Update ruby to 4.0

.github/workflows/bundle-update.yml

@@ -16,7 +16,7 @@ jobs:
       - name: Set up Ruby
         uses: ruby/setup-ruby@v1
         with:
-          ruby-version: '4.0.0-preview3'
+          ruby-version: '4.0'
 
       - name: Set up git
         run: |

.github/workflows/c-check.yml

@@ -12,7 +12,7 @@ jobs:
       - uses: actions/checkout@v6
       - uses: ruby/setup-ruby@v1
         with:
-          ruby-version: "4.0.0-preview3"
+          ruby-version: "4.0"
           bundler-cache: none
       - name: Set working directory as safe
         run: git config --global --add safe.directory $(pwd)

.github/workflows/comments.yml

@@ -10,13 +10,13 @@ on:
 jobs:
   comments:
     runs-on: "ubuntu-latest"
-    env:
-      RUBY_COMMIT: v4.0.0-preview3
+    # env:
+    #   RUBY_COMMIT: v4.0.0-preview2
     steps:
       - uses: actions/checkout@v6
       - uses: ruby/setup-ruby@v1
         with:
-          ruby-version: "4.0.0-preview3"
+          ruby-version: "4.0.0"
           bundler: none
       - name: Install dependencies
         run: |

.github/workflows/ruby.yml

@@ -13,24 +13,24 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: ['3.2', '3.3', '3.4', '4.0.0-preview3', head]
+        ruby: ['3.2', '3.3', '3.4', '4.0', head]
         rubyopt: [""]
         job:
           - test
         include:
           - ruby: head
             job: stdlib_test rubocop
-          - ruby: "4.0.0-preview3"
+          - ruby: "4.0"
             job: stdlib_test
-          - ruby: "4.0.0-preview3"
+          - ruby: "4.0"
             job: test
             rubyopt: "--enable-frozen-string-literal"
-          - ruby: "4.0.0-preview3"
+          - ruby: "4.0"
             job: stdlib_test
             rubyopt: "--enable-frozen-string-literal"
-          - ruby: "4.0.0-preview3"
+          - ruby: "4.0"
             job: rubocop validate test_doc build test_generate_stdlib raap
-          - ruby: "4.0.0-preview3"
+          - ruby: "4.0"
             job: typecheck_test
     env:
       RANDOMIZE_STDLIB_TEST_ORDER: "true"
@@ -74,7 +74,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: ['4.0.0-preview3', head]
+        ruby: ['4.0', head]
     steps:
       - uses: actions/checkout@v6
       - name: Install dependencies
@@ -100,4 +100,3 @@ jobs:
         run: |
           bin/setup
       - run: bundle exec rake clean compile_c99
-

bin/generate_docs.sh

@@ -3,7 +3,14 @@
 set -ex
 
 if [ -z ${RUBY_COMMIT} ]; then
-  RUBY_COMMIT=v`ruby -e 'puts RUBY_VERSION.gsub(".", "_")'`
+  RUBY_COMMIT=v`ruby -e '
+case
+when RUBY_VERSION >= "4.0.0"
+  puts RUBY_VERSION
+else
+  puts RUBY_VERSION.gsub(".", "_")
+end
+'`
 fi
 
 if [ -z ${RBS_RDOC_BASE_DIR} ]; then

core/array.rbs

@@ -2029,14 +2029,12 @@ class Array[unchecked out Elem] < Object
   # With a block given, calls the block with successive elements of the array;
   # returns the first element for which the block returns a truthy value:
   #
-  #     (0..9).find {|element| element > 2}                # => 3
+  #     [1, 3, 5].find {|element| element > 2}                # => 3
   #
   # If no such element is found, calls `if_none_proc` and returns its return
   # value.
   #
-  #     (0..9).find(proc {false}) {|element| element > 12} # => false
-  #     {foo: 0, bar: 1, baz: 2}.find {|key, value| key.start_with?('b') }            # => [:bar, 1]
-  #     {foo: 0, bar: 1, baz: 2}.find(proc {[]}) {|key, value| key.start_with?('c') } # => []
+  #     [1, 3, 5].find(proc {-1}) {|element| element > 12} # => -1
   #
   # With no block given, returns an Enumerator.
   #
@@ -3022,17 +3020,15 @@ class Array[unchecked out Elem] < Object
   # Returns the last element for which the block returns a truthy value.
   #
   # With a block given, calls the block with successive elements of the array in
-  # reverse order; returns the last element for which the block returns a truthy
+  # reverse order; returns the first element for which the block returns a truthy
   # value:
   #
-  #     (0..9).rfind {|element| element < 5}                # => 4
+  #     [1, 2, 3, 4, 5, 6].rfind {|element| element < 5}       # => 4
   #
   # If no such element is found, calls `if_none_proc` and returns its return
   # value.
   #
-  #     (0..9).rfind(proc {false}) {|element| element < -2} # => false
-  #     {foo: 0, bar: 1, baz: 2}.rfind {|key, value| key.start_with?('b') }            # => [:baz, 2]
-  #     {foo: 0, bar: 1, baz: 2}.rfind(proc {[]}) {|key, value| key.start_with?('c') } # => []
+  #     [1, 2, 3, 4].rfind(proc {0}) {|element| element < -2}  # => 0
   #
   # With no block given, returns an Enumerator.
   #

