Most probably:

Dynamic inference of static types for ruby,
Jong-hoon (David) An, Avik Chaudhuri, Jeffrey S. Foster, Michael Hicks,
January 2011, POPL '11: Proceedings of the 38th annual ACM 
SIGPLAN-SIGACT symposium on Principles of programming languages;

Abstract:
There have been several efforts to bring static type inference to
object-oriented dynamic languages such as Ruby, Python, and Perl.
In our experience, however, such type inference systems are extremely
difficult to develop, because dynamic languages are typically
complex, poorly specified, and include features, such as eval
and reflection, that are hard to analyze.
...

Regards,   Martin.

On 2011/10/26 10:07, SASADA Koichi wrote:
> Hi,
>
> (11/10/25 23:36), Carter Cheng wrote:
>> developments in trace trees (older notions like in Dynamo) or the latest
>> piece on Ruby in POPL 2011.
>
> Reference?
>
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