Check in codegen test expectations.

test/codegen/expect/language/regress_16640_test.js

Index: test/codegen/expect/language/regress_16640_test.js
diff --git a/test/codegen/expect/language/regress_16640_test.js b/test/codegen/expect/language/regress_16640_test.js
new file mode 100644
index 0000000000000000000000000000000000000000..2df8b2d2418170cfc502b3dcd61ff6b79be4fef5
--- /dev/null
+++ b/test/codegen/expect/language/regress_16640_test.js
@@ -0,0 +1,27 @@
+dart_library.library('language/regress_16640_test', null, /* Imports */[
+  'dart_sdk'
+], function load__regress_16640_test(exports, dart_sdk) {
+  'use strict';
+  const core = dart_sdk.core;
+  const dart = dart_sdk.dart;
+  const dartx = dart_sdk.dartx;
+  const regress_16640_test = Object.create(null);
+  let ConceptEntity = () => (ConceptEntity = dart.constFn(regress_16640_test.ConceptEntity$()))();
+  let ConceptEntityOfSegment = () => (ConceptEntityOfSegment = dart.constFn(regress_16640_test.ConceptEntity$(regress_16640_test.Segment)))();
+  let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [])))();
+  regress_16640_test.ConceptEntity$ = dart.generic(E => {
+    class ConceptEntity extends core.Object {}
+    dart.addTypeTests(ConceptEntity);
+    return ConceptEntity;
+  });
+  regress_16640_test.ConceptEntity = ConceptEntity();
+  regress_16640_test.SegmentGen = class SegmentGen extends regress_16640_test.ConceptEntity$(regress_16640_test.Segment) {};
+  dart.addSimpleTypeTests(regress_16640_test.SegmentGen);
+  regress_16640_test.Segment = class Segment extends regress_16640_test.SegmentGen {};
+  regress_16640_test.main = function() {
+    new (ConceptEntityOfSegment())();
+  };
+  dart.fn(regress_16640_test.main, VoidTodynamic());
+  // Exports:
+  exports.regress_16640_test = regress_16640_test;
+});