core/comparable.rbs

@@ -55,19 +55,26 @@
 module Comparable : _WithSpaceshipOperator
   # <!--
   #   rdoc-file=compar.c
-  #   - obj < other    -> true or false
+  #   - self < other -> true or false
   # -->
-  # Compares two objects based on the receiver's `<=>` method, returning true if
-  # it returns a value less than 0.
+  # Returns whether `self` is "less than" `other`; equivalent to `(self <=> other)
+  # < 0`:
+  #
+  #     'foo' < 'foo'  # => false
+  #     'foo' < 'food' # => true
   #
   def <: (untyped other) -> bool
 
   # <!--
   #   rdoc-file=compar.c
-  #   - obj <= other    -> true or false
+  #   - self <= other -> true or false
   # -->
-  # Compares two objects based on the receiver's `<=>` method, returning true if
-  # it returns a value less than or equal to 0.
+  # Returns whether `self` is "less than or equal to" `other`; equivalent to
+  # `(self <=> other) <= 0`:
+  #
+  #     'foo' <= 'foo'  # => true
+  #     'foo' <= 'food' # => true
+  #     'food' <= 'foo' # => false
   #
   def <=: (untyped other) -> bool
 

core/complex.rbs

@@ -277,15 +277,16 @@ class Complex < Numeric
 
   # <!--
   #   rdoc-file=complex.c
-  #   - complex <=> object -> -1, 0, 1, or nil
+  #   - self <=> other -> -1, 0, 1, or nil
   # -->
+  # Compares `self` and `other`.
+  #
   # Returns:
   #
-  # *   `self.real <=> object.real` if both of the following are true:
+  # *   `self.real <=> other.real` if both of the following are true:
   #
   #     *   `self.imag == 0`.
-  #     *   `object.imag == 0`. # Always true if object is numeric but not
-  #         complex.
+  #     *   `other.imag == 0` (always true if `other` is numeric but not complex).
   #
   # *   `nil` otherwise.
   #
@@ -298,6 +299,9 @@ class Complex < Numeric
   #     Complex.rect(1) <=> Complex.rect(1, 1) # => nil # object.imag not zero.
   #     Complex.rect(1) <=> 'Foo'              # => nil # object.imag not defined.
   #
+  # Class Complex includes module Comparable, each of whose methods uses
+  # Complex#<=> for comparison.
+  #
   def <=>: (untyped) -> Integer?
 
   # <!--

core/dir.rbs

@@ -171,7 +171,7 @@ class Dir
   # system's encoding is used:
   #
   #     Dir.new('.').read.encoding                       # => #<Encoding:UTF-8>
-  #     Dir.new('.', encoding: 'US-ASCII').read.encoding # => #<Encoding:US-ASCII>
+  #     Dir.new('.', encoding: Encoding::US_ASCI).read.encoding # => #<Encoding:US-ASCII>
   #
   def initialize: (path dir, ?encoding: encoding?) -> void
 
@@ -704,7 +704,7 @@ class Dir
   # system's encoding is used:
   #
   #     Dir.open('.').read.encoding                       # => #<Encoding:UTF-8>
-  #     Dir.open('.', encoding: 'US-ASCII').read.encoding # => #<Encoding:US-ASCII>
+  #     Dir.open('.', encoding: Encoding::US_ASCII).read.encoding # => #<Encoding:US-ASCII>
   #
   def self.open: (path dirname, ?encoding: encoding?) -> instance
                | [U] (path dirname, ?encoding: encoding?) { (instance) -> U } -> U

core/enumerator.rbs

@@ -186,6 +186,12 @@ class Enumerator[unchecked out Elem, out Return = void] < Object
   #     }
   #     traverser.size  # => 4
   #
+  #     # Finite enumerator with unknown size
+  #     calendar = Enumerator.produce(Date.today, size: nil) {
+  #       it.monday? ? raise(StopIteration) : it + 1
+  #     }
+  #     calendar.size  # => nil
+  #
   def self.produce: [T] () { (T? prev) -> T } -> Enumerator[T, bot]
                   | [T] (T initial) { (T prev) -> T } -> Enumerator[T, bot]
 
