NEWS in rdoc mode [ci skip]

* NEWS: reverted to rdoc mode.  markdown mode does not make
  class/module/method references in HTML.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65121 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

NEWS

@@ -1,6 +1,6 @@
-# -*- markdown -*- markup: Markdown
+# -*- rdoc -*-
 
-# NEWS for Ruby 2.6.0
+= NEWS for Ruby 2.6.0
 
 This document is a list of user visible feature changes made between
 releases except for bug fixes.
@@ -8,443 +8,420 @@ releases except for bug fixes.
 Note that each entry is kept so brief that no reason behind or reference
 information is supplied with.  For a full list of changes with all
 sufficient information, see the ChangeLog file or Redmine
-(e.g. `https://bugs.ruby-lang.org/issues/$FEATURE_OR_BUG_NUMBER`)
+(e.g. <tt>https://bugs.ruby-lang.org/issues/$FEATURE_OR_BUG_NUMBER</tt>)
 
-## Changes since the 2.5.0 release
+== Changes since the 2.5.0 release
 
-### Language changes
+=== Language changes
 
-* `$SAFE` is a process global state and we can set 0 again.
-  [Feature #14250]
+* <code>$SAFE</code> is a process global state and we can set 0 again. [Feature #14250]
 
 * refinements take place at block passing.  [Feature #14223]
 
-* `else` without `rescue` now causes a syntax error.  [EXPERIMENTAL]
+* +else+ without +rescue+ now causes a syntax error.  [EXPERIMENTAL]
 
-* constant names may start with a non-ASCII capital letter.
-  [Feature #13770]
+* constant names may start with a non-ASCII capital letter. [Feature #13770]
 
 * An endless range is introduced.  You can write a range that has no end,
-  like `(0..)`.  The following shows typical use cases.  [Feature #12912]
+  like <code>(0..)</code>.  The following shows typical use cases.  [Feature #12912]
 
-    ```ruby
     ary[1..]                            # identical to ary[1..-1]
     (1..).each {|index| ... }           # infinite loop from index 1
     ary.zip(1..) {|elem, index| ... }   # ary.each.with_index(1) { }
-    ```
 
-* Non-`Symbol` key in keyword arguments hash causes an exception.
+* Non- Symbol key in keyword arguments hash causes an exception.
 
-### Core classes updates (outstanding ones only)
+=== Core classes updates (outstanding ones only)
 
-* `Array`
+[Array]
 
-    * New methods:
+  [New methods]
 
-        * Added `Array#union` and `Array#difference` instance method.
-          [Feature #14097]
+    * Added Array#union and Array#difference instance method. [Feature #14097]
 
-    * Modified methods:
+  [Modified methods]
 
-        * `Array#to_h` now maps elements to new keys and values by the
-          block if given.  [Feature #15143]
+    * Array#to_h now maps elements to new keys and values by the
+      block if given.  [Feature #15143]
 
-    * Aliased methods:
+  [Aliased methods]
 
-        * `Array#filter` is a new alias for `Array#select`.
-          [Feature #13784]
-        * `Array#filter!` is a new alias for `Array#select!`.
-          [Feature #13784]
+    * Array#filter is a new alias for Array#select. [Feature #13784]
+    * Array#filter! is a new alias for Array#select!. [Feature #13784]
 
-* `Binding`
+[Binding]
 
-    * New methods:
+  [New methods]
 
-        * added `Binding#source_location`.  [Feature #14230]
+    * added Binding#source_location.  [Feature #14230]
 
-            This method returns the source location of binding, a 2-element
-            array of `__FILE__` and `__LINE__`.  Traditionally, the same
-            information could be retrieved by `eval("[__FILE__, __LINE__]",
-            binding)`, but we are planning to change this behavior so that
-            `Kernel#eval` ignores binding's source location [Bug #4352].
-            So, users should use this newly-introduced method instead of
-            `Kernel#eval`.
+      This method returns the source location of binding, a 2-element
+      array of __FILE__ and __LINE__.  Traditionally, the same
+      information could be retrieved by <code>eval("[__FILE__, __LINE__]",
+      binding)</code>, but we are planning to change this behavior so that
+      Kernel#eval ignores binding's source location [Bug #4352].
+      So, users should use this newly-introduced method instead of
+      Kernel#eval.
 
