Hello!

  I have found following strange behavior. Every time, when with() method is used, new Symbol is created and never released. Please, find sample code below.

Model:

class TestMemLeak
  include Mongoid::Document

  field :processed, type: Boolean, default: false
end

In controller:

def test_action

    GC.start()
    puts Symbol.all_symbols.size
    test_mem_leak.with(write: {w: 0, j: false}){|t| t.set(processed: true) }
    GC.start()
    puts Symbol.all_symbols.size

end

After execuring  line 

   test_mem_leak.with(write: {w: 0, j: false}){|t| t.set(processed: true) }

a number of symbols is always increased by one and never decreased by GC.

After replacing line above by this one:

 t.set(processed: true) 

issue cannot be reproduced anymore.

Tested on Ruby 2.7.2,  Rails 6.1.6.

Best Regards,

Ilya