Rails 6 requires Ruby 2.4.1+

Skipping over 2.4.0 to sidestep the `"symbol_from_string".to_sym.dup` bug.

References #32028

6 files changed, 24 insertions, 70 deletions

diff --git a/guides/CHANGELOG.md b/guides/CHANGELOG.md
index 64e8b51817..21b4ed4b9f 100644
--- a/guides/CHANGELOG.md
+++ b/guides/CHANGELOG.md
@@ -1,3 +1,8 @@
+## Rails 6.0.0.alpha (Unreleased) ##
+
+*   Rails 6 requires Ruby 2.4.1 or newer.
+
+    *Jeremy Daer*
 
 
 Please check [5-2-stable](https://github.com/rails/rails/blob/5-2-stable/guides/CHANGELOG.md) for previous changes.
diff --git a/guides/source/active_job_basics.md b/guides/source/active_job_basics.md
index 9b738e8cdd..4a29327d91 100644
--- a/guides/source/active_job_basics.md
+++ b/guides/source/active_job_basics.md
@@ -344,7 +344,7 @@ Supported types for arguments
 
 ActiveJob supports the following types of arguments by default:
 
-  - Basic types (`NilClass`, `String`, `Integer`, `Fixnum`, `Bignum`, `Float`, `BigDecimal`, `TrueClass`, `FalseClass`)
+  - Basic types (`NilClass`, `String`, `Integer`, `Float`, `BigDecimal`, `TrueClass`, `FalseClass`)
   - `Symbol`
   - `ActiveSupport::Duration`
   - `Date`
diff --git a/guides/source/active_support_core_extensions.md b/guides/source/active_support_core_extensions.md
index 6c980fb0e9..73b24b900a 100644
--- a/guides/source/active_support_core_extensions.md
+++ b/guides/source/active_support_core_extensions.md
@@ -135,16 +135,14 @@ NOTE: Defined in `active_support/core_ext/object/blank.rb`.
 
 ### `duplicable?`
 
-In Ruby 2.4 most objects can be duplicated via `dup` or `clone` except
-methods and certain numbers. Though Ruby 2.2 and 2.3 can't duplicate `nil`,
-`false`, `true`, and  symbols as well as instances `Float`, `Fixnum`,
-and `Bignum` instances.
+As of Ruby 2.5, most objects can be duplicated via `dup` or `clone`:
 
 ```ruby
 "foo".dup           # => "foo"
 "".dup              # => ""
-1.method(:+).dup    # => TypeError: allocator undefined for Method
-Complex(0).dup      # => TypeError: can't copy Complex
+Rational(1).dup     # => (1/1)
+Complex(0).dup      # => (0+0i)
+1.method(:+).dup    # => TypeError (allocator undefined for Method)
 ```
 
 Active Support provides `duplicable?` to query an object about this:
@@ -152,35 +150,18 @@ Active Support provides `duplicable?` to query an object about this:
 ```ruby
 "foo".duplicable?           # => true
 "".duplicable?              # => true
-Rational(1).duplicable?     # => false
-Complex(1).duplicable?      # => false
+Rational(1).duplicable?     # => true
+Complex(1).duplicable?      # => true
 1.method(:+).duplicable?    # => false
 ```
 
-`duplicable?` matches Ruby's `dup` according to the Ruby version.
-
-So in 2.4:
+`duplicable?` matches the current Ruby version's `dup` behavior,
+so results will vary according the version of Ruby you're using.
+In Ruby 2.4, for example, Complex and Rational are not duplicable:
 
 ```ruby
-nil.dup                 # => nil
-:my_symbol.dup          # => :my_symbol
-1.dup                   # => 1
-
-nil.duplicable?         # => true
-:my_symbol.duplicable?  # => true
-1.duplicable?           # => true
-```
-
-Whereas in 2.2 and 2.3:
-
-```ruby
-nil.dup                 # => TypeError: can't dup NilClass
-:my_symbol.dup          # => TypeError: can't dup Symbol
-1.dup                   # => TypeError: can't dup Fixnum
-
-nil.duplicable?         # => false
-:my_symbol.duplicable?  # => false
-1.duplicable?           # => false
+Rational(1).duplicable?     # => false
+Complex(1).duplicable?      # => false
 ```
 
 WARNING: Any class can disallow duplication by removing `dup` and `clone` or raising exceptions from them. Thus only `rescue` can tell whether a given arbitrary object is duplicable. `duplicable?` depends on the hard-coded list above, but it is much faster than `rescue`. Use it only if you know the hard-coded list is enough in your use case.
@@ -2776,20 +2757,6 @@ Active Record does not accept unknown options when building associations, for ex
 
 NOTE: Defined in `active_support/core_ext/hash/keys.rb`.
 
