repro of bug related to property derived from args

Example of this code working correctly in the glimmer playground: http://bit.ly/2syFV7c

src/ui/components/bodega-glimmer-test/component.ts

@@ -1,5 +1,13 @@
-import Component from '@glimmer/component';
+import Component, { tracked } from '@glimmer/component';
 
 export default class BodegaGlimmerTest extends Component {
+  @tracked myNumber = 1;
 
+  make2() {
+    this.myNumber = 2;
+  }
+
+  make3() {
+    this.myNumber = 3;
+  }
 }

src/ui/components/bodega-glimmer-test/template.hbs

@@ -1 +1,6 @@
-<div><h1>Welcome to Glimmer!</h1></div>
+<div>
+  <button onclick={{action make2}}>number: 2</button>
+  <button onclick={{action make3}}>number: 3</button>
+
+  <my-second-component @number={{myNumber}}></my-second-component>
+</div>

src/ui/components/my-second-component/component-test.ts

@@ -0,0 +1,13 @@
+import { setupRenderingTest } from '@glimmer/test-helpers';
+import hbs from '@glimmer/inline-precompile';
+
+const { module, test } = QUnit;
+
+module('Component: my-second-component', function(hooks) {
+  setupRenderingTest(hooks);
+
+  test('it renders', async function(assert) {
+    await this.render(hbs`<my-second-component />`);
+    assert.ok(this.containerElement.querySelector('div'));
+  });
+});

src/ui/components/my-second-component/component.ts

@@ -0,0 +1,8 @@
+import Component, { tracked } from '@glimmer/component';
+
+export default class MySecondComponent extends Component {
+  @tracked('args')
+  get multiplied() {
+    return this.args.number * 2;
+  }
+};

src/ui/components/my-second-component/template.hbs

@@ -0,0 +1 @@
+<div>HELLO: multiply: {{multiplied}} (@number: {{@number}})</div>