The error message for a missing requirement is confusing, even in the cases where it does not actually crash the compiler. See this thread for an example:
'unpickling' is an implementation term that has zero meaning to Scala programmers, and should not be the first word in the error message. I guess 'incomplete classpath while reading..' is a better approximation. Also, there is no reason to include debugging information in the error message by default (the list of all members in the enclosing package). A 100-line error message can freak out a lot of people.