// ok for them to have non-zero size (to allow for use of generator
	// symbols).
	if len(l.Data(c)) != 0 {
		panic("unexpected non-empty carrier symbol")
	}
	l.outer[s] = c
	// relocsym's foldSubSymbolOffset requires that we only
	// have a single level of containment-- enforce here.
	if l.outer[c] != 0 {
		panic("invalid nested carrier sym")
	}
}