# A type that's convertible to a `Complex`.
#
interface _ToC
  # Convert `self` to a `Complex`.
  #
  def to_c: () -> Complex
end

# A type that's convertible to a `Rational`.
#
interface _ToR
  # Convert `self` to a `Complex`.
  #
  def to_r: () -> Rational
end

# A type that's convertible to a `Float`.
#
interface _ToF
  # Convert `self` to a `Float`.
  #
  def to_f: () -> Float
end

# A type that's convertible to an `Integer`.
#
interface _ToI
  # Convert `self` to an `Integer`.
  #
  def to_i: () -> Integer
end

# A type that's implicitly convertible to an `Integer`.
#
# Implicit `.to_int` conversions are usable all over Ruby's stdlib, such as `Kernel#exit`,
# `File#chmod`, and `Array#take`. Virtually anywhere that accepts an `Integer` will also accept
# something that defines `.to_int`.
#
# Interestingly, types that define `.to_int` aren't immediately converted in math operations on
# `Integers` (eg `1 + defines_to_int`): Instead, `.coerce` must be defined on the right-hand-side
# value.
#
interface _ToInt
  # Converts `self` to an `Integer`.
  #
  def to_int: () -> Integer
end

# A type that's convertible to a `String`.
#
interface _ToS
  # Converts `self` to a `String`.
  #
  def to_s: () -> String
end

# A type that's implicitly convertible to a `String`.
#
# Implicit `.to_str` conversions are usable all over Ruby's stdlib, such as `Kernel#abort`,
# `String#+`, and `Object#send`. Virtually anywhere that accepts a `String` will also accept
# something that defines `.to_Str`.
#
# Types that define `.to_str` are also usable wherever paths are expected (See the `path` type
# alias).
#
interface _ToStr
  # Converts `self` to a `String`.
  #
  def to_str: () -> String
end

# A type that's explicitly convertible to a `String`.
#
# Interestingly enough, most methods that accept `Symbol` in the standard library _do not_ accept
# an object that defines `.to_sym` (unlike `String` and `.to_str`).
#
# There are only two places that `Symbol | _ToSym`, and they're quite obscure:
# - `Kernel#warn`'s `category:` optional parameter. (Oddly enough, not for  `Warning.warn`, though.)
# - `TracePoint#trace`'s `event`s parameter.
# Additionally, the `rb_iseq_load` C function, only accessible through `Fiddle`, uses `.to_sym`
# internally.
#
interface _ToSym
  # Converts `self` to a `Symbol`.
  #
  def to_sym: () -> Symbol
end

# A type that's convertible to a `Hash`.
#
interface _ToH[K, V]
  # Converts `self` to a `Hash`.
  #
  def to_h: () -> Hash[K, V]
end

# A type that's implicitly convertible to a `Hash`.
#
# Implicit `.to_hash` conversions are usable infrequently in Ruby's stdlib, such as `Io#popen`,
# `Kernel#sprintf`, and `Enumerable#tally`. It's also used with the `**` "splatsplat" operator.
#
interface _ToHash[K, V]
  # Converts `self` to a `Hash`.
  #
  def to_hash: () -> Hash[K, V]
end

# A type that's convertible to an `Array`.
#
interface _ToA[T]
  # Converts `self` to an `Array`.
  #
  def to_a: () -> Array[T]
end

# A type that's implicitly convertible to an `Array`.
#
# Implicit `.to_ary` conversions are usable semi-frequently in Ruby's stdlib, such as `Dir#glob`,
# `Regex#union`, and `Class#private`. It's also used with the `*` "splat" operator.
#
interface _ToAry[T]
  # Converts `self` to an `Array`.
  #
  def to_ary: () -> Array[T]
end

# A type that's convertible to a `Proc`.
#
# This is implicitly called when the `&` "block-passing" operator is used, in addition to a handful
# of other places, such as `Hash#default_proc=`.
#
interface _ToProc
  # Converts `self` to a `Proc.`
  #
  def to_proc: () -> Proc
end

