void checkNumRules(GrammarAST rulesNode) {
		if ( rulesNode.getChildCount()==0 ) {
			GrammarAST root = (GrammarAST)rulesNode.getParent();
			GrammarAST IDNode = (GrammarAST)root.getChild(0);
			g.tool.errMgr.grammarError(ErrorType.NO_RULES, g.fileName,
					null, IDNode.getText(), g);
		}
	}
Value of caseInsensitive option (false if not defined)
tool/src/org/antlr/v4/semantics/BasicSemanticChecks.java