-* `Dir`
+[Dir]
 
-    * New methods:
+  [New methods]
 
-        * added `Dir#each_child` and `Dir#children` instance methods.
-          [Feature #13969]
+    * added Dir#each_child and Dir#children instance methods. [Feature #13969]
 
-* `Enumerable`
+[Enumerable]
 
-    * Modified methods:
+  [Modified methods]
 
-        * `Enumerable#to_h` now maps elements to new keys and values
-          by the block if given.  [Feature #15143]
+    * Enumerable#to_h now maps elements to new keys and values by the block if
+      given.  [Feature #15143]
 
-    * Aliased methods:
+  [Aliased methods]
 
-        * `Enumerable#filter` is a new alias for `Enumerable#select`.
-          [Feature #13784]
+    * Enumerable#filter is a new alias for Enumerable#select. [Feature #13784]
 
-* `Enumerator::ArithmeticSequence`
+[Enumerator::ArithmeticSequence]
 
-    * This is a new class to represent a generator of an arithmetic sequence,
-      that is a number sequence defined by a common difference. It can be used
-      for representing what is similar to Python's slice. You can get an
-      instance of this class from `Numeric#step` and `Range#step`.
+  * This is a new class to represent a generator of an arithmetic sequence,
+    that is a number sequence defined by a common difference. It can be used
+    for representing what is similar to Python's slice. You can get an
+    instance of this class from Numeric#step and Range#step.
 
-* `Enumerator::Lazy`
+[Enumerator::Lazy]
 
-    * Aliased methods:
+  [Aliased methods]
 
-        * `Enumerator::Lazy#filter` is a new alias for
-          `Enumerator::Lazy#select`.  [Feature #13784]
+    * Enumerator::Lazy#filter is a new alias for
+      Enumerator::Lazy#select.  [Feature #13784]
 
-* `ENV`
+[ENV]
 
-    * Modified methods:
+  [Modified methods]
 
-        * `ENV.to_h` now maps names and values to new keys and values
-          by the block if given.  [Feature #15143]
+    * ENV.to_h now maps names and values to new keys and values
+      by the block if given.  [Feature #15143]
 
-* `Exception`
+[Exception]
 
-    * New options:
+  [New options]
 
-        * `Exception#full_message` takes `:highlight` and `:order` options.
-          [Bug #14324]
+    * Exception#full_message takes +:highlight+ and +:order+
+      options. [Bug #14324]
 
-* `Hash`
+[Hash]
 
-    * Modified methods:
+  [Modified methods]
 
-        * `Hash#merge`, `merge!`, and `update` now accept multiple
-           arguments.  [Feature #15111]
+    * Hash#merge, merge!, and update now accept multiple
+      arguments.  [Feature #15111]
 
-        * `Hash#to_h` now maps keys and values to new keys and values
-          by the block if given.  [Feature #15143]
+    * Hash#to_h now maps keys and values to new keys and values
+      by the block if given.  [Feature #15143]
 
-    * Aliased methods:
+  [Aliased methods]
 
-        * `Hash#filter` is a new alias for `Hash#select`.  [Feature #13784]
+    * Hash#filter is a new alias for Hash#select.  [Feature #13784]
 
-        * `Hash#filter!` is a new alias for `Hash#select!`.
-          [Feature #13784]
+    * Hash#filter! is a new alias for Hash#select!. [Feature #13784]
 
-* `IO`
+[IO]
 
-    * New options:
+  [New options]
 
-        * new mode character `'x'` to open files for exclusive access.
-          [Feature #11258]
+    * new mode character <code>'x'</code> to open files for exclusive
+      access. [Feature #11258]
 
-* `Kernel`
+[Kernel]
 
-    * Aliased methods:
+  [Aliased methods]
 
-        * `Kernel#then` is a new alias for `Kernel#yield_self`.
-          [Feature #14594]
+    * Kernel#then is a new alias for Kernel#yield_self. [Feature #14594]
 
-    * New options:
+  [New options]
 
