Ugh, C++ template errors, the bane of my existence (and why I personally avoid using anything beyond dead-simple ones unless I have to interface with STL).
Only thing worse are Java generics, if only because they literally tried to tack them in 10 (heck, getting close to 15 years now) years ago and we are still feeling the consequences of those design choices today, (unless Java 8+ made major fixes to this. Haven't used it in enough detail to make a judgement).
template errors blurb a big wall of text, but if you know how to read it it only takes a few second to find in your code where your problem is. You generally just have to look at the "required from here" (in clang and gcc at least) message which points to your own code 9 times out of ten.
Only thing worse are Java generics, if only because they literally tried to tack them in 10 (heck, getting close to 15 years now) years ago and we are still feeling the consequences of those design choices today, (unless Java 8+ made major fixes to this. Haven't used it in enough detail to make a judgement).