class RBS::Types::UntypedFunction

def ==(other)
  other.is_a?(UntypedFunction) && other.return_type == return_type
end

def each_param(&block)
  if block
    # noop
  else
    enum_for :each_param
  end
end

def each_type(&block)
  if block
    yield return_type
  else
    enum_for :each_type
  end
end

def empty?
  true
end

def free_variables(acc = Set.new)
  return_type.free_variables(acc)
end

def has_classish_type?
  return_type.has_classish_type?
end

def has_self_type?
  return_type.has_self_type?
end

def hash
  self.class.hash ^ return_type.hash
end

def initialize(return_type:)
  @return_type = return_type
end

def map_type(&block)
  if block
    update(return_type: yield(return_type))
  else
    enum_for :map_type
  end
end

def map_type_name(&block)
  UntypedFunction.new(
    return_type: return_type.map_type_name(&block)
  )
end

def param_to_s
  "?"
end

def return_to_s
  return_type.to_s(1)
end

def sub(subst)
  return self if subst.empty?
  map_type { _1.sub(subst) }
end

def to_json(state = _ = nil)
  {
    return_type: return_type
  }.to_json(state)
end

def update(return_type: self.return_type)
  UntypedFunction.new(return_type: return_type)
end

def with_nonreturn_void?
  false
end

def with_return_type(ty)
  update(return_type: ty)
end