[pypy-dev] funny observation with range

[Christian Tismer]

Samuele Pedroni wrote:

> Christian Tismer wrote:
...
>> I would like to understand why the annotator thinks this must
>> become a list, and how I can convince it to take a different action.
>> I think, using the variable variant would be adequate in this case.
> 
> you changed what happens on range calls annotation-wise, but not the 
> behavior of what should occur when types are mixed, this is specified by 
> the union operation which for list/ranges basically goes through the 
> ListItem.merge, which still has the behavior that mixing different-step
> ranges unifies to list:
> 
>    if other.range_step != self.range_step:
>        self.range_step = None
> 
> in listdef.py . If I have understood your changes you want 0 in this 
> case unless one of the range_step is already None meaning list.
> 
> Notice that if you change this you probably need to change 
> rtype_builtin_range because this assumes that it can use partially the 
> information in its arguments instead of about the result to decide
> what to produce.

Ah, thank you very much, that was the missing spot. No magic at all,
but more places to look into. I will add something to cope with this.

Although I don't believe it is worthwhile to do in this case,
I guess it would be much more difficult to specialize on step?

thanks again - ciao - chris

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