As per the rules for atom names (https://devmanual.gentoo.org/ebuild-writing/file-format/) a release candidate is named with "_rcX", "-rX" is intended for revisions. This causes 0.5.0-r2 to be ordered as newer than 0.5.0 proper, which is already available( and can be installed via https://github.com/JKrehl/julia-portage). A simple rename to julia-0.5.0-rc2 and the subsequent changes in the .ebuild do solve this. Sincerely
What is this about? julia-0.5.0-r2 clearly packages 0.5.0 release tarball.