Specialize crashes

Hi,

It seems like there are a few crashes related to specialization in the
tracker. Even checking for specialize and crash in the title alone
(not description or comments) shows 9 results, 4 of them reported this
month, but some that have been in the tracker for a while:

https://issues.scala-lang.org/secure/IssueNavigator.jspa?reset=true&jqlQ...

Given that specialization is the first feature that helps Scala
perform better than Java, it would be good to make sure it's stable
and solid.

Best,
Ismael