Check in codegen test expectations.

test/codegen/expect/language/interceptor9_test.js

Index: test/codegen/expect/language/interceptor9_test.js
diff --git a/test/codegen/expect/language/interceptor9_test.js b/test/codegen/expect/language/interceptor9_test.js
new file mode 100644
index 0000000000000000000000000000000000000000..426b88af39d0479db70a6fc4913a8365adf488ac
--- /dev/null
+++ b/test/codegen/expect/language/interceptor9_test.js
@@ -0,0 +1,41 @@
+dart_library.library('language/interceptor9_test', null, /* Imports */[
+  'dart_sdk',
+  'expect'
+], function load__interceptor9_test(exports, dart_sdk, expect) {
+  'use strict';
+  const core = dart_sdk.core;
+  const typed_data = dart_sdk.typed_data;
+  const dart = dart_sdk.dart;
+  const dartx = dart_sdk.dartx;
+  const expect$ = expect.expect;
+  const interceptor9_test = Object.create(null);
+  let dynamic__Todynamic = () => (dynamic__Todynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [dart.dynamic], [dart.dynamic])))();
+  let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [])))();
+  interceptor9_test.confuse = function(x, y) {
+    if (y === void 0) y = null;
+    return new core.DateTime.now().day == 42 ? y : x;
+  };
+  dart.fn(interceptor9_test.confuse, dynamic__Todynamic());
+  interceptor9_test.boom = function() {
+    let x = interceptor9_test.confuse(typed_data.Uint8List.new(22), "");
+    expect$.Expect.isTrue(typed_data.Uint8List.is(x));
+    dart.dsend(x, 'startsWith', "a");
+    dart.dsend(x, 'endsWith', "u");
+  };
+  dart.fn(interceptor9_test.boom, VoidTodynamic());
+  interceptor9_test.main = function() {
+    try {
+      let f = null;
+      if (dart.test(interceptor9_test.confuse(true))) {
+        f = interceptor9_test.boom;
+      }
+      dart.dcall(f);
+    } catch (e) {
+      if (expect$.ExpectException.is(e)) dart.throw(e);
+    }
+
+  };
+  dart.fn(interceptor9_test.main, VoidTodynamic());
+  // Exports:
+  exports.interceptor9_test = interceptor9_test;
+});