failing test for export default plus decorator

If a class is the default export from its module *and* if it has at least one decorated property or method, the classic-decorator babel plugin never sees it, which means it fails to get any of the runtime assertions.

Author: ef4

tests/dummy/app/components/bug-case.js

@@ -0,0 +1,11 @@
+// this gets imported directly into the test suite. It's in a separate file
+// because the bad behavior seems to depend specifically on `export default
+// class` plus a decorated property.
+
+import Component from '@ember/component';
+import { inject } from '@ember/service'
+
+export default class Example extends Component {
+  @inject router;
+}
+

tests/unit/classic-decorator-test.js

@@ -4,6 +4,7 @@ import EmberObject from '@ember/object';
 import Controller from '@ember/controller';
 import classic from 'ember-classic-decorator';
 import { DEBUG } from '@glimmer/env';
+import BugComponent from 'dummy/components/bug-case';
 
 module('@classic', () => {
   if (DEBUG) {
@@ -129,6 +130,14 @@ module('@classic', () => {
             FooController.reopenClass({});
           }, /You attempted to use the .reopen\(\) method on the FooController class/);
         });
+
+        test('throws without the decorator when combining export default and a decorated property', assert => {
+          assert.throws(() => {
+            // The BugComponent lives in a separate file because the bug only
+            // manifests when combining `export default` with decorators.
+            BugComponent.reopenClass({});
+          }, /You attempted to use the .reopen\(\) method on the @ember\/component class/);
+        });
       });
     });
   } else {