-        * `Kernel.#Complex`, `Kernel.#Float`, `Kernel.#Integer` and
-          `Kernel.#Rational` take `:exception` option to specify the way of
-          error handling.  [Feature #12732]
+    * Kernel#Complex, Kernel#Float, Kernel#Integer and
+      Kernel#Rational take +:exception+ option to specify the way of
+      error handling.  [Feature #12732]
 
-        * `Kernel.#system` takes `:exception` option to raise an exception
-          on failure.  [Feature #14386]
+    * Kernel#system takes +:exception+ option to raise an exception
+      on failure.  [Feature #14386]
 
-    * Incompatible changes:
+  [Incompatible changes]
 
-        * `system()` and `exec()` do not close non-standard file descriptors
-          (The default of `:close_others` option is changed to `false` by
-          default.  but we still set the `FD_CLOEXEC` flag on descriptors we
-          create).  [Misc #14907]
+    * Kernel#system and Kernel#exec do not close non-standard file descriptors
+      (The default of +:close_others+ option is changed to +false+ by
+      default.  but we still set the +FD_CLOEXEC+ flag on descriptors we
+      create).  [Misc #14907]
 
-* `KeyError`
+[KeyError]
 
-    * New options:
+  [New options]
 
-        * `KeyError#initialize` accepts `:receiver` and `:key` options to
-          set receiver and key in Ruby code.  [Feature #14313]
+    * KeyError#initialize accepts +:receiver+ and +:key+ options to
+      set receiver and key in Ruby code.  [Feature #14313]
 
-* `Module`
+[Module]
 
-    * New methods:
+  [New methods]
 
-        * `Module#method_defined?`, `Module#private_method_defined?` and
-          `Module#protected_method_defined?` now accepts the second
-          parameter as optional. If it's `true` (=default), checks ancestor
-          modules/classes, or checks only the class itself.
-          [Feature #14944]
+    * Module#method_defined?, Module#private_method_defined? and
+      Module#protected_method_defined? now accepts the second
+      parameter as optional. If it's +true+ (=default), checks ancestor
+      modules/classes, or checks only the class itself. [Feature #14944]
 
-* `NameError`
+[NameError]
 
-    * New options:
+  [New options]
 
-        * `NameError#initialize` accepts `:receiver` option to set receiver
-          in Ruby code.  [Feature #14313]
+    * NameError#initialize accepts +:receiver+ option to set receiver
+      in Ruby code.  [Feature #14313]
 
-* `NoMethodError`
+[NoMethodError]
 
-    * New options:
+  [New options]
 
-        * `NoMethodError#initialize` accepts `:receiver` option to set
-          receiver in Ruby code.  [Feature #14313]
+    * NoMethodError#initialize accepts +:receiver+ option to set receiver
+      in Ruby code.  [Feature #14313]
 
-* `Numeric`
+[Numeric]
 
-    * Incompatible changes:
+  [Incompatible changes]
 
-        * `Numeric#step` now returns an instance of
-          `Enumerator::ArithmeticSequence` class rather than one of
-          `Enumerator` class.
+    * Numeric#step now returns an instance of Enumerator::ArithmeticSequence
+      class rather than one of Enumerator class.
 
-* `Proc`
+[Proc]
 
-    * Incompatible changes:
+  [Incompatible changes]
 
-        * `Proc#call` doesn't change `$SAFE` any more.  [Feature #14250]
+    * Proc#call doesn't change <code>$SAFE</code> any more.  [Feature #14250]
 
-* `Random`
+[Random]
 
-    * New methods:
+  [New methods]
 
-        * added `Random.bytes`.  [Feature #4938]
+    * added Random.bytes.  [Feature #4938]
 
-* `Range`
+[Range]
 
-    * New methods:
+  [New methods]
 
-        * Added `Range#%` instance method.  [Feature #14697]
+    * Added Range#% instance method.  [Feature #14697]
 
-    * Incompatible changes:
+  [Incompatible changes]
 
-        * `Range#===` now uses `#cover?` instead of `#include?` method.
-          [Feature #14575]
-        * `Range#cover?` now accepts Range object. [Feature #14473]
-        * `Range#step` now returns an instance of
-          `Enumerator::ArithmeticSequence` class rather than one of
-          `Enumerator` class.
+    * Range#=== now uses #cover? instead of #include? method. [Feature #14575]
+    * Range#cover? now accepts Range object. [Feature #14473]
+    * Range#step now returns an instance of Enumerator::ArithmeticSequence
+      class rather than one of Enumerator class.
 
