules = model.mmodule_importation_hierarchy.linearize(mmodules)
		return defs[mmodules.last]
	end