# A type that's convertible to a `String` that contains a filepath.
#
# Implicit `.to_path` conversions are usable throughout Ruby's stdlib, whenever a file path is
# expected, such as `Dir#mkdir`, `File#open`, and `UNIXSocket#read`. These functions, however, also
# accept types that define `.to_str`. See the `path` type alias.
#
interface _ToPath
  # Converts `self` to a `String` containing a filepath.
  #
  def to_path: () -> String
end

# A type that's convertible to an `IO`.
#
# Implicit `.to_io` conversions are usuable infrequently in Ruby's stdlib, such as `IO#reopen`,
# `File.exist?`, and `Kernel#select`.
#
interface _ToIO
  # Converts `self` to an `IO` object.
  #
  def to_io: () -> IO
end

# A type that defines the `.inspect` method.
#
# Since `Object` defines `.inspect`, nearly every object in Ruby has it defined: Only those that
# derive from `BasicObject`, or `undef inspect` won't have it. It's used in a few locations,
# such as `Kernel#p` and `Array#join`.
#
interface _Inspect
  # Returns a debugging representation of `self`.
  #
  def inspect: () -> String
end

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

interface _EachEntry[out A]
  def each_entry: () { (A) -> void } -> self
end

interface _Reader
  def read: (?int? length, ?string outbuf) -> String?
end

interface _ReaderPartial
  def readpartial: (int maxlen, ?string outbuf) -> String
end

interface _Writer
  # Writes the +data+ string. Returns the number of bytes written
  #
  def write: (*_ToS data) -> Integer
end

interface _Rewindable
  # Positions the stream to the beginning of input, resetting `lineno` to zero.
  #
  def rewind: () -> Integer
end

# A type that's usable like a `Range[T]`.
#
# Implicit `_Range` usage is usable frequently in ruby's stdlib, such as `Comparable#clamp`,
# `String#[]`, and `Kernel#rand`.
#
interface _Range[T]
  # The beginning value, `nil` if there is no beginning.
  def begin: () -> T?

  # The ending value, `nil` if there is no ending.
  def end: () -> T?

  # Whether or not to include the end in the range.
  def exclude_end?: () -> bool
end

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

# Represents an `Integer`, or a type convertible to it (via `.to_int`).
#
type int = Integer | _ToInt

# Represents a `Float`, or a type convertible to it (via `.to_f`).
#
type float = Float | _ToF

# Represents a `Range[T]`, or a type that acts like it (via `.begin`, `.end`, and `.exclude_end?`).
#
type range[T] = Range[T] | _Range[T]

# Represents a `String`, or a type convertible to it (via `.to_str`).
#
type string = String | _ToStr

# Represents an `Array[T]`, or a type convertible to it (via `.to_ary`).
#
type array[T] = Array[T] | _ToAry[T]

# Represents a `Hash[K, V]`, or a type convertible to it (via `.to_hash`).
#
type hash[K, V] = Hash[K, V] | _ToHash[K, V]

# Represents an `IO`, or a type convertible to it (via `.to_io`).
#
type io = IO | _ToIO

# A filesystem path: Either something that defines `.to_path`, or a `String` (or a type that is
# convertible to a string via `.to_str`).
#
# If a type defines both `.to_path` and `.to_str`, the `.to_path` function is called.
#
type path = string | _ToPath

# An `Encoding`, or a `String` (or type that defines `.to_str`) that represents it.
#
type encoding = Encoding | string

# A real number, ie not a `Complex`.
#
type real = Integer | Float | Rational

# Represents a `Symbol` or a `string`.
#
# A lot of builtin functions accept either a Symbol, a String, or something which has `.to_str`
# defined.
#
type interned = Symbol | string

# `boolish` is a type for documentation.
# It means the value of this type is only for testing a condition.
# Unlike `bool` type, it doesn't require the value is one of `true` or `false`.
# Any Ruby object can have `boolish` type.
#
type boolish = top