Raise NameError instead of ArgumentError in ActiveSupport::Dependencies

ActiveSupport::Dependencies now raises NameError if it finds an existing
constant in load_missing_constant. This better reflects the nature of
the error which is usually caused by calling constantize on a nested constant.

Closes rails#1423

activerecord/lib/active_record/base.rb

@@ -1308,7 +1308,6 @@ def compute_type(type_name)
               rescue NameError => e
                 # We don't want to swallow NoMethodError < NameError errors
                 raise e unless e.instance_of?(NameError)
-              rescue ArgumentError
               end
             end
 

activerecord/test/cases/base_test.rb

@@ -1773,6 +1773,13 @@ def test_compute_type_no_method_error
     end
   end
 
+  def test_compute_type_argument_error
+    ActiveSupport::Dependencies.stubs(:constantize).raises(ArgumentError)
+    assert_raises ArgumentError do
+      ActiveRecord::Base.send :compute_type, 'InvalidModel'
+    end
+  end
+
   def test_clear_cache!
     # preheat cache
     c1 = Post.columns

activesupport/CHANGELOG

@@ -1,5 +1,7 @@
 *Rails 3.1.0 (unreleased)*
 
+* ActiveSupport::Dependencies now raises NameError if it finds an existing constant in load_missing_constant. This better reflects the nature of the error which is usually caused by calling constantize on a nested constant. [Andrew White]
+
 * Deprecated ActiveSupport::SecureRandom in favour of SecureRandom from the standard library [Jon Leighton]
 
 * New reporting method Kernel#quietly. [fxn]

activesupport/lib/active_support/dependencies.rb

@@ -474,7 +474,7 @@ def load_missing_constant(from_mod, const_name)
         raise ArgumentError, "A copy of #{from_mod} has been removed from the module tree but is still active!"
       end
 
-      raise ArgumentError, "#{from_mod} is not missing constant #{const_name}!" if local_const_defined?(from_mod, const_name)
+      raise NameError, "#{from_mod} is not missing constant #{const_name}!" if local_const_defined?(from_mod, const_name)
 
       qualified_name = qualified_name_for from_mod, const_name
       path_suffix = qualified_name.underscore

activesupport/test/dependencies_test.rb

@@ -441,7 +441,7 @@ def test_const_missing_should_not_double_load
     with_autoloading_fixtures do
       require_dependency '././counting_loader'
       assert_equal 1, $counting_loaded_times
-      assert_raise(ArgumentError) { ActiveSupport::Dependencies.load_missing_constant Object, :CountingLoader }
+      assert_raise(NameError) { ActiveSupport::Dependencies.load_missing_constant Object, :CountingLoader }
       assert_equal 1, $counting_loaded_times
     end
   end