Haml :: Util.html_safe ArgumentError：参数个数错误（0表示3）

Question

今天出现了这个错误，我完全不清楚导致它的原因。

Started GET "/" for 127.0.0.1 at 2014-06-27 13:35:11 +0200
Processing by UserSessionsController#new as HTML
  Rendered user_sessions/new.html.haml within layouts/application (3.9ms)
Completed 500 Internal Server Error in 9ms

ArgumentError - wrong number of arguments (0 for 3):
  haml (4.0.5) lib/haml/util.rb:89:in `html_safe'
  haml (4.0.5) lib/haml/helpers/xss_mods.rb:22:in `html_escape_with_haml_xss'
  haml (4.0.5) lib/haml/compiler.rb:445:in `block in build_attributes'
  haml (4.0.5) lib/haml/compiler.rb:428:in `build_attributes'
  haml (4.0.5) lib/haml/compiler.rb:503:in `prerender_tag'
  haml (4.0.5) lib/haml/compiler.rb:177:in `compile_tag'
  haml (4.0.5) lib/haml/compiler.rb:22:in `compile'
  haml (4.0.5) lib/haml/compiler.rb:22:in `block (2 levels) in compile'
  haml (4.0.5) lib/haml/compiler.rb:22:in `block in compile'
  haml (4.0.5) lib/haml/compiler.rb:95:in `compile_root'
  haml (4.0.5) lib/haml/compiler.rb:22:in `compile'
  haml (4.0.5) lib/haml/engine.rb:66:in `initialize'
  haml (4.0.5) lib/haml/template/plugin.rb:25:in `compile'
  haml (4.0.5) lib/haml/template/plugin.rb:30:in `call'
  actionview (4.1.2) lib/action_view/template.rb:270:in `compile'
  actionview (4.1.2) lib/action_view/template.rb:245:in `block (2 levels) in compile!'
  activesupport (4.1.2) lib/active_support/notifications.rb:161:in `instrument'
  actionview (4.1.2) lib/action_view/template.rb:339:in `instrument'
  actionview (4.1.2) lib/action_view/template.rb:244:in `block in compile!'
  actionview (4.1.2) lib/action_view/template.rb:232:in `compile!'
  actionview (4.1.2) lib/action_view/template.rb:144:in `block in render'
  activesupport (4.1.2) lib/active_support/notifications.rb:161:in `instrument'
  actionview (4.1.2) lib/action_view/template.rb:339:in `instrument'
  actionview (4.1.2) lib/action_view/template.rb:143:in `render'
  actionview (4.1.2) lib/action_view/renderer/template_renderer.rb:55:in `block (2 levels) in render_template'
  actionview (4.1.2) lib/action_view/renderer/abstract_renderer.rb:38:in `block in instrument'
  activesupport (4.1.2) lib/active_support/notifications.rb:159:in `block in instrument'
  activesupport (4.1.2) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
  activesupport (4.1.2) lib/active_support/notifications.rb:159:in `instrument'
  actionview (4.1.2) lib/action_view/renderer/abstract_renderer.rb:38:in `instrument'
  actionview (4.1.2) lib/action_view/renderer/template_renderer.rb:54:in `block in render_template'
  actionview (4.1.2) lib/action_view/renderer/template_renderer.rb:62:in `render_with_layout'
  actionview (4.1.2) lib/action_view/renderer/template_renderer.rb:53:in `render_template'
  actionview (4.1.2) lib/action_view/renderer/template_renderer.rb:17:in `render'
  actionview (4.1.2) lib/action_view/renderer/renderer.rb:42:in `render_template'
  actionview (4.1.2) lib/action_view/renderer/renderer.rb:23:in `render'
  actionview (4.1.2) lib/action_view/rendering.rb:99:in `_render_template'
  actionpack (4.1.2) lib/action_controller/metal/streaming.rb:217:in `_render_template'
  actionview (4.1.2) lib/action_view/rendering.rb:82:in `render_to_body'
  actionpack (4.1.2) lib/action_controller/metal/rendering.rb:32:in `render_to_body'
  actionpack (4.1.2) lib/action_controller/metal/renderers.rb:32:in `render_to_body'
