Add #hash and #eql? to ActiveSupport::Multibyte::Chars so you can use multibyte strings as hash keys without Ruby 1.9

I agree that it would be great if you could use Chars instances as hash keys, there are two problems.

The first problem is that your solution is too broad:

'1'.mb_chars.eql?(1) #=> true

I would suggest the following:

def eql?(other)
  other.acts_like?(:string) ? @wrapped_string.eql?(other.to_s) : super(other)
end

The other problem is a limitation caused by Hash#[] optimizations for String. So even if you do the following:

class String
  def eql_with_wrapped_string?(other)
    eql_without_wrapped_string?(other.acts_like?(:string) ? other.to_s : other)
  end
  alias_method_chain :eql?, :wrapped_string
end

The following will still be the case:

hash = {}
hash['string'] = 'value'
hash['string'.mb_chars] = 'other value'

hash.keys.map(&:to_s) #=> ['string', 'string']

So I'm not sure what the correct course of action is. Maybe we should just tell people to coerce the Chars instance to string before using it as a key?

I'm closing the ticket as incomplete for now, please pick it up again if you want this to move forward.

[bulk edit]

This issue has been automatically marked as stale because it has not been commented on for at least three months.

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