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

it is added to reference a block parameter. [[Feature #18980]]
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]]
```
* `String#+@` now duplicates when mutating the string would emit
a deprecation warning, offered as a replacement for the
`str.dup if str.frozen?` pattern.
```
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]]
The toplevel name ::Ruby is reserved now, and the definition will be warned when Warning[:deprecated]. [[Feature #20884]]

Core classes updates

Note: We're only listing outstanding class updates.

Array

* `Array#fetch_values` was added. [[Feature #20702]]

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]]

Fiber::Scheduler

* An optional `Fiber::Scheduler#blocking_operation_wait` hook allows blocking operations to be moved out of the
event loop in order to reduce latency and improve multi-core processor utilization. [[Feature #20876]]

* `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]]

Hash

* `Hash.new` now accepts an optional `capacity:` argument, to preallocate the hash with a given capacity.
This can improve performance when building large hashes incrementally by saving on reallocation and
rehashing of keys. [[Feature #19236]]

IO::Buffer

* `IO::Buffer#copy` can release the GVL, allowing other threads to run while copying data. [[Feature #20902]]

Integer

* `Integer#**` used to return `Float::INFINITY` when the return value is large, but now returns an `Integer`.
If the return value is extremely large, it raises an exception.
[[Feature #20811]]

MatchData

* `MatchData#bytebegin` and `MatchData#byteend` have been added. [[Feature #20576]]

Object

* `Object#singleton_method` now returns methods in modules prepended to or included in the
receiver's singleton class. [[Bug #20620]]

  ```ruby
  o = Object.new
  o.extend(Module.new{def a = 1})
  o.singleton_method(:a).call #=> 1
  ```

Ractor

* `require` in Ractor is allowed. The requiring process will be run on
the main Ractor.
`Ractor._require(feature)` is added to run requiring process on the
main Ractor.
[[Feature #20627]]

* `Ractor.main?` is added. [[Feature #20627]]

* `Ractor.[]` and `Ractor.[]=` are added to access the ractor local storage
of the current Ractor. [[Feature #20715]]

* `Ractor.store_if_absent(key){ init }` is added to initialize ractor local
variables in thread-safety. [[Feature #20875]]

Range

* `Range#size` now raises `TypeError` if the range is not iterable. [[Misc #18984]]
* `Range#step` now consistently has a semantics of iterating by using `+` operator
for all types, not only numerics. [[Feature #18368]]

  ```ruby
  (Time.utc(2022, 2, 24)..).step(24*60*60).take(3)
  #=> [2022-02-24 00:00:00 UTC, 2022-02-25 00:00:00 UTC, 2022-02-26 00:00:00 UTC]
  ```

Rational

* `Rational#**` used to return `Float::INFINITY` or `Float::NAN`
when the numerator of the return value is large, but now returns an `Rational`.
If it is extremely large, it raises an exception. [[Feature #20811]]

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]]

String

* `String#append_as_bytes` was added to more easily and efficiently work with binary buffers and protocols.
It directly concatenate the arguments into the string without any encoding validation or conversion.
[[Feature #20594]]

Symbol

* The string returned by `Symbol#to_s` now emits a deprecation warning when mutated, and will be
frozen in a future version of Ruby.
These warnings can be enabled with `-W:deprecated` or by setting `Warning[:deprecated] = true`.
[[Feature #20350]]

Time

* On Windows, now `Time#zone` encodes the system timezone name in UTF-8
instead of the active code page, if it contains non-ASCII characters.
[[Bug #20929]]

* `Time#xmlschema`, and its `Time#iso8601` alias have been moved into the core Time
class while previously it was an extension provided by the `time` gem. [[Feature #20707]]

Warning

* Add `Warning.categories` method which returns a list of possible warning categories.
[[Feature #20293]]

Stdlib updates

We only list stdlib changes that are notable feature changes.

