# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1236210342 -3600
# Node ID ad0b88c81a1f202a199b9edc23022be3cef970e0
# Parent  2066cb2e583ed5ebae2bbde2d9d51986e3a7d27a
Added more notes about, and a test of, class attribute context behaviour.

diff -r 2066cb2e583e -r ad0b88c81a1f docs/assignment.txt
--- a/docs/assignment.txt	Mon Mar 02 00:04:55 2009 +0100
+++ b/docs/assignment.txt	Thu Mar 05 00:45:42 2009 +0100
@@ -47,11 +47,13 @@
   local                             preserved           LoadName
   global (module)                   preserved           LoadAddress             LoadAttrIndex
   class                             preserved           LoadAddress             LoadAttrIndex
-  class via instance                overridden          LoadAddressContext      LoadAttrIndex
+  class via instance                overridden          LoadAddressContext (*)  LoadAttrIndex (*)
   instance                          preserved           LoadAttr                LoadAttrIndex
 
   Access to a namespace may not preserve the stored context
 
+  (*) Other modes of these instructions may exist for certain optimisations
+
 Access to class attributes via instances:
 
   Access to stored value with...    Effect on context
@@ -64,6 +66,20 @@
   LoadAddressContext and LoadAttrIndex must therefore check whether the
   context must be overridden
 
+Optimisation possibilities:
+
+  Class       Class attribute   Context of attribute  Instruction
+  -----       ---------------   --------------------  -----------
+  known       constant          preserved             LoadAddress
+  known       constant          overridden            LoadAddressContext
+  known       not constant      preserved             LoadAddress             (attribute may always be preserved)
+  known       not constant      overridden            LoadAddressContext      (attribute may always be overridden)
+  known       not constant      not known             LoadAddressContextCond
+  not known   not known         preserved             LoadAttrIndex           (attribute may have preserved context in all classes)
+  not known   not known         overridden            LoadAttrIndexContext    (attribute may have overridden context in all classes)
+  not known   not known         not known             LoadAttrIndexContextCond
+
   Since the object table encodes sufficient information (an instance must be
   compatible to access the class attribute, and compatibility information is
-  stored), an explicit compatibility test is not required at run-time
+  stored), an explicit compatibility test may not always be required at
+  run-time
diff -r 2066cb2e583e -r ad0b88c81a1f tests/attributes_class_multiple.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tests/attributes_class_multiple.py	Thu Mar 05 00:45:42 2009 +0100
@@ -0,0 +1,10 @@
+#!/usr/bin/env python
+
+class C:
+    clsattr = 123
+    clsattr = 456
+
+a = C
+b = C.clsattr
+
+# vim: tabstop=4 expandtab shiftwidth=4