Merge pull request swiftlang#9847 from apple/eliminate-_Element

[stdlib] Eliminate _Element

Author: Dave Abrahams

stdlib/public/SDK/Dispatch/Data.swift

@@ -315,7 +315,7 @@ public struct DispatchDataIterator : IteratorProtocol, Sequence {
 
 	/// Advance to the next element and return it, or `nil` if no next
 	/// element exists.
-	public mutating func next() -> DispatchData._Element? {
+	public mutating func next() -> DispatchData.Element? {
 		if _position == _count { return nil }
 		let element = _ptr.load(fromByteOffset: _position, as: UInt8.self)
 		_position = _position + 1

stdlib/public/core/Collection.swift

@@ -58,15 +58,7 @@ public protocol _IndexableBase {
   /// If the collection is empty, `endIndex` is equal to `startIndex`.
   var endIndex: Index { get }
 
-  // The declaration of _Element and subscript here is a trick used to
-  // break a cyclic conformance/deduction that Swift can't handle.  We
-  // need something other than a Collection.Element that can
-  // be used as IndexingIterator<T>'s Element.  Here we arrange for
-  // the Collection itself to have an Element type that's deducible from
-  // its subscript.  Ideally we'd like to constrain this Element to be the same
-  // as Collection.Element (see below), but we have no way of
-  // expressing it today.
-  associatedtype _Element
+  associatedtype Element
 
   /// Accesses the element at the specified position.
   ///
@@ -87,7 +79,7 @@ public protocol _IndexableBase {
   ///   `endIndex` property.
   ///
   /// - Complexity: O(1)
-  subscript(position: Index) -> _Element { get }
+  subscript(position: Index) -> Element { get }
 
   // WORKAROUND: rdar://25214066
   // FIXME(ABI)#178 (Type checker)
@@ -422,7 +414,7 @@ public struct IndexingIterator<
   ///   exists; otherwise, `nil`.
   @_inlineable
   @inline(__always)
-  public mutating func next() -> Elements._Element? {
+  public mutating func next() -> Elements.Element? {
     if _position == _elements.endIndex { return nil }
     let element = _elements[_position]
     _elements.formIndex(after: &_position)
@@ -1978,3 +1970,7 @@ extension Collection where Element : Equatable {
 @available(*, unavailable, message: "PermutationGenerator has been removed in Swift 3")
 public struct PermutationGenerator<C : Collection, Indices : Sequence> {}
 
+extension _IndexableBase {
+  @available(swift, deprecated: 3.2, renamed: "Element")
+  public typealias _Element = Element
+}

stdlib/public/core/MutableCollection.swift

@@ -67,7 +67,7 @@ public protocol _MutableIndexable : _Indexable {
   /// - Parameter position: The position of the element to access. `position`
   ///   must be a valid index of the collection that is not equal to the
   ///   `endIndex` property.
-  subscript(position: Index) -> _Element { get set }
+  subscript(position: Index) -> Element { get set }
 
   /// Accesses a contiguous subrange of the collection's elements.
   ///

stdlib/public/core/RangeReplaceableCollection.swift.gyb

@@ -49,14 +49,14 @@ public protocol _RangeReplaceableIndexable : _Indexable {
   ///   - repeatedValue: The element to repeat.
   ///   - count: The number of times to repeat the value passed in the
   ///     `repeating` parameter. `count` must be zero or greater.
-  init(repeating repeatedValue: _Element, count: Int)
+  init(repeating repeatedValue: Element, count: Int)
 
   /// Creates a new instance of a collection containing the elements of a
   /// sequence.
   ///
   /// - Parameter elements: The sequence of elements for the new collection.
   ///   `elements` must be finite.
-  init<S : Sequence>(_ elements: S) where S.Element == _Element
+  init<S : Sequence>(_ elements: S) where S.Element == Element
 
   /// Replaces the specified subrange of elements with the given collection.
   ///
@@ -97,7 +97,7 @@ public protocol _RangeReplaceableIndexable : _Indexable {
   mutating func replaceSubrange<C>(
     _ subrange: Range<Index>,
     with newElements: C
-  ) where C : Collection, C.Element == _Element
+  ) where C : Collection, C.Element == Element
 
   /// Inserts a new element into the collection at the specified position.
   ///
@@ -121,7 +121,7 @@ public protocol _RangeReplaceableIndexable : _Indexable {
   ///     valid index into the collection.
   ///
   /// - Complexity: O(*n*), where *n* is the length of the collection.
-  mutating func insert(_ newElement: _Element, at i: Index)
+  mutating func insert(_ newElement: Element, at i: Index)
 
