|| ( dev-libs/libedit sys-libs/readline:= ) := inside || is forbidden and broken. Also automagic switching between two libs is a bad idea.
commit d46a4711f181e81394f409f035c3b54b03f88038 Author: Michał Górny <mgorny@gentoo.org> AuthorDate: Tue Jun 21 21:19:38 2016 Commit: Michał Górny <mgorny@gentoo.org> CommitDate: Tue Jun 21 21:20:31 2016 www-servers/varnish: Remove invalid := slotop from || (), #586330 I've just removed the op to fix the immediate issue. However, you still need to fix the automagic dep.
I don't see a point to depending on either readline or libedit. I've just dropped this to sys-libs/readline:0= for the latest ebuild I added. Once 3.0.7 and 4.0.3 are off the tree, we should be rid of all the automagic.
Long gone from tree.