Load immutable flexible upper bound for 'Iterable<? super T>'
We load 'Collection<? super CharSequence>' as 'MutableCollection<in CharSequence>'
instead of 'MutableCollection<in CharSequence>..Collection<*>'
because it's obviously not typesafe to use any 'Collection<*>'
as argument for such type.
But there'se nothing bad with loading 'Iterable<? super CharSequence>'
as 'MutableIterable<*>..Collection<*>'. Same for other declarations that have
covariant mutable representation (currently Iterator, ListIterator).
Also there are useful use-cases when it's neccessary to use 'Iterable<*>'
as an argument for parameter with type 'Iterable<? super T>' (see matchers.kt test).
NB: Star-projections appear in examples because types like 'Collection<in CharSequence>'
with conflicting use-site projections are invalid in Kotlin, but they are valid in Java.
Mikhail Glukhikh