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# Objects of class Binding encapsulate the execution context at some particular
# place in the code and retain this context for future use. The variables,
# methods, value of `self`, and possibly an iterator block that can be accessed
# in this context are all retained. Binding objects can be created using
# Kernel#binding, and are made available to the callback of
# Kernel#set_trace_func and instances of TracePoint.
#
# These binding objects can be passed as the second argument of the Kernel#eval
# method, establishing an environment for the evaluation.
#
#     class Demo
#       def initialize(n)
#         @secret = n
#       end
#       def get_binding
#         binding
#       end
#     end
#
#     k1 = Demo.new(99)
#     b1 = k1.get_binding
#     k2 = Demo.new(-3)
#     b2 = k2.get_binding
#
#     eval("@secret", b1)   #=> 99
#     eval("@secret", b2)   #=> -3
#     eval("@secret")       #=> nil
#
# Binding objects have no class-specific methods.
#
class Binding
  public

  # Evaluates the Ruby expression(s) in *string*, in the *binding*'s context.  If
  # the optional *filename* and *lineno* parameters are present, they will be used
  # when reporting syntax errors.
  #
  #     def get_binding(param)
  #       binding
  #     end
  #     b = get_binding("hello")
  #     b.eval("param")   #=> "hello"
  #
  def eval: (String arg0, ?String filename, ?Integer lineno) -> untyped

  # Opens an IRB session where `binding.irb` is called which allows for
  # interactive debugging. You can call any methods or variables available in the
  # current scope, and mutate state if you need to.
  #
  # Given a Ruby file called `potato.rb` containing the following code:
  #
  #     class Potato
  #       def initialize
  #         @cooked = false
  #         binding.irb
  #         puts "Cooked potato: #{@cooked}"
  #       end
  #     end
  #
  #     Potato.new
  #
  # Running `ruby potato.rb` will open an IRB session where `binding.irb` is
  # called, and you will see the following:
  #
  #     $ ruby potato.rb
  #
  #     From: potato.rb @ line 4 :
  #
  #         1: class Potato
  #         2:   def initialize
  #         3:     @cooked = false
  #      => 4:     binding.irb
  #         5:     puts "Cooked potato: #{@cooked}"
  #         6:   end
  #         7: end
  #         8:
  #         9: Potato.new
  #
  #     irb(#<Potato:0x00007feea1916670>):001:0>
  #
  # You can type any valid Ruby code and it will be evaluated in the current
  # context. This allows you to debug without having to run your code repeatedly:
  #
  #     irb(#<Potato:0x00007feea1916670>):001:0> @cooked
  #     => false
  #     irb(#<Potato:0x00007feea1916670>):002:0> self.class
  #     => Potato
  #     irb(#<Potato:0x00007feea1916670>):003:0> caller.first
  #     => ".../2.5.1/lib/ruby/2.5.0/irb/workspace.rb:85:in `eval'"
  #     irb(#<Potato:0x00007feea1916670>):004:0> @cooked = true
  #     => true
  #
  # You can exit the IRB session with the `exit` command. Note that exiting will
  # resume execution where `binding.irb` had paused it, as you can see from the
  # output printed to standard output in this example:
  #
  #     irb(#<Potato:0x00007feea1916670>):005:0> exit
  #     Cooked potato: true
  #
  # See IRB@IRB+Usage for more information.
  #
  def irb: () -> void

  # Returns `true` if a local variable `symbol` exists.
  #
  #     def foo
  #       a = 1
  #       binding.local_variable_defined?(:a) #=> true
  #       binding.local_variable_defined?(:b) #=> false
  #     end
  #
  # This method is the short version of the following code:
  #
  #     binding.eval("defined?(#{symbol}) == 'local-variable'")
  #
  def local_variable_defined?: (String | Symbol symbol) -> bool

  # Returns the value of the local variable `symbol`.
  #
  #     def foo
  #       a = 1
  #       binding.local_variable_get(:a) #=> 1
  #       binding.local_variable_get(:b) #=> NameError
  #     end
  #
  # This method is the short version of the following code:
  #
  #     binding.eval("#{symbol}")
  #
  def local_variable_get: (String | Symbol symbol) -> untyped

  # Set local variable named `symbol` as `obj`.
  #
  #     def foo
  #       a = 1
  #       bind = binding
  #       bind.local_variable_set(:a, 2) # set existing local variable `a'
  #       bind.local_variable_set(:b, 3) # create new local variable `b'
  #                                      # `b' exists only in binding
  #
  #       p bind.local_variable_get(:a)  #=> 2
  #       p bind.local_variable_get(:b)  #=> 3
  #       p a                            #=> 2
  #       p b                            #=> NameError
  #     end
  #
  # This method behaves similarly to the following code:
  #
  #     binding.eval("#{symbol} = #{obj}")
  #
  # if `obj` can be dumped in Ruby code.
  #
  def local_variable_set: [U] (String | Symbol symbol, U obj) -> U

  # Returns the names of the binding's local variables as symbols.
  #
  #     def foo
  #       a = 1
  #       2.times do |n|
  #         binding.local_variables #=> [:a, :n]
  #       end
  #     end
  #
  # This method is the short version of the following code:
  #
  #     binding.eval("local_variables")
  #
  def local_variables: () -> Array[Symbol]

  # Returns the bound receiver of the binding object.
  #
  def receiver: () -> untyped

  # Returns the Ruby source filename and line number of the binding object.
  #
  def source_location: () -> [ String, Integer ]
end