class T::Private::Methods::Signature

def initialize(method:, method_name:, raw_arg_types:, raw_return_type:, bind:, mode:, check_level:, parameters: method.parameters, on_failure:, override_allow_incompatible: false)
  @method = method
  @method_name = method_name
  @arg_types = []
  @kwarg_types = {}
  @block_type = nil
  @block_name = nil
  @rest_type = nil
  @rest_name = nil
  @keyrest_type = nil
  @keyrest_name = nil
  @return_type = T::Utils.coerce(raw_return_type)
  @bind = bind ? T::Utils.coerce(bind) : bind
  @mode = mode
  @check_level = check_level
  @req_arg_count = 0
  @req_kwarg_names = []
  @has_rest = false
  @has_keyrest = false
  @parameters = parameters
  @on_failure = on_failure
  @override_allow_incompatible = override_allow_incompatible
  declared_param_names = raw_arg_types.keys
  # If sig params are declared but there is a single parameter with a missing name
  # **and** the method ends with a "=", assume it is a writer method generated
  # by attr_writer or attr_accessor
  writer_method = declared_param_names != [nil] && parameters == [[:req]] && method_name[-1] == "="
  # For writer methods, map the single parameter to the method name without the "=" at the end
  parameters = [[:req, method_name[0...-1].to_sym]] if writer_method
  param_names = parameters.map {|_, name| name}
  missing_names = param_names - declared_param_names
  extra_names = declared_param_names - param_names
  if !missing_names.empty?
    raise "The declaration for `#{method.name}` is missing parameter(s): #{missing_names.join(', ')}"
  end
  if !extra_names.empty?
    raise "The declaration for `#{method.name}` has extra parameter(s): #{extra_names.join(', ')}"
  end
  parameters.zip(raw_arg_types) do |(param_kind, param_name), (type_name, raw_type)|
    if type_name != param_name
      hint = ""
      # Ruby reorders params so that required keyword arguments
      # always precede optional keyword arguments. We can't tell
      # whether the culprit is the Ruby reordering or user error, so
      # we error but include a note
      if param_kind == :keyreq && parameters.any? {|k, _| k == :key}
        hint = "\n\nNote: Any required keyword arguments must precede any optional keyword " \
               "arguments. If your method declaration matches your `def`, try reordering any " \
               "optional keyword parameters to the end of the method list."
      end
      raise "Parameter `#{type_name}` is declared out of order (declared as arg number " \
            "#{declared_param_names.index(type_name) + 1}, defined in the method as arg number " \
            "#{param_names.index(type_name) + 1}).#{hint}\nMethod: #{method_desc}"
    end
    type = T::Utils.coerce(raw_type)
    case param_kind
    when :req
      if @arg_types.length > @req_arg_count
        # Note that this is actually is supported by Ruby, but it would add complexity to
        # support it here, and I'm happy to discourage its use anyway.
        raise "Required params after optional params are not supported in method declarations. Method: #{method_desc}"
      end
      @arg_types << [param_name, type]
      @req_arg_count += 1
    when :opt
      @arg_types << [param_name, type]
    when :key, :keyreq
      @kwarg_types[param_name] = type
      if param_kind == :keyreq
        @req_kwarg_names << param_name
      end
    when :block
      @block_name = param_name
      @block_type = type
    when :rest
      @has_rest = true
      @rest_name = param_name
      @rest_type = type
    when :keyrest
      @has_keyrest = true
      @keyrest_name = param_name
      @keyrest_type = type
    else
      raise "Unexpected param_kind: `#{param_kind}`. Method: #{method_desc}"
    end
  end
end