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