//===--- ExistentialCollection.swift.gyb ----------------------*- swift -*-===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2016 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See http://swift.org/LICENSE.txt for license information
// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//

// TODO: swift-3-indexing-model: perform type erasure on the associated
// `Indices` type.

import SwiftShims

%{
traversals = ['Forward', 'Bidirectional', 'RandomAccess']

def collectionForTraversal(traversal):
    if traversal == 'Forward':
        return 'Collection'
    if traversal == 'Bidirectional':
        return 'BidirectionalCollection'
    if traversal == 'RandomAccess':
        return 'RandomAccessCollection'
    assert False, "unknown traversal"
}%

@noreturn @inline(never)
internal func _abstract(file: StaticString = #file, line: UInt = #line) {
  fatalError("Method must be overridden", file: file, line: line)
}

//===--- Iterator ---------------------------------------------------------===//
//===----------------------------------------------------------------------===//

/// A type-erased iterator of `Element`.
///
/// This iterator forwards its `next()` method to an arbitrary underlying
/// iterator having the same `Element` type, hiding the specifics of the
/// underlying `IteratorProtocol`.
///
/// - seealso:
///   - `struct AnySequence<S : Sequence>`
public struct AnyIterator<Element> : IteratorProtocol {
  /// Create a `IteratorProtocol` instance that wraps `base` but whose type
  /// depends only on the type of `I.Element`.
  ///
  /// Example:
  ///
  ///     func digits() -> AnyIterator<String> {
  ///       let lazyStrings = (0..<10).lazy.map { String($0) }
  ///
  ///       // This is a really complicated type of no interest to our
  ///       // clients.
  ///       let iterator: MapSequenceIterator<RangeIterator<Int>, String>
  ///         = lazyStrings.makeIterator()
  ///       return AnyIterator(iterator)
  ///     }
  public init<I : IteratorProtocol where I.Element == Element>(_ base: I) {
    self._box = _IteratorBox(base)
  }

  /// Create a `IteratorProtocol` instance whose `next` method invokes
  /// `body` and returns the result.
  ///
  /// Example:
  ///
  ///     var x = 7
  ///     let iterator = AnyIterator { x < 15 ? x++ : nil }
  ///     let a = Array(iterator) // [ 7, 8, 9, 10, 11, 12, 13, 14 ]
  public init(body: () -> Element?) {
    self._box = _IteratorBox(_ClosureBasedIterator(body))
  }

  internal init(_box: _AnyIteratorBoxBase<Element>) {
    self._box = _box
  }

  /// Advance to the next element and return it, or `nil` if no next
  /// element exists.
  public func next() -> Element? {
    return _box.next()
  }

  internal let _box: _AnyIteratorBoxBase<Element>
}

/// Every `IteratorProtocol` can also be a `Sequence`.  Note that
/// traversing the sequence consumes the iterator.
extension AnyIterator : Sequence {}

internal struct _ClosureBasedIterator<Element> : IteratorProtocol {
  internal init(_ body: () -> Element?) {
    self._body = body
  }
  internal func next() -> Element? { return _body() }
  internal let _body: () -> Element?
}

internal class _AnyIteratorBoxBase<Element> : IteratorProtocol {
  /// Advance to the next element and return it, or `nil` if no next
  /// element exists.
  ///
  /// - Note: Subclasses must override this method.
  internal func next() -> Element? { _abstract() }
}

internal final class _IteratorBox<
  Base : IteratorProtocol
> : _AnyIteratorBoxBase<Base.Element> {
  internal init(_ base: Base) { self._base = base }
  internal override func next() -> Base.Element? { return _base.next() }
  internal var _base: Base
}

@warn_unused_result
internal func _typeID(instance: AnyObject) -> ObjectIdentifier {
  return ObjectIdentifier(instance.dynamicType)
}

//===--- Sequence ---------------------------------------------------------===//
//===----------------------------------------------------------------------===//

internal class _AnySequenceBox<Element> {
  @warn_unused_result
  internal func makeIterator() -> AnyIterator<Element> { _abstract() }

  internal var _underestimatedCount: Int { _abstract() }

  @warn_unused_result
  internal func _copyContents(initializing ptr: UnsafeMutablePointer<Element>)
    -> UnsafeMutablePointer<Element> {
    _abstract()
  }

