Qt4 is dead and going away. There is a new release 3.41 available and INSTALL suggests the gui does now requiren Qt5 instead, which would be nice.
The bug has been referenced in the following commit(s): https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=2f12fa9a90ebe234620dd6d2947369ac1919fbd0 commit 2f12fa9a90ebe234620dd6d2947369ac1919fbd0 Author: Andreas Sturmlechner <asturm@gentoo.org> AuthorDate: 2018-02-04 16:30:03 +0000 Commit: Andreas Sturmlechner <asturm@gentoo.org> CommitDate: 2018-02-04 17:38:52 +0000 app-text/highlight: 3.42 version bump Bug: https://bugs.gentoo.org/641932 Package-Manager: Portage-2.3.24, Repoman-2.3.6 app-text/highlight/Manifest | 1 + app-text/highlight/highlight-3.42.ebuild | 86 ++++++++++++++++++++++++++++++++ 2 files changed, 87 insertions(+)}
Old versions dropped in git commit 7935447af9153c10b5451877775593d0f20fd327