PR# 16052 Compiler reports bogus "construct not reported" error after sequence of changes

fter a sequence of changes in a large system, the compiler reports an
incorrect "construct not supported" error:

-------------------------------------------------------------------------------

Error code: NOT_SUPPORTED
Error: The following construct is not supported in the current
  version of ISE Eiffel.
What to do: replace by equivalent construct if possible.

Class: DELTA_GRAPHIC_APPLICATION
Source class: DELTA_APPLICATION
Feature: select_run_closing_steps
Error message: Agent creation on `unsubscribe_events' is not supported because it is either an attribute, a constant or an external feature
Line: 311
        selection_ifc.hard_undo_actions.extend (agent process_steps (selection_ifc, session, Undo_and_discard_requested, ?))
->      selection_ifc.cancel_actions.extend (agent selection_ifc.unsubscribe_events)
        selection_ifc.cancel_actions.extend (agent terminate_current_session)

-------------------------------------------------------------------------------

I have a BACKUP directory.  There are a very large number of classes but the
number of compilations is only 10.

Use BACKUP directory.  I tried to upload it but it is a bit over 4 MB after
compression with bzip2 and the upload failed.  I will try the upload again and
if it fails, I will put the BACKUP directory tar file on your ftp site.

Fixed in rev#82602 of EiffelStudio 6.6 intermediate release.

I found a simple way to reproduce this incrementality bug, which only seems
to happen when full class checking is enabled.  Added eweasel test incr338
for this bug.  This is higher priority than some of the other bugs I have reported
since we encountered it while doing real work (as opposed to bug hunting).

I used the files in the BACKUP directory and successfully reproduced the
bogus "construct not supported" error on 6.3, so it was not a one-time glitch.
I used the command line compiler.  We should be able to construct an eweasel
test for this, but it might be painful, due to the large number of files involved.

I put the file bug#16052_BACKUP.tar.bz2 on your FTP server (support site
wouldn't accept it, presumably because it was too big - size is
4476628 bytes).