Since this just happened to an user over in #gentoo-it it might be worth looking into this. When removing a GCC version, it would be a nice idea to ensure that the gcc-config profile selected is still valid; this should avoid that removing 4.2 (with --purge or --depclean) puts the system in an unrunnable state. I guess the issue here would be if one were to remove the highest version, but then they are fscked anyway so I wouldn't even bother to consider it a special case. Guys?
*** This bug has been marked as a duplicate of bug 130772 ***