My suspicion is that when a query type is present not all of the symbols
get substituted "correctly" when the function is copied. It might be
possible to fix this behavior by adding a loop to instantiate() that
substitutes type-variables as they become available. This would get rid of
a recursive call in the (newly re-named) filterCandidate family of
functions, thus simplifying the codebase and also removing some redundant
work from the function resolution process. This would also probably allow
us to call computeActualFormalAlignment and computeGenericSubs once instead
of multiple times like we are now.
While addressing this issue would certainly make my life easier it isn't
strictly necessary for my work. I would certainly be willing to work with
you on this if you are interested.
- Chris
On Wed, Dec 11, 2013 at 4:49 PM, Tom Hildebrandt <[email protected]> wrote:
> Hello Chris:
>
> I am aware of this behavior. If I recall correctly, generic
> instantiation can resolve more than one argument at a time, but does not
> necessarily resolve all generic arguments at one go. I have not discovered
> the cause for when generic arguments are resolved in multiple batches. It
> appears that once all generic arguments are resolved, we make one more pass
> through resolution.
>
> I suspect that this is intended to catch cases where generic arguments
> are resolved ambiguously. However, in practice I think we quit from
> generic instantiation as soon as we have instantiated any non-generic
> version. If those impressions are correct, we could probably collapse out
> the last recursive call to gatherCandidates and obtain the same behavior
> overall.
>
> It's probably relatively easy for me to add precision to my claims
> above; if you need that information right away, let me know and I will fill
> in the gaps.
>
> Tom Hildebrandt
> ------------------------------
> *From:* Chris Wailes [[email protected]]
> *Sent:* Wednesday, December 11, 2013 1:18 PM
> *To:* [email protected]
> *Subject:* [Chapel-developers] The instantiate Function and Generics with
> Query Types
>
> If a generic function with a query type is passed to the instantiate()
> function another generic function will be returned. It ends up taking
> several round trips between addCandidate() and instantiate() to produce a
> non-generic function. This seems like both odd and expensive behavior.
> Unfortunately I don't have the time to puzzle this one out so I wanted to
> alert the developer community in the hopes that someone else might be able
> to fix this.
>
> - Chris
>
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