@@ -463,6 +469,25 @@ class Enumerator[unchecked out Elem, out Return = void] < Object
   #     loop.size # => Float::INFINITY
   #     (1..100).drop_while.size # => nil
   #
+  # Note that enumerator size might be inaccurate, and should be rather treated as
+  # a hint. For example, there is no check that the size provided to ::new is
+  # accurate:
+  #
+  #     e = Enumerator.new(5) { |y| 2.times { y << it} }
+  #     e.size # => 5
+  #     e.to_a.size # => 2
+  #
+  # Another example is an enumerator created by ::produce without a `size`
+  # argument. Such enumerators return `Infinity` for size, but this is inaccurate
+  # if the passed block raises StopIteration:
+  #
+  #     e = Enumerator.produce(1) { it + 1 }
+  #     e.size # => Infinity
+  #
+  #     e = Enumerator.produce(1) { it > 3 ? raise(StopIteration) : it + 1 }
+  #     e.size # => Infinity
+  #     e.to_a.size # => 4
+  #
   def size: () -> (Integer | Float)?
 
   # <!--

core/fiber.rbs

@@ -404,27 +404,35 @@ class Fiber < Object
 
   # <!--
   #   rdoc-file=cont.c
-  #   - fiber.raise                                 -> obj
-  #   - fiber.raise(string)                         -> obj
-  #   - fiber.raise(exception [, string [, array]]) -> obj
+  #   - raise(exception, message = exception.to_s, backtrace = nil, cause: $!)
+  #   - raise(message = nil, cause: $!)
   # -->
   # Raises an exception in the fiber at the point at which the last `Fiber.yield`
-  # was called. If the fiber has not been started or has already run to
-  # completion, raises `FiberError`. If the fiber is yielding, it is resumed. If
-  # it is transferring, it is transferred into. But if it is resuming, raises
-  # `FiberError`.
-  #
-  # With no arguments, raises a `RuntimeError`. With a single `String` argument,
-  # raises a `RuntimeError` with the string as a message.  Otherwise, the first
-  # parameter should be the name of an `Exception` class (or an object that
-  # returns an `Exception` object when sent an `exception` message). The optional
-  # second parameter sets the message associated with the exception, and the third
-  # parameter is an array of callback information. Exceptions are caught by the
-  # `rescue` clause of `begin...end` blocks.
+  # was called.
+  #
+  #     f = Fiber.new {
+  #       puts "Before the yield"
+  #       Fiber.yield 1 # -- exception will be raised here
+  #       puts "After the yield"
+  #     }
+  #
+  #     p f.resume
+  #     f.raise "Gotcha"
+  #
+  # Output
+  #
+  #     Before the first yield
+  #     1
+  #     t.rb:8:in 'Fiber.yield': Gotcha (RuntimeError)
+  #       from t.rb:8:in 'block in <main>'
+  #
+  # If the fiber has not been started or has already run to completion, raises
+  # `FiberError`. If the fiber is yielding, it is resumed. If it is transferring,
+  # it is transferred into. But if it is resuming, raises `FiberError`.
   #
   # Raises `FiberError` if called on a Fiber belonging to another `Thread`.
   #
-  # See Kernel#raise for more information.
+  # See Kernel#raise for more information on arguments.
   #
   def raise: (?string msg, ?cause: Exception?) -> untyped
            | (_Exception, ?string msg, ?Array[string] | Array[Thread::Backtrace::Location] | nil backtrace, ?cause: Exception?) -> untyped

core/file.rbs

@@ -2455,16 +2455,31 @@ class File::Stat < Object
 
   # <!--
   #   rdoc-file=file.c
-  #   - stat <=> other_stat    -> -1, 0, 1, nil
+  #   - self <=> other -> -1, 0, 1, or nil
   # -->
-  # Compares File::Stat objects by comparing their respective modification times.
+  # Compares `self` and `other`, by comparing their modification times; that is,
+  # by comparing `self.mtime` and `other.mtime`.
   #
-  # `nil` is returned if `other_stat` is not a File::Stat object
+  # Returns:
   #
-  #     f1 = File.new("f1", "w")
-  #     sleep 1
-  #     f2 = File.new("f2", "w")
-  #     f1.stat <=> f2.stat   #=> -1
+  # *   `-1`, if `self.mtime` is earlier.
+  # *   `0`, if the two values are equal.
+  # *   `1`, if `self.mtime` is later.
+  # *   `nil`, if `other` is not a File::Stat object.
+  #
+  # Examples:
+  #
+  #     stat0 = File.stat('README.md')
+  #     stat1 = File.stat('NEWS.md')
+  #     stat0.mtime         # => 2025-12-20 15:33:05.6972341 -0600
+  #     stat1.mtime         # => 2025-12-20 16:02:08.2672945 -0600
+  #     stat0 <=> stat1     # => -1
+  #     stat0 <=> stat0.dup # => 0
+  #     stat1 <=> stat0     # => 1
+  #     stat0 <=> :foo      # => nil
+  #
+  # Class File::Stat includes module Comparable, each of whose methods uses
+  # File::Stat#<=> for comparison.
   #
   def <=>: (File::Stat other) -> Integer
          | (untyped) -> nil