  actionpack (4.1.2) lib/abstract_controller/rendering.rb:25:in `render'
  actionpack (4.1.2) lib/action_controller/metal/rendering.rb:16:in `render'
  actionpack (4.1.2) lib/action_controller/metal/instrumentation.rb:41:in `block (2 levels) in render'
  activesupport (4.1.2) lib/active_support/core_ext/benchmark.rb:12:in `block in ms'
  /Users/krpec/.rvm/rubies/ruby-2.1.1/lib/ruby/2.1.0/benchmark.rb:294:in `realtime'
  activesupport (4.1.2) lib/active_support/core_ext/benchmark.rb:12:in `ms'
  actionpack (4.1.2) lib/action_controller/metal/instrumentation.rb:41:in `block in render'
  actionpack (4.1.2) lib/action_controller/metal/instrumentation.rb:84:in `cleanup_view_runtime'
  activerecord (4.1.2) lib/active_record/railties/controller_runtime.rb:25:in `cleanup_view_runtime'
  actionpack (4.1.2) lib/action_controller/metal/instrumentation.rb:40:in `render'
  actionpack (4.1.2) lib/action_controller/metal/implicit_render.rb:10:in `default_render'
  actionpack (4.1.2) lib/action_controller/metal/implicit_render.rb:5:in `send_action'
  actionpack (4.1.2) lib/abstract_controller/base.rb:189:in `process_action'
  actionpack (4.1.2) lib/action_controller/metal/rendering.rb:10:in `process_action'
  actionpack (4.1.2) lib/abstract_controller/callbacks.rb:20:in `block in process_action'
  activesupport (4.1.2) lib/active_support/callbacks.rb:113:in `call'
  activesupport (4.1.2) lib/active_support/callbacks.rb:149:in `block in halting_and_conditional'
  activesupport (4.1.2) lib/active_support/callbacks.rb:149:in `block in halting_and_conditional'
  activesupport (4.1.2) lib/active_support/callbacks.rb:166:in `block in halting'
  activesupport (4.1.2) lib/active_support/callbacks.rb:229:in `block in halting'
  activesupport (4.1.2) lib/active_support/callbacks.rb:229:in `block in halting'
  activesupport (4.1.2) lib/active_support/callbacks.rb:166:in `block in halting'
  activesupport (4.1.2) lib/active_support/callbacks.rb:166:in `block in halting'
  activesupport (4.1.2) lib/active_support/callbacks.rb:166:in `block in halting'
  activesupport (4.1.2) lib/active_support/callbacks.rb:166:in `block in halting'
  activesupport (4.1.2) lib/active_support/callbacks.rb:86:in `run_callbacks'
  actionpack (4.1.2) lib/abstract_controller/callbacks.rb:19:in `process_action'
  actionpack (4.1.2) lib/action_controller/metal/rescue.rb:29:in `process_action'
  actionpack (4.1.2) lib/action_controller/metal/instrumentation.rb:31:in `block in process_action'
  activesupport (4.1.2) lib/active_support/notifications.rb:159:in `block in instrument'
  activesupport (4.1.2) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
  activesupport (4.1.2) lib/active_support/notifications.rb:159:in `instrument'
  actionpack (4.1.2) lib/action_controller/metal/instrumentation.rb:30:in `process_action'
  actionpack (4.1.2) lib/action_controller/metal/params_wrapper.rb:250:in `process_action'
  activerecord (4.1.2) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
  actionpack (4.1.2) lib/abstract_controller/base.rb:136:in `process'
  actionview (4.1.2) lib/action_view/rendering.rb:30:in `process'
  actionpack (4.1.2) lib/action_controller/metal.rb:196:in `dispatch'
  actionpack (4.1.2) lib/action_controller/metal/rack_delegation.rb:13:in `dispatch'
  actionpack (4.1.2) lib/action_controller/metal.rb:232:in `block in action'
