I'm not sure if this is useful or common enough to out in the stdlib. Not sure about the naming at least.

Surely array.compact_map { |x| x if x.is_a?(T) } is short enough to use in the rare case you need to do something like this.

I'm not sure if this is useful or common enough to out in the stdlib. Not sure about the naming at least.

It's from Ruby. And it works with klass === elem, but not for ary << (compiler checks is_a?, but not ===).

Surely array.compact_map { |x| x if x.is_a?(T) } is short enough to use in the rare case you need to do something like this.

I found a wish to create shortcut for .map(&.as(Type)) (from you), and now you're suggesting a longer way to the similar task.

.map(&.as(Type)) is entirely different and probably more common than filtering instances of a particular class from an array.

Unfortunately I don't think we're going to merge this. If we find in the future that this is a common operation i'm fine to reopen this :)