protected AssemblySymbol expects() {
		if (!isComplete()) {
			AssemblySentential<?> rhs = prod.getRHS();
			return rhs.getSymbol(rhs.size() - substs.size() - 1);
		}
		return null;
	}
See what symbol is expected next

<p>
The child added next must be associated with the token expected next.

@return the symbol
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/app/plugin/assembler/sleigh/tree/AssemblyParseBranch.java