@Override
	protected void enterLexerCommand(GrammarAST tree) {
		checkElementIsOuterMostInSingleAlt(tree);

		if (inFragmentRule) {
			String fileName = tree.token.getInputStream().getSourceName();
			String ruleName = currentRuleName;
			g.tool.errMgr.grammarError(ErrorType.FRAGMENT_ACTION_IGNORED, fileName, tree.token, ruleName);
		}
	}
Value of caseInsensitive option (false if not defined)
tool/src/org/antlr/v4/semantics/BasicSemanticChecks.java