RubyGems
- Add --attestation option to gem push. It enabled to store signature of build artifact to sigstore.dev.
Bundler
- Add a lockfile_checksums configuration to include checksums in fresh lockfiles.
- Add bundle lock --add-checksums to add checksums to an existing lockfile.

JSON

* Performance improvements `JSON.parse` about 1.5 times faster than json-2.7.x.

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]]

win32/sspi.rb

* This library is now extracted from the Ruby repository to [ruby/net-http-sspi].
[[Feature #20775]]

Socket

* `Socket::ResolutionError` and `Socket::ResolutionError#error_code` was added.
[[Feature #20018]]

IRB

* Interactive method completion is now improved with type information by default.
[[Feature #20778]]

Other changes are listed in the following sections. we also listed release history from the previous bundled version that is Ruby 3.3.0 if it has GitHub releases.

The following default gem is added.

win32-registry 0.1.0

The following default gems are updated.

RubyGems 3.6.2
- 3.5.3 to [v3.5.4][RubyGems-v3.5.4], [v3.5.5][RubyGems-v3.5.5], [v3.5.6][RubyGems-v3.5.6], [v3.5.7][RubyGems-v3.5.7], [v3.5.8][RubyGems-v3.5.8], [v3.5.9][RubyGems-v3.5.9], [v3.5.10][RubyGems-v3.5.10], [v3.5.11][RubyGems-v3.5.11], [v3.5.12][RubyGems-v3.5.12], [v3.5.13][RubyGems-v3.5.13], [v3.5.14][RubyGems-v3.5.14], [v3.5.15][RubyGems-v3.5.15], [v3.5.16][RubyGems-v3.5.16], [v3.5.17][RubyGems-v3.5.17], [v3.5.18][RubyGems-v3.5.18], [v3.5.19][RubyGems-v3.5.19], [v3.5.20][RubyGems-v3.5.20], [v3.5.21][RubyGems-v3.5.21], [v3.5.22][RubyGems-v3.5.22], [v3.5.23][RubyGems-v3.5.23], [v3.6.0][RubyGems-v3.6.0], [v3.6.1][RubyGems-v3.6.1], [v3.6.2][RubyGems-v3.6.2]
benchmark 0.4.0
- 0.3.0 to [v0.4.0][benchmark-v0.4.0]
bundler 2.6.2
- 2.5.3 to [v2.5.4][bundler-v2.5.4], [v2.5.5][bundler-v2.5.5], [v2.5.6][bundler-v2.5.6], [v2.5.7][bundler-v2.5.7], [v2.5.8][bundler-v2.5.8], [v2.5.9][bundler-v2.5.9], [v2.5.10][bundler-v2.5.10], [v2.5.11][bundler-v2.5.11], [v2.5.12][bundler-v2.5.12], [v2.5.13][bundler-v2.5.13], [v2.5.14][bundler-v2.5.14], [v2.5.15][bundler-v2.5.15], [v2.5.16][bundler-v2.5.16], [v2.5.17][bundler-v2.5.17], [v2.5.18][bundler-v2.5.18], [v2.5.19][bundler-v2.5.19], [v2.5.20][bundler-v2.5.20], [v2.5.21][bundler-v2.5.21], [v2.5.22][bundler-v2.5.22], [v2.5.23][bundler-v2.5.23], [v2.6.0][bundler-v2.6.0], [v2.6.1][bundler-v2.6.1], [v2.6.2][bundler-v2.6.2]
