tree 71a9bb4e810bbb936dca64369f49098a4a225196
parent 2306d246e8c5bb928a432726178047b8d50776f5
author Guido van Rossum <guido@python.org> 1001389422 +0000
committer Guido van Rossum <guido@python.org> 1001389422 +0000
HG:extra convert_revision:svn%3A6015fed2-1504-0410-9fe1-9d1591cc4771/python/branches/legacy-trunk%4023330

Make __class__ assignment possible, when the object structures are the
same.  I hope the test for structural equivalence is stringent enough.
It only allows the assignment if the old and new types:

- have the same basic size
- have the same item size
- have the same dict offset
- have the same weaklist offset
- have the same GC flag bit
- have a common base that is the same except for maybe the dict and
  weaklist (which may have been added separately at the same offsets
  in both types)