-### Working with Values
-
-#### `transform_values` && `transform_values!`
-
-The method `transform_values` accepts a block and returns a hash that has applied the block operations to each of the values in the receiver.
-
-```ruby
-{ nil => nil, 1 => 1, :x => :a }.transform_values { |value| value.to_s.upcase }
-# => {nil=>"", 1=>"1", :x=>"A"}
-```
-There's also the bang variant `transform_values!` that applies the block operations to values in the very receiver.
-
-NOTE: Defined in `active_support/core_ext/hash/transform_values.rb`.
-
 ### Slicing
 
 Ruby has built-in support for taking slices out of strings and arrays. Active Support extends slicing to hashes:
@@ -2890,24 +2857,6 @@ 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`
 ---------------------
 
diff --git a/guides/source/command_line.md b/guides/source/command_line.md
index b574516392..b41e8bbec6 100644
--- a/guides/source/command_line.md
+++ b/guides/source/command_line.md
@@ -431,16 +431,16 @@ INFO: You can also use `bin/rails -T`  to get the list of tasks.
 ```bash
 $ bin/rails about
 About your application's environment
-Rails version             5.1.0
+Rails version             6.0.0
 Ruby version              2.5.0 (x86_64-linux)
-RubyGems version          2.4.6
-Rack version              2.0.1
+RubyGems version          2.7.3
+Rack version              2.0.4
 JavaScript Runtime        Node.js (V8)
 Middleware:               Rack::Sendfile, ActionDispatch::Static, ActionDispatch::Executor, ActiveSupport::Cache::Strategy::LocalCache::Middleware, Rack::Runtime, Rack::MethodOverride, ActionDispatch::RequestId, ActionDispatch::RemoteIp, Sprockets::Rails::QuietAssets, Rails::Rack::Logger, ActionDispatch::ShowExceptions, WebConsole::Middleware, ActionDispatch::DebugExceptions, ActionDispatch::Reloader, ActionDispatch::Callbacks, ActiveRecord::Migration::CheckPending, ActionDispatch::Cookies, ActionDispatch::Session::CookieStore, ActionDispatch::Flash, Rack::Head, Rack::ConditionalGet, Rack::ETag
 Application root          /home/foobar/commandsapp
 Environment               development
 Database adapter          sqlite3
-Database schema version   20110805173523
+Database schema version   20180205173523
 ```
 
 ### `assets`
diff --git a/guides/source/getting_started.md b/guides/source/getting_started.md
index e90f6d0546..f545b90103 100644
--- a/guides/source/getting_started.md
+++ b/guides/source/getting_started.md
@@ -87,10 +87,10 @@ current version of Ruby installed:
 
 ```bash
 $ ruby -v
-ruby 2.3.1p112
+ruby 2.5.0
 ```
 
-Rails requires Ruby version 2.3.0 or later. If the version number returned is
+Rails requires Ruby version 2.4.1 or later. If the version number returned is
 less than that number, you'll need to install a fresh copy of Ruby.
 
 TIP: A number of tools exist to help you quickly install Ruby and Ruby
diff --git a/guides/source/upgrading_ruby_on_rails.md b/guides/source/upgrading_ruby_on_rails.md
index 14e54db1f2..ff7ccfd47d 100644
--- a/guides/source/upgrading_ruby_on_rails.md
+++ b/guides/source/upgrading_ruby_on_rails.md
@@ -35,7 +35,7 @@ You can find a list of all released Rails versions [here](https://rubygems.org/g
 
 Rails generally stays close to the latest released Ruby version when it's released:
 
-* Rails 6 requires Ruby 2.3.0 or newer.
+* Rails 6 requires Ruby 2.4.1 or newer.
 * Rails 5 requires Ruby 2.2.2 or newer.
 * Rails 4 prefers Ruby 2.0 and requires 1.9.3 or newer.
 * Rails 3.2.x is the last branch to support Ruby 1.8.7.