[Haml] Fixed CSS id concatenation when a numeric id is given as an attribute.

doc-src/HAML_CHANGELOG.md

@@ -8,6 +8,9 @@
 * Got rid of trailing whitespace produced when opening a conditional comment
   (thanks to [Norman Clarke](http://blog.njclarke.com/)).
 
+* Fixed CSS id concatenation when a numeric id is given as an attribute.
+  (thanks to [Norman Clarke](http://blog.njclarke.com/)).
+
 ## [2.2.4](http://github.com/nex3/haml/commit/2.2.4)
 
 * Allow `end` to be used for silent script when it's followed by code.

lib/haml/buffer.rb

@@ -245,7 +245,7 @@ RUBY
     # @return [Hash<String, String>] `to`, after being merged
     def self.merge_attrs(to, from)
       if to['id'] && from['id']
-        to['id'] << '_' << from.delete('id')
+        to['id'] << '_' << from.delete('id').to_s
       elsif to['id'] || from['id']
         from['id'] ||= to['id']
       end

test/haml/engine_test.rb

@@ -107,6 +107,11 @@ class EngineTest < Test::Unit::TestCase
     assert_equal("<div class='atlantis' style='ugly'></div>", render(".atlantis{:style => 'ugly'}").chomp)
   end
 
+  def test_css_id_as_attribute_should_be_appended_with_underscore
+    assert_equal("<div id='my_id_1'></div>", render("#my_id{:id => '1'}").chomp)
+    assert_equal("<div id='my_id_1'></div>", render("#my_id{:id => 1}").chomp)
+  end
+
   def test_ruby_code_should_work_inside_attributes
     author = 'hcatlin'
     assert_equal("<p class='3'>foo</p>", render("%p{:class => 1+2} foo").chomp)