  @warn_unused_result
  internal func _copyToNativeArrayBuffer() -> _ContiguousArrayStorageBase {
    _abstract()
  }

  @warn_unused_result
  internal func _dropFirst(n: Int) -> _AnySequenceBox<Element> { _abstract() }

  @warn_unused_result
  internal func _prefix(maxLength: Int) -> _AnySequenceBox<Element> {
    _abstract()
  }
}

internal class _AnyCollectionBox<Element> : _AnySequenceBox<Element> {
  internal subscript(i: _AnyIndexBox) -> Element { _abstract() }
  internal subscript(start: _AnyIndexBox, end: _AnyIndexBox)
    -> _AnyCollectionBox<Element> { _abstract() }
  internal var _count: IntMax { _abstract() }
  // TODO: swift-3-indexing-model: forward the following methods.
  /*
  internal func _failEarlyRangeCheck(
    index: Index,
    bounds: Range<Index>)
  internal func _failEarlyRangeCheck(
    range: Range<Index>,
    bounds: Range<Index>)
  var _indices: Indices
  */
  @warn_unused_result
  internal func _successor(of i: _AnyIndexBox) -> _AnyIndexBox { _abstract() }
  internal func _formSuccessor(i: _AnyIndexBox) { _abstract() }

  // TODO: swift-3-indexing-model: forward the following methods.
  /*
  @warn_unused_result
  func prefix(upTo end: Index) -> SubSequence

  @warn_unused_result
  func suffix(from start: Index) -> SubSequence

  @warn_unused_result
  func prefix(through position: Index) -> SubSequence

  var isEmpty: Bool { get }

  var count: IndexDistance { get }

  @warn_unused_result
  func _customIndexOfEquatableElement(element: Iterator.Element) -> Index??

  var first: Iterator.Element? { get }

  @warn_unused_result
  func advance(i: Index, by n: IndexDistance) -> Index

  @warn_unused_result
  func advance(i: Index, by n: IndexDistance, limit: Index) -> Index

  @warn_unused_result
  func distance(from start: Index, to end: Index) -> IndexDistance
  */

  internal init(
    _startIndex: _AnyIndexBox,
    endIndex: _AnyIndexBox
  ) {
    self._startIndex = _startIndex
    self._endIndex = endIndex
  }

  internal let _startIndex: _AnyIndexBox
  internal let _endIndex: _AnyIndexBox
}

internal class _AnyBidirectionalCollectionBox<Element>
  : _AnyCollectionBox<Element> {

  internal func _predecessor(of i: _AnyIndexBox) -> _AnyIndexBox { _abstract() }
  internal func _formPredecessor(i: _AnyIndexBox) { _abstract() }

  // TODO: swift-3-indexing-model: forward the following methods.
  /*
  var last: Iterator.Element? { _abstract() }
  */

  internal override init(
    _startIndex: _AnyIndexBox,
    endIndex: _AnyIndexBox
  ) {
    super.init(_startIndex: _startIndex, endIndex: endIndex)
  }
}

internal class _AnyRandomAccessCollectionBox<Element>
  : _AnyBidirectionalCollectionBox<Element> {

  internal override init(
    _startIndex: _AnyIndexBox,
    endIndex: _AnyIndexBox
  ) {
    super.init(_startIndex: _startIndex, endIndex: endIndex)
  }
}

% for Kind in ['Sequence', 'Collection', 'BidirectionalCollection', 'RandomAccessCollection']:
internal final class _${Kind}Box<
  S : ${Kind}
  where
  S.SubSequence : ${Kind},
  S.SubSequence.Iterator.Element == S.Iterator.Element,
  S.SubSequence.SubSequence == S.SubSequence
%   if Kind != 'Sequence':
  ,
  S.Indices : ${Kind},
  S.Indices.Iterator.Element == S.Index,
  S.Indices.Index == S.Index,
  S.Indices.SubSequence == S.Indices
%   end
> : _Any${Kind}Box<S.Iterator.Element> {
  internal typealias Element = S.Iterator.Element

