[Ironpython-users] Problem with the "in" operator for

[Jeff Hardy]

On Fri, Aug 7, 2015 at 12:47 AM, Markus Schaber <m.schaber at codesys.com> wrote:
> Hi, Jeff,
>
> Von: Jeff Hardy [mailto:jdhardy at gmail.com]
>> On Thu, Jul 9, 2015 at 11:50 PM, Markus Schaber
>> <m.schaber at codesys.com> wrote:
>> > Hi, Ivan,
>> >
>> > Von: Ivan Pozdeev [mailto:vano at mail.mipt.ru]
>> >
>> >> > As far as I can see, the "in" operator should return true if any
>> >> > object in the enumerable is "equal" to the object given as
>> >> >reference:
>> >>
>> >> Indeed,
>> >> https://docs.python.org/2/reference/expressions.html#membership-test-details states:
>> >>
>> >> For the list and tuple types, x in y is true if and only if there
>> >> exists an index i such that x == y[i] is true.
>> >>
>> >> Now, to check if IronPython honors this.
>> >>
>> >> > assert a in (a,), 'a is in (a,)'
>> >> > assert a in (b,), 'a is in (b,)' # this one fails...
>> >>
>> >> > As far as I can see via breakpoints, the Equals methods of the
>> >> > objects are never actually called, except on the first assertion
>> >> > with the == operator.
>> >>
>> >> My guess is it's cutting corners by comparing hashes instead.
>> >
>> > Hm, the GetHashCode() method in my example is hardcoded to return
>> > 0, and it is not even called (at least, the breakpoint is not hit.
>> >
>> > There must be something more subtle...
>>
>> In theory it should be creating a dynamic call site for "equals" that
>> will handle all of the cases (except for types that have a
>> __contains__ method) including IDMOP. Which there could very likely
>> be a bug in how that is generated; I'm not sure the IDMOP is stuff
>> gets excersized as much as it should.
>
> What to do now?
>
> Should I file a bug report on https://github.com/IronLanguages/main/issues ?

That's probably the best bet, with as minimal a reproduction as
possible. These code generation bugs are the hardest to deal with
because I have to page everything involved back into my brain, and
it's an absolute knot of code to sort through. So, no promises that
I'll get to it anytime soon. :(

- Jeff