Commit: https://github.com/ruby/ruby/commit/9ca738927293df1c7a2a1ed7e2d6cf89527b5438
Discussion: https://bugs.ruby-lang.org/issues/14473

It seems to be compatible with the original ActiveSupport's
implementation, at least based on the test suite.

It also works faster:

```
Warming up --------------------------------------
 Ruby's Range#cover?     1.196M i/100ms
ActiveSupport's Range#cover?
                       396.369k i/100ms
Calculating -------------------------------------
 Ruby's Range#cover?     11.889M (± 1.7%) i/s -     59.820M in   5.033066s
ActiveSupport's Range#cover?
                          3.951M (± 1.2%) i/s -     19.818M in   5.017176s

Comparison:
 Ruby's Range#cover?: 11888979.3 i/s
ActiveSupport's Range#cover?:  3950671.0 i/s - 3.01x  (± 0.00) slower
```

Benchmark script:

```ruby
require "minitest/autorun"
require "benchmark/ips"

module ActiveSupportRange
  def active_support_cover?(value)
    if value.is_a?(::Range)
      is_backwards_op = value.exclude_end? ? :>= : :>
      return false if value.begin && value.end && value.begin.public_send(is_backwards_op, value.end)
      # 1...10 covers 1..9 but it does not cover 1..10.
      # 1..10 covers 1...11 but it does not cover 1...12.
      operator = exclude_end? && !value.exclude_end? ? :< : :<=
      value_max = !exclude_end? && value.exclude_end? ? value.max : value.last
      cover?(value.first) && (self.end.nil? || value_max.public_send(operator, last))
    else
      cover?
    end
  end
end

class BugTest < Minitest::Test
  def test_range_cover
    Range.prepend(ActiveSupportRange)

    range = (1..10000)

    Benchmark.ips do |x|
      x.report("Ruby's Range#cover?") do
        range.cover?((100..20))
      end

      x.report("ActiveSupport's Range#cover?") do
        range.active_support_cover?((100..20))
      end

      x.compare!
    end
  end
end
```