-* `RubyVM::AST`
+[RubyVM::AST]
 
-    * New methods:
+  [New methods]
 
-        * `RubyVM::AST.parse` parses a given string and returns AST nodes.
-          [experimental]
+    * RubyVM::AST.parse parses a given string and returns AST
+      nodes. [experimental]
 
-        * `RubyVM::AST.parse_file` parses a given file and returns AST
-          nodes.  [experimental]
+    * RubyVM::AST.parse_file parses a given file and returns AST
+      nodes.  [experimental]
 
-* `String`
+[String]
 
-    * New features:
+  [New features]
 
-        * `String#split` yields each substring to the block if given.
-          [Feature #4780]
+    * String#split yields each substring to the block if given. [Feature #4780]
 
-* `Struct`
+[Struct]
 
-    * Modified methods:
+  [Modified methods]
 
-        * `Struct#to_h` now maps keys and values to new keys and values
-          by the block if given.  [Feature #15143]
+    * Struct#to_h now maps keys and values to new keys and values
+      by the block if given.  [Feature #15143]
 
-    * Aliased method:
+  [Aliased method]
 
-        * `Struct#filter` is a new alias for `Struct#select` [Feature #13784]
+    * Struct#filter is a new alias for Struct#select [Feature #13784]
 
-* `Time`
+[Time]
 
-    * New features:
+  [New features]
 
-        * `Time.new` and `Time#getlocal` accept a timezone object as
-          well as UTC offset string. `Time#+`, `Time#-` and `Time#succ`
-          also preserve the timezone.  [Feature #14850]
+    * Time.new and Time#getlocal accept a timezone object as well as
+      UTC offset string. Time#+, Time#- and Time#succ also preserve
+      the timezone.  [Feature #14850]
 
-* `TracePoint`
+[TracePoint]
 
-    * New methods:
+  [New methods]
 
-        * `TracePoint#parameters` [Feature #14694]
+    * TracePoint#parameters [Feature #14694]
 
-### Stdlib updates (outstanding ones only)
+=== Stdlib updates (outstanding ones only)
 
-* `ERB`
+[ERB]
 
-    * New options:
+  [New options]
 
-        * Add `:trim_mode` and `:eoutvar` keyword arguments to `ERB.new`.
-          Now non-keyword arguments other than first one are softly
-          deprecated and will be removed when Ruby 2.5 becomes EOL.
-          [Feature #14256]
+    * Add +:trim_mode+ and +:eoutvar+ keyword arguments to ERB.new.
+      Now non-keyword arguments other than first one are softly deprecated
+      and will be removed when Ruby 2.5 becomes EOL. [Feature #14256]
 
-        * erb command's `-S` option is deprecated, which will be removed in
-          the next version.
+    * erb command's <tt>-S</tt> option is deprecated, which will be removed
+      in the next version.
 
-* `FileUtils`
+[FileUtils]
 
-    * New method:
+  [New method]
 
-        * `FileUtils#cp_lr`.  [Feature #4189]
+    * FileUtils#cp_lr.  [Feature #4189]
 
-* `Matrix`
+[Matrix]
 
-    * New methods:
+  [New methods]
 
-        * `Matrix#antisymmetric?`
+    * Matrix#antisymmetric?
 
-        * `Matrix#reflexive?`
+    * Matrix#reflexive?
 
-* `Net`
+[Net]
 
-    * New options:
+  [New options]
 
-        * Add `:write_timeout` keyword argument to `Net::BufferedIO.new`.
-          [Feature #13396]
+    * Add +:write_timeout+ keyword argument to Net::HTTP.new. [Feature #13396]
 
-    * New methods:
+  [New methods]
 
-        * Add `Net::BufferedIO#write_timeout`,
-          `Net::BufferedIO#write_timeout=`, `Net::HTTP#write_timeout`, and
-          `Net::HTTP#write_timeout=`.  [Feature #13396]
+    * Add Net::HTTP#write_timeout, and Net::HTTP#write_timeout=.  [Feature #13396]
 
-    * New constant:
+  [New constant]
 