   /// Inserts the elements of a sequence into the collection at the specified
   /// position.
@@ -152,7 +152,7 @@ public protocol _RangeReplaceableIndexable : _Indexable {
   ///   `newElements`.
   mutating func insert<S : Collection>(
     contentsOf newElements: S, at i: Index
-  ) where S.Element == _Element
+  ) where S.Element == Element
 
   /// Removes and returns the element at the specified position.
   ///
@@ -175,7 +175,7 @@ public protocol _RangeReplaceableIndexable : _Indexable {
   ///
   /// - Complexity: O(*n*), where *n* is the length of the collection.
   @discardableResult
-  mutating func remove(at i: Index) -> _Element
+  mutating func remove(at i: Index) -> Element
 
   /// Removes the specified subrange of elements from the collection.
   ///

stdlib/public/core/Reverse.swift

@@ -52,7 +52,7 @@ public struct _ReverseIndexingIterator<
 
   @_inlineable
   @inline(__always)
-  public mutating func next() -> Elements._Element? {
+  public mutating func next() -> Elements.Element? {
     guard _fastPath(_position != _elements.startIndex) else { return nil }
     _position = _elements.index(before: _position)
     return _elements[_position]

stdlib/public/core/Slice.swift.gyb

@@ -131,7 +131,7 @@ public struct ${Self}<Base : ${BaseRequirements}>
     return _endIndex
   }
 
-  public subscript(index: Index) -> Base._Element {
+  public subscript(index: Index) -> Base.Element {
     get {
       _failEarlyRangeCheck(index, bounds: startIndex..<endIndex)
       return _base[index]
@@ -223,7 +223,7 @@ public struct ${Self}<Base : ${BaseRequirements}>
     self._endIndex = _base.endIndex
   }
 
-  public init(repeating repeatedValue: Base._Element, count: Int) {
+  public init(repeating repeatedValue: Base.Element, count: Int) {
     self._base = Base(repeating: repeatedValue, count: count)
     self._startIndex = _base.startIndex
     self._endIndex = _base.endIndex
@@ -232,7 +232,7 @@ public struct ${Self}<Base : ${BaseRequirements}>
   public init<S>(_ elements: S)
     where
     S : Sequence,
-    S.Element == Base._Element {
+    S.Element == Base.Element {
 
     self._base = Base(elements)
     self._startIndex = _base.startIndex
@@ -243,7 +243,7 @@ public struct ${Self}<Base : ${BaseRequirements}>
     _ subRange: Range<Index>, with newElements: C
   ) where
     C : Collection,
-    C.Element == Base._Element {
+    C.Element == Base.Element {
 
     // FIXME: swift-3-indexing-model: range check.
 %     if Traversal == 'Forward':
@@ -280,7 +280,7 @@ public struct ${Self}<Base : ${BaseRequirements}>
 %     end
   }
 
-  public mutating func insert(_ newElement: Base._Element, at i: Index) {
+  public mutating func insert(_ newElement: Base.Element, at i: Index) {
     // FIXME: swift-3-indexing-model: range check.
 %     if Traversal == 'Forward':
     let sliceOffset: IndexDistance =
@@ -311,7 +311,7 @@ public struct ${Self}<Base : ${BaseRequirements}>
   public mutating func insert<S>(contentsOf newElements: S, at i: Index)
     where
     S : Collection,
-    S.Element == Base._Element {
+    S.Element == Base.Element {
 
     // FIXME: swift-3-indexing-model: range check.
 %     if Traversal == 'Forward':
@@ -344,7 +344,7 @@ public struct ${Self}<Base : ${BaseRequirements}>
 %     end
   }
 
-  public mutating func remove(at i: Index) -> Base._Element {
+  public mutating func remove(at i: Index) -> Base.Element {
     // FIXME: swift-3-indexing-model: range check.
 %     if Traversal == 'Forward':
     let sliceOffset: IndexDistance =

stdlib/public/core/WriteBackMutableSlice.swift

@@ -17,7 +17,7 @@ internal func _writeBackMutableSlice<C, Slice_>(
 ) where
   C : MutableCollection,
   Slice_ : Collection,
-  C._Element == Slice_.Element,
+  C.Element == Slice_.Element,
   C.Index == Slice_.Index {
 
   self_._failEarlyRangeCheck(bounds, bounds: self_.startIndex..<self_.endIndex)

test/Prototypes/UnicodeDecoders.swift

@@ -39,8 +39,7 @@ extension Unicode {
   struct DefaultScalarView<
     CodeUnits: BidirectionalCollection,
     Encoding: Unicode.Encoding
-  > where CodeUnits.Element == Encoding.CodeUnit, 
-          CodeUnits._Element == CodeUnits.Element {
+  > where CodeUnits.Element == Encoding.CodeUnit {
     var codeUnits: CodeUnits
     init(
       _ codeUnits: CodeUnits,