date 3.4.1
- 3.3.4 to [v3.4.0][date-v3.4.0], [v3.4.1][date-v3.4.1]
delegate 0.4.0
- 0.3.1 to [v0.4.0][delegate-v0.4.0]
did_you_mean 2.0.0
- 1.6.3 to [v2.0.0][did_you_mean-v2.0.0]
digest 3.2.0
- 3.1.1 to [v3.2.0.pre0][digest-v3.2.0.pre0], [v3.2.0][digest-v3.2.0]
erb 4.0.4
- 4.0.3 to [v4.0.4][erb-v4.0.4]
error_highlight 0.7.0
- 0.6.0 to [v0.7.0][error_highlight-v0.7.0]
etc 1.4.5
- 1.4.3 to [v1.4.4][etc-v1.4.4], [v1.4.5][etc-v1.4.5]
fcntl 1.2.0
- 1.1.0 to [v1.2.0][fcntl-v1.2.0]
fiddle 1.1.6
- 1.1.2 to [v1.1.3][fiddle-v1.1.3], [v1.1.4][fiddle-v1.1.4], [v1.1.5][fiddle-v1.1.5], [v1.1.6][fiddle-v1.1.6]
fileutils 1.7.3
- 1.7.2 to [v1.7.3][fileutils-v1.7.3]
io-console 0.8.0
- 0.7.1 to [v0.7.2][io-console-v0.7.2], [v0.8.0.beta1][io-console-v0.8.0.beta1], [v0.8.0][io-console-v0.8.0]
io-nonblock 0.3.1
- 0.3.0 to [v0.3.1][io-nonblock-v0.3.1]
ipaddr 1.2.7
- 1.2.6 to [v1.2.7][ipaddr-v1.2.7]
irb 1.14.3
- 1.11.0 to [v1.11.1][irb-v1.11.1], [v1.11.2][irb-v1.11.2], [v1.12.0][irb-v1.12.0], [v1.13.0][irb-v1.13.0], [v1.13.1][irb-v1.13.1], [v1.13.2][irb-v1.13.2], [v1.14.0][irb-v1.14.0], [v1.14.1][irb-v1.14.1], [v1.14.2][irb-v1.14.2], [v1.14.3][irb-v1.14.3]
json 2.9.1
- 2.7.1 to [v2.7.2][json-v2.7.2], [v2.7.3.rc1][json-v2.7.3.rc1], [v2.7.3][json-v2.7.3], [v2.7.4][json-v2.7.4], [v2.7.5][json-v2.7.5], [v2.7.6][json-v2.7.6], [v2.8.0][json-v2.8.0], [v2.8.1][json-v2.8.1], [v2.8.2][json-v2.8.2], [v2.9.0][json-v2.9.0], [v2.9.1][json-v2.9.1]
logger 1.6.4
- 1.6.0 to [v1.6.1][logger-v1.6.1], [v1.6.2][logger-v1.6.2], [v1.6.3][logger-v1.6.3], [v1.6.4][logger-v1.6.4]
net-http 0.6.0
- 0.4.0 to [v0.4.1][net-http-v0.4.1], [v0.5.0][net-http-v0.5.0], [v0.6.0][net-http-v0.6.0]
open-uri 0.5.0
- 0.4.1 to [v0.5.0][open-uri-v0.5.0]
optparse 0.6.0
- 0.4.0 to [v0.5.0][optparse-v0.5.0], [v0.6.0][optparse-v0.6.0]
ostruct 0.6.1
- 0.6.0 to [v0.6.1][ostruct-v0.6.1]
pathname 0.4.0
- 0.3.0 to [v0.4.0][pathname-v0.4.0]
pp 0.6.2
- 0.5.0 to [v0.6.0][pp-v0.6.0], [v0.6.1][pp-v0.6.1], [v0.6.2][pp-v0.6.2]
prism 1.2.0
- 0.19.0 to [v0.20.0][prism-v0.20.0], [v0.21.0][prism-v0.21.0], [v0.22.0][prism-v0.22.0], [v0.23.0][prism-v0.23.0], [v0.24.0][prism-v0.24.0], [v0.25.0][prism-v0.25.0], [v0.26.0][prism-v0.26.0], [v0.27.0][prism-v0.27.0], [v0.28.0][prism-v0.28.0], [v0.29.0][prism-v0.29.0], [v0.30.0][prism-v0.30.0], [v1.0.0][prism-v1.0.0], [v1.1.0][prism-v1.1.0], [v1.2.0][prism-v1.2.0]
