Unsafe iteration of instances with flatten

[klayoutmatthias]

The following code gives an error when run with the attached layout:

lv = RBA::Application.instance.main_window.current_view
lay = lv.cellview(lv.active_cellview_index).layout
top = lay.top_cell

top.each_inst  do |ci|
  cname = ci.cell.name
  if (cname.start_with?("Circle"))
    ci.flatten
  end
end

This solution works fine:

lv = RBA::Application.instance.main_window.current_view
lay = lv.cellview(lv.active_cellview_index).layout
top = lay.top_cell

insts_to_flatten = []
top.each_inst  do |ci|
  cname = ci.cell.name
  if (cname.start_with?("Circle"))
    insts_to_flatten << ci
  end
end

insts_to_flatten.each do |ci|
  ci.flatten(8)
end

In general, iteration of a container (the instances) is unsafe while it's modified (in flatten which removes instances). However, in this case, the duplicate cell instance seems to cause the issue.

Maybe there is a reason to rectify this issue and allow iteration during manipulation. This would be more intuitive.

test.gds.zip