  internal override func makeIterator() -> AnyIterator<Element> {
    return AnyIterator(_base.makeIterator())
  }
  internal override var _underestimatedCount: Int {
    return _base.underestimatedCount
  }
  internal override func _copyContents(initializing ptr: UnsafeMutablePointer<Element>)
    -> UnsafeMutablePointer<Element> {
    return _base._copyContents(initializing: ptr)
  }
  internal override func _copyToNativeArrayBuffer() -> _ContiguousArrayStorageBase {
    return _base._copyToNativeArrayBuffer()._storage
  }
%   if Kind == 'Sequence':
  internal override func _dropFirst(n: Int) -> _AnySequenceBox<Element> {
    return _SequenceBox<S.SubSequence>(_base: _base.dropFirst(n))
  }
  internal override func _prefix(maxLength: Int) -> _AnySequenceBox<Element> {
    return _SequenceBox<S.SubSequence>(_base: _base.prefix(maxLength))
  }
%   end

%   if Kind == 'Sequence':
  internal init(_base: S) {
    self._base = _base
  }
%   else:
  internal override var _count: IntMax {
    return numericCast(_base.count)
  }

  internal func _unbox(
    position: _AnyIndexBox, file: StaticString = #file, line: UInt = #line
  ) -> S.Index {
    if let i = position._unbox() as S.Index? {
      return i
    }
    fatalError("Index type mismatch!", file: file, line: line)
  }
  
  internal override subscript(position: _AnyIndexBox) -> Element {
    return _base[_unbox(position)]
  }
  
  internal init(
    _base: S,
    startIndex: _AnyIndexBox,
    endIndex: _AnyIndexBox
  ) {
    self._base = _base
    super.init(_startIndex: startIndex, endIndex: endIndex)
  }
  
  @warn_unused_result
  internal override func _successor(of position: _AnyIndexBox) -> _AnyIndexBox {
    return _IndexBox(_base: _base.successor(of: _unbox(position)))
  }
  
  internal override func _formSuccessor(position: _AnyIndexBox) {
    if let p = position as? _IndexBox<S.Index> {
      return _base.formSuccessor(&p._base)
    }
    fatalError("Index type mismatch!")
  }
  
%     if Kind in ['BidirectionalCollection', 'RandomAccessCollection']:

  @warn_unused_result
  internal override func _predecessor(of position: _AnyIndexBox) -> _AnyIndexBox {
    return _IndexBox(_base: _base.predecessor(of: _unbox(position)))
  }
  
  internal override func _formPredecessor(position: _AnyIndexBox) {
    if let p = position as? _IndexBox<S.Index> {
      return _base.formPredecessor(&p._base)
    }
    fatalError("Index type mismatch!")
  }

%     end

%   end
  internal var _base: S
}
% end

internal struct _ClosureBasedSequence<Iterator : IteratorProtocol>
  : Sequence {

  internal init(_ makeUnderlyingIterator: () -> Iterator) {
    self._makeUnderlyingIterator = makeUnderlyingIterator
  }

  internal func makeIterator() -> Iterator {
    return _makeUnderlyingIterator()
  }

  internal var _makeUnderlyingIterator: () -> Iterator
}

/// A type-erased sequence.
///
/// Forwards operations to an arbitrary underlying sequence having the
/// same `Element` type, hiding the specifics of the underlying
/// `Sequence`.
///
/// - SeeAlso: `AnyIterator<Element>`.
public struct AnySequence<Element> : Sequence {
  @available(*, unavailable, renamed: "Element")
  public typealias T = Element

  /// Wrap and forward operations to `base`.
  public init<
    S : Sequence
    where
    S.Iterator.Element == Element,
    S.SubSequence : Sequence,
    S.SubSequence.Iterator.Element == Element,
    S.SubSequence.SubSequence == S.SubSequence
  >(_ base: S) {
    self._box = _SequenceBox(_base: base)
  }

  /// Create a sequence whose `makeIterator()` method forwards to
  /// `makeUnderlyingIterator`.
  public init<I : IteratorProtocol where I.Element == Element>(
    _ makeUnderlyingIterator: () -> I
  ) {
    self.init(_ClosureBasedSequence(makeUnderlyingIterator))
  }

  internal init(_box: _AnySequenceBox<Element>) {
    self._box = _box
  }

  /// Returns an iterator over the elements of this sequence.
  ///
  /// - Complexity: O(1).
  public func makeIterator() -> AnyIterator<Element> {
    return _box.makeIterator()
  }

  internal let _box: _AnySequenceBox<Element>
}

extension AnySequence {
  @warn_unused_result
  public func dropFirst(n: Int) -> AnySequence<Element> {
    return AnySequence(_box: _box._dropFirst(n))
  }