pstore 0.1.4
- 0.1.3 to [v0.1.4][pstore-v0.1.4]
psych 5.2.2
- 5.1.2 to [v5.2.0.beta1][psych-v5.2.0.beta1], [v5.2.0.beta2][psych-v5.2.0.beta2], [v5.2.0.beta3][psych-v5.2.0.beta3], [v5.2.0.beta4][psych-v5.2.0.beta4], [v5.2.0.beta5][psych-v5.2.0.beta5], [v5.2.0.beta6][psych-v5.2.0.beta6], [v5.2.0.beta7][psych-v5.2.0.beta7], [v5.2.0][psych-v5.2.0], [v5.2.1][psych-v5.2.1], [v5.2.2][psych-v5.2.2]
rdoc 6.10.0
- 6.6.2 to [v6.7.0][rdoc-v6.7.0], [v6.8.0][rdoc-v6.8.0], [v6.8.1][rdoc-v6.8.1], [v6.9.0][rdoc-v6.9.0], [v6.9.1][rdoc-v6.9.1], [v6.10.0][rdoc-v6.10.0]
reline 0.6.0
- 0.4.1 to [v0.4.2][reline-v0.4.2], [v0.4.3][reline-v0.4.3], [v0.5.0.pre.1][reline-v0.5.0.pre.1], [v0.5.0][reline-v0.5.0], [v0.5.1][reline-v0.5.1], [v0.5.2][reline-v0.5.2], [v0.5.3][reline-v0.5.3], [v0.5.4][reline-v0.5.4], [v0.5.5][reline-v0.5.5], [v0.5.6][reline-v0.5.6], [v0.5.7][reline-v0.5.7], [v0.5.8][reline-v0.5.8], [v0.5.9][reline-v0.5.9], [v0.5.10][reline-v0.5.10], [v0.5.11][reline-v0.5.11], [v0.5.12][reline-v0.5.12], [v0.6.0][reline-v0.6.0]
resolv 0.6.0
- 0.3.0 to [v0.4.0][resolv-v0.4.0], [v0.5.0][resolv-v0.5.0], [v0.6.0][resolv-v0.6.0]
securerandom 0.4.1
- 0.3.1 to [v0.3.2][securerandom-v0.3.2], [v0.4.0][securerandom-v0.4.0], [v0.4.1][securerandom-v0.4.1]
set 1.1.1
- 1.1.0 to [v1.1.1][set-v1.1.1]
shellwords 0.2.2
- 0.2.0 to [v0.2.1][shellwords-v0.2.1], [v0.2.2][shellwords-v0.2.2]
singleton 0.3.0
- 0.2.0 to [v0.3.0][singleton-v0.3.0]
stringio 3.1.2
- 3.1.0 to [v3.1.1][stringio-v3.1.1], [v3.1.2][stringio-v3.1.2]
strscan 3.1.2
- 3.0.7 to [v3.0.8][strscan-v3.0.8], [v3.0.9][strscan-v3.0.9], [v3.1.0][strscan-v3.1.0], [v3.1.1][strscan-v3.1.1], [v3.1.2][strscan-v3.1.2]
syntax_suggest 2.0.2
- 2.0.0 to [v2.0.1][syntax_suggest-v2.0.1], [v2.0.2][syntax_suggest-v2.0.2]
tempfile 0.3.1
- 0.2.1 to [v0.3.0][tempfile-v0.3.0], [v0.3.1][tempfile-v0.3.1]
time 0.4.1
- 0.3.0 to [v0.4.0][time-v0.4.0], [v0.4.1][time-v0.4.1]
timeout 0.4.3
- 0.4.1 to [v0.4.2][timeout-v0.4.2], [v0.4.3][timeout-v0.4.3]
tmpdir 0.3.1
- 0.2.0 to [v0.3.0][tmpdir-v0.3.0], [v0.3.1][tmpdir-v0.3.1]
uri 1.0.2
- 0.13.0 to [v0.13.1][uri-v0.13.1], [v1.0.0][uri-v1.0.0], [v1.0.1][uri-v1.0.1], [v1.0.2][uri-v1.0.2]
win32ole 1.9.1
- 1.8.10 to [v1.9.0][win32ole-v1.9.0], [v1.9.1][win32ole-v1.9.1]
yaml 0.4.0
- 0.3.0 to [v0.4.0][yaml-v0.4.0]
zlib 3.2.1
- 3.1.0 to [v3.1.1][zlib-v3.1.1], [v3.2.0][zlib-v3.2.0], [v3.2.1][zlib-v3.2.1]

