Fixed crash for v flag in regexp/optimal-quantifier-concatenation (#660)

* fix: crash for v flag in `regexp/optimal-quantifier-concatenation`

* Create chilly-pumpkins-raise.md

* Update lib/rules/optimal-quantifier-concatenation.ts

Co-authored-by: Michael Schmidt <[email protected]>

* fix

---------

Co-authored-by: Michael Schmidt <[email protected]>

Author: ota-meshi

.changeset/chilly-pumpkins-raise.md

@@ -0,0 +1,5 @@
+---
+"eslint-plugin-regexp": patch
+---
+
+Fixed crash for v flag in `regexp/optimal-quantifier-concatenation`

lib/rules/optimal-quantifier-concatenation.ts

@@ -64,7 +64,8 @@ function getSingleConsumedChar(
     element: Element | Alternative,
     flags: ReadonlyFlags,
 ): SingleConsumedChar {
-    const empty = flags.unicode ? EMPTY_UNICODE : EMPTY_UTF16
+    const empty =
+        flags.unicode || flags.unicodeSets ? EMPTY_UNICODE : EMPTY_UTF16
 
     switch (element.type) {
         case "Alternative":

tests/lib/rules/optimal-quantifier-concatenation.ts

@@ -25,6 +25,7 @@ tester.run("optimal-quantifier-concatenation", rule as any, {
         },
         String.raw`/^(?:\[\[\[?.+?\]?\]\]|<<.+?>>)$/`,
         String.raw`/a\s*?(?=\r?\n|\r)/`,
+        String.raw`/(?:a|b)?c/v`,
     ],
     invalid: [
         {