By default we would render 'MutableCollection<String>.addAll(Collection<String>)' as
'(LCollection<String>;)' (without wildcard) because String is final and
effectively it's the same as '(LCollection<? extends String>;)'.
But that's wrong signature in a sense that java.util.Collection has different
signature: '(LCollection<? extends E>)'.
Actually the problem is much wider than collections,
it concerns any Java code that uses Kotlin classes with covariant
parameters without '? extends E' wildcards.
Temporary solution is just to hardcode/enumerate builtin methods
with special signature.
Denis Zharkov