It looks like qtcore-4.8.6 split out dev-qt/qttranslations which collides with qtcore in version 4.8.5. Can we please add a blocker to ease downgrade? I know it's not typical, but it shouldn't hurt anything. DEPEND="!dev-qt/qttranslations:4" seems appropriate if I had to guess.... You may ignore this, but I hit collision while testing the -Os bug in x86 so I figured it was worth reporting.
qt4-build.eclass has this gem: ewarn "Downgrading Qt is completely unsupported and can break your system!" So if you attempt that, you're on your own anyway. That said, I'm not against adding the blocker for completeness.
(In reply to Ben de Groot from comment #1) > > ewarn "Downgrading Qt is completely unsupported and can break your system!" That's mostly for historical reasons, and mainly refers to potential breakages (missing symbols) at the ABI level when downgrading, i.e. something outside our control. The file collision is a packaging bug instead, and must be fixed.
29 Mar 2015; Davide Pesavento <pesa@gentoo.org> qtcore-4.8.5-r2.ebuild: Add blocker to prevent file collision on downgrade, thanks to Zero_Chaos in bug #544666.
