# NEWS for Ruby 3.4.0

This document is a list of user-visible feature changes
since the **3.3.0** release, except for bug fixes.

Note that each entry is kept to a minimum, see links for details.

## Language changes

* String literals in files without a `frozen_string_literal` comment now emit a deprecation warning
  when they are mutated.
  These warnings can be enabled with `-W:deprecated` or by setting `Warning[:deprecated] = true`.
  To disable this change, you can run Ruby with the `--disable-frozen-string-literal`
  command line argument. [[Feature #20205]]

* `it` is added to reference a block parameter. [[Feature #18980]]

* Keyword splatting `nil` when calling methods is now supported.
  `**nil` is treated similarly to `**{}`, passing no keywords,
  and not calling any conversion methods.  [[Bug #20064]]

* Block passing is no longer allowed in index assignment
  (e.g. `a[0, &b] = 1`).  [[Bug #19918]]

* Keyword arguments are no longer allowed in index assignment
  (e.g. `a[0, kw: 1] = 2`).  [[Bug #20218]]

* `GC.config` added to allow setting configuration variables on the Garbage
  Collector. [[Feature #20443]]

* GC configuration parameter `rgengc_allow_full_mark` introduced. When `false`
  GC will only mark young objects. Default is `true`. [[Feature #20443]]

## Core classes updates

Note: We're only listing outstanding class updates.

* Exception

  * Exception#set_backtrace now accepts arrays of `Thread::Backtrace::Location`.
    `Kernel#raise`, `Thread#raise` and `Fiber#raise` also accept this new format. [[Feature #13557]]

* Range

  * Range#size now raises TypeError if the range is not iterable. [[Misc #18984]]

* RubyVM::AbstractSyntaxTree

  * Add `RubyVM::AbstractSyntaxTree::Node#locations` method which returns location objects
    associated with the AST node. [[Feature #20624]]
  * Add `RubyVM::AbstractSyntaxTree::Location` class which holds location information. [[Feature #20624]]

## Stdlib updates

* Tempfile

    * The keyword argument `anonymous: true` is implemented for `Tempfile.create`.
      `Tempfile.create(anonymous: true)` removes the created temporary file immediately.
      So applications don't need to remove the file.
      [[Feature #20497]]

The following default gems are updated.

* RubyGems 3.6.0.dev
* bundler 2.6.0.dev
* erb 4.0.4
* fiddle 1.1.3
* io-console 0.7.2
* irb 1.14.0
* json 2.7.2
* net-http 0.4.1
* optparse 0.5.0
* prism 0.30.0
* rdoc 6.7.0
* reline 0.5.9
* resolv 0.4.0
* stringio 3.1.2
* strscan 3.1.1

The following bundled gems are updated.

* minitest 5.24.1
* rake 13.2.1
* test-unit 3.6.2
* rexml 3.3.2
* net-ftp 0.3.7
* net-imap 0.4.14
* net-smtp 0.5.0
* rbs 3.5.2
* typeprof 0.21.11
* debug 1.9.2
* racc 1.8.0

The following bundled gems are promoted from default gems.

* mutex_m 0.2.0
* getoptlong 0.2.1
* base64 0.2.0
* bigdecimal 3.1.8
* observer 0.1.2
* abbrev 0.1.2
* resolv-replace 0.1.1
* rinda 0.2.0
* drb 2.2.1
* nkf 0.2.0
* syslog 0.1.2
* csv 3.3.0

See GitHub releases like [GitHub Releases of Logger](https://github.com/ruby/logger/releases) or changelog for details of the default gems or bundled gems.

## Supported platforms

## Compatibility issues

* Error messages and backtrace displays have been changed.
  * Use a single quote instead of a backtick as a opening quote. [[Feature #16495]]
  * Display a class name before a method name (only when the class has a permanent name). [[Feature #19117]]
  * `Kernel#caller`, `Thread::Backtrace::Location`'s methods, etc. are also changed accordingly.
  ```
  Old:
  test.rb:1:in `foo': undefined method `time' for an instance of Integer
          from test.rb:2:in `<main>'

  New:
  test.rb:1:in 'Object#foo': undefined method 'time' for an instance of Integer
          from test.rb:2:in `<main>'
  ```

## Stdlib compatibility issues

## C API updates

* `rb_newobj` and `rb_newobj_of` (and corresponding macros `RB_NEWOBJ`, `RB_NEWOBJ_OF`, `NEWOBJ`, `NEWOBJ_OF`) have been removed. [[Feature #20265]]
* Removed deprecated function `rb_gc_force_recycle`. [[Feature #18290]]

## Implementation improvements

* `Array#each` is rewritten in Ruby for better performance [[Feature #20182]].

## JIT

## Miscellaneous changes

* Passing a block to a method which doesn't use the passed block will show
  a warning on verbose mode (`-w`).
  [[Feature #15554]]

* Redefining some core methods that are specially optimized by the interpreter
  and JIT like `String.freeze` or `Integer#+` now emits a performance class
  warning (`-W:performance` or `Warning[:performance] = true`).
  [[Feature #20429]]

[Feature #13557]: https://bugs.ruby-lang.org/issues/13557
[Feature #15554]: https://bugs.ruby-lang.org/issues/15554
[Feature #16495]: https://bugs.ruby-lang.org/issues/16495
[Feature #18290]: https://bugs.ruby-lang.org/issues/18290
[Feature #18980]: https://bugs.ruby-lang.org/issues/18980
[Misc #18984]:    https://bugs.ruby-lang.org/issues/18984
[Feature #19117]: https://bugs.ruby-lang.org/issues/19117
[Bug #19918]:     https://bugs.ruby-lang.org/issues/19918
[Bug #20064]:     https://bugs.ruby-lang.org/issues/20064
[Feature #20182]: https://bugs.ruby-lang.org/issues/20182
[Feature #20205]: https://bugs.ruby-lang.org/issues/20205
[Bug #20218]:     https://bugs.ruby-lang.org/issues/20218
[Feature #20265]: https://bugs.ruby-lang.org/issues/20265
[Feature #20429]: https://bugs.ruby-lang.org/issues/20429
[Feature #20443]: https://bugs.ruby-lang.org/issues/20443
[Feature #20497]: https://bugs.ruby-lang.org/issues/20497
[Feature #20624]: https://bugs.ruby-lang.org/issues/20624