Check in codegen test expectations.

test/codegen/expect/language/regress_23500_test_01_multi.js

+dart_library.library('language/regress_23500_test_01_multi', null, /* Imports */[
+  'dart_sdk',
+  'expect'
+], function load__regress_23500_test_01_multi(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_23500_test_01_multi = Object.create(null);
+  let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [])))();
+  regress_23500_test_01_multi.foo = function() {
+    return dart.async(function*() {
+      try {
+        try {
+          let it = async.StreamIterator.new(async.Stream.fromIterable([]));
+          try {
+            while (yield it.moveNext()) {
+              let c = it.current;
+            }
+          } finally {
+            yield it.cancel();
+          }
+        } catch (error) {
+        }
+
+      } catch (error) {
+      }
+
+      dart.throw("error");
+    }, dart.dynamic);
+  };
+  dart.fn(regress_23500_test_01_multi.foo, VoidTodynamic());
+  regress_23500_test_01_multi.main = function() {
+    return dart.async(function*() {
+      let error = "no error";
+      try {
+        yield regress_23500_test_01_multi.foo();
+      } catch (e) {
+        error = core.String._check(e);
+      }
+
+      expect$.Expect.equals("error", error);
+    }, dart.dynamic);
+  };
+  dart.fn(regress_23500_test_01_multi.main, VoidTodynamic());
+  // Exports:
+  exports.regress_23500_test_01_multi = regress_23500_test_01_multi;
+});