struct.rbs

# <!-- rdoc-file=struct.c -->
# Class Struct provides a convenient way to create a simple class that can store
# and fetch values.
#
# This example creates a subclass of `Struct`, `Struct::Customer`; the first
# argument, a string, is the name of the subclass; the other arguments, symbols,
# determine the *members* of the new subclass.
#
#     Customer = Struct.new('Customer', :name, :address, :zip)
#     Customer.name       # => "Struct::Customer"
#     Customer.class      # => Class
#     Customer.superclass # => Struct
#
# Corresponding to each member are two methods, a writer and a reader, that
# store and fetch values:
#
#     methods = Customer.instance_methods false
#     methods # => [:zip, :address=, :zip=, :address, :name, :name=]
#
# An instance of the subclass may be created, and its members assigned values,
# via method `::new`:
#
#     joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
#     joe # => #<struct Struct::Customer name="Joe Smith", address="123 Maple, Anytown NC", zip=12345>
#
# The member values may be managed thus:
#
#     joe.name    # => "Joe Smith"
#     joe.name = 'Joseph Smith'
#     joe.name    # => "Joseph Smith"
#
# And thus; note that member name may be expressed as either a string or a
# symbol:
#
#     joe[:name]  # => "Joseph Smith"
#     joe[:name] = 'Joseph Smith, Jr.'
#     joe['name'] # => "Joseph Smith, Jr."
#
# See Struct::new.
#
# ## What's Here
#
# First, what's elsewhere. Class Struct:
#
# *   Inherits from [class Object](rdoc-ref:Object@What-27s+Here).
# *   Includes [module Enumerable](rdoc-ref:Enumerable@What-27s+Here), which
#     provides dozens of additional methods.
#
# See also Data, which is a somewhat similar, but stricter concept for defining
# immutable value objects.
#
# Here, class Struct provides methods that are useful for:
#
# *   [Creating a Struct
#     Subclass](rdoc-ref:Struct@Methods+for+Creating+a+Struct+Subclass)
# *   [Querying](rdoc-ref:Struct@Methods+for+Querying)
# *   [Comparing](rdoc-ref:Struct@Methods+for+Comparing)
# *   [Fetching](rdoc-ref:Struct@Methods+for+Fetching)
# *   [Assigning](rdoc-ref:Struct@Methods+for+Assigning)
# *   [Iterating](rdoc-ref:Struct@Methods+for+Iterating)
# *   [Converting](rdoc-ref:Struct@Methods+for+Converting)
#
# ### Methods for Creating a Struct Subclass
#
# *   ::new: Returns a new subclass of Struct.
#
# ### Methods for Querying
#
# *   #hash: Returns the integer hash code.
# *   #size (aliased as #length): Returns the number of members.
#
# ### Methods for Comparing
#
# *   #==: Returns whether a given object is equal to `self`, using `==` to
#     compare member values.
# *   #eql?: Returns whether a given object is equal to `self`, using `eql?` to
#     compare member values.
#
# ### Methods for Fetching
#
# *   #[]: Returns the value associated with a given member name.
# *   #to_a (aliased as #values, #deconstruct): Returns the member values in
#     `self` as an array.
# *   #deconstruct_keys: Returns a hash of the name/value pairs for given member
#     names.
# *   #dig: Returns the object in nested objects that is specified by a given
#     member name and additional arguments.
# *   #members: Returns an array of the member names.
# *   #select (aliased as #filter): Returns an array of member values from
#     `self`, as selected by the given block.
# *   #values_at: Returns an array containing values for given member names.
#
# ### Methods for Assigning
#
# *   #[]=: Assigns a given value to a given member name.
#
# ### Methods for Iterating
#
# *   #each: Calls a given block with each member name.
# *   #each_pair: Calls a given block with each member name/value pair.
#
# ### Methods for Converting
#
# *   #inspect (aliased as #to_s): Returns a string representation of `self`.
# *   #to_h: Returns a hash of the member name/value pairs in `self`.
#
class Struct[Elem]
  include Enumerable[Elem]

  # The types that can be used when "indexing" into a `Struct` via `[]`, `[]=`, `dig`, and
  # `deconstruct_keys`.
  #
  type index = String | Symbol | int

