Generalize Sequence: ~Copyable & ~Escapable

Author: natecook1000

benchmark/single-source/DataBenchmarks.swift

@@ -327,14 +327,20 @@ let large = sampleData(.large)
 let array809 = byteArray(size: 809)
 
 struct Count0<S: Sequence> : Sequence {
+  @available(macOS 9999, *)
+  public typealias BorrowingIterator = BorrowingIteratorAdapter<S.Iterator>
+
   let base: S
   init (_ base:S) { self.base = base }
   func makeIterator() -> S.Iterator { return base.makeIterator() }
   var underestimatedCount: Int { return 0 }
 }
 
 struct Bytes: Sequence, IteratorProtocol {
-    let count: Int
+  @available(macOS 9999, *)
+  public typealias BorrowingIterator = BorrowingIteratorAdapter<Self>
+
+  let count: Int
     let exact: Bool
     var  i: Int = 0
     init(count: Int, exact: Bool) {

stdlib/private/SwiftReflectionTest/SwiftReflectionTest.swift

@@ -227,6 +227,8 @@ internal struct Section {
 /// Holds the addresses and sizes of sections related to reflection.
 internal struct ReflectionInfo : Sequence {
   internal typealias Element = Section?
+  @available(macOS 9999, *)
+  internal typealias BorrowingIterator = BorrowingIteratorAdapter<AnyIterator<Section?>>
 
   /// The name of the loaded image.
   internal let imageName: String

stdlib/public/Concurrency/Deque/Deque+Collection.swift

@@ -19,6 +19,8 @@ extension _Deque: Sequence {
   // This custom implementation performs direct storage access to eliminate any
   // and all index validation overhead. It also optimizes away repeated
   // conversions from indices to storage slots.
+  @available(macOS 9999, *)
+  internal typealias BorrowingIterator = BorrowingIteratorAdapter<Iterator>
 
   /// An iterator over the members of a deque.
   struct Iterator: IteratorProtocol {

stdlib/public/RuntimeModule/Base64.swift

@@ -217,6 +217,8 @@ public struct Base64Encoder<S: Sequence>: Sequence
 public struct Base64Decoder<S: Sequence>: Sequence
   where S.Element == UTF8.CodeUnit
 {
+  @available(macOS 9999, *)
+  public typealias BorrowingIterator = BorrowingIteratorAdapter<Iterator>
   public typealias Element = UInt8
 
   var source: S

stdlib/public/core/Sequence.swift

@@ -322,7 +322,7 @@ public protocol IteratorProtocol<Element> {
 /// makes no other requirements about element access, so routines that
 /// traverse a sequence should be considered O(*n*) unless documented
 /// otherwise.
-public protocol Sequence<Element> /* : ~Copyable, ~Escapable */ {
+public protocol Sequence<Element>: ~Copyable, ~Escapable {
   /// A type representing the sequence's elements.
   associatedtype Element
 
@@ -331,7 +331,7 @@ public protocol Sequence<Element> /* : ~Copyable, ~Escapable */ {
   associatedtype Iterator: IteratorProtocol<Element>
 
   @available(SwiftStdlib 6.3, *)
-  associatedtype BorrowingIterator: BorrowingIteratorProtocol<Element> & ~Copyable & ~Escapable = BorrowingIteratorAdapter<Self>
+  associatedtype BorrowingIterator: BorrowingIteratorProtocol<Element> & ~Copyable & ~Escapable = BorrowingIteratorAdapter<Iterator>
 
   // FIXME: <rdar://problem/34142121>
   // This typealias should be removed as it predates the source compatibility
@@ -459,16 +459,16 @@ public protocol Sequence<Element> /* : ~Copyable, ~Escapable */ {
 }
 
 @available(SwiftStdlib 6.3, *)
-public struct BorrowingIteratorAdapter<S: Sequence>: /* & ~Copyable & ~Escapable */
-  BorrowingIteratorProtocol where S.Element: Copyable
+public struct BorrowingIteratorAdapter<Iterator: IteratorProtocol>: /* & ~Copyable & ~Escapable */
+  BorrowingIteratorProtocol where Iterator.Element: Copyable
 {
-  var iterator: S.Iterator
-  var curValue: S.Element?
+  var iterator: Iterator
+  var curValue: Iterator.Element?
 
-  public typealias Element = S.Element
+  public typealias Element = Iterator.Element
 
   @lifetime(&self)
-  public mutating func nextSpan(maximumCount: Int) -> Span<S.Element> {
+  public mutating func nextSpan(maximumCount: Int) -> Span<Iterator.Element> {
     curValue = iterator.next()
     return curValue._span
   }
@@ -486,7 +486,7 @@ extension NeverIterator: IteratorProtocol { /* where Element: ~Copyable */
 }
 
 @available(SwiftStdlib 6.3, *)
-extension Sequence where BorrowingIterator == BorrowingIteratorAdapter<Self> {
+extension Sequence where BorrowingIterator == BorrowingIteratorAdapter<Iterator> {
   public func makeBorrowingIterator() -> BorrowingIterator {
     BorrowingIteratorAdapter(iterator: makeIterator())
   }