Would be great if could be possible to have cmake with slots by major version, that would help to deal with this kind of cases where a previous version of cmake is required even not related to a bug. This way would be possible to set env config in portage to the required ebuilds, as a similar approach as we do with gcc. As an example for the utility of this feature just reference the issue https://bugs.gentoo.org/756034.
CMake is not intended to be slotted software. Each version has backward compatible with previous version. Even if it get implemented you'll get lots of headaches about compatibility and coexistence with other softwares. RHEL/Fedora already made this mistake, divided cmake 2.x and cmake 3.x into two packages. https://bugs.gentoo.org/756034 is only regression in CMake/LLVM which already fixed.
Azamat thanks for your heads up. I was think in other distros that have made that division between releases. Since cmake is not intended to be slotted (opposed to what I admitted when I opened this bug), I close this as wontfix. For me works the temporary downgrade to solve this kind of issues for related ebuilds.