The following bundled gem is added.

repl_type_completor 0.1.9

The following bundled gems are updated.

minitest 5.25.4
- 5.20.0 to [v5.25.4][minitest-v5.25.4]
power_assert 2.0.5
- 2.0.3 to [v2.0.4][power_assert-v2.0.4], [v2.0.5][power_assert-v2.0.5]
rake 13.2.1
- 13.1.0 to [v13.2.0][rake-v13.2.0], [v13.2.1][rake-v13.2.1]
test-unit 3.6.7
- 3.6.1 to [3.6.2][test-unit-3.6.2], [3.6.3][test-unit-3.6.3], [3.6.4][test-unit-3.6.4], [3.6.5][test-unit-3.6.5], [3.6.6][test-unit-3.6.6], [3.6.7][test-unit-3.6.7]
rexml 3.4.0
- 3.2.6 to [v3.2.7][rexml-v3.2.7], [v3.2.8][rexml-v3.2.8], [v3.2.9][rexml-v3.2.9], [v3.3.0][rexml-v3.3.0], [v3.3.1][rexml-v3.3.1], [v3.3.2][rexml-v3.3.2], [v3.3.3][rexml-v3.3.3], [v3.3.4][rexml-v3.3.4], [v3.3.5][rexml-v3.3.5], [v3.3.6][rexml-v3.3.6], [v3.3.7][rexml-v3.3.7], [v3.3.8][rexml-v3.3.8], [v3.3.9][rexml-v3.3.9], [v3.4.0][rexml-v3.4.0]
rss 0.3.1
- 0.3.0 to [0.3.1][rss-0.3.1]
net-ftp 0.3.8
- 0.3.3 to [v0.3.4][net-ftp-v0.3.4], [v0.3.5][net-ftp-v0.3.5], [v0.3.6][net-ftp-v0.3.6], [v0.3.7][net-ftp-v0.3.7], [v0.3.8][net-ftp-v0.3.8]
net-imap 0.5.4
- 0.4.9 to [v0.4.9.1][net-imap-v0.4.9.1], [v0.4.10][net-imap-v0.4.10], [v0.4.11][net-imap-v0.4.11], [v0.4.12][net-imap-v0.4.12], [v0.4.13][net-imap-v0.4.13], [v0.4.14][net-imap-v0.4.14], [v0.4.15][net-imap-v0.4.15], [v0.4.16][net-imap-v0.4.16], [v0.4.17][net-imap-v0.4.17], [v0.5.0][net-imap-v0.5.0], [v0.4.18][net-imap-v0.4.18], [v0.5.1][net-imap-v0.5.1], [v0.5.2][net-imap-v0.5.2], [v0.5.3][net-imap-v0.5.3], [v0.5.4][net-imap-v0.5.4]
net-smtp 0.5.0
- 0.4.0 to [v0.4.0.1][net-smtp-v0.4.0.1], [v0.5.0][net-smtp-v0.5.0]
prime 0.1.3
- 0.1.2 to [v0.1.3][prime-v0.1.3]
rbs 3.8.0
- 3.4.0 to [v3.4.1][rbs-v3.4.1], [v3.4.2][rbs-v3.4.2], [v3.4.3][rbs-v3.4.3], [v3.4.4][rbs-v3.4.4], [v3.5.0.pre.1][rbs-v3.5.0.pre.1], [v3.5.0.pre.2][rbs-v3.5.0.pre.2], [v3.5.0][rbs-v3.5.0], [v3.5.1][rbs-v3.5.1], [v3.5.2][rbs-v3.5.2], [v3.5.3][rbs-v3.5.3], [v3.6.0.dev.1][rbs-v3.6.0.dev.1], [v3.6.0.pre.1][rbs-v3.6.0.pre.1], [v3.6.0.pre.2][rbs-v3.6.0.pre.2], [v3.6.0.pre.3][rbs-v3.6.0.pre.3], [v3.6.0][rbs-v3.6.0], [v3.6.1][rbs-v3.6.1], [v3.7.0.dev.1][rbs-v3.7.0.dev.1], [v3.7.0.pre.1][rbs-v3.7.0.pre.1], [v3.7.0][rbs-v3.7.0], [v3.8.0.pre.1][rbs-v3.8.0.pre.1] [v3.8.0][rbs-v3.8.0]
typeprof 0.30.1
- 0.21.9 to [v0.30.1][typeprof-v0.30.1]
debug 1.10.0
- 1.9.1 to [v1.9.2][debug-v1.9.2], [v1.10.0][debug-v1.10.0]
racc 1.8.1
- 1.7.3 to [v1.8.0][racc-v1.8.0], [v1.8.1][racc-v1.8.1]