  actionpack (4.1.2) lib/action_dispatch/routing/route_set.rb:82:in `dispatch'
  actionpack (4.1.2) lib/action_dispatch/routing/route_set.rb:50:in `call'
  actionpack (4.1.2) lib/action_dispatch/journey/router.rb:71:in `block in call'
  actionpack (4.1.2) lib/action_dispatch/journey/router.rb:59:in `call'
  actionpack (4.1.2) lib/action_dispatch/routing/route_set.rb:678:in `call'
  rack (1.5.2) lib/rack/etag.rb:23:in `call'
  rack (1.5.2) lib/rack/conditionalget.rb:25:in `call'
  rack (1.5.2) lib/rack/head.rb:11:in `call'
  actionpack (4.1.2) lib/action_dispatch/middleware/params_parser.rb:27:in `call'
  actionpack (4.1.2) lib/action_dispatch/middleware/flash.rb:254:in `call'
  rack (1.5.2) lib/rack/session/abstract/id.rb:225:in `context'
  rack (1.5.2) lib/rack/session/abstract/id.rb:220:in `call'
  actionpack (4.1.2) lib/action_dispatch/middleware/cookies.rb:560:in `call'
  activerecord (4.1.2) lib/active_record/query_cache.rb:36:in `call'
  activerecord (4.1.2) lib/active_record/connection_adapters/abstract/connection_pool.rb:621:in `call'
  activerecord (4.1.2) lib/active_record/migration.rb:380:in `call'
  actionpack (4.1.2) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
  activesupport (4.1.2) lib/active_support/callbacks.rb:82:in `run_callbacks'
  actionpack (4.1.2) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
  actionpack (4.1.2) lib/action_dispatch/middleware/reloader.rb:73:in `call'
  actionpack (4.1.2) lib/action_dispatch/middleware/remote_ip.rb:76:in `call'
  better_errors (1.1.0) lib/better_errors/middleware.rb:84:in `protected_app_call'
  better_errors (1.1.0) lib/better_errors/middleware.rb:79:in `better_errors_call'
  better_errors (1.1.0) lib/better_errors/middleware.rb:56:in `call'
  actionpack (4.1.2) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call'
  actionpack (4.1.2) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
  railties (4.1.2) lib/rails/rack/logger.rb:38:in `call_app'
  railties (4.1.2) lib/rails/rack/logger.rb:20:in `block in call'
  activesupport (4.1.2) lib/active_support/tagged_logging.rb:68:in `block in tagged'
  activesupport (4.1.2) lib/active_support/tagged_logging.rb:26:in `tagged'
  activesupport (4.1.2) lib/active_support/tagged_logging.rb:68:in `tagged'
  railties (4.1.2) lib/rails/rack/logger.rb:20:in `call'
  actionpack (4.1.2) lib/action_dispatch/middleware/request_id.rb:21:in `call'
  request_store (1.0.6) lib/request_store/middleware.rb:8:in `call'
  rack (1.5.2) lib/rack/methodoverride.rb:21:in `call'
  rack (1.5.2) lib/rack/runtime.rb:17:in `call'
  activesupport (4.1.2) lib/active_support/cache/strategy/local_cache_middleware.rb:26:in `call'
  rack (1.5.2) lib/rack/lock.rb:17:in `call'
  actionpack (4.1.2) lib/action_dispatch/middleware/static.rb:64:in `call'
  rack (1.5.2) lib/rack/sendfile.rb:112:in `call'
  railties (4.1.2) lib/rails/engine.rb:514:in `call'
  railties (4.1.2) lib/rails/application.rb:144:in `call'
  rack (1.5.2) lib/rack/lock.rb:17:in `call'
  rack (1.5.2) lib/rack/content_length.rb:14:in `call'
  rack (1.5.2) lib/rack/handler/webrick.rb:60:in `service'
  /Users/krpec/.rvm/rubies/ruby-2.1.1/lib/ruby/2.1.0/webrick/httpserver.rb:138:in `service'
  /Users/krpec/.rvm/rubies/ruby-2.1.1/lib/ruby/2.1.0/webrick/httpserver.rb:94:in `run'
  /Users/krpec/.rvm/rubies/ruby-2.1.1/lib/ruby/2.1.0/webrick/server.rb:295:in `block in start_thread'

