interface _ToI
  def to_i: -> Integer
end

interface _ToInt
  def to_int: -> Integer
end

interface _ToS
  def to_s: -> String
end

interface _ToStr
  def to_str: () -> String
end

interface _ToHash[K, V]
  def to_hash: () -> Hash[K, V]
end

interface _ToProc
  def to_proc: () -> untyped
end

interface _ToPath
  def to_path: () -> String
end

interface _Each[out A, out B]
  def each: { (A) -> void } -> B
end

interface _Exception
  def exception: () -> Exception
               | (String arg0) -> Exception
end

class BigDecimal
end

type int = Integer | _ToInt
type real = Integer | Float | Rational

type string = String | _ToStr
type encoding = Encoding | string