sys-libs/slang-2.2.4-r1 depend on missing package sys-libs/readline-6.2_p5-r1 and can't be merged and cause world emerge problems Reproducible: Always quick fix: just replace sys-libs/readline-6.2_p5-r1 to sys-libs/readline-6.2_p1-r1 in ebuild dependency list which exists in portage tree suggested fix: add sys-libs/readline-6.2_p5-r1 to portage tree from main gentoo tree
I see readline-6.3_p8-r3.ebuild in https://gitweb.gentoo.org/repo/proj/prefix.git/tree/sys-libs/readline today.