currentWhen issue

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle'
});

router.js

import Ember from 'ember';
import config from './config/environment';

const Router = Ember.Router.extend({
  location: 'none',
  rootURL: config.rootURL
});

Router.map(function() {
  this.route('foo');
  this.route('users', { resetNamespace: true }, function() {
    this.route('users.show', { resetNamespace: true, path: '/:user_id' }, function() {
      this.route('posts', { resetNamespace: true }, function() {
        	this.route('all');
          this.route('show', { path: '/:post_id' });
          this.route('edit', { path: '/:post_id/edit' });
      });
     });
   });
});

export default Router;

routes.posts.edit.js

import Ember from 'ember';

export default Ember.Route.extend({
   model(params) {
    return params.post_id;
  }
});

routes.posts.show.js

import Ember from 'ember';

export default Ember.Route.extend({
   model(params) {
    return params.post_id;
  }
});

routes.users.show.index.js

import Ember from 'ember';

export default Ember.Route.extend({
});

routes.users.show.js

import Ember from 'ember';

export default Ember.Route.extend({
   model(params) {
    return params.user_id;
  }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}

LINKS
{{#link-to "users.show" 1}}USER SHOW{{/link-to}}
<br>
<br>

templates.posts.all.hbs

ALL

{{#link-to "posts.show" 1 2}}POST SHOW{{/link-to}}

templates.posts.edit.hbs

POST EDIT

templates.posts.show.hbs

POST

{{#link-to "posts.edit" 1 2}}test{{/link-to}}

templates.users.show.hbs

USER

{{outlet}}

{{#link-to "posts.all" current-when="posts.show"}}POST INDEX{{/link-to}}

twiddle.json

{
  "version": "0.10.6",
  "EmberENV": {
    "FEATURES": {}
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "1.13.13",
    "ember-template-compiler": "1.13.13"
  },
  "addons": {}
}