# <!-- rdoc-file=object.c -->
# The class of the singleton object `nil`.
#
class NilClass
  public

  def !: () -> true

  # <!--
  #   rdoc-file=object.c
  #   - false & obj   -> false
  #   - nil & obj     -> false
  # -->
  # And---Returns `false`. *obj* is always evaluated as it is the argument to a
  # method call---there is no short-circuit evaluation in this case.
  #
  def &: (untyped obj) -> false

  # <!--
  #   rdoc-file=object.c
  #   - obj === other   -> true or false
  # -->
  # Case Equality -- For class Object, effectively the same as calling `#==`, but
  # typically overridden by descendants to provide meaningful semantics in `case`
  # statements.
  #
  def ===: (nil) -> true
         | (untyped obj) -> false

  # <!--
  #   rdoc-file=object.c
  #   - nil =~ other  -> nil
  # -->
  # Dummy pattern matching -- always returns nil.
  #
  def =~: (untyped obj) -> nil

  # <!--
  #   rdoc-file=object.c
  #   - false ^ obj    -> true or false
  #   - nil   ^ obj    -> true or false
  # -->
  # Exclusive Or---If *obj* is `nil` or `false`, returns `false`; otherwise,
  # returns `true`.
  #
  def ^: (nil) -> false
       | (false) -> false
       | (untyped obj) -> true

  # <!--
  #   rdoc-file=object.c
  #   - nil.inspect  -> "nil"
  # -->
  # Always returns the string "nil".
  #
  def inspect: () -> "nil"

  # <!--
  #   rdoc-file=object.c
  #   - nil.nil?               -> true
  # -->
  # Only the object *nil* responds `true` to `nil?`.
  #
  def nil?: () -> true

  # <!--
  #   rdoc-file=rational.c
  #   - nil.rationalize([eps])  ->  (0/1)
  # -->
  # Returns zero as a rational.  The optional argument `eps` is always ignored.
  #
  def rationalize: (?untyped eps) -> Rational

  # <!--
  #   rdoc-file=object.c
  #   - nil.to_a    -> []
  # -->
  # Always returns an empty array.
  #
  #     nil.to_a   #=> []
  #
  def to_a: () -> [ ]

  # <!--
  #   rdoc-file=complex.c
  #   - nil.to_c  ->  (0+0i)
  # -->
  # Returns zero as a complex.
  #
  def to_c: () -> Complex

  # <!--
  #   rdoc-file=nilclass.rb
  #   - nil.to_f    -> 0.0
  # -->
  # Always returns zero.
  #
  #     nil.to_f   #=> 0.0
  #
  def to_f: () -> Float

  # <!--
  #   rdoc-file=object.c
  #   - nil.to_h    -> {}
  # -->
  # Always returns an empty hash.
  #
  #     nil.to_h   #=> {}
  #
  def to_h: () -> ::Hash[untyped, untyped]

  # <!--
  #   rdoc-file=nilclass.rb
  #   - nil.to_i -> 0
  # -->
  # Always returns zero.
  #
  #     nil.to_i   #=> 0
  #
  def to_i: () -> 0

  # <!--
  #   rdoc-file=rational.c
  #   - nil.to_r  ->  (0/1)
  # -->
  # Returns zero as a rational.
  #
  def to_r: () -> Rational

  # <!--
  #   rdoc-file=object.c
  #   - nil.to_s    -> ""
  # -->
  # Always returns the empty string.
  #
  def to_s: () -> ""

  # <!--
  #   rdoc-file=object.c
  #   - false | obj   ->   true or false
  #   - nil   | obj   ->   true or false
  # -->
  # Or---Returns `false` if *obj* is `nil` or `false`; `true` otherwise.
  #
  def |: (nil) -> false
       | (false) -> false
       | (untyped obj) -> true

  def clone: (?freeze: true?) -> self
end