qt 5.13 is out now. so let's upgrade to 5.13. but, emerge says qt-5.12 is conflicting with 5.13. WHY? because KDE wants qt-5.12. but really? NO KDE package ever write =dev-qt/qtcore-5.12 so why? why emerge says KDE wants qt-5.12?
As I said in bug 836680, more information is needed, but let's please troubleshoot this in a support forum. *** This bug has been marked as a duplicate of bug 836680 ***