# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1351812961 -3600
# Node ID e341cf363eae3be2a9b239a5dd35e123ac9b5850
# Parent  69bb1e2b79a5f4593e4d1c35ade839fbe1785f2d
Updated the "to do" list, adding notes about using instantiation to filter
relevant types and attributes.

diff -r 69bb1e2b79a5 -r e341cf363eae TO_DO.txt
--- a/TO_DO.txt	Fri Nov 02 00:34:27 2012 +0100
+++ b/TO_DO.txt	Fri Nov 02 00:36:01 2012 +0100
@@ -76,7 +76,19 @@
 types for a name, and the final set of names leading to such type deductions might be a
 useful annotation to be added alongside _attrcombined.
 
-  Update the reports to group identical sets of attribute names.
+  (Update the reports to group identical sets of attribute names.)
+
+Attribute usage on attributes might be possible if one can show that the expression of an
+attribute access is constant and that the attribute target is also constant or only refers
+to a single type. For example, in the sys module:
+
+  stderr = file()
+
+If no work is done to associate the result of the invocation with the stderr name, then
+one could instead at least attempt to determine whether stderr is assigned only once. If
+so, it might be possible to record attribute usage on references to the name. For example:
+
+  sys.stderr.write(...) # sys.stderr supports write -> {file, ...}
 
 Interface/Type Generalisation
 -----------------------------
@@ -99,7 +111,7 @@
 
 **** Constant attribute users need not maintain usage since they are already resolved. ****
 
-Self-related Usage
+Self-Related Usage
 ------------------
 
 Perform attribute usage on attributes of self as names, potentially combining observations
@@ -137,13 +149,22 @@
 Instantiation Deduction
 -----------------------
 
-Consider handling CallFunc in micropython.inspect in order to produce instances of specific classes.
-Then, consider adding support for guard removal/verification where known instances are involved. For
-example:
+Consider handling Const in micropython.inspect in order to produce instances of specific
+classes. Then, consider adding support for guard removal/verification where known
+instances are involved. For example:
 
   l = []
   l.append(123) # type deductions are filtered using instantiation knowledge
 
+Handling CallFunc in a similar way is more challenging. Consider the definitions in the sys module:
+
+  stderr = file()
+
+It must first be established that file only ever refers to the built-in file class, and
+only then can the assumption be made that stderr in this case refers to instances of file.
+If file can also refer to other objects, potential filtering operations are more severely
+limited.
+
 Frame Optimisations
 ===================