Fix false positives for quantifier in regexp/no-useless-non-capturing-group rule (#66)

Author: ota-meshi

lib/rules/no-useless-non-capturing-group.ts

@@ -47,7 +47,8 @@ export default createRule("no-useless-non-capturing-group", {
                     const parent = gNode.parent
                     if (
                         parent.type === "Quantifier" &&
-                        alt.elements.length > 1
+                        (alt.elements.length > 1 ||
+                            alt.elements[0].type === "Quantifier")
                     ) {
                         // e.g. /(?:ab)?/
                         return

tests/lib/rules/no-useless-non-capturing-group.ts

@@ -17,6 +17,7 @@ tester.run("no-useless-non-capturing-group", rule as any, {
         String.raw`/()\1(?:0)/`,
         String.raw`/\1(?:0)/`,
         String.raw`/\0(?:1)/`,
+        String.raw`/(\d)(?=(?:\d{3})+(?!\d))/g`,
     ],
     invalid: [
         {