  @warn_unused_result
  public func prefix(maxLength: Int) -> AnySequence<Element> {
    return AnySequence(_box: _box._prefix(maxLength))
  }
}

% for Kind in ['Sequence', 'Collection', 'BidirectionalCollection', 'RandomAccessCollection']:
extension Any${Kind} {
  public var underestimatedCount: Int {
    return _box._underestimatedCount
  }

  public func _copyContents(initializing ptr: UnsafeMutablePointer<Element>)
    -> UnsafeMutablePointer<Element> {
    return _box._copyContents(initializing: ptr)
  }

  public func _copyToNativeArrayBuffer() -> _ContiguousArrayBuffer<Element> {
    return _ContiguousArrayBuffer(self._box._copyToNativeArrayBuffer())
  }
}

% end

//===--- Index ------------------------------------------------------------===//
//===----------------------------------------------------------------------===//

internal protocol _AnyIndexBox : class {
  var _typeID: ObjectIdentifier { get }

  @warn_unused_result
  func _unbox<T : Comparable>() -> T?

  @warn_unused_result
  func _equal(to rhs: _AnyIndexBox) -> Bool

  @warn_unused_result
  func _notEqual(to rhs: _AnyIndexBox) -> Bool

  @warn_unused_result
  func _less(than rhs: _AnyIndexBox) -> Bool

  @warn_unused_result
  func _lessOrEqual(to rhs: _AnyIndexBox) -> Bool

  @warn_unused_result
  func _greater(than rhs: _AnyIndexBox) -> Bool

  @warn_unused_result
  func _greaterOrEqual(to rhs: _AnyIndexBox) -> Bool
}

internal final class _IndexBox<
  BaseIndex : Comparable
> : _AnyIndexBox {
  internal var _base: BaseIndex

  internal init(_base: BaseIndex) {
    self._base = _base
  }

  @warn_unused_result
  internal func _unsafeUnbox(other: _AnyIndexBox) -> BaseIndex {
    return unsafeDowncast(other, to: _IndexBox.self)._base
  }

  internal var _typeID: ObjectIdentifier {
    return Swift._typeID(self)
  }

  @warn_unused_result
  internal func _unbox<T : Comparable>() -> T? {
    return (self as _AnyIndexBox as? _IndexBox<T>)?._base
  }
  
  @warn_unused_result
  internal func _equal(to rhs: _AnyIndexBox) -> Bool {
    return _base == _unsafeUnbox(rhs)
  }

  @warn_unused_result
  internal func _notEqual(to rhs: _AnyIndexBox) -> Bool {
    return _base != _unsafeUnbox(rhs)
  }

  @warn_unused_result
  internal func _less(than rhs: _AnyIndexBox) -> Bool {
    return _base < _unsafeUnbox(rhs)
  }

  @warn_unused_result
  internal func _lessOrEqual(to rhs: _AnyIndexBox) -> Bool {
    return _base <= _unsafeUnbox(rhs)
  }

  @warn_unused_result
  internal func _greater(than rhs: _AnyIndexBox) -> Bool {
    return _base > _unsafeUnbox(rhs)
  }

  @warn_unused_result
  internal func _greaterOrEqual(to rhs: _AnyIndexBox) -> Bool {
    return _base >= _unsafeUnbox(rhs)
  }
}

/// A wrapper over an underlying index that hides
/// the specific underlying type.
///
/// - SeeAlso: `AnyCollection`
public struct AnyIndex : Comparable {
  /// Wrap and forward operations to `base`.
  public init<BaseIndex : Comparable>(_ base: BaseIndex) {
    self._box = _IndexBox(_base: base)
  }

  internal init(_box: _AnyIndexBox) {
    self._box = _box
  }

  internal var _typeID: ObjectIdentifier {
    return _box._typeID
  }

  internal var _box: _AnyIndexBox
}

/// Returns `true` iff `lhs` and `rhs` wrap equal underlying indices.
///
/// - Precondition: The types of indices wrapped by `lhs` and `rhs` are
///   identical.
@warn_unused_result
public func == (lhs: AnyIndex, rhs: AnyIndex) -> Bool {
  precondition(lhs._typeID == rhs._typeID, "base index types differ")
  return lhs._box._equal(to: rhs._box)
}