-        * Add `Net::HTTPClientException` to deprecate
-          `Net::HTTPServerException`, whose name is misleading.  [Bug #14688]
+    * Add Net::HTTPClientException to deprecate Net::HTTPServerException,
+      whose name is misleading.  [Bug #14688]
 
-* `REXML`
+[REXML]
 
-    * Improved some XPath implementations:
+  [Improved some XPath implementations]
 
-        * `concat()` function: Stringify all arguments before concatenating
+    * <code>concat()</code> function: Stringify all arguments before concatenating
 
-        * `string()` function: Support context node
+    * <code>string()</code> function: Support context node
 
-        * `string()` function: Support processing instruction node
+    * <code>string()</code> function: Support processing instruction node
 
-        * Support `"*:#{ELEMENT_NAME}"` syntax in XPath 2.0
+    * Support <code>"*:#{ELEMENT_NAME}"</code> syntax in XPath 2.0
 
-    * Fixed some XPath implementations:
+  [Fixed some XPath implementations]
 
-        * `"//#{ELEMENT_NAME}[#{POSITION}]"` case
+    * <code>"//#{ELEMENT_NAME}[#{POSITION}]"</code> case
 
-        * `string()` function: Fix `function(document)` returns nodes that
-          are out of root elements.
+    * <code>string()</code> function: Fix <code>function(document)</code>
+      returns nodes that are out of root elements.
 
-        * `"/ #{ELEMENT_NAME} "` case
+    * <code>"/ #{ELEMENT_NAME} "</code> case
 
-        * `"/ #{ELEMENT_NAME} [ #{PREDICATE} ]"` case
+    * <code>"/ #{ELEMENT_NAME} [ #{PREDICATE} ]"</code> case
 
-        * `"/ #{AXIS}:: #{ELEMENT_NAME} "` case
+    * <code>"/ #{AXIS}::#{ELEMENT_NAME}"</code> case
 
-        * `"#{N}-#{M}"` case: One or more white spaces were required before
-          `"-"`
+    * <code>"#{N}-#{M}"</code> case: One or more white spaces were required
+      before <code>"-"</code>
 
-        * `"/child::node()"` case
+    * <code>"/child::node()"</code> case
 
-        * `"#{FUNCTION}()/#{PATH}"` case
+    * <code>"#{FUNCTION}()/#{PATH}"</code> case
 
-        * `"@#{ATTRIBUTE}/parent::"` case
+    * <code>"@#{ATTRIBUTE}/parent::"</code> case
 
-        * `"name(#{NODE_SET})"` case
+    * <code>"name(#{NODE_SET})"</code> case
 
-* `RSS`
+[RSS]
 
-    * New options:
+  [New options]
 
-        * `RSS::Parser.parse`: Accept options as `Hash`. `:validate`,
-          `:ignore_unknown_element`, `:parser_class` options are available.
+    * RSS::Parser.parse: Accept options as Hash. +:validate+ ,
+      +:ignore_unknown_element+ , +:parser_class+ options are available.
 
-* `Set`
+[Set]
 
-    * Aliased methods:
+  [Aliased methods]
 
-        * `Set#filter!` is a new alias for `Set#select!`.  [Feature #13784]
+    * Set#filter! is a new alias for Set#select!.  [Feature #13784]
 
-* `URI`
+[URI]
 
-    * New constant:
+  [New constant]
 
-        * Add `URI::File` to handle file URI scheme.  [Feature #14035]
+    * Add URI::File to handle file URI scheme.  [Feature #14035]
 
-### Compatibility issues (excluding feature bug fixes)
+=== Compatibility issues (excluding feature bug fixes)
 
-* `File`
+[File]
 
-    * `File.read`, `File.binread`, `File.write`, `File.binwrite`,
-      `File.foreach`, and `File.readlines` do not invoke external commands
-      even if the path starts with the pipe character `'|'`.
-      [Feature #14245]
+  * File.read, File.binread, File.write, File.binwrite, File.foreach, and
+    File.readlines do not invoke external commands even if the path starts
+    with the pipe character <code>'|'</code>. [Feature #14245]
 
-* `Dir`
+[Dir]
 