  # <!--
  #   rdoc-file=struct.c
  #   - Struct.new(*member_names, keyword_init: nil){|Struct_subclass| ... } -> Struct_subclass
  #   - Struct.new(class_name, *member_names, keyword_init: nil){|Struct_subclass| ... } -> Struct_subclass
  #   - Struct_subclass.new(*member_names) -> Struct_subclass_instance
  #   - Struct_subclass.new(**member_names) -> Struct_subclass_instance
  # -->
  # `Struct.new` returns a new subclass of `Struct`.  The new subclass:
  #
  # *   May be anonymous, or may have the name given by `class_name`.
  # *   May have members as given by `member_names`.
  # *   May have initialization via ordinary arguments, or via keyword arguments
  #
  # The new subclass has its own method `::new`; thus:
  #
  #     Foo = Struct.new('Foo', :foo, :bar) # => Struct::Foo
  #     f = Foo.new(0, 1)                   # => #<struct Struct::Foo foo=0, bar=1>
  #
  # **Class Name**
  #
  # With string argument `class_name`, returns a new subclass of `Struct` named
  # `Struct::<em>class_name</em>`:
  #
  #     Foo = Struct.new('Foo', :foo, :bar) # => Struct::Foo
  #     Foo.name                            # => "Struct::Foo"
  #     Foo.superclass                      # => Struct
  #
  # Without string argument `class_name`, returns a new anonymous subclass of
  # `Struct`:
  #
  #     Struct.new(:foo, :bar).name # => nil
  #
  # **Block**
  #
  # With a block given, the created subclass is yielded to the block:
  #
  #     Customer = Struct.new('Customer', :name, :address) do |new_class|
  #       p "The new subclass is #{new_class}"
  #       def greeting
  #         "Hello #{name} at #{address}"
  #       end
  #     end           # => Struct::Customer
  #     dave = Customer.new('Dave', '123 Main')
  #     dave # =>     #<struct Struct::Customer name="Dave", address="123 Main">
  #     dave.greeting # => "Hello Dave at 123 Main"
  #
  # Output, from `Struct.new`:
  #
  #     "The new subclass is Struct::Customer"
  #
  # **Member Names**
  #
  # Symbol arguments `member_names` determines the members of the new subclass:
  #
  #     Struct.new(:foo, :bar).members        # => [:foo, :bar]
  #     Struct.new('Foo', :foo, :bar).members # => [:foo, :bar]
  #
  # The new subclass has instance methods corresponding to `member_names`:
  #
  #     Foo = Struct.new('Foo', :foo, :bar)
  #     Foo.instance_methods(false) # => [:foo, :bar, :foo=, :bar=]
  #     f = Foo.new                 # => #<struct Struct::Foo foo=nil, bar=nil>
  #     f.foo                       # => nil
  #     f.foo = 0                   # => 0
  #     f.bar                       # => nil
  #     f.bar = 1                   # => 1
  #     f                           # => #<struct Struct::Foo foo=0, bar=1>
  #
  # **Singleton Methods**
  #
  # A subclass returned by Struct.new has these singleton methods:
  #
  # *   Method `::new ` creates an instance of the subclass:
  #
  #         Foo.new          # => #<struct Struct::Foo foo=nil, bar=nil>
  #         Foo.new(0)       # => #<struct Struct::Foo foo=0, bar=nil>
  #         Foo.new(0, 1)    # => #<struct Struct::Foo foo=0, bar=1>
  #         Foo.new(0, 1, 2) # Raises ArgumentError: struct size differs
  #
  #         # Initialization with keyword arguments:
  #         Foo.new(foo: 0)         # => #<struct Struct::Foo foo=0, bar=nil>
  #         Foo.new(foo: 0, bar: 1) # => #<struct Struct::Foo foo=0, bar=1>
  #         Foo.new(foo: 0, bar: 1, baz: 2)
  #         # Raises ArgumentError: unknown keywords: baz
  #
  # *   Method `:inspect` returns a string representation of the subclass:
  #
  #         Foo.inspect
  #         # => "Struct::Foo"
  #
  # *   Method `::members` returns an array of the member names:
  #
  #         Foo.members # => [:foo, :bar]
  #
  # **Keyword Argument**
  #
  # By default, the arguments for initializing an instance of the new subclass can
  # be both positional and keyword arguments.
  #
  # Optional keyword argument `keyword_init:` allows to force only one type of
  # arguments to be accepted:
  #
  #     KeywordsOnly = Struct.new(:foo, :bar, keyword_init: true)
  #     KeywordsOnly.new(bar: 1, foo: 0)
  #     # => #<struct KeywordsOnly foo=0, bar=1>
  #     KeywordsOnly.new(0, 1)
  #     # Raises ArgumentError: wrong number of arguments
  #
  #     PositionalOnly = Struct.new(:foo, :bar, keyword_init: false)
  #     PositionalOnly.new(0, 1)
  #     # => #<struct PositionalOnly foo=0, bar=1>
  #     PositionalOnly.new(bar: 1, foo: 0)
  #     # => #<struct PositionalOnly foo={:foo=>1, :bar=>2}, bar=nil>
  #     # Note that no error is raised, but arguments treated as one hash value
  #
  #     # Same as not providing keyword_init:
  #     Any = Struct.new(:foo, :bar, keyword_init: nil)
  #     Any.new(foo: 1, bar: 2)
  #     # => #<struct Any foo=1, bar=2>
  #     Any.new(1, 2)
  #     # => #<struct Any foo=1, bar=2>
  #
  def self.new: (string? classname, *interned fields, ?keyword_init: boolish?) ?{ (singleton(Struct)) [self: singleton(Struct)] -> void } -> untyped
              | (Symbol field1, *interned fields, ?keyword_init: boolish?) ?{ (singleton(Struct)) [self: singleton(Struct)] -> void } -> untyped