The following bundled gems are promoted from default gems.

mutex_m 0.3.0
- 0.2.0 to [v0.3.0][mutex_m-v0.3.0]
getoptlong 0.2.1
base64 0.2.0
bigdecimal 3.1.8
- 3.1.5 to [v3.1.6][bigdecimal-v3.1.6], [v3.1.7][bigdecimal-v3.1.7], [v3.1.8][bigdecimal-v3.1.8]
observer 0.1.2
abbrev 0.1.2
resolv-replace 0.1.1
rinda 0.2.0
drb 2.2.1
- 2.2.0 to [v2.2.1][drb-v2.2.1]
nkf 0.2.0
- 0.1.3 to [v0.2.0][nkf-v0.2.0]
syslog 0.2.0
- 0.1.2 to [v0.2.0][syslog-v0.2.0]
csv 3.3.2
- 3.2.8 to [v3.2.9][csv-v3.2.9], [v3.3.0][csv-v3.3.0], [v3.3.1][csv-v3.3.1], [v3.3.2][csv-v3.3.2]

Supported platforms

Compatibility issues

Error messages and backtrace displays have been changed.

* Use a single quote instead of a backtick as an opening quote. [[Feature #16495]]
* Display a class name before a method name (only when the class has a permanent name). [[Feature #19117]]
* Extra `rescue`/`ensure` frames are no longer available on the backtrace. [[Feature #20275]]
* `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>'
  ```

Hash#inspect rendering have been changed. [[Bug #20433]]

* Symbol keys are displayed using the modern symbol key syntax: `"{user: 1}"`
* Other keys now have spaces around `=>`: `'{"user" => 1}'`, while previously they didn't: `'{"user"=>1}'`

Kernel#Float() now accepts a decimal string with decimal part omitted. [[Feature #20705]]