-    * `Dir.glob` with `'\0'`-separated pattern list will be deprecated, and
-      is now warned.  [Feature #14643]
+  * Dir.glob with <code>'\0'</code>-separated pattern list will be deprecated,
+    and is now warned.  [Feature #14643]
 
-### Stdlib compatibility issues (excluding feature bug fixes)
+=== Stdlib compatibility issues (excluding feature bug fixes)
 
-### C API updates
+=== C API updates
 
-### Supported platform changes
+=== Supported platform changes
 
-### Implementation improvements
+=== Implementation improvements
 
-* Speedup `Proc#call` because we don't need to care about `$SAFE` any more.
-  [Feature #14318]
+* Speedup Proc#call because we don't need to care about <code>$SAFE</code>
+  any more. [Feature #14318]
 
-    With `lc_fizzbuzz` benchmark which uses so many `Proc#call` we can
-    measure x1.4 improvements.  [Bug #10212]
+  With +lc_fizzbuzz+ benchmark which uses so many Proc#call we can
+  measure x1.4 improvements.  [Bug #10212]
 
-* Speedup `block.call` where `block` is passed block parameter.
-  [Feature #14330]
+* Speedup block.call where +block+ is passed block parameter. [Feature #14330]
 
-    Ruby 2.5 improves block passing performance. [Feature #14045]
+  Ruby 2.5 improves block passing performance. [Feature #14045]
 
-    Additionally, Ruby 2.6 improves the performance of passed block calling.
+  Additionally, Ruby 2.6 improves the performance of passed block calling.
 
-* Introduce an initial implementation of JIT (Just-in-time) compiler.
-  [Feature #14235] [experimental]
-    * `--enable=jit` option is added to enable JIT. `--jit-verbose=1` is good for
-      inspection.  See `ruby --help` for others.
-    * This JIT relies on C compiler used to build Ruby, on runtime.  Only
-      gcc and clang are supported for the JIT for now, and MinGW support has
-      some issues.
-    * As of 2.6.0-preview1, we're just preparing infrastructure for JIT and
-      very few optimizations are implemented.  So it's not ready for
-      benchmarking Ruby's JIT performance yet. It's known that current JIT
-      enablement makes Rails application slower for now.
-    * rb_waitpid reimplemented on Unix-like platforms to maintain
-      compatibility [Bug #14867]
+* Introduce an initial implementation of JIT (Just-in-time) compiler. [Feature #14235] [experimental]
 
-* VM generator script renewal; makes the generated VM more optimized.
-  [GH-1779]
+  * <tt>--enable=jit</tt> option is added to enable JIT. <tt>--jit-verbose=1</tt>
+    is good for inspection.  See <tt>ruby --help</tt> for others.
+  * This JIT relies on C compiler used to build Ruby, on runtime.  Only
+    gcc and clang are supported for the JIT for now, and MinGW support has
+    some issues.
+  * As of 2.6.0-preview1, we're just preparing infrastructure for JIT and
+    very few optimizations are implemented.  So it's not ready for
+    benchmarking Ruby's JIT performance yet. It's known that current JIT
+    enablement makes Rails application slower for now.
+  * rb_waitpid reimplemented on Unix-like platforms to maintain
+    compatibility [Bug #14867]
 
-* Thread cache enabled for pthreads platforms (for `Thread.new` and
-  `Thread.start`).  [Feature #14757]
+* VM generator script renewal; makes the generated VM more optimized. [GH-1779]
+
+* Thread cache enabled for pthreads platforms (for Thread.new and
+  Thread.start).  [Feature #14757]
 
 * timer thread is eliminated for platforms with POSIX timers [Misc #14937]
 
-### Miscellaneous changes
+=== Miscellaneous changes
 
 * On macOS, shared libraries no longer include a full version number of ruby
   in their names.  This eliminates the burden of each teeny upgrade on the
   platform that users need to rebuild every extension library.
 
-  * Before:
+  [Before]
     * libruby.2.6.0.dylib
     * libruby.2.6.dylib -> libruby.2.6.0.dylib
     * libruby.dylib -> libruby.2.6.0.dylib
 
-  * After:
+  [After]
     * libruby.2.6.dylib
     * libruby.dylib -> libruby.2.6.dylib
 
-### Misc
+=== Misc
 
 * Extracted misc/*.el files to https://github.com/ruby/elisp