undefined method `delegate_template_exists?'

error_log

edison$ rails s
=> Booting Mongrel
=> Rails 3.1.0.rc1 application starting in development on http://0.0.0.0:3000
=> Call with -d to detach
=> Ctrl-C to shutdown server
Exiting
/Users/edison/.rvm/gems/ruby-1.9.2-p180/gems/haml-3.1.1/lib/haml/template/patch.rb:16:in `alias_method': undefined method `delegate_template_exists?' for class `ActionView::Base' (NameError)
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/gems/haml-3.1.1/lib/haml/template/patch.rb:16:in `<class:Base>'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/gems/haml-3.1.1/lib/haml/template/patch.rb:12:in `<module:ActionView>'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/gems/haml-3.1.1/lib/haml/template/patch.rb:11:in `<top (required)>'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/activesupport/lib/active_support/dependencies.rb:236:in `require'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/activesupport/lib/active_support/dependencies.rb:236:in `block in require'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/activesupport/lib/active_support/dependencies.rb:222:in `block in load_dependency'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/activesupport/lib/active_support/dependencies.rb:616:in `new_constants_in'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/activesupport/lib/active_support/dependencies.rb:222:in `load_dependency'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/activesupport/lib/active_support/dependencies.rb:236:in `require'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/gems/haml-3.1.1/lib/haml/template.rb:60:in `<top (required)>'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/activesupport/lib/active_support/dependencies.rb:236:in `require'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/activesupport/lib/active_support/dependencies.rb:236:in `block in require'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/activesupport/lib/active_support/dependencies.rb:222:in `block in load_dependency'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/activesupport/lib/active_support/dependencies.rb:616:in `new_constants_in'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/activesupport/lib/active_support/dependencies.rb:222:in `load_dependency'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/activesupport/lib/active_support/dependencies.rb:236:in `require'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/gems/haml-3.1.1/lib/haml.rb:41:in `block in init_rails'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/gems/haml-3.1.1/lib/haml.rb:41:in `each'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/gems/haml-3.1.1/lib/haml.rb:41:in `init_rails'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/gems/haml-3.1.1/lib/haml/railtie.rb:16:in `block (2 levels) in <top (required)>'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/activesupport/lib/active_support/lazy_load_hooks.rb:36:in `instance_eval'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/activesupport/lib/active_support/lazy_load_hooks.rb:36:in `execute_hook'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/activesupport/lib/active_support/lazy_load_hooks.rb:26:in `on_load'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/gems/haml-3.1.1/lib/haml/railtie.rb:15:in `block in <top (required)>'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/activesupport/lib/active_support/lazy_load_hooks.rb:36:in `instance_eval'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/activesupport/lib/active_support/lazy_load_hooks.rb:36:in `execute_hook'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/activesupport/lib/active_support/lazy_load_hooks.rb:43:in `block in run_load_hooks'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/activesupport/lib/active_support/lazy_load_hooks.rb:42:in `each'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/activesupport/lib/active_support/lazy_load_hooks.rb:42:in `run_load_hooks'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/railties/lib/rails/application/bootstrap.rb:68:in `block in <module:Bootstrap>'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/railties/lib/rails/initializable.rb:25:in `instance_exec'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/railties/lib/rails/initializable.rb:25:in `run'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/railties/lib/rails/initializable.rb:50:in `block in run_initializers'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/railties/lib/rails/initializable.rb:49:in `each'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/railties/lib/rails/initializable.rb:49:in `run_initializers'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/railties/lib/rails/application.rb:96:in `initialize!'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/railties/lib/rails/railtie/configurable.rb:28:in `method_missing'
	from /Users/edison/Sites/beta.foco/config/environment.rb:5:in `<top (required)>'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/activesupport/lib/active_support/dependencies.rb:236:in `require'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/activesupport/lib/active_support/dependencies.rb:236:in `block in require'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/activesupport/lib/active_support/dependencies.rb:222:in `block in load_dependency'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/activesupport/lib/active_support/dependencies.rb:616:in `new_constants_in'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/activesupport/lib/active_support/dependencies.rb:222:in `load_dependency'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/activesupport/lib/active_support/dependencies.rb:236:in `require'
	from /Users/edison/Sites/beta.foco/config.ru:4:in `block in <main>'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.3.0/lib/rack/builder.rb:51:in `instance_eval'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.3.0/lib/rack/builder.rb:51:in `initialize'
	from /Users/edison/Sites/beta.foco/config.ru:1:in `new'
	from /Users/edison/Sites/beta.foco/config.ru:1:in `<main>'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.3.0/lib/rack/builder.rb:40:in `eval'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.3.0/lib/rack/builder.rb:40:in `parse_file'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.3.0/lib/rack/server.rb:200:in `app'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/railties/lib/rails/commands/server.rb:46:in `app'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.3.0/lib/rack/server.rb:301:in `wrapped_app'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.3.0/lib/rack/server.rb:252:in `start'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/railties/lib/rails/commands/server.rb:70:in `start'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/railties/lib/rails/commands.rb:58:in `block in <top (required)>'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/railties/lib/rails/commands.rb:53:in `tap'
	from /Users/edison/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-badc72f3e645/railties/lib/rails/commands.rb:53:in `<top (required)>'
	from script/rails:6:in `require'
	from script/rails:6:in `<main>'

I'm having the same issue, anyone found a solution yet ?

I dint't try to fix yet, Im using rails from branch 3-1-stable for now.
Open issue here: rails/rails#1321

It seems it's a Haml issue and not a rails issue, Rails removed autoloading a file, I try reverting it and it works, so Haml should update it

I opened an issue on Haml https://github.com/nex3/haml/issues/395

Fixed: https://github.com/nex3/haml/pull/398

Issue closed. Thanks @lorensr

Had to update haml gem that's all, thanks! :)