RegExp.prototype is an ordinary object.

test/mjsunit/messages.js

 // Copyright 2015 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.
 
 // Flags: --stack-size=100 --harmony --harmony-reflect --harmony-regexps
 // Flags: --harmony-simd --strong-mode
 
 function test(f, expected, type) {
   try {
     f();
@@ skipping 118 matching lines @@
 // kGeneratorRunning
 test(function() {
   var iter;
   function* generator() { yield iter.next(); }
   var iter = generator();
   iter.next();
 }, "Generator is already running", TypeError);
 
 // kIncompatibleMethodReceiver
 test(function() {
-  RegExp.prototype.compile.call(RegExp.prototype);
-}, "Method RegExp.prototype.compile called on incompatible receiver " +
-   "[object RegExp]", TypeError);
+  Set.prototype.add.call([]);
+}, "Method Set.prototype.add called on incompatible receiver [object Array]",
+TypeError);
 
 // kInstanceofFunctionExpected
 test(function() {
   1 instanceof 1;
 }, "Expecting a function in instanceof check, but got 1", TypeError);
 
 // kInstanceofNonobjectProto
 test(function() {
   function f() {}
   var o = new f();
@@ skipping 311 matching lines @@
   Number(1).toString(100);
 }, "toString() radix argument must be between 2 and 36", RangeError);
 
 
 // === URIError ===
 
 // kURIMalformed
 test(function() {
   decodeURI("%%");
 }, "URI malformed", URIError);