Check in codegen test expectations.

test/codegen/expect/language/regress_23498_test.js

Index: test/codegen/expect/language/regress_23498_test.js
diff --git a/test/codegen/expect/language/regress_23498_test.js b/test/codegen/expect/language/regress_23498_test.js
new file mode 100644
index 0000000000000000000000000000000000000000..a05392b7498cede713a7022f09ac4b9516841be8
--- /dev/null
+++ b/test/codegen/expect/language/regress_23498_test.js
@@ -0,0 +1,46 @@
+dart_library.library('language/regress_23498_test', null, /* Imports */[
+  'dart_sdk',
+  'expect'
+], function load__regress_23498_test(exports, dart_sdk, expect) {
+  'use strict';
+  const core = dart_sdk.core;
+  const async = dart_sdk.async;
+  const dart = dart_sdk.dart;
+  const dartx = dart_sdk.dartx;
+  const expect$ = expect.expect;
+  const regress_23498_test = Object.create(null);
+  let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [])))();
+  regress_23498_test.foo = function() {
+    return dart.async(function*() {
+      try {
+        try {
+          yield async.Future.error('error');
+        } catch (error) {
+          core.print("caught once");
+          dart.throw('error');
+        }
+
+      } catch (error) {
+        core.print("caught twice");
+        dart.throw('error');
+      }
+
+    }, dart.dynamic);
+  };
+  dart.fn(regress_23498_test.foo, VoidTodynamic());
+  regress_23498_test.main = function() {
+    return dart.async(function*() {
+      let error = "no error";
+      try {
+        yield regress_23498_test.foo();
+      } catch (e) {
+        error = core.String._check(e);
+      }
+
+      expect$.Expect.equals("error", error);
+    }, dart.dynamic);
+  };
+  dart.fn(regress_23498_test.main, VoidTodynamic());
+  // Exports:
+  exports.regress_23498_test = regress_23498_test;
+});