define Range#match? if Ruby < 2.4

See the rationale in the documentation included in this patch.

We are going to gradually introduce this predicate in the code base.

activesupport/CHANGELOG.md

@@ -1,3 +1,9 @@
*   Defines `Regexp.match?` for Ruby versions prior to 2.4. The predicate
    has the same interface, but it does not have the performance boost. It's
    purpose is to be able to write 2.4 compatible code.

    *Xavier Noria*

*   Allow MessageEncryptor to take advantage of authenticated encryption modes.

    AEAD modes like `aes-256-gcm` provide both confidentiality and data
@@ -55,7 +61,7 @@

    *John Gesimondo*

*   `travel/travel_to` travel time helpers, now raise on nested calls, 
*   `travel/travel_to` travel time helpers, now raise on nested calls,
     as this can lead to confusing time stubbing.

     Instead of:
@@ -69,7 +75,7 @@

     preferred way to achieve above is:

         travel 2.days do 
         travel 2.days do
           # 2 days from today
         end

activesupport/lib/active_support/core_ext/regexp.rb

@@ -2,4 +2,8 @@ class Regexp #:nodoc:
  def multiline?
    options & MULTILINE == MULTILINE
  end

  def match?(string, pos=0)
    !! match(string, pos)
  end unless //.respond_to?(:match?)
end

activesupport/test/core_ext/regexp_ext_test.rb

@@ -7,4 +7,28 @@ def test_multiline
    assert_equal false, //.multiline?
    assert_equal false, /(?m:)/.multiline?
  end

  # Based on https://github.com/ruby/ruby/blob/trunk/test/ruby/test_regexp.rb.
  def test_match_p
    /back(...)/ =~ 'backref'
    # must match here, but not in a separate method, e.g., assert_send,
    # to check if $~ is affected or not.
    assert_equal false, //.match?(nil)
    assert_equal true, //.match?("")
    assert_equal true, /.../.match?(:abc)
    assert_raise(TypeError) { /.../.match?(Object.new) }
    assert_equal true, /b/.match?('abc')
    assert_equal true, /b/.match?('abc', 1)
    assert_equal true, /../.match?('abc', 1)
    assert_equal true, /../.match?('abc', -2)
    assert_equal false, /../.match?("abc", -4)
    assert_equal false, /../.match?("abc", 4)
    assert_equal true, /\z/.match?("")
    assert_equal true, /\z/.match?("abc")
    assert_equal true, /R.../.match?("Ruby")
    assert_equal false, /R.../.match?("Ruby", 1)
    assert_equal false, /P.../.match?("Ruby")
    assert_equal 'backref', $&
    assert_equal 'ref', $1
  end
end

guides/source/active_support_core_extensions.md

@@ -2916,6 +2916,24 @@ end

NOTE: Defined in `active_support/core_ext/regexp.rb`.

### `match?`

Rails implements `Regexp#match?` for Ruby versions prior to 2.4:

```ruby
/oo/.match?('foo')    # => true
/oo/.match?('bar')    # => false
/oo/.match?('foo', 1) # => true
```

The backport has the same interface and lack of side-effects in the caller like
not setting `$1` and friends, but it does not have the speed benefits. Its
purpose is to be able to write 2.4 compatible code. Rails itself uses this
predicate internally for example.

Active Support defines `Regexp#match?` only if not present, so code running
under 2.4 or later does run the original one and gets the performance boost.

Extensions to `Range`
---------------------