  # <!--
  #   rdoc-file=struct.c
  #   - StructClass::members -> array_of_symbols
  # -->
  # Returns the member names of the Struct descendant as an array:
  #
  #     Customer = Struct.new(:name, :address, :zip)
  #     Customer.members # => [:name, :address, :zip]
  #
  def self.members: () -> Array[Symbol]

  # <!--
  #   rdoc-file=struct.c
  #   - StructClass::keyword_init? -> true or falsy value
  # -->
  # Returns `true` if the class was initialized with `keyword_init: true`.
  # Otherwise returns `nil` or `false`.
  #
  # Examples:
  #     Foo = Struct.new(:a)
  #     Foo.keyword_init? # => nil
  #     Bar = Struct.new(:a, keyword_init: true)
  #     Bar.keyword_init? # => true
  #     Baz = Struct.new(:a, keyword_init: false)
  #     Baz.keyword_init? # => false
  #
  def self.keyword_init?: () -> bool?

  # <!--
  #   rdoc-file=struct.c
  #   - self == other -> true or false
  # -->
  # Returns  `true` if and only if the following are true; otherwise returns
  # `false`:
  #
  # *   `other.class == self.class`.
  # *   For each member name `name`, `other.name == self.name`.
  #
  # Examples:
  #
  #     Customer = Struct.new(:name, :address, :zip)
  #     joe    = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
  #     joe_jr = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
  #     joe_jr == joe # => true
  #     joe_jr[:name] = 'Joe Smith, Jr.'
  #     # => "Joe Smith, Jr."
  #     joe_jr == joe # => false
  #
  def ==: (untyped other) -> bool

  # <!--
  #   rdoc-file=struct.c
  #   - eql?(other) -> true or false
  # -->
  # Returns `true` if and only if the following are true; otherwise returns
  # `false`:
  #
  # *   `other.class == self.class`.
  # *   For each member name `name`, `other.name.eql?(self.name)`.
  #
  #         Customer = Struct.new(:name, :address, :zip)
  #         joe    = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
  #         joe_jr = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
  #         joe_jr.eql?(joe) # => true
  #         joe_jr[:name] = 'Joe Smith, Jr.'
  #         joe_jr.eql?(joe) # => false
  #
  # Related: Object#==.
  #
  def eql?: (untyped other) -> bool

