Check in codegen test expectations.

test/codegen/expect/language/issue4157508_test.js

+dart_library.library('language/issue4157508_test', null, /* Imports */[
+  'dart_sdk'
+], function load__issue4157508_test(exports, dart_sdk) {
+  'use strict';
+  const core = dart_sdk.core;
+  const dart = dart_sdk.dart;
+  const dartx = dart_sdk.dartx;
+  const issue4157508_test = Object.create(null);
+  let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [])))();
+  issue4157508_test.Issue4157508Test = class Issue4157508Test extends core.Object {
+    new(v) {
+      let d = new core.DateTime.fromMillisecondsSinceEpoch(core.int._check(v), {isUtc: true});
+    }
+    static testMain() {
+      let d = new issue4157508_test.Issue4157508Test(0);
+    }
+  };
+  dart.setSignature(issue4157508_test.Issue4157508Test, {
+    constructors: () => ({new: dart.definiteFunctionType(issue4157508_test.Issue4157508Test, [dart.dynamic])}),
+    statics: () => ({testMain: dart.definiteFunctionType(dart.void, [])}),
+    names: ['testMain']
+  });
+  issue4157508_test.main = function() {
+    issue4157508_test.Issue4157508Test.testMain();
+  };
+  dart.fn(issue4157508_test.main, VoidTodynamic());
+  // Exports:
+  exports.issue4157508_test = issue4157508_test;
+});