Rails 2.0.2 Bug: belongs_to association reader fails to call loaded on bad foreign keys

Hi, first time submitting a bug.

In at least Rails 2.0.2 through 2.3.2, belongs_to association_reader fails to call association.loaded on bad foreign keys. So for example:

class Contact < ActiveRecord::Base
  belongs_to :company
end

c1 = Contact.new(:company_id => 1)          # This exists
c2 = Contact.new(:company_id => 9287123987) # This doesn't exist

Benchmark.bm do |x|
  x.report {500.times do; c1.company; end}
  x.report {500.times do; c2.company; end}
end

Gives result:
      user     system      total        real
  0.015000   0.000000   0.015000 (  0.035000)
  0.671000   0.359000   1.030000 (  1.224000)

Of course, c2.company is nil, but c2.company should call association.loaded so that we don't go to the database 500 times to find nil 500 times.

I'm not sure where the call to association.loaded should come. Let me know if you need more information. Let me know if this has already been fixed.

Thanks!

Results on 2.2.2; still seems to be an issue:

r1 = Recipe.new(:category_id => 1)          # This exists
r2 = Recipe.new(:category_id => 9287123987) # This doesn't exist

Benchmark.bm do |x|
  x.report {1000.times do; r1.category; end}
  x.report {1000.times do; r2.category; end}
  x.report {1000.times do; r1.category(true); end}
  x.report {1000.times do; r2.category(true); end}
end

      user     system      total        real
  0.000000   0.000000   0.000000 (  0.000000)
  0.514000   0.203000   0.717000 (  0.717000)
  0.578000   0.234000   0.812000 (  0.843000)
  0.546000   0.156000   0.702000 (  0.702000)

Results on 2.3.2; still seems to be an issue:

      user     system      total        real
  0.000000   0.000000   0.000000 (  0.000000)
  0.531000   0.218000   0.749000 (  0.749000)
  0.671000   0.203000   0.874000 (  0.874000)
  0.592000   0.141000   0.733000 (  0.795000)