Check in codegen test expectations.

test/codegen/expect/language/list_length_tracer_test.js

+dart_library.library('language/list_length_tracer_test', null, /* Imports */[
+  'dart_sdk',
+  'expect'
+], function load__list_length_tracer_test(exports, dart_sdk, expect) {
+  'use strict';
+  const core = dart_sdk.core;
+  const dart = dart_sdk.dart;
+  const dartx = dart_sdk.dartx;
+  const expect$ = expect.expect;
+  const list_length_tracer_test = Object.create(null);
+  let VoidTovoid = () => (VoidTovoid = dart.constFn(dart.definiteFunctionType(dart.void, [])))();
+  let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [])))();
+  list_length_tracer_test.a = 42;
+  list_length_tracer_test.b = null;
+  let const$;
+  list_length_tracer_test.main = function() {
+    expect$.Expect.throws(dart.fn(() => dart.dload(list_length_tracer_test.b, 'length'), VoidTovoid()));
+    list_length_tracer_test.b = const$ || (const$ = dart.constList([42], core.int));
+  };
+  dart.fn(list_length_tracer_test.main, VoidTodynamic());
+  // Exports:
+  exports.list_length_tracer_test = list_length_tracer_test;
+});