Rails bug when routing escaped entities

routing_bug.rb

begin
  require 'bundler/inline'
rescue LoadError => e
  $stderr.puts 'Bundler version 1.10 or later is required. Please update your Bundler'
  raise e
end

gemfile(true) do
  source 'https://rubygems.org'
  # Activate the gem you are reporting the issue against.
  gem 'rails', '4.2.3'
end

require 'rack/test'
require 'action_controller/railtie'

class TestApp < Rails::Application
  config.root = File.dirname(__FILE__)
  config.session_store :cookie_store, key: 'cookie_store_key'
  secrets.secret_token    = 'secret_token'
  secrets.secret_key_base = 'secret_key_base'

  config.logger = Logger.new($stdout)
  Rails.logger  = config.logger

  routes.draw do
    get '/' => 'test#index'
    get '/fails/@:user' => 'test#foobar'
    get '/passes/:at:user' => 'test#foobar', constraints: { at: /@|%40/ }, defaults: { at: "@" }
  end
end

class TestController < ActionController::Base
  include Rails.application.routes.url_helpers

  def index
    render plain: 'Home'
  end

  def foobar
    render plain: 'foobar'
  end
end

require 'minitest/autorun'

# Ensure backward compatibility with Minitest 4
Minitest::Test = MiniTest::Unit::TestCase unless defined?(Minitest::Test)

class BugTest < Minitest::Test
  include Rack::Test::Methods

  def test_returns_success
    get '/'
    assert last_response.ok?
  end

  def test_workaround_raw_symbol
    get '/passes/@foobar'
    assert last_response.ok?
  end

  def test_workaround_escaped_symbol
    get '/passes/%40foobar'
    assert last_response.ok?
  end

  def test_normal_raw_symbol
    get '/fails/@foobar'
    assert last_response.ok?
  end

  def test_normal_escaped_symbol
    get '/fails/%40foobar'
    assert last_response.ok?
  end

  private
    def app
      Rails.application
    end
end

Hello,
get '/fails/%40foobar' and get '/fails/@:user' => 'test#foobar' cannot be matched since they are differenet.
Anyway trying to find a solution if possible.