Check in codegen test expectations.

test/codegen/expect/language/issue14242_test.js

Index: test/codegen/expect/language/issue14242_test.js
diff --git a/test/codegen/expect/language/issue14242_test.js b/test/codegen/expect/language/issue14242_test.js
new file mode 100644
index 0000000000000000000000000000000000000000..acd1843257d050fc775838bb8bd21b8c452cec97
--- /dev/null
+++ b/test/codegen/expect/language/issue14242_test.js
@@ -0,0 +1,27 @@
+dart_library.library('language/issue14242_test', null, /* Imports */[
+  'dart_sdk'
+], function load__issue14242_test(exports, dart_sdk) {
+  'use strict';
+  const core = dart_sdk.core;
+  const dart = dart_sdk.dart;
+  const dartx = dart_sdk.dartx;
+  const issue14242_test = Object.create(null);
+  let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [])))();
+  issue14242_test.A = class A extends core.Object {
+    new() {
+      this.foo = dart.map();
+      this.bar = null;
+    }
+  };
+  issue14242_test.main = function() {
+    let a = new issue14242_test.A();
+    a.foo[dartx.set](dart.wrapType(core.Object), 54);
+    a.bar = 42;
+    if (!core.Type.is(a.foo[dartx.keys][dartx.first])) {
+      dart.throw('Test failed');
+    }
+  };
+  dart.fn(issue14242_test.main, VoidTodynamic());
+  // Exports:
+  exports.issue14242_test = issue14242_test;
+});