Check in codegen test expectations.

test/codegen/expect/corelib/reg_exp5_test.js

+dart_library.library('corelib/reg_exp5_test', null, /* Imports */[
+  'dart_sdk',
+  'expect'
+], function load__reg_exp5_test(exports, dart_sdk, expect) {
+  'use strict';
+  const core = dart_sdk.core;
+  const dart = dart_sdk.dart;
+  const dartx = dart_sdk.dartx;
+  const expect$ = expect.expect;
+  const reg_exp5_test = Object.create(null);
+  let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [])))();
+  reg_exp5_test.main = function() {
+    let str = "";
+    try {
+      let ex = core.RegExp.new(str);
+    } catch (e) {
+      if (!core.ArgumentError.is(e)) {
+        expect$.Expect.fail(dart.str`Expected: ArgumentError got: ${e}`);
+      }
+    }
+
+    expect$.Expect.isFalse(core.RegExp.new("^\\w+$").hasMatch(str));
+    let fm = core.RegExp.new("^\\w+$").firstMatch(str);
+    expect$.Expect.equals(null, fm);
+    let am = core.RegExp.new("^\\w+$").allMatches(str);
+    expect$.Expect.isFalse(am[dartx.iterator].moveNext());
+    expect$.Expect.equals(null, core.RegExp.new("^\\w+$").stringMatch(str));
+  };
+  dart.fn(reg_exp5_test.main, VoidTodynamic());
+  // Exports:
+  exports.reg_exp5_test = reg_exp5_test;
+});