```ruby
Float("1.")    #=> 1.0 (previously, an ArgumentError was raised)
Float("1.E-1") #=> 0.1 (previously, an ArgumentError was raised)
```

String#to_f now accepts a decimal string with decimal part omitted. [[Feature #20705]] Note that the result changes when an exponent is specified.
```
```ruby
"1.".to_f    #=> 1.0
"1.E-1".to_f #=> 0.1 (previously, 1.0 was returned)
```
```
Refinement#refined_class has been removed. [[Feature #19714]]

Stdlib compatibility issues

DidYouMean

* `DidYouMean::SPELL_CHECKERS[]=` and `DidYouMean::SPELL_CHECKERS.merge!` are removed.

Net::HTTP

* Removed the following deprecated constants:
  * `Net::HTTP::ProxyMod`
  * `Net::NetPrivate::HTTPRequest`
  * `Net::HTTPInformationCode`
  * `Net::HTTPSuccessCode`
  * `Net::HTTPRedirectionCode`
  * `Net::HTTPRetriableCode`
  * `Net::HTTPClientErrorCode`
  * `Net::HTTPFatalErrorCode`
  * `Net::HTTPServerErrorCode`
  * `Net::HTTPResponseReceiver`
  * `Net::HTTPResponceReceiver`

These constants were deprecated from 2012.

Timeout

* Reject negative values for `Timeout.timeout`. [[Bug #20795]]

URI

* Switched default parser to RFC 3986 compliant from RFC 2396 compliant.
[[Bug #19266]]

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

The default parser is now Prism. To use the conventional parser, use the command-line argument --parser=parse.y. [[Feature #20564]]
Happy Eyeballs version 2 (RFC8305), an algorithm that ensures faster and more reliable connections by attempting IPv6 and IPv4 concurrently, is used in Socket.tcp and TCPSocket.new. To disable it globally, set the environment variable RUBY_TCP_NO_FAST_FALLBACK=1 or call Socket.tcp_fast_fallback=false. Or to disable it on a per-method basis, use the keyword argument fast_fallback: false. [[Feature #20108]] [[Feature #20782]]
Alternative garbage collector (GC) implementations can be loaded dynamically through the modular garbage collector feature. To enable this feature, configure Ruby with --with-modular-gc at build time. GC libraries can be loaded at runtime using the environment variable RUBY_GC_LIBRARY. [[Feature #20351]]
Ruby's built-in garbage collector has been split into a separate file at gc/default/default.c and interacts with Ruby using an API defined in gc/gc_impl.h. The built-in garbage collector can now also be built as a library using make modular-gc MODULAR_GC=default and enabled using the environment variable RUBY_GC_LIBRARY=default. [[Feature #20470]]
An experimental GC library is provided based on MMTk. This GC library can be built using make modular-gc MODULAR_GC=mmtk and enabled using the environment variable RUBY_GC_LIBRARY=mmtk. This requires the Rust toolchain on the build machine. [[Feature #20860]]

YJIT

New features

Command-line options
- --yjit-mem-size introduces a unified memory limit (default 128MiB) to track total YJIT memory usage, providing a more intuitive alternative to the old --yjit-exec-mem-size option.
- --yjit-trace-exits=COUNTER allows tracing of counted exits and fallbacks.
- --yjit-perf=codegen allows profiling of JIT code based on YJIT's codegen functions.
- --yjit-log enables a compilation log to track what gets compiled.
Ruby API
- RubyVM::YJIT.enable(log: true) also enables a compilation log.
- RubyVM::YJIT.log provides access to the tail of the compilation log at run-time.
YJIT stats
- RubyVM::YJIT.runtime_stats now always provides additional statistics on invalidation, inlining, and metadata encoding.
- RubyVM::YJIT.runtime_stats[:iseq_calls] is added to profile non-inlined Ruby method calls.
- RubyVM::YJIT.runtime_stats[:cfunc_calls] is truncated to the top 20 entries for better performance.

New optimizations

Compressed context reduces memory needed to store YJIT metadata
Allocate registers for local variables and Ruby method arguments

When YJIT is enabled, use more Core primitives written in Ruby:

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

Ability to inline small/trivial methods such as:

* Empty methods
* Methods returning a constant
* Methods returning `self`
* Methods directly returning an argument

Specialized codegen for many more runtime methods
Optimize String#getbyte, String#setbyte and other string methods
Optimize bitwise operations to speed up low-level bit/byte manipulation
Support shareable constants in multi-ractor mode
Various other incremental optimizations

Miscellaneous changes

Passing a block to a method which doesn't use the passed block will show a warning on verbose mode (-w). In connection with this, a new strict_unused_block warning category was introduced. Turn them on with -W:strict_unused_block or Warning[:strict_unused_block] = true. [[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]]