Crystal GC troubles

r.cr

# r.cr
#
# This results in 
#
#   ~> crystal r.cr 
#   GC Warning: Finalization cycle involving 0x10424fe00
#
# No finalizer has been called.
#
class Parent
  def add_child; @child = Child.new(self); end
  def finalize; puts "finalize Parent"; end
end

class Child
  def initialize(@parent); end
  def finalize; puts "finalize Child"; end
end

def f(cnt)
  (0...cnt).each do 
    p = Parent.new
    p.add_child
  end
end

f(1)

GC.collect