  # <!--
  #   rdoc-file=struct.c
  #   - hash -> integer
  # -->
  # Returns the integer hash value for `self`.
  #
  # Two structs of the same class and with the same content will have the same
  # hash code (and will compare using Struct#eql?):
  #
  #     Customer = Struct.new(:name, :address, :zip)
  #     joe    = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
  #     joe_jr = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
  #     joe.hash == joe_jr.hash # => true
  #     joe_jr[:name] = 'Joe Smith, Jr.'
  #     joe.hash == joe_jr.hash # => false
  #
  # Related: Object#hash.
  #
  def hash: () -> Integer

  # <!--
  #   rdoc-file=struct.c
  #   - inspect -> string
  # -->
  # Returns a string representation of `self`:
  #
  #     Customer = Struct.new(:name, :address, :zip) # => Customer
  #     joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
  #     joe.inspect # => "#<struct Customer name=\"Joe Smith\", address=\"123 Maple, Anytown NC\", zip=12345>"
  #
  def inspect: () -> String

  # <!-- rdoc-file=struct.c -->
  # Returns a string representation of `self`:
  #
  #     Customer = Struct.new(:name, :address, :zip) # => Customer
  #     joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
  #     joe.inspect # => "#<struct Customer name=\"Joe Smith\", address=\"123 Maple, Anytown NC\", zip=12345>"
  #
  alias to_s inspect

  # <!--
  #   rdoc-file=struct.c
  #   - to_a     -> array
  # -->
  # Returns the values in `self` as an array:
  #
  #     Customer = Struct.new(:name, :address, :zip)
  #     joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
  #     joe.to_a # => ["Joe Smith", "123 Maple, Anytown NC", 12345]
  #
  # Related: #members.
  #
  def to_a: () -> Array[Elem]

  # <!--
  #   rdoc-file=struct.c
  #   - to_h -> hash
  #   - to_h {|name, value| ... } -> hash
  # -->
  # Returns a hash containing the name and value for each member:
  #
  #     Customer = Struct.new(:name, :address, :zip)
  #     joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
  #     h = joe.to_h
  #     h # => {:name=>"Joe Smith", :address=>"123 Maple, Anytown NC", :zip=>12345}
  #
  # If a block is given, it is called with each name/value pair; the block should
  # return a 2-element array whose elements will become a key/value pair in the
  # returned hash:
  #
  #     h = joe.to_h{|name, value| [name.upcase, value.to_s.upcase]}
  #     h # => {:NAME=>"JOE SMITH", :ADDRESS=>"123 MAPLE, ANYTOWN NC", :ZIP=>"12345"}
  #
  # Raises ArgumentError if the block returns an inappropriate value.
  #
  def to_h: () -> Hash[Symbol, Elem]
          | [K, V] () { (Symbol key, Elem value) -> [K, V] } -> Hash[K, V]

  # <!-- rdoc-file=struct.c -->
  # Returns the values in `self` as an array:
  #
  #     Customer = Struct.new(:name, :address, :zip)
  #     joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
  #     joe.to_a # => ["Joe Smith", "123 Maple, Anytown NC", 12345]
  #
  # Related: #members.
  #
  alias values to_a

  # <!--
  #   rdoc-file=struct.c
  #   - size -> integer
  # -->
  # Returns the number of members.
  #
  #     Customer = Struct.new(:name, :address, :zip)
  #     joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
  #     joe.size #=> 3
  #
  def size: () -> Integer

  # <!-- rdoc-file=struct.c -->
  # Returns the number of members.
  #
  #     Customer = Struct.new(:name, :address, :zip)
  #     joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
  #     joe.size #=> 3
  #
  alias length size

  # <!--
  #   rdoc-file=struct.c
  #   - each {|value| ... } -> self
  #   - each -> enumerator
  # -->
  # Calls the given block with the value of each member; returns `self`:
  #
  #     Customer = Struct.new(:name, :address, :zip)
  #     joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
  #     joe.each {|value| p value }
  #
  # Output:
  #
  #     "Joe Smith"
  #     "123 Maple, Anytown NC"
  #     12345
  #
  # Returns an Enumerator if no block is given.
  #
  # Related: #each_pair.
  #
  def each: () -> Enumerator[Elem, self]
          | () { (Elem value) -> void } -> self

