fix some possible String#split polyfill problems in V8 5.1

CHANGELOG.md

@@ -1,6 +1,7 @@
 ## Changelog
 ##### Unreleased
 - Fixed some cases of `Function#toString` with multiple `core-js` instances
+- Fixed some possible `String#split` polyfill problems in V8 5.1
 
 ##### 3.12.0 - 2021.05.06
 - Added well-known symbol `Symbol.metadata` for [decorators stage 2 proposal](https://github.com/tc39/proposal-decorators)

packages/core-js/internals/fix-regexp-well-known-symbol-logic.js

@@ -2,11 +2,13 @@
 // TODO: Remove from `core-js@4` since it's moved to entry points
 require('../modules/es.regexp.exec');
 var redefine = require('../internals/redefine');
+var regexpExec = require('../internals/regexp-exec');
 var fails = require('../internals/fails');
 var wellKnownSymbol = require('../internals/well-known-symbol');
 var createNonEnumerableProperty = require('../internals/create-non-enumerable-property');
 
 var SPECIES = wellKnownSymbol('species');
+var RegExpPrototype = RegExp.prototype;
 
 var REPLACE_SUPPORTS_NAMED_GROUPS = !fails(function () {
   // #replace needs built-in support for named groups.
@@ -94,7 +96,8 @@ module.exports = function (KEY, length, exec, sham) {
   ) {
     var nativeRegExpMethod = /./[SYMBOL];
     var methods = exec(SYMBOL, ''[KEY], function (nativeMethod, regexp, str, arg2, forceStringMethod) {
-      if (regexp.exec === RegExp.prototype.exec) {
+      var $exec = regexp.exec;
+      if ($exec === regexpExec || $exec === RegExpPrototype.exec) {
         if (DELEGATES_TO_SYMBOL && !forceStringMethod) {
           // The native String method already delegates to @@method (this
           // polyfilled function), leasing to infinite recursion.
@@ -112,7 +115,7 @@ module.exports = function (KEY, length, exec, sham) {
     var regexMethod = methods[1];
 
     redefine(String.prototype, KEY, stringMethod);
-    redefine(RegExp.prototype, SYMBOL, length == 2
+    redefine(RegExpPrototype, SYMBOL, length == 2
       // 21.2.5.8 RegExp.prototype[@@replace](string, replaceValue)
       // 21.2.5.11 RegExp.prototype[@@split](string, limit)
       ? function (string, arg) { return regexMethod.call(string, this, arg); }
@@ -122,5 +125,5 @@ module.exports = function (KEY, length, exec, sham) {
     );
   }
 
-  if (sham) createNonEnumerableProperty(RegExp.prototype[SYMBOL], 'sham', true);
+  if (sham) createNonEnumerableProperty(RegExpPrototype[SYMBOL], 'sham', true);
 };