@warn_unused_result
public func != (lhs: AnyIndex, rhs: AnyIndex) -> Bool {
  precondition(lhs._typeID == rhs._typeID, "base index types differ")
  return lhs._box._notEqual(to: rhs._box)
}

@warn_unused_result
public func < (lhs: AnyIndex, rhs: AnyIndex) -> Bool {
  precondition(lhs._typeID == rhs._typeID, "base index types differ")
  return lhs._box._less(than: rhs._box)
}

@warn_unused_result
public func <= (lhs: AnyIndex, rhs: AnyIndex) -> Bool {
  precondition(lhs._typeID == rhs._typeID, "base index types differ")
  return lhs._box._lessOrEqual(to: rhs._box)
}

@warn_unused_result
public func > (lhs: AnyIndex, rhs: AnyIndex) -> Bool {
  precondition(lhs._typeID == rhs._typeID, "base index types differ")
  return lhs._box._greater(than: rhs._box)
}

@warn_unused_result
public func >= (lhs: AnyIndex, rhs: AnyIndex) -> Bool {
  precondition(lhs._typeID == rhs._typeID, "base index types differ")
  return lhs._box._greaterOrEqual(to: rhs._box)
}

//===--- Collections ------------------------------------------------------===//
//===----------------------------------------------------------------------===//

/// A protocol for `AnyCollection<Element>`,
/// `AnyBidirectionalCollection<Element>`, and
/// `AnyRandomAccessCollection<Element>`.
///
/// This protocol can be considered an implementation detail of the
/// `===` and `!==` implementations for these types.
public protocol AnyCollectionProtocol : Collection {
  /// Identifies the underlying collection stored by `self`. Instances
  /// copied from one another have the same `_underlyingCollectionID`.
  var _underlyingCollectionID: ObjectIdentifier { get }
}

/// Returns `true` iff `lhs` and `rhs` store the same underlying collection.
@warn_unused_result
public func === <
  L : AnyCollectionProtocol, R : AnyCollectionProtocol
>(lhs: L, rhs: R) -> Bool {
  return lhs._underlyingCollectionID == rhs._underlyingCollectionID
}

/// Returns `false` iff `lhs` and `rhs` store the same underlying collection.
@warn_unused_result
public func !== <
  L : AnyCollectionProtocol, R : AnyCollectionProtocol
>(lhs: L, rhs: R) -> Bool {
  return lhs._underlyingCollectionID != rhs._underlyingCollectionID
}

% for (ti, Traversal) in enumerate(traversals):
%   SelfProtocol = collectionForTraversal(Traversal)
%   Self = 'Any' + SelfProtocol
/// A type-erased wrapper over any collection with indices that
/// support ${Traversal.lower().replace('omacc', 'om acc')} traversal.
///
/// Forwards operations to an arbitrary underlying collection having the
/// same `Element` type, hiding the specifics of the underlying
/// `Collection`.
///
/// - SeeAlso: ${', '.join('`Any%sType`' % t for t in (2 * traversals)[ti + 1 : ti + 3]) }
public struct ${Self}<Element>
  : AnyCollectionProtocol, ${SelfProtocol} {

%   for SubTraversal in traversals[ti:]:
%     SubProtocol = collectionForTraversal(SubTraversal)
  /// Create an `${Self}` that
  /// stores `base` as its underlying collection.
  ///
  /// - Complexity: O(1).
  public init<
    C : ${SubProtocol}
    where
    C.Iterator.Element == Element,

    // FIXME(compiler limitation): these constraints should be applied to
    // associated types of Collection.
    C.SubSequence : ${SubProtocol},
    C.SubSequence.Iterator.Element == Element,
    C.SubSequence.Index == C.Index,
    C.SubSequence.SubSequence == C.SubSequence,
    C.Indices : ${SubProtocol},
    C.Indices.Iterator.Element == C.Index,
    C.Indices.Index == C.Index,
    C.Indices.SubSequence == C.Indices
  >(_ base: C) {
    // Traversal: ${Traversal}
    // SubTraversal: ${SubTraversal}
    self._box = _${SubProtocol}Box<C>(
      _base: base,
      startIndex: _IndexBox(_base: base.startIndex),
      endIndex: _IndexBox(_base: base.endIndex))
  }