  # <!--
  #   rdoc-file=struct.c
  #   - each_pair {|(name, value)| ... } -> self
  #   - each_pair -> enumerator
  # -->
  # Calls the given block with each member name/value pair; returns `self`:
  #
  #     Customer = Struct.new(:name, :address, :zip) # => Customer
  #     joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
  #     joe.each_pair {|(name, value)| p "#{name} => #{value}" }
  #
  # Output:
  #
  #     "name => Joe Smith"
  #     "address => 123 Maple, Anytown NC"
  #     "zip => 12345"
  #
  # Returns an Enumerator if no block is given.
  #
  # Related: #each.
  #
  def each_pair: () -> Enumerator[[Symbol, Elem], self]
               | () { ([Symbol, Elem] key_value) -> void } -> self

  # <!--
  #   rdoc-file=struct.c
  #   - struct[name] -> object
  #   - struct[n] -> object
  # -->
  # Returns a value from `self`.
  #
  # With symbol or string argument `name` given, returns the value for the named
  # member:
  #
  #     Customer = Struct.new(:name, :address, :zip)
  #     joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
  #     joe[:zip] # => 12345
  #
  # Raises NameError if `name` is not the name of a member.
  #
  # With integer argument `n` given, returns `self.values[n]` if `n` is in range;
  # see Array@Array+Indexes:
  #
  #     joe[2]  # => 12345
  #     joe[-2] # => "123 Maple, Anytown NC"
  #
  # Raises IndexError if `n` is out of range.
  #
  def []: (index name_or_position) -> Elem

  # <!--
  #   rdoc-file=struct.c
  #   - struct[name] = value -> value
  #   - struct[n] = value -> value
  # -->
  # Assigns a value to a member.
  #
  # With symbol or string argument `name` given, assigns the given `value` to the
  # named member; returns `value`:
  #
  #     Customer = Struct.new(:name, :address, :zip)
  #     joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
  #     joe[:zip] = 54321 # => 54321
  #     joe # => #<struct Customer name="Joe Smith", address="123 Maple, Anytown NC", zip=54321>
  #
  # Raises NameError if `name` is not the name of a member.
  #
  # With integer argument `n` given, assigns the given `value` to the `n`-th
  # member if `n` is in range; see Array@Array+Indexes:
  #
  #     joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
  #     joe[2] = 54321           # => 54321
  #     joe[-3] = 'Joseph Smith' # => "Joseph Smith"
  #     joe # => #<struct Customer name="Joseph Smith", address="123 Maple, Anytown NC", zip=54321>
  #
  # Raises IndexError if `n` is out of range.
  #
  def []=: (index name_or_position, Elem value) -> Elem

  # <!--
  #   rdoc-file=struct.c
  #   - select {|value| ... } -> array
  #   - select -> enumerator
  # -->
  # With a block given, returns an array of values from `self` for which the block
  # returns a truthy value:
  #
  #     Customer = Struct.new(:name, :address, :zip)
  #     joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
  #     a = joe.select {|value| value.is_a?(String) }
  #     a # => ["Joe Smith", "123 Maple, Anytown NC"]
  #     a = joe.select {|value| value.is_a?(Integer) }
  #     a # => [12345]
  #
  # With no block given, returns an Enumerator.
  #
  def select: () -> Enumerator[Elem, Array[Elem]]
            | () { (Elem value) -> boolish } -> Array[Elem]

  # <!-- rdoc-file=struct.c -->
  # With a block given, returns an array of values from `self` for which the block
  # returns a truthy value:
  #
  #     Customer = Struct.new(:name, :address, :zip)
  #     joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
  #     a = joe.select {|value| value.is_a?(String) }
  #     a # => ["Joe Smith", "123 Maple, Anytown NC"]
  #     a = joe.select {|value| value.is_a?(Integer) }
  #     a # => [12345]
  #
  # With no block given, returns an Enumerator.
  #
  alias filter select

