AssociationCollection#load_target triggers MassAssignmentSecurity warning

On a project I'm working on, we've been using a monkey-patch that raises on mass assignment security errors (used to be in AR::Base#log_protected_attribute_removal). This helps us prevent silent failure.

I'm in the process of porting our app to Rails 3, and spent some time today reimplementing this monkey-patch on WhiteList and BlackList.

Upon doing so, I discovered an unexpected failure when accessing an association after building instances on the association. It turns out that AssociationCollection#load_target performs mass-assignment calls (#attributes=) to update non-dirty, non-id fields on the in-memory instances.

I'm pretty sure that this call to #attributes= should bypass mass-assignment protection, since it's assigning values from the database to in-memory instances. I'm proposing to change:

@target.delete_at(i).tap do |t|
  keys = ["id"] + t.changes.keys + (f.attribute_names - t.attribute_names)
  t.attributes = f.attributes.except(*keys)
end

to:

@target.delete_at(i).tap do |t|
  keys = ["id"] + t.changes.keys + (f.attribute_names - t.attribute_names)
  t.send(:attributes=, f.attributes.except(*keys), false)
end

I'm pretty sure this should be an uncontroversial change, and I'd love to see it patched in ActiveRecord. Should I submit a patch for this change?