public static void setNodeOptions(GrammarAST node, GrammarAST options) {
		if ( options==null ) return;
		GrammarASTWithOptions t = (GrammarASTWithOptions)node;
		if ( t.getChildCount()==0 || options.getChildCount()==0 ) return;
		for (Object o : options.getChildren()) {
			GrammarAST c = (GrammarAST)o;
			if ( c.getType()==ANTLRParser.ASSIGN ) {
				t.setOption(c.getChild(0).getText(), (GrammarAST)c.getChild(1));
			}
			else {
				t.setOption(c.getText(), null); // no arg such as ID<VarNodeType>
			}
		}
	}
Given ^(TOKEN_REF ^(OPTIONS ^(ELEMENT_OPTIONS (= assoc right))))
 set option assoc=right in TOKEN_REF.
tool/src/org/antlr/v4/tool/Grammar.java