test/SILGen/foreach.swift

@@ -117,7 +117,7 @@ func trivialStructBreak(_ xx: [Int]) {
 // CHECK:   br [[LOOP_DEST:bb[0-9]+]]
 //
 // CHECK: [[LOOP_DEST]]:
-// CHECK:   [[FUNC_REF:%.*]] = function_ref @_T0s16IndexingIteratorV4next8_ElementQzSgyF : $@convention(method)
+// CHECK:   [[FUNC_REF:%.*]] = function_ref @_T0s16IndexingIteratorV4next7ElementQzSgyF : $@convention(method)
 // CHECK:   [[GET_ELT_STACK:%.*]] = alloc_stack $Optional<Int>
 // CHECK:   [[WRITE:%.*]] = begin_access [modify] [unknown] [[PROJECT_ITERATOR_BOX]] : $*IndexingIterator<Array<Int>>
 // CHECK:   apply [[FUNC_REF]]<[Int]>([[GET_ELT_STACK]], [[WRITE]])
@@ -223,7 +223,7 @@ func existentialBreak(_ xx: [P]) {
 // CHECK:   br [[LOOP_DEST:bb[0-9]+]]
 //
 // CHECK: [[LOOP_DEST]]:
-// CHECK:   [[FUNC_REF:%.*]] = function_ref @_T0s16IndexingIteratorV4next8_ElementQzSgyF : $@convention(method)
+// CHECK:   [[FUNC_REF:%.*]] = function_ref @_T0s16IndexingIteratorV4next7ElementQzSgyF : $@convention(method)
 // CHECK:   [[WRITE:%.*]] = begin_access [modify] [unknown] [[PROJECT_ITERATOR_BOX]] : $*IndexingIterator<Array<P>> // users: %16, %15
 // CHECK:   apply [[FUNC_REF]]<[P]>([[ELT_STACK]], [[WRITE]])
 // CHECK:   switch_enum_addr [[ELT_STACK]] : $*Optional<P>, case #Optional.some!enumelt.1: [[SOME_BB:bb[0-9]+]], case #Optional.none!enumelt: [[NONE_BB:bb[0-9]+]]
@@ -388,7 +388,7 @@ func genericStructBreak<T>(_ xx: [GenericStruct<T>]) {
 // CHECK:   br [[LOOP_DEST:bb[0-9]+]]
 //
 // CHECK: [[LOOP_DEST]]:
-// CHECK:   [[FUNC_REF:%.*]] = function_ref @_T0s16IndexingIteratorV4next8_ElementQzSgyF : $@convention(method)
+// CHECK:   [[FUNC_REF:%.*]] = function_ref @_T0s16IndexingIteratorV4next7ElementQzSgyF : $@convention(method)
 // CHECK:   [[WRITE:%.*]] = begin_access [modify] [unknown] [[PROJECT_ITERATOR_BOX]] : $*IndexingIterator<Array<GenericStruct<T>>>
 // CHECK:   apply [[FUNC_REF]]<[GenericStruct<T>]>([[ELT_STACK]], [[WRITE]])
 // CHECK:   switch_enum_addr [[ELT_STACK]] : $*Optional<GenericStruct<T>>, case #Optional.some!enumelt.1: [[SOME_BB:bb[0-9]+]], case #Optional.none!enumelt: [[NONE_BB:bb[0-9]+]]

test/SILOptimizer/prespecialize.swift

@@ -13,8 +13,8 @@
 // function_ref specialized Collection<A where ...>.makeIterator() -> IndexingIterator<A>
 // CHECK: function_ref @_T0s10CollectionPssAARzs16IndexingIteratorVyxG0C0RtzlE04makeC0AEyFs14CountableRangeVySiG_Tgq5
 //
-// function_ref specialized IndexingIterator.next() -> A._Element?
-// CHECK: function_ref @_T0s16IndexingIteratorV4next8_ElementQzSgyFs14CountableRangeVySiG_Tgq5
+// function_ref specialized IndexingIterator.next() -> A.Element?
+// CHECK: function_ref @_T0s16IndexingIteratorV4next7ElementQzSgyFs14CountableRangeVySiG_Tgq5
 //
 // Look for generic specialization <Swift.Int> of Swift.Array.subscript.getter : (Swift.Int) -> A
 // CHECK: function_ref {{@_T0Sa9subscriptxSicfgSi_Tgq5|@_TTSg5Si___TFSaap9subscriptFSix}}