skip u flag before parse

rules/regex-shorthand.js

@@ -9,12 +9,18 @@ const message = 'Use regex shorthands to improve readability.';
 const create = context => {
 	return {
 		'Literal[regex]': node => {
-			const {type, value} = context.getSourceCode().getFirstToken(node);
+			const {type, value, regex} = context.getSourceCode().getFirstToken(node);
 
 			if (type !== 'RegularExpression') {
 				return;
 			}
 
+			// regex with `u` flag is not well handled by `regexp-tree`
+			// https://github.com/DmitrySoshnikov/regexp-tree/issues/162
+			if (regex.flags.includes('u')) {
+				return;
+			}
+
 			let parsedSource;
 			try {
 				parsedSource = parse(value);
@@ -31,12 +37,6 @@ const create = context => {
 				return;
 			}
 
-			// `u` flag regex is not well handled by `regexp-tree`
-			// https://github.com/DmitrySoshnikov/regexp-tree/issues/162
-			if (parsedSource.flags.includes('u')) {
-				return;
-			}
-
 			const originalRegex = generate(parsedSource).toString();
 			const optimizedRegex = optimize(value).toString();