typed<E>  static method 
Creates a wrapper that asserts the types of values in base.
This soundly converts a Set without a generic type to a Set<E> by
asserting that its elements are instances of E whenever they're
accessed. If they're not, it throws a TypeError. Note that even if an
operation throws a TypeError, it may still mutate the underlying
collection.
This forwards all operations to base, so any changes in base will be
reflected in this. If base is already a Set<E>, it's returned
unmodified.
Implementation
@Deprecated('Use set.cast<E> instead.')
static Set<E> typed<E>(Set base) => base.cast<E>();