[regexp] Fix fallback path in RegExpExec

test/mjsunit/regexp-regexpexec.js

Index: test/mjsunit/regexp-regexpexec.js
diff --git a/test/message/arrow-invalid-rest-2.js b/test/mjsunit/regexp-regexpexec.js
similarity index 50%
copy from test/message/arrow-invalid-rest-2.js
copy to test/mjsunit/regexp-regexpexec.js
index 3517803d30256b09e78a1aa1f43817e733dc060e..bfc42b6a164655ef2c5370dc6bcab123a78f4d05 100644
--- a/test/message/arrow-invalid-rest-2.js
+++ b/test/mjsunit/regexp-regexpexec.js
@@ -1,8 +1,8 @@
 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
-//
-//
 
-var f = (a, ...x = 10) => x;
-f(1, 2, 3, 4, 5);
+// Test that the fallback path in RegExpExec executes the default exec
+// implementation.
+delete RegExp.prototype.exec;
+assertEquals("b", "aba".replace(/a/g, ""));