  # <!--
  #   rdoc-file=struct.c
  #   - values_at(*integers) -> array
  #   - values_at(integer_range) -> array
  # -->
  # Returns an array of values from `self`.
  #
  # With integer arguments `integers` given, returns an array containing each
  # value given by one of `integers`:
  #
  #     Customer = Struct.new(:name, :address, :zip)
  #     joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
  #     joe.values_at(0, 2)    # => ["Joe Smith", 12345]
  #     joe.values_at(2, 0)    # => [12345, "Joe Smith"]
  #     joe.values_at(2, 1, 0) # => [12345, "123 Maple, Anytown NC", "Joe Smith"]
  #     joe.values_at(0, -3)   # => ["Joe Smith", "Joe Smith"]
  #
  # Raises IndexError if any of `integers` is out of range; see
  # Array@Array+Indexes.
  #
  # With integer range argument `integer_range` given, returns an array containing
  # each value given by the elements of the range; fills with `nil` values for
  # range elements larger than the structure:
  #
  #     joe.values_at(0..2)
  #     # => ["Joe Smith", "123 Maple, Anytown NC", 12345]
  #     joe.values_at(-3..-1)
  #     # => ["Joe Smith", "123 Maple, Anytown NC", 12345]
  #     joe.values_at(1..4) # => ["123 Maple, Anytown NC", 12345, nil, nil]
  #
  # Raises RangeError if any element of the range is negative and out of range;
  # see Array@Array+Indexes.
  #
  def values_at: (*int | range[int?] positions) -> Array[Elem]

  # <!--
  #   rdoc-file=struct.c
  #   - members -> array_of_symbols
  # -->
  # Returns the member names from `self` as an array:
  #
  #     Customer = Struct.new(:name, :address, :zip)
  #     Customer.new.members # => [:name, :address, :zip]
  #
  # Related: #to_a.
  #
  def members: () -> Array[Symbol]

  # <!--
  #   rdoc-file=struct.c
  #   - dig(name, *identifiers) -> object
  #   - dig(n, *identifiers) -> object
  # -->
  # Finds and returns an object among nested objects. The nested objects may be
  # instances of various classes. See [Dig Methods](rdoc-ref:dig_methods.rdoc).
  #
  # Given symbol or string argument `name`, returns the object that is specified
  # by `name` and `identifiers`:
  #
  #     Foo = Struct.new(:a)
  #     f = Foo.new(Foo.new({b: [1, 2, 3]}))
  #     f.dig(:a) # => #<struct Foo a={:b=>[1, 2, 3]}>
  #     f.dig(:a, :a) # => {:b=>[1, 2, 3]}
  #     f.dig(:a, :a, :b) # => [1, 2, 3]
  #     f.dig(:a, :a, :b, 0) # => 1
  #     f.dig(:b, 0) # => nil
  #
  # Given integer argument `n`, returns the object that is specified by `n` and
  # `identifiers`:
  #
  #     f.dig(0) # => #<struct Foo a={:b=>[1, 2, 3]}>
  #     f.dig(0, 0) # => {:b=>[1, 2, 3]}
  #     f.dig(0, 0, :b) # => [1, 2, 3]
  #     f.dig(0, 0, :b, 0) # => 1
  #     f.dig(:b, 0) # => nil
  #
  def dig: (index name_or_position) -> Elem
         | (index name_or_position, untyped, *untyped) -> untyped

  # <!-- rdoc-file=struct.c -->
  # Returns the values in `self` as an array:
  #
  #     Customer = Struct.new(:name, :address, :zip)
  #     joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
  #     joe.to_a # => ["Joe Smith", "123 Maple, Anytown NC", 12345]
  #
  # Related: #members.
  #
  alias deconstruct to_a

  # <!--
  #   rdoc-file=struct.c
  #   - deconstruct_keys(array_of_names) -> hash
  # -->
  # Returns a hash of the name/value pairs for the given member names.
  #
  #     Customer = Struct.new(:name, :address, :zip)
  #     joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
  #     h = joe.deconstruct_keys([:zip, :address])
  #     h # => {:zip=>12345, :address=>"123 Maple, Anytown NC"}
  #
  # Returns all names and values if `array_of_names` is `nil`:
  #
  #     h = joe.deconstruct_keys(nil)
  #     h # => {:name=>"Joseph Smith, Jr.", :address=>"123 Maple, Anytown NC", :zip=>12345}
  #
  def deconstruct_keys: (Array[index & Hash::_Key]? indices) -> Hash[index & Hash::_Key, Elem]
end