Ruby

Deprecate passing arguments to Set#to_set and Enumerable#to_set

Array#to_a, Hash#to_h, Enumerable#to_a, and Enumerable#to_h do not
allow you to specify subclasses. This has undesired behavior when
passing non-Set subclasses. All of these are currently allowed, and
none make sense:

enum = [1,2,3].to_enum

enum.to_set(Hash)
enum.to_set(Struct.new("A", :a))
enum.to_set(ArgumentError)
enum.to_set(Thread){}

Users who want to create instances of a subclass of Set from an
enumerable should pass the enumerable to SetSubclass.new instead of
using to_set.