Gentoo ndowens # emerge =x11-proto/xproto-7.0.7
Calculating dependencies... done!

!!! Error: the >=x11-proto/xproto-7.0.6 package conflicts with another package;
!!!        the two packages cannot be installed on the same system together.
!!!        Please use 'emerge --pretend' to determine blockers.

For more information about Blocked Packages, please refer to the following
section of the Gentoo Linux x86 Handbook (architecture is irrelevant):