RE: [sv-ac] 1678 name resolution and the rewriting algorithm of 1549

John,

Can you give an example of name conflict with the up to date 1549?

I don't see it.

Doron

-----Original Message-----
From: owner-sv-ac@server.eda.org [mailto:owner-sv-ac@server.eda.org] On
Behalf Of John Havlicek
Sent: Friday, November 02, 2007 4:26 PM
To: sv-ac@server.eda.org
Subject: [sv-ac] 1678 name resolution and the rewriting algorithm of
1549

Hi Folks:

In 1549, we introduced a local variable declaration notation 
in the abstract syntax.

In revising the rewriting algorithm, I deleted the parts about
making local variable names unique.  The rules for overshadowing
in 1549 make this unnecessary in some cases.  Doron asked about
this, but I seemed to convince him that the overshadowing took 
care of the problems.

However, 1678 points out that a naive treatment of local variable
identifiers results in name resolution issues when local variables are
passed as actual arguments to other instances.  The overshadowing
mechanism of 1549 does not take care of this problem.

I do not think that this problem is specific to local variables.  When
rewriting and substituting actual arguments, we must respect name
resolution.  Simply looking at the identifiers, references,
etc. written in the source code is not good enough.  There can be
incorrect aliasing for all sorts of things other than local variables.

In order to resolve 1678, I think we need to add some language
(hopefully a small amount) to say that name resolution still needs to
be taken care of properly when following the rewriting algorithm.

Name resolution is not something that we should be trying to capture
in Annex F, so I don't think we should make a special point about
making local variable identifiers unique.  That would give the wrong
impression that other references do not also need to be accounted for
with care.

I have uploaded to Mantis 1678 and attached below an example of
carrying out the rewriting algorithm while paying attention to name
resolution.  I don't envision it being added to the LRM.

J.H.


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