  /// Create an `Any${Traversal}Collection` having the same underlying
  /// collection as `other`.
  ///
  /// - Postcondition: The result is `===` to `other`.
  ///
  /// - Complexity: O(1).
  public init(
    _ other: Any${SubProtocol}<Element>
  ) {
    self._box = other._box
  }
%   end

%   for SuperTraversal in traversals[:ti]:
  /// If the underlying collection stored by `other` satisfies
  /// `${SelfProtocol}`, create an `${Self}` having the same
  /// underlying collection as `other`.  Otherwise, the result is
  /// `nil`.
  ///
  /// - Complexity: O(1).
  public init?(
    _ other: Any${collectionForTraversal(SuperTraversal)}<Element>
  ) {
    guard let box =
      other._box as? _${Self}Box<Element> else {
      return nil
    }
    self._box = box
  }
%   end

  /// Returns an iterator over the elements of this collection.
  ///
  /// - Complexity: O(1).
  public func makeIterator() -> AnyIterator<Element> {
    return _box.makeIterator()
  }

  public typealias Index = AnyIndex
  public typealias IndexDistance = IntMax

  /// The position of the first element in a non-empty collection.
  ///
  /// In an empty collection, `startIndex == endIndex`.
  public var startIndex: AnyIndex {
    return AnyIndex(_box: _box._startIndex)
  }

  /// The collection's "past the end" position.
  ///
  /// `endIndex` is not a valid argument to `subscript`, and is always
  /// reachable from `startIndex` by zero or more applications of
  /// `successor()`.
  public var endIndex: AnyIndex {
    return AnyIndex(_box: _box._endIndex)
  }

  /// Access the element indicated by `position`.
  ///
  /// - Precondition: `position` indicates a valid position in `self` and
  ///   `position != endIndex`.
  public subscript(position: AnyIndex) -> Element {
    return _box[position._box]
  }

  public subscript(bounds: Range<AnyIndex>)
    -> ${Self}<Element>
  {
    fatalError("FIXME: swift-3-indexing-model: implement")
  }

  /// The number of elements.
  ///
  /// - Complexity: ${'O(1)' if Traversal == 'RandomAccess' else 'O(N)'}.
  public var count: IntMax {
    return _box._count
  }

  @warn_unused_result
  public func successor(of i: AnyIndex) -> AnyIndex {
    return AnyIndex(_box: _box._successor(of: i._box))
  }

  public func formSuccessor(i: inout AnyIndex) {
    if _isUnique(&i._box) {
      _box._formSuccessor(i._box)
    }
    else {
      i = successor(of: i)
    }
  }

%   if Traversal == 'Bidirectional' or Traversal == 'RandomAccess':
  public func predecessor(of i: AnyIndex) -> AnyIndex {
    return AnyIndex(_box: _box._predecessor(of: i._box))
  }

  public func formPredecessor(i: inout AnyIndex) {
    if _isUnique(&i._box) {
      _box._formPredecessor(i._box)
    }
    else {
      i = predecessor(of: i)
    }
  }
%   end

  /// Uniquely identifies the stored underlying collection.
  public // Due to language limitations only
  var _underlyingCollectionID: ObjectIdentifier {
    return ObjectIdentifier(_box)
  }

  internal let _box: _${Self}Box<Element>
}
% end

@available(*, unavailable, renamed: "AnyIterator")
public struct AnyGenerator<Element> {}

extension AnyIterator {
  @available(*, unavailable, renamed: "iterator")
  public func generate() -> AnyIterator<Element> {
    fatalError("unavailable function can't be called")
  }
}

% for Kind in ['Sequence', 'Collection', 'BidirectionalCollection', 'RandomAccessCollection']:
extension Any${Kind} {

  @available(*, unavailable, message: "Please use underestimatedCount property instead.")
  public var underestimateCount: Int {
    fatalError("unavailable function can't be called")
  }
}
%end

@available(*, unavailable, renamed: "AnyCollectionProtocol")
public typealias AnyCollectionType = AnyCollectionProtocol

extension AnyCollectionProtocol {
  @available(*, unavailable, renamed: "iterator")
  public func generate() -> AnyIterator<Iterator.Element> {
    fatalError("unavailable function can't be called")
  }
}