无论我尝试什么样的路径，它总是以这个ArgumentError结束。唯一不同的是当我尝试访问受保护的页面时（before_action过滤器要求用户登录），更好的错误屏幕上有不同的行：redirect_to signin_path来自此方法：

def require_user
    unless current_user
        store_location
        flash[:warning] = "You must be logged in to access this page"
        redirect_to signin_path
        return false
    end
end

以下是bundle list：

的结果

Gems included by the bundle:
  * actionmailer (4.1.2)
  * actionpack (4.1.2)
  * actionview (4.1.2)
  * activemodel (4.1.2)
  * activerecord (4.1.2)
  * activesupport (4.1.2)
  * ancestry (2.1.0)
  * arel (5.0.1.20140414130214)
  * authlogic (3.4.2)
  * bcrypt (3.1.7)
  * bcrypt-ruby (3.1.5)
  * better_errors (1.1.0)
  * binding_of_caller (0.7.2)
  * bootstrap-datepicker-rails (1.3.0.2)
  * bootstrap-sass (3.1.1.1)
  * bootstrap-will_paginate (0.0.10)
  * builder (3.2.2)
  * bundler (1.6.2)
  * cancancan (1.8.0)
  * capybara (2.3.0)
  * celluloid (0.15.2)
  * chartkick (1.2.4)
  * childprocess (0.3.6)
  * coderay (1.1.0)
  * coffee-rails (4.0.1)
  * coffee-script (2.2.0)
  * coffee-script-source (1.7.0)
  * database_cleaner (1.2.0)
  * debug_inspector (0.0.2)
  * diff-lcs (1.2.5)
  * enumerize (0.8.0)
  * erubis (2.7.0)
  * execjs (2.2.1)
  * factory_girl (4.4.0)
  * factory_girl_rails (4.4.1)
  * faker (1.1.2)
  * ffi (1.9.3)
  * ffi-compiler (0.1.3)
  * formatador (0.2.5)
  * guard (2.6.1)
  * guard-rspec (4.2.10)
  * guard-spork (1.5.1)
  * haml (4.0.5)
  * hike (1.2.3)
  * i18n (0.6.9)
  * jbuilder (1.0.2)
  * jquery-rails (3.0.4)
  * json (1.8.1)
  * listen (2.7.9)
  * lumberjack (1.0.9)
  * mail (2.5.4)
  * method_source (0.8.2)
  * mime-types (1.25.1)
  * mini_portile (0.6.0)
  * minitest (5.3.5)
  * multi_json (1.10.1)
  * mysql2 (0.3.16)
  * nokogiri (1.6.2.1)
  * nyan-cat-formatter (0.9.0)
  * polyglot (0.3.5)
  * pry (0.10.0)
  * rack (1.5.2)
  * rack-test (0.6.2)
  * rails (4.1.2)
  * railties (4.1.2)
  * rake (10.3.2)
  * rb-fsevent (0.9.4)
  * rb-inotify (0.9.5)
  * rdoc (3.12.2)
  * request_store (1.0.6)
  * rspec (3.0.0)
  * rspec-core (3.0.2)
  * rspec-expectations (3.0.2)
  * rspec-mocks (3.0.2)
  * rspec-rails (3.0.1)
  * rspec-support (3.0.2)
  * rubyzip (0.9.9)
  * sass (3.2.13)
  * sass-rails (4.0.2)
  * scrypt (1.2.1)
  * sdoc (0.3.20)
  * selenium-webdriver (2.35.1)
  * slop (3.5.0)
  * spork (1.0.0rc4)
  * spork-rails (4.0.0)
  * sprockets (2.11.0)
  * sprockets-rails (2.0.1)
  * thor (0.19.1)
  * thread_safe (0.3.4)
  * tilt (1.4.1)
  * timers (1.1.0)
  * treetop (1.4.15)
  * turbolinks (1.1.1)
  * tzinfo (1.2.1)
  * uglifier (2.1.1)
  * websocket (1.0.7)
  * will_paginate (3.0.5)
  * xpath (2.0.0)

提前感谢任何建议！

更新：此处为new.html.haml

- provide(:title, t('views.user_session.title'))
.row.sign-in
    .col-md-4.col-md-offset-4
        .well.well-sm
            = form_for(:user_session, url: user_sessions_path, html: { class: "form-signin" }) do |f|
                %h2.text-center.form-signin-heading= t('views.user_session.heading')
                = f.email_field :email, placeholder: t('activerecord.attributes.user_session.email'), class: "form-control"
                = f.password_field :password, placeholder: t('activerecord.attributes.user_session.password'), class: "form-control"
                = f.submit t('views.user_session.sign_in_button'), class: "btn btn-primary"