Check in codegen test expectations.

test/codegen/expect/language/regress_21912_test_none_multi.js

+dart_library.library('language/regress_21912_test_none_multi', null, /* Imports */[
+  'dart_sdk'
+], function load__regress_21912_test_none_multi(exports, dart_sdk) {
+  'use strict';
+  const core = dart_sdk.core;
+  const dart = dart_sdk.dart;
+  const dartx = dart_sdk.dartx;
+  const regress_21912_test_none_multi = Object.create(null);
+  let Function2 = () => (Function2 = dart.constFn(regress_21912_test_none_multi.Function2$()))();
+  let VoidTovoid = () => (VoidTovoid = dart.constFn(dart.definiteFunctionType(dart.void, [])))();
+  regress_21912_test_none_multi.A = class A extends core.Object {};
+  regress_21912_test_none_multi.B = class B extends regress_21912_test_none_multi.A {};
+  regress_21912_test_none_multi.Function2$ = dart.generic((S, T) => {
+    const Function2 = dart.typedef('Function2', () => dart.functionType(T, [S]));
+    return Function2;
+  });
+  regress_21912_test_none_multi.Function2 = Function2();
+  regress_21912_test_none_multi.AToB = dart.typedef('AToB', () => dart.functionType(regress_21912_test_none_multi.B, [regress_21912_test_none_multi.A]));
+  regress_21912_test_none_multi.BToA = dart.typedef('BToA', () => dart.functionType(regress_21912_test_none_multi.A, [regress_21912_test_none_multi.B]));
+  regress_21912_test_none_multi.main = function() {
+    {
+      let t1 = null;
+      let t2 = null;
+      let left = null;
+    }
+  };
+  dart.fn(regress_21912_test_none_multi.main, VoidTovoid());
+  // Exports:
+  exports.regress_21912_test_none_multi = regress_21912_test_none_multi;
+});