Check in codegen test expectations.

test/codegen/expect/language/issue12023_test.js

+dart_library.library('language/issue12023_test', null, /* Imports */[
+  'dart_sdk',
+  'expect'
+], function load__issue12023_test(exports, dart_sdk, expect) {
+  'use strict';
+  const core = dart_sdk.core;
+  const _interceptors = dart_sdk._interceptors;
+  const dart = dart_sdk.dart;
+  const dartx = dart_sdk.dartx;
+  const expect$ = expect.expect;
+  const issue12023_test = Object.create(null);
+  let JSArrayOfString = () => (JSArrayOfString = dart.constFn(_interceptors.JSArray$(core.String)))();
+  let VoidTovoid = () => (VoidTovoid = dart.constFn(dart.definiteFunctionType(dart.void, [])))();
+  issue12023_test.main = function() {
+    let test = JSArrayOfString().of(["f", "5", "s", "6"]);
+    let length = test[dartx.length];
+    for (let i = 0; i < dart.notNull(length);) {
+      let action = test[dartx.get](i++);
+      switch (action) {
+        case "f":
+        case "s":
+        {
+          action = test[dartx.get](i - 1);
+          let value = core.int.parse(core.String._check(test[dartx.get](i++)));
+          if (dart.equals(action, "f")) {
+            expect$.Expect.equals(5, value);
+          } else {
+            expect$.Expect.equals(6, value);
+          }
+          break;
+        }
+      }
+    }
+  };
+  dart.fn(issue12023_test.main, VoidTovoid());
+  // Exports:
+  exports.issue12023_test = issue12023_test;
+});