[m-rev.] for review by Mark: a note on bug 154

[Zoltan Somogyi]

On 24-Sep-2010, Mark Brown <mark at csse.unimelb.edu.au> wrote:
> Hi,
> 
> On 15-Sep-2010, Zoltan Somogyi <zs at csse.unimelb.edu.au> wrote:
> > Mark, I would appreciate your opinion on the comment I added to hlds_rtti.m.
> 
> I agree with the analysis.  Regarding the possible fixes, what is wrong with
> the solution proposed in Mantis?  If an existentially typed value is created
> in two separate branches, then it effectively doesn't have the same type in
> each one.  So I think the best fix would be to clone the corresponding
> information in rtti_varmaps.  Am I missing something?

That would not be sufficient. With a progvar, you can have two branches
of an ite or switch define its value using different code, as long as
both assign the result to the same progvar by the end of the branch.
There is no way to do that with tvars.

Zoltan.
--------------------------------------------------------------------------
mercury-reviews mailing list
Post messages to:       mercury-reviews at csse.unimelb.edu.au
Administrative Queries: owner-mercury-reviews at csse.unimelb.edu.au
Subscriptions:          mercury-reviews-request at csse.unimelb.edu.au
--------------------------------------------------------------------------